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1

Pearson's Product-Moment Coefficient of Correlation  

NSDL National Science Digital Library

This tutorial, created by Thomas W. MacFarland of Nova Southeastern University, explains the theory and use of Pearson's Product Moment Coefficient of Correlation and demonstrates it with an example on GPA and test scores. Data sets are provided in both SPSS and Minitab code. This is a great resource for anyone looking for a more in-depth study of statistics. This could be used as either a teaching guide for educators or simply further practice for students.

Macfarland, Thomas W.

2009-09-11

2

Computer Program to Generate Pearson, Spearman, and Kendall Correlations.  

National Technical Information Service (NTIS)

The computer program SPEKEN computes Pearson, Spearman, and Kendall correlation coefficients for multivariate data. Special features of the program include exclusion of pairs of data values where at least one value is missing. Additionally, the Spearman a...

V. E. Kane N. M. Larson V. C. Nall

1977-01-01

3

Sample size requirements for estimating pearson, kendall and spearman correlations  

Microsoft Academic Search

Interval estimates of the Pearson, Kendall tau-a and Spearman correlations are reviewed and an improved standard error for the Spearman correlation is proposed. The sample size required to yield a confidence interval having the desired width is examined. A two-stage approximation to the sample size requirement is shown to give accurate results.

Douglas G. Bonett; Thomas A. Wright

2000-01-01

4

t-Test for Independent or Correlated Samples  

NSDL National Science Digital Library

This page, by Richard Lowry of Vassar College, will compute the t-test for either correlated or independent samples. One may copy and paste data in or type the data in individually. Visitors will also find a link to Lowry's companion online textbook, Concepts and Applications of Inferential Statistics.

Lowry, Richard, 1940-

2008-09-04

5

Computer program to generate Pearson, Spearman, and Kendall correlations. [SPEKEN, in FORTRAN IV for IBM 360  

Microsoft Academic Search

The computer program SPEKEN computes Pearson, Spearman, and Kendall correlation coefficients for multivariate data. Special features of the program include exclusion of pairs of data values where at least one value is missing. Additionally, the Spearman and Kendall nonparametric measures of correlation have adjustments for tied rankings. The hypothesis of independence between each pair of variables can be tested by

V. E. Kane; N. M. Larson; V. C. Nall

1977-01-01

6

Robustness of Two Formulas to Correct Pearson Correlation for Restriction of Range  

ERIC Educational Resources Information Center

|Many research studies involving Pearson correlations are conducted in settings where one of the two variables has a restricted range in the sample. For example, this situation occurs when tests are used for selecting candidates for employment or university admission. Often after selection, there is interest in correlating the selection variable,…

tran, minh

2011-01-01

7

SPEKEN; Pearson, Spearman and Kendall correlation. [IBM360,370; FORTRAN IV  

Microsoft Academic Search

SPEKEN computes Pearson, Spearman, and Kendall correlation coefficients and associated significance levels for multivariate data. Special features of the program include exclusion of pairs of data values where one value is missing, and adjustment for tied rankings. The hypothesis of independence between each pair of variables can be tested using the obtained significance level for each correlation.IBM360,370; FORTRAN IV; OS\\/360,370;

2008-01-01

8

SPSS and SAS programs for comparing Pearson correlations and OLS regression coefficients.  

PubMed

Several procedures that use summary data to test hypotheses about Pearson correlations and ordinary least squares regression coefficients have been described in various books and articles. To our knowledge, however, no single resource describes all of the most common tests. Furthermore, many of these tests have not yet been implemented in popular statistical software packages such as SPSS and SAS. In this article, we describe all of the most common tests and provide SPSS and SAS programs to perform them. When they are applicable, our code also computes 100 × (1 - ?)% confidence intervals corresponding to the tests. For testing hypotheses about independent regression coefficients, we demonstrate one method that uses summary data and another that uses raw data (i.e., Potthoff analysis). When the raw data are available, the latter method is preferred, because use of summary data entails some loss of precision due to rounding. PMID:23344734

Weaver, Bruce; Wuensch, Karl L

2013-09-01

9

Correlational Analysis of Ordinal Data: From Pearson's "r" to Bayesian Polychoric Correlation  

ERIC Educational Resources Information Center

Correlational analyses are one of the most popular quantitative methods, yet also one of the mostly frequently misused methods in social and behavioral research, especially when analyzing ordinal data from Likert or other rating scales. Although several correlational analysis options have been developed for ordinal data, there seems to be a lack…

Choi, Jaehwa; Peters, Michelle; Mueller, Ralph O.

2010-01-01

10

A novel fractal image compression scheme with block classification and sorting based on Pearson's correlation coefficient.  

PubMed

Fractal image compression (FIC) is an image coding technology based on the local similarity of image structure. It is widely used in many fields such as image retrieval, image denoising, image authentication, and encryption. FIC, however, suffers from the high computational complexity in encoding. Although many schemes are published to speed up encoding, they do not easily satisfy the encoding time or the reconstructed image quality requirements. In this paper, a new FIC scheme is proposed based on the fact that the affine similarity between two blocks in FIC is equivalent to the absolute value of Pearson's correlation coefficient (APCC) between them. First, all blocks in the range and domain pools are chosen and classified using an APCC-based block classification method to increase the matching probability. Second, by sorting the domain blocks with respect to APCCs between these domain blocks and a preset block in each class, the matching domain block for a range block can be searched in the selected domain set in which these APCCs are closer to APCC between the range block and the preset block. Experimental results show that the proposed scheme can significantly speed up the encoding process in FIC while preserving the reconstructed image quality well. PMID:23797251

Wang, Jianji; Zheng, Nanning

2013-06-17

11

Random matrix theory analysis of cross-correlations in the US stock market: Evidence from Pearson's correlation coefficient and detrended cross-correlation coefficient  

NASA Astrophysics Data System (ADS)

In this study, we first build two empirical cross-correlation matrices in the US stock market by two different methods, namely the Pearson's correlation coefficient and the detrended cross-correlation coefficient (DCCA coefficient). Then, combining the two matrices with the method of random matrix theory (RMT), we mainly investigate the statistical properties of cross-correlations in the US stock market. We choose the daily closing prices of 462 constituent stocks of S&P 500 index as the research objects and select the sample data from January 3, 2005 to August 31, 2012. In the empirical analysis, we examine the statistical properties of cross-correlation coefficients, the distribution of eigenvalues, the distribution of eigenvector components, and the inverse participation ratio. From the two methods, we find some new results of the cross-correlations in the US stock market in our study, which are different from the conclusions reached by previous studies. The empirical cross-correlation matrices constructed by the DCCA coefficient show several interesting properties at different time scales in the US stock market, which are useful to the risk management and optimal portfolio selection, especially to the diversity of the asset portfolio. It will be an interesting and meaningful work to find the theoretical eigenvalue distribution of a completely random matrix R for the DCCA coefficient because it does not obey the Mar?enko–Pastur distribution.

Wang, Gang-Jin; Xie, Chi; Chen, Shou; Yang, Jiao-Jiao; Yang, Ming-Yan

2013-09-01

12

Correcting Two-Sample "z" and "t" Tests for Correlation: An Alternative to One-Sample Tests on Difference Scores  

ERIC Educational Resources Information Center

|In order to circumvent the influence of correlation in paired-samples and repeated measures experimental designs, researchers typically perform a one-sample Student "t" test on difference scores. That procedure entails some loss of power, because it employs N - 1 degrees of freedom instead of the 2N - 2 degrees of freedom of the…

Zimmerman, Donald W.

2012-01-01

13

Pearson's Functions to Describe FSW Weld Geometry  

NASA Astrophysics Data System (ADS)

Friction stir welding (FSW) is a relatively new joining technique particularly for aluminium alloys that are difficult to fusion weld. In this study, the geometry of the weld has been investigated and modelled using Pearson's functions. It has been demonstrated that the Pearson's parameters (mean, standard deviation, skewness, kurtosis and geometric constant) can be used to characterize the weld geometry and the tensile strength of the weld assembly. Pearson's parameters and process parameters are strongly correlated allowing to define a control process procedure for FSW assemblies which make radiographic or ultrasonic controls unnecessary. Finally, an optimisation using a Generalized Gradient Method allows to determine the geometry of the weld which maximises the assembly tensile strength.

Lacombe, D.; Gutierrez-Orrantia, M. E.; Coupard, D.; Tcherniaeff, S.; Girot, F.

2011-01-01

14

Corneal endothelial dysfunction in Pearson syndrome.  

PubMed

Mitochondrial disorders are associated with well recognized ocular manifestations. Pearson syndrome is an often fatal, multisystem, mitochondrial disorder that causes variable bone marrow, hepatic, renal and pancreatic exocrine dysfunction. Phenotypic progression of ocular disease in a 12-year-old male with Pearson syndrome is described. This case illustrates phenotypic drift from Pearson syndrome to Kearns-Sayre syndrome given the patient's longevity. Persistent corneal endothelial failure was noted in addition to ptosis, chronic external ophthalmoplegia and mid-peripheral pigmentary retinopathy. We propose that corneal edema resulting from corneal endothelial metabolic pump failure occurs within a spectrum of mitochondrial disorders. PMID:21936618

Kasbekar, Shivani A; Gonzalez-Martin, Jose A; Shafiq, Ayad E; Chandna, Arvind; Willoughby, Colin E

2011-09-21

15

Drew Pearson's Washington Merry-Go-Round  

NSDL National Science Digital Library

The name Drew Pearson might not be well known today to most people, but from the early 1930s until 1969, he wrote the highly influential (and controversial) syndicated column, "Washington Merry-Go-Round". The column served a muck-racking function for the highest levels of government in the United States. During his long tenure, Pearson wrote on the subject of unscrupulous public officials and became known for his flair for the dramatic. During his long career, Pearson also wrote ten books, including "U.S.A.: Second Class Power?" This excellent collection from American University brings together many of his columns from 1932 to 1969, along with a biography of Pearson and a bibliography of related works. Visitors should feel free to dive right in, and they can also browse by titles and dates.

16

On the Intellectual Versatility of Karl Pearson  

Microsoft Academic Search

This paper displays the impressive versatility of Karl Pearson, focusing not only on his contributions to statistics and other quantitative disciplines but also on his research and publications in religion, politics, literary criticism, philosophy of science, Darwinism, biology, history, freethought, evolution, genetics, socialism, anthropology, eugenics, and emancipation of women. Being the chairman of a first class academic department and the

Richard H. Williams; Bruno D. Zumbo; Donald Ross; W. Zimmerman

17

Performance Measures for Neyman-Pearson Classification  

Microsoft Academic Search

Abstract In the Neyman-Pearson (NP) classification paradigm, the goal is to learn a classifier from labeled training data such that the probability of a false negative is minimized,while the probability of a false positive is below a user-specified level fi 2 (0,1). This work addresses the question of how to evaluate and compare,classifiers in the NP setting. Simply reporting false

Clayton Scott

2007-01-01

18

Single Sample t-Test  

NSDL National Science Digital Library

This page will perform a t-test for the significance of the difference between the observed mean of a sample and a hypothetical mean of the population from which the sample is randomly drawn. The user will be asked to specify the sample size as the page opens.

Lowry, Richard, 1940-

2008-09-05

19

Karl Pearson’s Theoretical Errors and the Advances They Inspired  

Microsoft Academic Search

Karl Pearson played an enormous role in determining the content and organization of statistical research in his day, through his research, his teaching, his establishment of laboratories, and his initiation of a vast publishing program. His technical contributions had initially and continue today to have a profound impact upon the work of both applied and theoretical statisticians, partly through their

Stephen M. Stigler

2008-01-01

20

Parental Socio-Economic Status as Correlate of Child Labour in Ile-Ife, Nigeria  

ERIC Educational Resources Information Center

|This study investigated the relationship between parental socio-economic status and child labour practices in Ile-Ife, Nigeria. The study employed survey method to gather data from 200 parents which constituted the study population. Pearson Product Moment Correlation and t-test statistics were used for the data analyses. The outcome of the study…

Elegbeleye, O. S.; Olasupo, M. O.

2012-01-01

21

18. TYPE F, BUILDING #516732 PEARSON ROAD, INTERIOR, THIRD FLOOR, ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

18. TYPE F, BUILDING #516-732 PEARSON ROAD, INTERIOR, THIRD FLOOR, BEDROOM, NORTHWEST VIEW. - Wright-Patterson Air Force Base, Brick Officers' Quarters, Types E & F, Area A, Dayton, Montgomery County, OH

22

Clinical manifestations and management of four children with Pearson syndrome.  

PubMed

Pearson marrow-pancreas syndrome is a fatal disorder mostly diagnosed during infancy and caused by mutations of mitochondrial DNA. We hereby report on four children affected by Pearson syndrome with hematological disorders at onset. The disease was fatal to three of them and the fourth one, who received hematopoietic stem cell transplantation, died of secondary malignancy. In this latter patient transplantation corrected hematological and non-hematological issues like metabolic acidosis, and we therefore argue that it could be considered as a useful option in an early stage of the disease. PMID:22012855

Tumino, Manuela; Meli, Concetta; Farruggia, Piero; La Spina, Milena; Faraci, Maura; Castana, Cinzia; Di Raimondo, Vincenzo; Alfano, Marivana; Pittalà, Annarita; Lo Nigro, Luca; Russo, Giovanna; Di Cataldo, Andrea

2011-10-19

23

The One-Sample t Test  

NSDL National Science Digital Library

This section, part of a larger site produced by the School of Psychology at the University of New England, focuses on "Common Statistical Tests" using an example on faculty publications to show users how to perform a one-sample t test. Additionally, there is a discussion that includes one-tailed and two-tailed tests.

Price, Ian

2009-01-13

24

Bayesian Estimation Supersedes the "t" Test  

ERIC Educational Resources Information Center

|Bayesian estimation for 2 groups provides complete distributions of credible values for the effect size, group means and their difference, standard deviations and their difference, and the normality of the data. The method handles outliers. The decision rule can accept the null value (unlike traditional "t" tests) when certainty in the estimate…

Kruschke, John K.

2013-01-01

25

Pearson's System of Frequency Curves Digital Computer Program.  

National Technical Information Service (NTIS)

The report describes a Fortran II digital computer program that classified a series of data as one of the three main types of Pearson's frequency curves, calculates an approximating frequency function, and applies a Chi-square goodness of fit test. The th...

L. Greene N. R. Rich R. C. Graham

1971-01-01

26

Comparing Pearson, Spearman and Hoeffding's D measure for gene expression association analysis.  

PubMed

DNA microarrays have become a powerful tool to describe gene expression profiles associated with different cellular states, various phenotypes and responses to drugs and other extra- or intra-cellular perturbations. In order to cluster co-expressed genes and/or to construct regulatory networks, definition of distance or similarity between measured gene expression data is usually required, the most common choices being Pearson's and Spearman's correlations. Here, we evaluate these two methods and also compare them with a third one, namely Hoeffding's D measure, which is used to infer nonlinear and non-monotonic associations, i.e. independence in a general sense. By comparing three different variable association approaches, namely Pearson's correlation, Spearman's correlation and Hoeffding's D measure, we aimed at assessing the most appropriate one for each purpose. Using simulations, we demonstrate that the Hoeffding's D measure outperforms Pearson's and Spearman's approaches in identifying nonlinear associations. Our results demonstrate that Hoeffding's D measure is less sensitive to outliers and is a more powerful tool to identify nonlinear and non-monotonic associations. We have also applied Hoeffding's D measure in order to identify new putative genes associated with tp53. Therefore, we propose the Hoeffding's D measure to identify nonlinear associations between gene expression profiles. PMID:19634197

Fujita, André; Sato, João Ricardo; Demasi, Marcos Angelo Almeida; Sogayar, Mari Cleide; Ferreira, Carlos Eduardo; Miyano, Satoru

2009-08-01

27

Student's t-Test for Matched Pairs  

NSDL National Science Digital Library

This tutorial, created by Thomas W. McFarland of Nova Southeastern University, explains the theory and use of Student's t-test for matched pairs and demonstrates it with an example on project quality. Data sets are provided in both SPSS and Minitab code. This is a nice resource for both students and teachers. It can be used for a more in-depth look at statistical testing.

Macfarland, Thomas W.

2009-01-21

28

Student's t-Test for Independent Samples  

NSDL National Science Digital Library

This tutorial, created by Thomas W. MacFarland of Nova Southeastern University, explains the theory and use of Student's t-test and demonstrates it with an example on final exam scores. Data sets are provided in both SPSS and Minitab code. This is a great resource, or even lesson plan, for anyone interested in a more in-depth look at statistical testing.

Macfarland, Thomas W.

2009-01-21

29

A New Family of Solvable Pearson-Dirichlet Random Walks  

Microsoft Academic Search

An n-step Pearson-Gamma random walk in ?\\u000a d\\u000a starts at the origin and consists of n independent steps with gamma distributed lengths and uniform orientations. The gamma distribution of each step length has\\u000a a shape parameter q>0. Constrained random walks of n steps in ?\\u000a d\\u000a are obtained from the latter walks by imposing that the sum of the step

Gérard Le Caër

2011-01-01

30

A New Family of Solvable Pearson-Dirichlet Random Walks  

Microsoft Academic Search

An n-step Pearson-Gamma random walk in R d starts at the origin and consists of n independent steps with gamma distributed lengths and uniform orientations. The gamma distribution of each step length has a shape parameter q>0. Constrained random walks of n steps in R d are obtained from the latter walks by imposing that the sum of the step

Gérard Le Caër

2011-01-01

31

Bayesian estimation supersedes the t test.  

PubMed

Bayesian estimation for 2 groups provides complete distributions of credible values for the effect size, group means and their difference, standard deviations and their difference, and the normality of the data. The method handles outliers. The decision rule can accept the null value (unlike traditional t tests) when certainty in the estimate is high (unlike Bayesian model comparison using Bayes factors). The method also yields precise estimates of statistical power for various research goals. The software and programs are free and run on Macintosh, Windows, and Linux platforms. PMID:22774788

Kruschke, John K

2012-07-09

32

A New Family of Solvable Pearson-Dirichlet Random Walks  

NASA Astrophysics Data System (ADS)

An n-step Pearson-Gamma random walk in ? d starts at the origin and consists of n independent steps with gamma distributed lengths and uniform orientations. The gamma distribution of each step length has a shape parameter q>0. Constrained random walks of n steps in ? d are obtained from the latter walks by imposing that the sum of the step lengths is equal to a fixed value. Simple closed-form expressions were obtained in particular for the distribution of the endpoint of such constrained walks for any d? d 0 and any n?2 when q is either q = d/2 - 1 ( d 0=3) or q= d-1 ( d 0=2) (Le Caër in J. Stat. Phys. 140:728-751, 2010). When the total walk length is chosen, without loss of generality, to be equal to 1, then the constrained step lengths have a Dirichlet distribution whose parameters are all equal to q and the associated walk is thus named a Pearson-Dirichlet random walk. The density of the endpoint position of a n-step planar walk of this type ( n?2), with q= d=2, was shown recently to be a weighted mixture of 1+ floor( n/2) endpoint densities of planar Pearson-Dirichlet walks with q=1 (Beghin and Orsingher in Stochastics 82:201-229, 2010). The previous result is generalized to any walk space dimension and any number of steps n?2 when the parameter of the Pearson-Dirichlet random walk is q= d>1. We rely on the connection between an unconstrained random walk and a constrained one, which have both the same n and the same q= d, to obtain a closed-form expression of the endpoint density. The latter is a weighted mixture of 1+ floor( n/2) densities with simple forms, equivalently expressed as a product of a power and a Gauss hypergeometric function. The weights are products of factors which depends both on d and n and Bessel numbers independent of d.

Le Caër, Gérard

2011-07-01

33

Karl pearson's mathematization of inheritance: From ancestral heredity to Mendelian genetics (1895–1909)  

Microsoft Academic Search

Long-standing claims have been made for nearly the entire twentieth century that the biometrician, Karl Pearson, and his colleague, W. F. R. Weldon, rejected Mendelism as a theory of inheritance. It is shown that at the end of the nineteenth century Pearson considered various theories of inheritance (including Francis Galton's law of ancestral heredity for characters underpinned by continuous variation),

M. Eileen Magnello

1998-01-01

34

Student T-tests for Potentially Abnormal Data‡  

PubMed Central

SUMMARY When the one sample or two-sample t-test is either taught in the class room, or applied in practice to small samples, there is considerable divergence of opinion as to whether or not the inferences drawn are valid. Many point to the “Robustness” of the t-test to violations of assumptions, while others use rank or other robust methods because they believe the t-test is not robust against violations of such assumptions. It is quite likely, despite the apparent divergence of these two opinions, that both arguments have considerable merit. If we agree that this question cannot possibly be resolved in general, the issue becomes one of determining, before any actual data have been collected, whether the t-test will or will not be robust in a specific application. This paper describes Statistical Analysis System (SAS) software, covering a large collection of potential input probability distributions, to investigate both the null and power properties of various one and two sample t-tests and their normal approximations, as well as the Wilcoxon two-sample and sign-rank one sample tests, allowing potential practitioners to determine, at the study design stage, whether the t-test will be robust in their specific application. Sample size projections, based on these actual distributions, are also included. This paper is not intended as a tool to assess robustness after the data have been collected.

Shuster, Jonathan J.

2013-01-01

35

Mitochondrial DNA deletion in a patient with combined features of Leigh and Pearson syndromes  

SciTech Connect

We describe a heteroplasmic 4237 bp mitochondrial DNA (mtDNA) deletion in an 11 year old girl who has suffered from progressive illness since birth. She has some features of Leigh syndrome (global developmental delay with regression, brainstem dysfunction and lactic acidosis), together with other features suggestive of Pearson syndrome (history of pancytopenia and failure to thrive). The deletion was present at a level greater than 50% in skeletal muscle, but barely detectable in skin fibroblasts following Southern blot analysis, and only observed in blood following PCR analysis. The deletion spanned nt 9498 to nt 13734, and was flanked by a 12 bp direct repeat. Genes for cytochrome c oxidase subunit III, NADH dehydrogenase subunits 3, 4L, 4 and 5, and tRNAs for glycine, arginine, histidine, serine({sup AGY}) and leucine({sup CUN}) were deleted. Southern blotting also revealed an altered Apa I restriction site which was shown by sequence analysis to be caused by G{r_arrow}A nucleotide substitution at nt 1462 in the 12S rRNA gene. This was presumed to be a polymorphism. No abnormalities of mitochondrial ultrastructure, distribution or of respiratory chain enzyme complexes I-IV in skeletal muscle were observed. Mitochondrial disorders with clinical features overlapping more than one syndrome have been reported previously. This case further demonstrates the difficulty in correlating observed clinical features with a specific mitochondrial DNA mutation.

Blok, R.B.; Thorburn, D.R.; Danks, D.M. [Royal Children`s Hospital, Melbourne (Australia)] [and others

1994-09-01

36

The Evolution of Pearsons Correlation Coefficient/Exploring Relationships between Two Quantitative Variables  

NSDL National Science Digital Library

The evolution of ideas is often ignored in the teaching of statistics. It is important to show students how definitions and formulas evolve. This activity describes a fairly straightforward activity of how measures of association can evolve.

Kader, Gary

37

Pearson versus Spearman Kendall's Tau Correlation Analysis on StructureActivity Relationships of Biologic Active Compounds  

Microsoft Academic Search

Abstract Asample,of sixty-seven pyrimidine derivatives with inhibitory activity on E. coli dihydrofolate reductase (DHFR) was ,studied by the ,use of molecular descriptors family on structure-activity relationships. Starting from the results obtained by applying ,of MDF-SAR methodology ,on pyrimidine ,derivatives and from the assumption ,that the measured activity (compounds’ inhibitory activity) of a ,biologically active compounds ,is a semi-quantitative outcome (can

Sorana-daniela Bolboac?; Lorentz Jäntschi

38

"It was a young man's life": G.A. Pearson (P-53) - Treesearch  

Treesearch

Gustaf A. Pearson was the first in a distinguished line of USFS scientists to live and ... toward understanding nature's methods of ponderosa pine regeneration. ... This paper looks at the cultural history of FVEF and provides introduction to the  ...

39

Sample Size for Correlation Estimates.  

National Technical Information Service (NTIS)

This thesis examines the classical measure of correlation (Pearson's R) and two nonparametric measures of correlation (Spearman's r and Kendall's tau) with the goal of determining the number of samples needed to estimate a correlation coefficient with a 9...

K. Salar

1989-01-01

40

The Beta Distribution,moment method, Karl Pearson and R.A.Fisher  

SciTech Connect

Simulation studies provide four moment approximating distributions to each of the four parameters of a beta distribution (Pearson Type I). Two of the parameters refer to origin and scale, two to shape (skewness and kurtosis). Type I random number generator is checked out, and the stability of moments of random samples of size n over cycles; particular attention is paid to shape parameter moments. In Type I region of validity (referred to skewness and kurtosis), moment methods become unstable in the neighborhood of Type III ({chi}{sup 2}) line, and ultimately abort. Thus extremely large variances and large higher moments arise. We probe the cause of this phenomenon. Simulation studies are turned to since alternative power series methods are forbiddingly complicated. However, use is made of the delta method to provide asymptotic variances of the estimators, and asymptotic variances of percentage points of the basic distribution. An account of work on the subject by K. Pearson, some of it a century ago, is given. In particular an important paper by Pearson and Filon provides some estimates of probable errors of moment parameter estimators such as the basic distribution parameters, the mode, the skewness and others. The heated controversy between Pearson and Fisher is considered.

Bowman, Kimiko o [ORNL

2007-01-01

41

Karl Pearson's mathematization of inheritance: from ancestral heredity to Mendelian genetics (1895-1909).  

PubMed

Long-standing claims have been made for nearly the entire twentieth century that the biometrician, Karl Pearson, and colleague, W. F. R. Weldon, rejected Mendelism as a theory of inheritance. It is shown that at the end of the nineteenth century Pearson considered various theories of inheritance (including Francis Galton's law of ancestral heredity for characters underpinned by continuous variation), and by 1904 he 'accepted the fundamental idea of Mendel' as a theory of inheritance for discontinuous variation. Moreover, in 1909, he suggested a synthesis of biometry and Mendelism. Despite the many attempts made by a number of geneticists (including R. A. Fisher in 1936) to use Pearson's chi-square (X2, P) goodness-of-fit test on Mendel's data, which produced results that were 'too good to be true', Weldon reached the same conclusion in 1902, but his results were never acknowledged. The geneticist and arch-rival of the biometricians, Williams Bateson, was instead exceptionally critical of this work and interpreted this as Weldon's rejection of Mendelism. Whilst scholarship on Mendel, by historians of science in the last 18 years, has led to a balanced perspective of Mendel, it is suggested that a better balanced and more rounded view of the hereditarian-statistical work of Pearson, Weldon, and the biometricians is long overdue. PMID:11619806

Magnello, M E

1998-01-01

42

Evaluation of a Neyman-Pearson heart-rate turbulence detector  

Microsoft Academic Search

In this paper we propose and evaluate a Neyman-Pearson approach to detect and characterize heart-rate turbulence after ventricular premature beats (VPB). For quantification of the detection performance an evaluation dataset was built based on real RR interval series. The ROC curves obtained from the test set show the proposed method to outperform the detection capability of the two parameters currently

Juan Pablo Martinez; Pablo Laguna; Kristian Solem; Leif Sornmo

2008-01-01

43

"Describing our whole experience": the statistical philosophies of W. F. R. Weldon and Karl Pearson.  

PubMed

There are two motivations commonly ascribed to historical actors for taking up statistics: to reduce complicated data to a mean value (e.g., Quetelet), and to take account of diversity (e.g., Galton). Different motivations will, it is assumed, lead to different methodological decisions in the practice of the statistical sciences. Karl Pearson and W. F. R. Weldon are generally seen as following directly in Galton's footsteps. I argue for two related theses in light of this standard interpretation, based on a reading of several sources in which Weldon, independently of Pearson, reflects on his own motivations. First, while Pearson does approach statistics from this "Galtonian" perspective, he is, consistent with his positivist philosophy of science, utilizing statistics to simplify the highly variable data of biology. Weldon, on the other hand, is brought to statistics by a rich empiricism and a desire to preserve the diversity of biological data. Secondly, we have here a counterexample to the claim that divergence in motivation will lead to a corresponding separation in methodology. Pearson and Weldon, despite embracing biometry for different reasons, settled on precisely the same set of statistical tools for the investigation of evolution. PMID:22035721

Pence, Charles H

2011-12-01

44

Study of two error functions to approximate the Neyman-pearson detector using supervised learning machines  

Microsoft Academic Search

A study of the possibility of approximating the Neyman-Pearson detector using supervised learning machines is presented. Two error functions are considered for training: the sum-of-squares error and the Minkowski error with R = 1. The study is based on the calculation of the function the learning machine approximates to during training, and the application of a sufficient condition previously formulated.

María-Pilar Jarabo-Amores; Manuel Rosa-Zurera; Roberto Gil-Pita; Francisco Lopez-Ferreras

2009-01-01

45

Sufficient condition for an adaptive system to approximate the neyman-pearson detector  

Microsoft Academic Search

The application of adaptive systems to approximate the Neyman-Pearson detector is considered. The training error function is proved to be the key parameter that determines the possibility of approximating this detector. Based on the calculus of the approximated function for the selected error criterion, a sufficient condition is derived. Decision rules based on expressions of the optimum Bayes discriminant function,

Pilar Jarabo-Amores; Manuel Rosa-Zurera; Roberto Gil-Pita; F. Lopez-Ferreras

2005-01-01

46

mtDNA Deletion in an Iranian Infant with Pearson Marrow Syndrome  

PubMed Central

Background Pearson syndrome (PS) is a rare multisystem mitochondrial disorder of hematopoietic system, characterized by refractory sideroblastic anemia, pancytopenia, exocrine pancreatic insufficiency, and variable neurologic, hepatic, renal, and endocrine failure. Case Presentation We describe a six-month-old female infant with Pearson marrow syndrome who presented with neurological manifestations. She had several episodes of seizures. Hematopoietic abnormalities were macrocytic anemia and neutropenia. Bone marrow aspiration revealed a cellular marrow with marked vacuolization of erythroid and myeloid precursors. Analysis of mtDNA in peripheral blood showed 8.5 kb deletion that was compatible with the diagnosis of PS. Conclusion PS should be considered in infants with neurologic diseases, in patients with cytopenias, and also in patients with acidosis or refractory anemia.

Arzanian, Mohammad Taghi; Eghbali, Aziz; Karimzade, Parvaneh; Ahmadi, Mitra; Houshmand, Massoud; Rezaei, Nima

2010-01-01

47

Pearson's marrow-pancreas syndrome. A multisystem mitochondrial disorder in infancy.  

PubMed Central

Pearson's marrow-pancreas syndrome (McKusick No. 26056) is a fatal disorder of hitherto unknown etiology involving the hematopoietic system, exocrine pancreas, liver, and kidneys. The observation of high lactate/pyruvate molar ratios in plasma and abnormal oxidative phosphorylation in lymphocytes led us to postulate that Pearson's syndrome belongs to the group of mitochondrial cytopathies. Since rearrangements of the mitochondrial genome between direct DNA repeats were consistently found in all tissues tested, our results show that this disease is in fact a multisystem mitochondrial disorder, as suggested by the clinical course of the patients. Based on these observations, we would suggest giving consideration to the hypothesis of a defect of oxidative phosphorylation in elucidating the origin of other syndromes, especially those associated with an abnormal oxidoreduction status in plasma. Images

Rotig, A; Cormier, V; Blanche, S; Bonnefont, J P; Ledeist, F; Romero, N; Schmitz, J; Rustin, P; Fischer, A; Saudubray, J M

1990-01-01

48

Approximating the Neyman-Pearson Detector for Swerling I Targets with Low Complexity Neural Networks  

Microsoft Academic Search

\\u000a This paper deals with the application of neural networks to approximate the Neyman-Pearson detector. The detection of Swerling\\u000a I targets in white gaussian noise is considered. For this case, the optimum detector and the optimum decision boundaries are\\u000a calculated. Results prove that the optimum detector is independent on TSNR, so, under good training conditions, neural network\\u000a performance should be independent

D. De La Mata-moya; Pilar Jarabo Amores; Manuel Rosa-zurera; Francisco López-ferreras; Raul Vicen-bueno

2005-01-01

49

Choosing the Best Correction Formula for the Pearson r[superscript 2] Effect Size  

ERIC Educational Resources Information Center

In the present Monte Carlo simulation study, the authors compared bias and precision of 7 sampling error corrections to the Pearson r[superscript 2] under 6 x 3 x 6 conditions (i.e., population ? values of 0.0, 0.1, 0.3, 0.5, 0.7, and 0.9, respectively; population shapes normal, skewness = kurtosis = 1, and skewness = -1.5 with kurtosis = 3.5;…

Skidmore, Susan Troncoso; Thompson, Bruce

2011-01-01

50

t-Test: The Good, the Bad, the Ugly, & the Remedy  

ERIC Educational Resources Information Center

The t-test is one of the most commonly used significance tests to assess whether the means of two groups are statistically significantly different from each other. The use of t-test has become a natural choice, and rarely practitioners question its appropriateness. This article reviews and discusses t-test's value in providing a rough comparison…

Zhang, Guili

2009-01-01

51

[Clinical correlation of vascular parkinsonism].  

PubMed

Vascular parkinsonism has not been well defined and the clinical correlation of vascular parkinsonism is still not clear. The aim of the study was to estimate prevalence of occurrence of vascular parkinsonism, analysis of risk factors leading to its development and to identify clinical features that suggest a vascular origin. 214 patients with Parkinson's disease were examined. Their ages ranged from 37 to 88 years (median 66.4 years). Evidence of vascular parkinsonism was assessed using a vascular rating scale previously described by Winikates and Jankovic. Statistical analysis was performed with Mann-Whitney U test, chi 2 Pearson test, chi 2 Yates test, Spearman rank correlation and Student's t test. Out of 214 patients 8 were proved to have developed Parkinson's disease due to vascular disease, what gave 3.74%. Out of risk factors for stroke 5 patients had hypertension, 3 had diabetes mellitus, 2 suffered from heart disease, 2 had infarctus myocardii, 1 had hyperlipidemia, 1 had atrial fibrillation. Additionally, those patients had neuroimaging (CT or MRI) evidence of vascular disease in one or more vascular territories. Patients with vascular parkinsonism were older, had shorter duration of disease, were more likely to present rigidity rather than tremor. Dementia and incontinence were more common in vascular group than in Parkinson's disease group. Patients with vascular parkinsonism were also significantly more likely to have corticospinal findings. Proving that Parkinson's disease had vascular etiology is extremely difficult. The test results are inconclusive. PMID:15098342

Honczarenko, Krystyna; Budzianowska, Anna

2003-01-01

52

Pearson-type goodness-of-fit test with bootstrap maximum likelihood estimation  

PubMed Central

The Pearson test statistic is constructed by partitioning the data into bins and computing the difference between the observed and expected counts in these bins. If the maximum likelihood estimator (MLE) of the original data is used, the statistic generally does not follow a chi-squared distribution or any explicit distribution. We propose a bootstrap-based modification of the Pearson test statistic to recover the chi-squared distribution. We compute the observed and expected counts in the partitioned bins by using the MLE obtained from a bootstrap sample. This bootstrap-sample MLE adjusts exactly the right amount of randomness to the test statistic, and recovers the chi-squared distribution. The bootstrap chi-squared test is easy to implement, as it only requires fitting exactly the same model to the bootstrap data to obtain the corresponding MLE, and then constructs the bin counts based on the original data. We examine the test size and power of the new model diagnostic procedure using simulation studies and illustrate it with a real data set.

Yin, Guosheng; Ma, Yanyuan

2013-01-01

53

Correlation  

NSDL National Science Digital Library

The applets, created by Virginia Tech's Department of Statistics, allow you to see how different bivariate data look under different correlation structures. The "Movie" applet either creates data for a particular correlation or animates a multitude data sets ranging correlations from -1 to 1. The "Creation" applet allows the user to create a data set by adding or deleting points from the screen.

Anderson-Cook, C.; Robinson, T.; Dorai-Raj, S.

2009-09-14

54

Correlation of Masseter Muscle Thickness and Intermolar Width - An Ultrasonography Study  

PubMed Central

Background: To determine the association between the thickness of masseter muscle and the maxillary dental arch width. To explore the influence of gender on masseter muscle thickness. Materials & methods: Seventy subjects (35 females and 35 males) of age 18 to 25 years were selected for the study based on class I molar relationship. The masseter muscle thickness of the right and left sides in every subject were found out through ultrasound scanning of the muscle, in both relaxed and clenched states. The maxillary dental arch width was measured on the study model with an electronic caliper. Student t test, Pearson’s Correlation Coefficient was performed to assess the sample. Results: Masseter Muscle Thickness showed a positive correlation with Maxillary Dental Arch Width r ?0.74. The masseter muscle thickness is greater in male subjects in both relaxed (0.001

Correlation of Masseter Muscle Thickness and Intermolar Width - An Ultrasonography Study. J Int Oral Health 2013; 5(2):28-34.

Tircoveluri, Saritha; Singh, Johar Rajvinder; Rayapudi, Naveen; Karra, Arjun; Begum, Mohammadi; Challa, Padmalatha

2013-01-01

55

The Robustness of the Student T Test when Sampling from A Weibull Distribution.  

National Technical Information Service (NTIS)

When testing with the t-test, it is assumed that the sample under investigation is from a normal population. The purpose of this thesis is to examine the sensitivity of the t-test to violations of this normality assumption. A computer simulation was perfo...

D. P. Allen

1970-01-01

56

Gene Feature Extraction Using T-Test Statistics and Kernel Partial Least Squares  

Microsoft Academic Search

In this paper, we propose a gene extraction method by us- ing two standard feature extraction methods, namely the T-test method and kernel partial least squares (KPLS), in tandem. First, a preprocess- ing step based on the T-test method is used to filter irrelevant and noisy genes. KPLS is then used to extract features with high information con- tent. Finally,

Shutao Li; Chen Liao; James T. Kwok

2006-01-01

57

When "t"-Tests or Wilcoxon-Mann-Whitney Tests Won't Do  

ERIC Educational Resources Information Center

|"t"-Tests are widely used by researchers to compare the average values of a numeric outcome between two groups. If there are doubts about the suitability of the data for the requirements of a "t"-test, most notably the distribution being non-normal, the Wilcoxon-Mann-Whitney test may be used instead. However, although often applied, both tests…

McElduff, Fiona; Cortina-Borja, Mario; Chan, Shun-Kai; Wade, Angie

2010-01-01

58

On the Relative Power of the Paired Samples t Test and Wilcoxon's Signed-Ranks Test.  

ERIC Educational Resources Information Center

|Monte Carlo methods were employed to assess the relative power of the paired samples t test and Wilcoxon's signed-ranks test under ten population shapes. Results of the study indicated that: (1) each of the two statistics was more powerful than the other in given situations; (2) the power advantages of the t test under normal theory were small;…

Blair, R. Clifford; Higgins, James J.

59

Performance evaluation for epileptic electroencephalogram (EEG) detection by using Neyman-Pearson criteria and a support vector machine  

NASA Astrophysics Data System (ADS)

The diagnosis of several neurological disorders is based on the detection of typical pathological patterns in electroencephalograms (EEGs). This is a time-consuming task requiring significant training and experience. A lot of effort has been devoted to developing automatic detection techniques which might help not only in accelerating this process but also in avoiding the disagreement among readers of the same record. In this work, Neyman-Pearson criteria and a support vector machine (SVM) are applied for detecting an epileptic EEG. Decision making is performed in two stages: feature extraction by computing the wavelet coefficients and the approximate entropy (ApEn) and detection by using Neyman-Pearson criteria and an SVM. Then the detection performance of the proposed method is evaluated. Simulation results demonstrate that the wavelet coefficients and the ApEn are features that represent the EEG signals well. By comparison with Neyman-Pearson criteria, an SVM applied on these features achieved higher detection accuracies.

Wang, Chun-mei; Zhang, Chong-ming; Zou, Jun-zhong; Zhang, Jian

2012-02-01

60

A General Class of Correlation Coefficients for the 2 × 2 Crossover Design  

Microsoft Academic Search

Summary The Pearson correlation coefficient and the Kendall correlation coefficient are two popular statistics for assessing the correlation between two variables in a bivariate sample. We indicate how both of these statistics are special cases of a general class of correlation statistics that is parameterized by g 2 (0, 1). The Pearson correlation coefficient is characterized by g ¼ 1

Vernon M. Chinchilli; Brenda R. Phillips; David T. Mauger

2005-01-01

61

Correlation  

NSDL National Science Digital Library

Three hypothetical rock sections along an East-West transect are provided. Students correlate the three sections using the biostratigraphy of planktic forams (as a proxy for age), benthic forams (as a proxy of depth), and lithology (as a proxy of environment). Students are asked to provide an interpretation of the history of this depositional basin. An ash bed of known age is added and students are asked to determine if this new information affects their interpretation. Finally, an interesting lithologic feature is added, and students are asked to provide a geological explanation.

Higgins, Pennilyn

62

Detection and characterization of mitochondrial DNA rearrangements in Pearson and Kearns-Sayre syndromes by long PCR  

Microsoft Academic Search

We used a strategy based on long PCR (polymerase chain reaction) for detection and characterization of mitochondrial DNA (mtDNA)\\u000a rearrangements in two patients with clinical signs suggesting Pearson syndrome and Kearns-Sayre syndrome (KSS), respectively,\\u000a and one patient with myopathic symptoms of unidentified origin. Mitochondrial DNA rearrangements were detected by amplification\\u000a of the complete mitochondrial genome (16.6 kb) using long PCR

S. Kleinle; U. Wiesmann; A. Superti-Furga; S. Krähenbühl; E. Boltshauser; J. Reichen; S. Liechti-Gallati

1997-01-01

63

Kearns-Sayre's syndrome developing in a boy who survived Pearson's syndrome caused by mitochondrial DNA deletion  

Microsoft Academic Search

A 7-year-old boy presented with bilateral ptosis and atypical retinitis pigmentosa. Before age two, he had had an Fe-refractory anemia, with neutropenia and thrombopenia. Just prior to the ophthalmic examination, the patient developed lactate acidosis, muscular hypotonia, ataxia and increased protein in the spinal fluid. Pancytopenia, pancreas dysfunction and growth retardation are the main features of Pearson's syndrome, most children

H. J. Simonsz; K. Bärlocher; A. Rötig

1992-01-01

64

Use of "t"-Test and ANOVA in Career-Technical Education Research  

ERIC Educational Resources Information Center

Use of t-tests and analysis of variance (ANOVA) procedures in published research from three scholarly journals in career and technical education (CTE) during a recent 5-year period was examined. Information on post hoc analyses, reporting of effect size, alpha adjustments to account for multiple tests, power, and examination of assumptions…

Rojewski, Jay W.; Lee, In Heok; Gemici, Sinan

2012-01-01

65

T.E.S.T.S. (Taking Every Student to Success): Another Way To Assess.  

ERIC Educational Resources Information Center

This article on the T.E.S.T.S. (Taking Every Student To Success) strategy promotes using a variety of assessment strategies in order to alleviate the stress students experience during exams, enabling those who are not "good test takers" to achieve a higher degree of success. If the primary purpose of giving a test is to determine whether or not a…

McDaniel, Lindy C.

66

Comparing Groups in a Before-After Design: When t Test and ANCOVA Produce Different Results  

ERIC Educational Resources Information Center

|Background: Researchers often test people before and after some treatment and compare these scores with a control group. Sometimes it is not possible to allocate people into conditions randomly, which means the initial scores for the two groups may differ. There are two main approaches: t test on the gain scores and ANCOVA partialling out the…

Wright, Daniel B.

2006-01-01

67

Two-Sample t-Test for Equal Means (Engineering Statistics Handbook)  

NSDL National Science Digital Library

Gives textbook-like explanation with some real-life data to compute a t-test and determine if two population means are equal. Also has some links for case studies and a web-based program called Dataplot. There is a printer-friendly version on the main homepage (see source). Overall, this is a great resource for anyone interested in either engineering or mathematics.

Filliben, James; Heckert, Alan

2008-12-31

68

The predictive value of the bedside troponin T test for patients with acute chest pain  

PubMed Central

BACKGROUND The evaluation of patients with acute chest pain is time consuming and complicated. In the present study, the role of the bedside troponin T (TnT) test was prospectively investigated for predicting the risk of death and acute heart failure (AHF) in patients with acute chest pain. METHODS Five hundred two consecutive patients admitted in the 24 h after the onset of chest pain were enrolled in the study. Tests of bedside TnT, qualitative troponin I, myoglobin, creatine kinase and creatine kinase (muscle-brain), and electrocardiography were performed on these patients. RESULTS For the bedside TnT test, 160 (31.9%) patients had positive results and 323 (64.3%) patients had negative results. During 30 days of follow-up, the differences between TnT-positive and TnT-negative patients were as follows: 139 (86.9%) positive patients and seven (2.2%) negative patients were diagnosed with acute myocardial infarction (AMI) (OR=298.8 for AMI in positive versus negative patients); 51 (31.9%) positive patients and 37 (11.5%) negative patients had AHF (OR=3.6 for AHF in positive versus negative patients); 39 (24.4%) positive patients and 15 (4.6%) negative patients died (OR=6.7 for all-cause death in positive versus negative patients); 31 (19.4%) positive patients and five (1.5%) negative patients died due to a cardiac event (OR=15.8 for cardiac death in positive versus negative patients). The sensitivity and specificity of the bedside TnT test for diagnosing AMI were 95.2% and 93.8%, respectively. CONCLUSIONS The bedside TnT test is a powerful, independent and valuable tool for risk stratification in patients with acute chest pain.

Guo, Xiaobi; Feng, Jianzhang; Guo, Hengshan

2006-01-01

69

Degree of pelvic sexual dimorphism in human populations. A greene t-test application  

Microsoft Academic Search

The knowledge of sexual dimorphisms is important in many aspects of paleodemography and paleobiology. One major problem lies\\u000a in a correct sexual diagnosis. However, due to the different methodologies employed to estimate the degree of sexual dimorphism,\\u000a the comparison of the results remains difficult. The Greene t-test (1989) is accurate for a comparative analysis of raw data.\\u000a On the basis

J. Bruzek

1996-01-01

70

Correlation between endodontic broken instrument and nickel level in urine.  

PubMed

This study aims to evaluate the correlation between the presences of separated endodontic instrument inside the dental canal and the nickel (Ni) level in the urine samples of subjected patients. Same-gendered and near-aged participants were selected and were instructed to collect their urine in sterile nickel-free plastic containers. The procedures were carried out in the office, and samples were stored in low-temperature cooler for 1 day and then they were transferred to the laboratory for electrothermal atomic absorption spectrometry. The level of Ni was measured and the correlation coefficient was calculated. Data were analyzed using t tests, Pearson's correlation coefficients, and linear regression analysis, at a level of significance P < 0.05. The statistical analysis has showed significant difference in Ni level between endodontic and control groups (P < 0.05). There was no correlation between Ni level in urine and the age or time period of broken instrument inside the canal; however, Ni level of urine and the age of participants in experimental group has demonstrated a positive correlation. The amount of Ni element can be increased in the urine of patients who have experienced broken endodontic instrument inside the dental canal. However, there is no positive correlation between the remaining pieces of instruments inside the canal and the elevation of nickel amount in urine during the tested time period. This issue suggested that the aging of remaining broken instrument inside the canal does not show any remarkable concern regarding the Ni elevation in the urine excreted by an individual. PMID:23861099

Saghiri, Mohammad Ali; Sheibani, Nader; Garcia-Godoy, Franklin; Asatourian, Armen; Mehriar, Peiman; Scarbecz, Mark

2013-07-17

71

A closer look at the effect of preliminary goodness-of-fit testing for normality for the one-sample t-test.  

PubMed

Student's one-sample t-test is a commonly used method when inference about the population mean is made. As advocated in textbooks and articles, the assumption of normality is often checked by a preliminary goodness-of-fit (GOF) test. In a paper recently published by Schucany and Ng it was shown that, for the uniform distribution, screening of samples by a pretest for normality leads to a more conservative conditional Type I error rate than application of the one-sample t-test without preliminary GOF test. In contrast, for the exponential distribution, the conditional level is even more elevated than the Type I error rate of the t-test without pretest. We examine the reasons behind these characteristics. In a simulation study, samples drawn from the exponential, lognormal, uniform, Student's t-distribution with 2 degrees of freedom (t(2) ) and the standard normal distribution that had passed normality screening, as well as the ingredients of the test statistics calculated from these samples, are investigated. For non-normal distributions, we found that preliminary testing for normality may change the distribution of means and standard deviations of the selected samples as well as the correlation between them (if the underlying distribution is non-symmetric), thus leading to altered distributions of the resulting test statistics. It is shown that for skewed distributions the excess in Type I error rate may be even more pronounced when testing one-sided hypotheses. PMID:21973094

Rochon, Justine; Kieser, Meinhard

2010-12-06

72

Robust radar detection of CA, GO and SO CFAR in Pearson measurements based on a non linear compression procedure for clutter reduction  

Microsoft Academic Search

This paper deals with the constant false alarm rate (CFAR) radar detection of targets embedded in Pearson distributed clutter.\\u000a We develop new CFAR detection algorithms-notably cell averaging (CA), greatest of selection (GO) and smallest of selection\\u000a SO-CFAR operating in Pearson measurements based on a non-linear compression method for spiky clutter reduction. The technique\\u000a is similar to that used in non

Z. Messali; Faouzi Soltani; Mohamed Sahmoudi

2008-01-01

73

Detecting background changes in environments with dynamic foreground by separating probability distribution function mixtures using Pearson's method of moments  

NASA Astrophysics Data System (ADS)

This paper presents parameter estimation techniques useful for detecting background changes in a video sequence with extreme foreground activity. A specific application of interest is automated detection of the covert placement of threats (e.g., a briefcase bomb) inside crowded public facilities. We propose that a histogram of pixel intensity acquired from a fixed mounted camera over time for a series of images will be a mixture of two Gaussian functions: the foreground probability distribution function and background probability distribution function. We will use Pearson's Method of Moments to separate the two probability distribution functions. The background function can then be "remembered" and changes in the background can be detected. Subsequent comparisons of background estimates are used to detect changes. Changes are flagged to alert security forces to the presence and location of potential threats. Results are presented that indicate the significant potential for robust parameter estimation techniques as applied to video surveillance.

Jenkins, Colleen; Jordan, Jay; Carlson, Jeff

2007-02-01

74

Radar detection with the Neyman-Pearson criterion using supervised-learning-machines trained with the cross-entropy error  

NASA Astrophysics Data System (ADS)

The application of supervised learning machines trained to minimize the Cross-Entropy error to radar detection is explored in this article. The detector is implemented with a learning machine that implements a discriminant function, which output is compared to a threshold selected to fix a desired probability of false alarm. The study is based on the calculation of the function the learning machine approximates to during training, and the application of a sufficient condition for a discriminant function to be used to approximate the optimum Neyman-Pearson (NP) detector. In this article, the function a supervised learning machine approximates to after being trained to minimize the Cross-Entropy error is obtained. This discriminant function can be used to implement the NP detector, which maximizes the probability of detection, maintaining the probability of false alarm below or equal to a predefined value. Some experiments about signal detection using neural networks are also presented to test the validity of the study.

Jarabo-Amores, María-Pilar; la Mata-Moya, David de; Gil-Pita, Roberto; Rosa-Zurera, Manuel

2013-12-01

75

A Relationship Between the 2-body Energy of Kaxiras Pandey and Pearson Takai Halicioglu Tiller Potential Functions  

NASA Astrophysics Data System (ADS)

A parametric relationship between the Pearson Takai Halicioglu Tiller (PTHT) and the Kaxiras Pandey (KP) empirical potential energy functions is developed for the case of 2-body interaction. The need for such relationship arises when preferred parametric data and adopted software correspond to different potential functions. The analytical relationship was obtained by equating the potential functions' derivatives at zeroth, first and second order with respect to the interatomic distance at the equilibrium bond length, followed by comparison of coefficients in the repulsive and attractive terms. Plots of non-dimensional 2-body energy versus the nondimensional interatomic distance verified the analytical relationships developed herein. The discrepancy revealed in theoretical plots suggests that the 2-body PTHT and KP potentials are more suitable for curve-fitting "softer" and "harder" bonds respectively.

Lim, Teik-Cheng

2004-01-01

76

Discrete Pearson distributions  

SciTech Connect

These distributions are generated by a first order recursive scheme which equates the ratio of successive probabilities to the ratio of two corresponding quadratics. The use of a linearized form of this model will produce equations in the unknowns matched by an appropriate set of moments (assumed to exist). Given the moments we may find valid solutions. These are two cases; (1) distributions defined on the non-negative integers (finite or infinite) and (2) distributions defined on negative integers as well. For (1), given the first four moments, it is possible to set this up as equations of finite or infinite degree in the probability of a zero occurrence, the sth component being a product of s ratios of linear forms in this probability in general. For (2) the equation for the zero probability is purely linear but may involve slowly converging series; here a particular case is the discrete normal. Regions of validity are being studied. 11 refs.

Bowman, K.O. [Oak Ridge National Lab., TN (United States); Shenton, L.R. [Georgia Univ., Athens, GA (United States); Kastenbaum, M.A. [Kastenbaum (M.A.), Basye, VA (United States)

1991-11-01

77

The Utility and General Definition of Correlation Coefficients  

Microsoft Academic Search

Previous attempts at defining other correlation measures mostly tried to generalize the inner product definition used in Pearson's correlation coefficient. This does not allow for certain useful correlation's, like the Greatest Deviation, or Gini's. In this work the idea in Gideon and Hollister (1987) of seeing correlation, as the difference between distance from perfect negative and perfect positive correlation will

Rudy A. Gideon

78

Correlation control in small sample Monte Carlo type simulations II: Analysis of estimation formulas, random correlation and perfect uncorrelatedness  

Microsoft Academic Search

This paper presents a number of theoretical and numerical results regarding correlation coefficients and two norms of correlation matrices in relation to correlation control in Monte Carlo type sampling and the designs of experiments. The paper studies estimation formulas for Pearson linear, Spearman and Kendall rank-order correlation coefficients and formulates the lower bounds on the performance of correlation control techniques

M. Vo?echovský

79

"Unplanned drinking and alcohol-related problems: A preliminary test of the model of unplanned drinking behavior": Correction to Pearson and Henson (2012).  

PubMed

Reports an error in "Unplanned Drinking and Alcohol-Related Problems: A Preliminary Test of the Model of Unplanned Drinking Behavior" by Matthew R. Pearson and James M. Henson (Psychology of Addictive Behaviors, Advanced Online Publication, Dec 31, 2012, np). There was an error in Table 4. The correlation between the Alternative to Drinking and Gender was given as -.22, but should have been .22. (The following abstract of the original article appeared in record 2012-34891-001.) Much research links impulsivity with alcohol use and problems. In 2 studies, unplanned (or impulsive) drinking is assessed directly to determine whether it has direct effects on alcohol use and alcohol-related problems. In Study 1, we examined whether unplanned drinking serves as a proximal mediator of the effects of impulsivity-like traits on alcohol-related outcomes. With a sample of 211 college student drinkers, we found that the Unplanned Drinking Scale was significantly related to alcohol use, and perhaps more important, had a direct effect on alcohol-related problems even after controlling for frequency and quantity of alcohol use. Furthermore, unplanned drinking partially mediated the effects of negative urgency on alcohol-related problems. In Study 2, we examined whether unplanned drinking accounts for unique variance in alcohol-related outcomes when controlling for use of protective behavioral strategies. With a sample of 170 college students, we replicated the findings of Study 1 in that the Unplanned Drinking Scale had a significant direct effect on alcohol-related problems even after controlling for alcohol use; this effect was maintained when controlling for use of protective behavioral strategies. Limitations include the modest sample sizes and the cross-sectional design. Future directions for testing the Model of Unplanned Drinking Behavior are proposed. (PsycINFO Database Record (c) 2013 APA, all rights reserved). PMID:24059829

Pearson, Matthew R; Henson, James M

2013-09-01

80

Support vector machine with a Pearson VII function kernel for discriminating halophilic and non-halophilic proteins.  

PubMed

Understanding of proteins adaptive to hypersaline environment and identifying them is a challenging task and would help to design stable proteins. Here, we have systematically analyzed the normalized amino acid compositions of 2121 halophilic and 2400 non-halophilic proteins. The results showed that halophilic protein contained more Asp at the expense of Lys, Ile, Cys and Met, fewer small and hydrophobic residues, and showed a large excess of acidic over basic amino acids. Then, we introduce a support vector machine method to discriminate the halophilic and non-halophilic proteins, by using a novel Pearson VII universal function based kernel. In the three validation check methods, it achieved an overall accuracy of 97.7%, 91.7% and 86.9% and outperformed other machine learning algorithms. We also address the influence of protein size on prediction accuracy and found the worse performance for small size proteins might be some significant residues (Cys and Lys) were missing in the proteins. PMID:23764527

Zhang, Guangya; Ge, Huihua

2013-05-17

81

Correlation Between Intrasac Pressure Measurements of a Pressure Sensor and an Angiographic Catheter During Endovascular Repair of Abdominal Aortic Aneurysm  

PubMed Central

PURPOSE To establish a correlation between intrasac pressure measurements of a pressure sensor and an angiographic catheter placed in the same aneurysm sac before and after its exclusion by an endoprosthesis. METHODS Patients who underwent endovascular abdominal aortic aneurysm repair and received an EndoSureTM wireless pressure sensor implant between March 19 and December 11, 2004 were enrolled in the study. Simultaneous readings of systolic, diastolic, mean, and pulse pressure within the aneurysm sac were obtained from the catheter and the sensor, both before and after sac exclusion by the endoprosthesis (Readings 1 and 2, respectively). Intrasac pressure measurements were compared using Pearson’s correlation and Student’s t test. Statistical significance was set at p<0.05. RESULTS Twenty-five patients had the pressure sensor implanted, with simultaneous readings (i.e., recorded by both devices) obtained in 19 patients for Reading 1 and in 10 patients for Reading 2. There was a statistically significant correlation for all pressure variables during both readings, with p<0.01 for all except the pulse pressure in Reading 1 (p<0.05). Statistical significance of pressure variations before and after abdominal aortic aneurysm exclusion was coincident between the sensor and catheter for diastolic (p>0.05), mean (p>0.05), and pulse (p<0.01) pressures; the sole disagreement was observed for systolic pressure, which varied, on average, 31.23 mmHg by the catheter (p<0.05) and 22 mmHg (p>0.05) by the sensor. CONCLUSION The excellent agreement between intrasac pressure readings recorded by the catheter and the sensor justifies use of the latter for detection of post-exclusion abdominal aortic aneurysm pressurization.

Silveira, Pierre Galvagni; Miller, Christopher William Teixeira; Mendes, Rafael Freygang; Galego, Gilberto Nascimento

2008-01-01

82

Comparisons of two moments-based estimators that utilize historical and paleoflood data for the log Pearson type III distribution  

NASA Astrophysics Data System (ADS)

The expected moments algorithm (EMA) [, 1997] and the Bulletin 17B [, 1982] historical weighting procedure (B17H) for the log Pearson type III distribution are compared by Monte Carlo computer simulation for cases in which historical and/or paleoflood data are available. The relative performance of the estimators was explored for three cases: fixed-threshold exceedances, a fixed number of large floods, and floods generated from a different parent distribution. EMA can effectively incorporate four types of historical and paleoflood data: floods where the discharge is explicitly known, unknown discharges below a single threshold, floods with unknown discharge that exceed some level, and floods with discharges described in a range. The B17H estimator can utilize only the first two types of historical information. Including historical/paleoflood data in the simulation experiments significantly improved the quantile estimates in terms of mean square error and bias relative to using gage data alone. EMA performed significantly better than B17H in nearly all cases considered. B17H performed as well as EMA for estimating X100 in some limited fixed-threshold exceedance cases. EMA performed comparatively much better in other fixed-threshold situations, for the single large flood case, and in cases when estimating extreme floods equal to or greater than X500. B17H did not fully utilize historical information when the historical period exceeded 200 years. Robustness studies using GEV-simulated data confirmed that EMA performed better than B17H. Overall, EMA is preferred to B17H when historical and paleoflood data are available for flood frequency analysis.

England, John F.; Salas, José D.; Jarrett, Robert D.

2003-09-01

83

Comparisons of two moments-based estimators that utilize historical and paleoflood data for the log Pearson type III distribution  

USGS Publications Warehouse

The expected moments algorithm (EMA) [Cohn et al., 1997] and the Bulletin 17B [Interagency Committee on Water Data, 1982] historical weighting procedure (B17H) for the log Pearson type III distribution are compared by Monte Carlo computer simulation for cases in which historical and/or paleoflood data are available. The relative performance of the estimators was explored for three cases: fixed-threshold exceedances, a fixed number of large floods, and floods generated from a different parent distribution. EMA can effectively incorporate four types of historical and paleoflood data: floods where the discharge is explicitly known, unknown discharges below a single threshold, floods with unknown discharge that exceed some level, and floods with discharges described in a range. The B17H estimator can utilize only the first two types of historical information. Including historical/paleoflood data in the simulation experiments significantly improved the quantile estimates in terms of mean square error and bias relative to using gage data alone. EMA performed significantly better than B17H in nearly all cases considered. B17H performed as well as EMA for estimating X100 in some limited fixed-threshold exceedance cases. EMA performed comparatively much better in other fixed-threshold situations, for the single large flood case, and in cases when estimating extreme floods equal to or greater than X500. B17H did not fully utilize historical information when the historical period exceeded 200 years. Robustness studies using GEV-simulated data confirmed that EMA performed better than B17H. Overall, EMA is preferred to B17H when historical and paleoflood data are available for flood frequency analysis.

England, Jr. , J. F.; Salas, J. D.; Jarrett, R. D.

2003-01-01

84

Concerning Kendall's tau, a nonparametric correlation coefficient  

Microsoft Academic Search

There are a number of circumstances in which the use of the Pearson product-moment correlation is inappropriate and a rank order procedure (Tau) is required. The advantages of Tau over Spearman's rho technique are discussed. Definitional and computational formulae of Tau, tests of significance, the confidence limits of Tau, and the relationship between Tau and the product-moment correlation, are presented.

Maurice S. Schaeffer; Eugene E. Levitt

1956-01-01

85

Calculating inverse cv, skew and pwm functions for pearson3, log-normal, extreme-value and log-logistic distributions  

Microsoft Academic Search

Equations are presented to calculate inverse CV, skew and PWM functions for the Pearson-3, log-normal, extreme-value and log-logistic distributions. Such inverse functions are used for moment and PWM estimates. Close numerical approximations are derived for the inverse functions that do not exist explicitly. This is intended to overcome the intractable nature of moment and PWM estimates.

R. W. Donaldson

1996-01-01

86

Wanted: guidelines for reporting correlations  

NSDL National Science Digital Library

Recently (1ÃÂ3), there have been guidelines published for authors regarding what and how statistics should be reported when describing the differences between groups of observations. There seems to be a paucity of such guidance with respect to describing the correlation between groups of observations. Of particular concern to me is the way in which Pearson product-moment correlations are reported in many journals.

Bartholomew Kay (University of Auckland Sport and Exercise Science)

2009-06-01

87

Prognostic value of stromal and epithelial periostin expression in human prostate cancer: correlation with clinical pathological features and the risk of biochemical relapse or death  

PubMed Central

Background The purpose of the present study was to evaluate the prognostic value of POSTN expression following prostatectomy. Methods Periostin (POSTN) expression in prostate cancer (PCa) and in normal specimens was evaluated in 90 patients by an immuno-reactive score(IRS) based on the intensity of immunostaining and on the quantity of stained cells. The t-test was applied to compare IRS values in cancer specimens to values in normal specimens. Pearson’s test was used to correlate POSTN expression to clinical pathologic features. PSA progression-free and survival curves were constructed by the Kaplan–Meier method and compared using the log-rank test. Multi-parametric models were constructed according to the Cox technique adding all the covariates predicting for either PSA progression or death into the models after univariate analysis. Results Both stromal and epithelial POSTN expression were significantly increased in tumor tissues. In particular, we found stromal expression to be significantly higher than epithelial expression as compared to normal tissues (p<0.000 and p=0.001).A significant correlation between POSTN epithelial expression and extra-prostatic extension was found (p=0.03). While high stromal expression was significantly associated with shorter survival (p=0.008), a low epithelial score significantly correlated with shorter PSA-free survival (p=0.04), suggesting that POSTN plays an apparently opposing biological role depending on its compartmentalization.Regardless of the mechanism that is involved, patients showing both high stromal and low epithelial expression made up a subgroup with a very bleak prognosis. Conclusions Although requiring further validation through larger studies, our findings show that POSTN might represent a novel prognostic marker for PCa.

2012-01-01

88

Robustness of Inference for One-sample Problem with Correlated Observations  

Microsoft Academic Search

The inference about the population mean based on the standard t-test involves the assumption of normal population as well as independence of the observations. In this paper we examine the robustness of the inference in the presence of correlations among the observations. We consider the simplest correlation structure AR(1) and its impact on the t-test. A modification of the t-test

Perla Subbaiah; George Xia

2007-01-01

89

Assessment of correlation between knee notch width index and the three-dimensional notch volume.  

PubMed

This study was done to determine whether there is a correlation between the notch volume and the notch width index (NWI) as measured on the three most frequently used radiographic views: the Holmblad 45 degrees, Holmblad 70 degrees, and Rosenberg view. The notch volume of 20 cadaveric knees was measured using Computed Tomography (CT). The Holmblad 45 degrees, Holmblad 70 degrees, and Rosenberg notch view radiographs were digitally re-created from the CT scans for each specimen, and the NWI was measured by two observers. The Pearson correlation coefficient between the NWI and notch volume was calculated, as well as between the three views. An independent t test was performed to determine the difference in NWI and notch volume between male and female specimens. The reliability for each view was also determined. There was no correlation between the NWI as measured on the Holmblad 45 degrees, Holmblad 70 degrees, or Rosenberg view and the notch volume. All three radiographic views proved reliable, but showed only a moderate correlation with each other. Men had larger notch volumes than women, but there was no difference in NWI. A knee with a small intercondylar notch is often considered an increased risk for ACL rupture. The NWI is a frequently used two-dimensional method to determine notch size. However, in the present study, this index was not positively correlated with the overall volume of the notch. Based on the results of the current study, the authors would advice to use caution when using notch view radiographs in a clinical setting to predict risk of ACL rupture. PMID:20376620

van Eck, Carola F; Martins, Cesar A Q; Lorenz, Stephan G F; Fu, Freddie H; Smolinski, P

2010-04-08

90

Forward search added-variable t-tests and the effect of masked outliers on model selection  

Microsoft Academic Search

Monitoring the t-tests for individual regression coefficients in 'forward' search fails to identify the importance of observations to the significance of the individual regressors. This failure is due to the ordering of the data by the search. We introduce an added-variable test which has the desired properties since the projection leading to residuals destroys the effect of the ordering. An

Anthony C. Atkinson

2002-01-01

91

Evaluation of climate change on flood event by using parametric T-test and non-parametric Mann-Kendall test in Barcelonnette basin, France  

NASA Astrophysics Data System (ADS)

The existence of a trend in hydrological and meteorological time series is detected by statistical tests. The trend analysis of hydrological and meteorological series is important to consider, because of the effects of global climate change. Parametric or non-parametric statistical tests can be used to decide whether there is a statistically significant trend. In this paper, first a homogeneity analysis was performed by using the non-parametric Bartlett test. Then, trend detection was estimated by using non-parametric Mann-Kendall test. The null hypothesis in the Mann-Kendall test is that the data are independent and randomly ordered. The result of Mann-Kendall test was compared with the parametric T-Test for finding the existence of trend. To reach this purpose, the significance of trends was analyzed on monthly data of Ubaye river in Barcelonnette watershed in southeast of France at an elevation of 1132 m (3717 ft) during the period from 1928 to 2009 bases with the nonparametric Mann-Kendall test and parametric T-Test for river discharge and for meteorological data. The result shows that a rainfall event does not necessarily have an immediate impact on discharge. Visual inspection suggests that the correlation between observations made at the same time point is not very strong. In the results of the trend tests the p-value of the discharge is slightly smaller than the p-value of the precipitation but it seems that in both there is no statistically significant trend. In statistical hypothesis testing, a test statistic is a numerical summary of a set of data that reduces the data to one or a small number of values that can be used to perform a hypothesis test. Statistical hypothesis testing is determined if there is a significant trend or not. Negative test statistics and MK test in both precipitation and discharge data indicate downward trends. As conclusion we can say extreme flood event during recent years is strongly depending on: 1) location of the city: It is situated in an elongated form extending below mountain slopes and along a river channel. 2) Seasonal Changes: During spring, the melting of snow result in an increase water level in river channels and this will be amplified whenever a warm rainfall occurs. Then it could be conclude that climate change did not has a significant effect on flood in case study area Keywords: Trend, parametric and non parametric test, T-Test, Mann-Kendall test

Ramesh, Azadeh; Glade, Thomas; Malet, Jean-Philippe

2010-09-01

92

How to quantify support for and against the null hypothesis: A flexible WinBUGS implementation of a default Bayesian t test  

Microsoft Academic Search

We propose a sampling-based Bayesian t test that allows researchers to quantify the statistical evidence in favor of the null\\u000a hypothesis. This Savage—Dickey (SD) t test is inspired by the Jeffreys—Zellner—Siow (JZS) t test recently proposed by Rouder,\\u000a Speckman, Sun, Morey, and Iverson (2009). The SD test retains the key concepts of the JZS test but is applicable to a

Ruud Wetzels; Jeroen G. W. Raaijmakers; Emöke Jakab; Eric-Jan Wagenmakers

2009-01-01

93

Wilcoxon-Mann-Whitney or t-test? On assumptions for hypothesis tests and multiple interpretations of decision rules*  

PubMed Central

In a mathematical approach to hypothesis tests, we start with a clearly defined set of hypotheses and choose the test with the best properties for those hypotheses. In practice, we often start with less precise hypotheses. For example, often a researcher wants to know which of two groups generally has the larger responses, and either a t-test or a Wilcoxon-Mann-Whitney (WMW) test could be acceptable. Although both t-tests and WMW tests are usually associated with quite different hypotheses, the decision rule and p-value from either test could be associated with many different sets of assumptions, which we call perspectives. It is useful to have many of the different perspectives to which a decision rule may be applied collected in one place, since each perspective allows a different interpretation of the associated p-value. Here we collect many such perspectives for the two-sample t-test, the WMW test and other related tests. We discuss validity and consistency under each perspective and discuss recommendations between the tests in light of these many different perspectives. Finally, we briefly discuss a decision rule for testing genetic neutrality where knowledge of the many perspectives is vital to the proper interpretation of the decision rule.

Fay, Michael P.; Proschan, Michael A.

2010-01-01

94

Multi-scale correlations between topography and vegetation in a hillside catchment of Honduras  

Microsoft Academic Search

All systems have causes and effects that can be appreciated at different spatial scales. Understanding and representing the complexity of multi?scale patterns in maps and spatial models are key research objectives. We describe the use of three types of correlation analyses: (1) a standard Pearson correlation coefficient, (2) a ‘global’ multi?scale correlation, and (3) local geographically weighted correlation. These methods

A. Nelson; T. Oberthür; S. Cook

2007-01-01

95

Francis Galton's Account of the Invention of Correlation  

Microsoft Academic Search

Francis Galton's invention of correlation dates from late in the year 1888, and it arose when he recognized a common thread in three different scientific problems he was studying. Galton's own 1890 account of the moment of discovery is discussed and contrasted with Karl Pearson's widely known association of correlation with a retreat into a recess at Naworth Castle. The

Stephen M. Stigler

1989-01-01

96

Oximetry in glaucoma: correlation of metabolic change with structural and functional damage.  

PubMed

Purpose:? To determine whether retinal vessel oxygen saturation in patients with glaucoma is associated with structural optic disc and retinal nerve fibre layer (RNFL) changes and visual field (VF) defects. Methods:? Fifty-nine patients with confirmed glaucoma were recruited at University Hospitals Leuven. Retinal oxygen saturation in patients with glaucoma was measured with a noninvasive spectrophotometric retinal oximeter (Oxymap ehf, Reykjavik, Iceland). VF and Heidelberg retinal tomographies (HRTs) were performed on the same day. Statistical analysis was performed using Student's t-test and Pearson's or Spearman correlation coefficient. Results:? The mean oxygen saturation in venules was higher in patients with severe VF defects compared to those patients with mild VF defects (69?±?3% versus 65?±?6% respectively; p?=?0.0003; n?=?59). Accordingly, the arteriovenous (AV) difference in oxygen saturation was lower in patients with worse VF compared to those with better VF (29?±?3% versus 33?±?6% respectively; p?=?0.002). The oxygen saturation in venules correlated with the VF mean defects (r?=?-0.42; p?=?0.001; n?=?59) as well as with the structural HRT parameters rim area and RNFL thickness (r?=?-0.39; p?=?0.008 and r?=?-0.26; p?=?0.05 respectively; n?=?53). The AV difference decreased significantly as the VF defect worsened (r?=?0.38; p?=?0.003), as the rim area diminished (r?=?0.29; p?=?0.03) and as the RNFL thickness decreased (r?=?0.27; p?=?0.05). No correlation was found between the oxygen saturation in retinal arterioles and either of these parameters. Conclusion:? Severe glaucomatous damage is associated with increased oxygen saturation in retinal venules and decreased AV difference in oxygen saturation. These data suggest that in eyes with severe glaucomatous damage, reduced retinal oxygen consumption is consistent with tissue loss. PMID:23323611

Vandewalle, Evelien; Abegão Pinto, L; Olafsdottir, Olof B; De Clerck, Eline; Stalmans, Peter; Van Calster, Joachim; Zeyen, Thierry; Stefánsson, Einar; Stalmans, Ingeborg

2013-01-17

97

An Inequality between the Weighted Average and the Rowwise Correlation Coefficient for Proximity Matrices.  

ERIC Educational Resources Information Center

|To assess association between rows of proximity matrices, H. de Vries (1993) introduces weighted average and row-wise average variants for Pearson's product-moment correlation, Spearman's rank correlation, and Kendall's rank correlation. For all three, the absolute value of the first variant is greater than or equal to the second. (SLD)|

Krijnen, Wim P.

1994-01-01

98

Perceived stress in HIV-infected individuals: Physiological and psychological correlates  

Microsoft Academic Search

The purpose of this study was to determine the correlation of perceived stress with selected physiological and psychological factors in an HIV-infected, predominantly African American population and to assess the multivariable effects on perceived stress. The variables that correlated significantly with perceived stress were entered into a backward stepwise regression model. Pearson's r analysis showed significant correlations between perceived stress

G. A. Hand; K. D. Phillips; W. D. Dudgeion

2006-01-01

99

DeFries-Fulker and Pearson-Aitken model-fitting analyses of reading performance data from selected and unselected twin pairs.  

PubMed

Although a comparison of concordance rates for deviant scores in identical and fraternal twin pairs can provide prima facie evidence for a genetic etiology, information is not fully utilized when continuous measures are analyzed in a dichotomous manner. Thus, DeFries and Fulker (Behav Genet 15:467-473, 1985; Acta Genet Med Gemellol, 37:205-216, 1988) developed a regression-based methodology (DF analysis) to assess genetic etiology in both selected and unselected twin samples. While the DF analysis is a very versatile and relatively powerful statistical approach, it is not easily extended to the multivariate case. In contrast, structural equation models may be readily extended to analyze multivariate data sets (Neale and Cardon, Methodology for genetic studies of twins and families, 1992). However, such methodologies may yield biased estimates of additive genetic, shared environmental, and non-shared environmental influences when multivariate models are fitted to selected twin data. Therefore, the Pearson-Aitken (PA) selection formula (Aitken, Proc Edinburgh Math Soc B, 4:106-110, 1934) was used to analyze reading performance data from twins with reading difficulties (selected sample) and a population of normally-achieving twin pairs (control sample). As a comparison, DF models were also fitted to these same data sets. In general, resulting estimates of additive genetic, shared environmental, and non-shared environmental influences were similar when the DF and PA models were fitted to the data. However, the PA selection formula may be more readily generalized to the multivariate case. PMID:18213514

Hawke, Jesse L; Stallings, Michael C; Wadsworth, Sally J; DeFries, John C

2008-01-23

100

Understanding Correlation: Factors that Affect the Size of r  

ERIC Educational Resources Information Center

The authors describe and illustrate 6 factors that affect the size of a Pearson correlation: (a) the amount of variability in the data, (b) differences in the shapes of the 2 distributions, (c) lack of linearity, (d) the presence of 1 or more "outliers," (e) characteristics of the sample, and (f) measurement error. Also discussed are ways to…

Goodwin, Laura D.; Leech, Nancy L.

2006-01-01

101

Gene interaction networks based on kernel correlation metrics.  

PubMed

In this paper, a Kernel correlation coefficient (KCC) method is proposed to elucidate the gene nonlinear relationships as a distance metric. To evaluate the performance of this nonlinear distance measure, a biological network of the Gaussian Kernel on a public dataset of yeast genes is constructed by using a graph theory. Specifically, the distribution and properties of this new measure are analysed and compared with the classical Pearson correlation method. The reliability and advantages of our proposed Kernel correlation metric is verified and shown formally on ten showcases of the DREAM (Dialogue for Reverse Engineering Assessments and Methods) project. Test experiment results demonstrate that the proposed Kernel correlation coefficient measure has a strong capability in identifying interaction genes, and that the proposed method can detect accurately the key genes and functional interactions (also known as the cliques) as compared to the commonly used Pearson correlation and Mutual Information measures. PMID:23428475

Cheng, Lijun; Khorasani, K; Ding, Yongsheng; Guo, Xihong

2013-02-21

102

Point-of-Care Troponin T Testing in the Management of Patients with Chest Pain in the Swedish Primary Care  

PubMed Central

Objective. To investigate the diagnostic accuracy and clinical benefit of point-of-care Troponin T testing (POCT-TnT) in the management of patients with chest pain. Design. Observational, prospective, cross-sectional study with followup. Setting. Three primary health care (PHC) centres using POCT-TnT and four PHC centres not using POCT-TnT in the southeast of Sweden. Patients. All patients ?35 years old, contacting one of the primary health care centres for chest pain, dyspnoea on exertion, unexplained weakness, and/or fatigue with no other probable cause than cardiac, were included. Symptoms should have commenced or worsened during the last seven days. Main Outcome Measures. Emergency referrals, patients with acute myocardial infarctions (AMI), or unstable angina (UA) within 30 days of study enrolment. Results. 25% of the patients from PHC centres with POCT-TnT and 43% from PHC centres without POCT-TnT were emergently referred by the GP (P = 0.011 ). Seven patients (5.5%) from PHC centres with POCT-TnT and six (8.8%) from PHC centres without POCT-TnT were diagnosed as AMI or UA (P = 0.369). Two patients with AMI or UA from PHC centres with POCT-TnT were judged as missed cases in primary health care. Conclusion. The use of POCT-TnT may reduce emergency referrals but probably at the cost of an increased risk to miss patients with AMI or UA.

Nilsson, Staffan; Andersson, Per O.; Borgquist, Lars; Grodzinsky, Ewa; Janzon, Magnus; Kvick, Magnus; Landberg, Eva; Nilsson, Hakan; Karlsson, Jan-Erik

2013-01-01

103

Correlation of Point B and Lymph Node Dose in 3D-Planned High-Dose-Rate Cervical Cancer Brachytherapy  

SciTech Connect

Purpose: To compare high dose rate (HDR) point B to pelvic lymph node dose using three-dimensional-planned brachytherapy for cervical cancer. Methods and Materials: Patients with FIGO Stage IB-IIIB cervical cancer received 70 tandem HDR applications using CT-based treatment planning. The obturator, external, and internal iliac lymph nodes (LN) were contoured. Per fraction (PF) and combined fraction (CF) right (R), left (L), and bilateral (Bil) nodal doses were analyzed. Point B dose was compared with LN dose-volume histogram (DVH) parameters by paired t test and Pearson correlation coefficients. Results: Mean PF and CF doses to point B were R 1.40 Gy +- 0.14 (CF: 7 Gy), L 1.43 +- 0.15 (CF: 7.15 Gy), and Bil 1.41 +- 0.15 (CF: 7.05 Gy). The correlation coefficients between point B and the D100, D90, D50, D2cc, D1cc, and D0.1cc LN were all less than 0.7. Only the D2cc to the obturator and the D0.1cc to the external iliac nodes were not significantly different from the point B dose. Significant differences between R and L nodal DVHs were seen, likely related to tandem deviation from irregular tumor anatomy. Conclusions: With HDR brachytherapy for cervical cancer, per fraction nodal dose approximates a dose equivalent to teletherapy. Point B is a poor surrogate for dose to specific nodal groups. Three-dimensional defined nodal contours during brachytherapy provide a more accurate reflection of delivered dose and should be part of comprehensive planning of the total dose to the pelvic nodes, particularly when there is evidence of pathologic involvement.

Lee, Larissa J. [Harvard Radiation Oncology Program, Brigham and Women's Hospital, Boston, MA (United States); Sadow, Cheryl A. [Department of Radiology, Brigham and Women's Hospital, Boston, MA (United States); Russell, Anthony [Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA (United States); Viswanathan, Akila N., E-mail: aviswanathan@lroc.harvard.ed [Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA (United States)

2009-11-01

104

Utilization of two sample t-test statistics from redundant probe sets to evaluate different probe set algorithms in GeneChip studies  

PubMed Central

Background The choice of probe set algorithms for expression summary in a GeneChip study has a great impact on subsequent gene expression data analysis. Spiked-in cRNAs with known concentration are often used to assess the relative performance of probe set algorithms. Given the fact that the spiked-in cRNAs do not represent endogenously expressed genes in experiments, it becomes increasingly important to have methods to study whether a particular probe set algorithm is more appropriate for a specific dataset, without using such external reference data. Results We propose the use of the probe set redundancy feature for evaluating the performance of probe set algorithms, and have presented three approaches for analyzing data variance and result bias using two sample t-test statistics from redundant probe sets. These approaches are as follows: 1) analyzing redundant probe set variance based on t-statistic rank order, 2) computing correlation of t-statistics between redundant probe sets, and 3) analyzing the co-occurrence of replicate redundant probe sets representing differentially expressed genes. We applied these approaches to expression summary data generated from three datasets utilizing individual probe set algorithms of MAS5.0, dChip, or RMA. We also utilized combinations of options from the three probe set algorithms. We found that results from the three approaches were similar within each individual expression summary dataset, and were also in good agreement with previously reported findings by others. We also demonstrate the validity of our findings by independent experimental methods. Conclusion All three proposed approaches allowed us to assess the performance of probe set algorithms using the probe set redundancy feature. The analyses of redundant probe set variance based on t-statistic rank order and correlation of t-statistics between redundant probe sets provide useful tools for data variance analysis, and the co-occurrence of replicate redundant probe sets representing differentially expressed genes allows estimation of result bias. The results also suggest that individual probe set algorithms have dataset-specific performance.

Hu, Zihua; Willsky, Gail R

2006-01-01

105

Meta-Analysis of Correlations Revisited: Attempted Replication and Extension of Field's (2001) Simulation Studies  

ERIC Educational Resources Information Center

In 2 Monte Carlo studies of fixed- and random-effects meta-analysis for correlations, A. P. Field (2001) ostensibly evaluated Hedges-Olkin-Vevea Fisher-[zeta] and Schmidt-Hunter Pearson-r estimators and tests in 120 conditions. Some authors have cited those results as evidence not to meta-analyze Fisher-[zeta] correlations, especially with…

Hafdahl, Adam R.; Williams, Michelle A.

2009-01-01

106

Should we abandon the t-test in the analysis of gene expression microarray data: a comparison of variance modeling strategies.  

PubMed

High-throughput post-genomic studies are now routinely and promisingly investigated in biological and biomedical research. The main statistical approach to select genes differentially expressed between two groups is to apply a t-test, which is subject of criticism in the literature. Numerous alternatives have been developed based on different and innovative variance modeling strategies. However, a critical issue is that selecting a different test usually leads to a different gene list. In this context and given the current tendency to apply the t-test, identifying the most efficient approach in practice remains crucial. To provide elements to answer, we conduct a comparison of eight tests representative of variance modeling strategies in gene expression data: Welch's t-test, ANOVA [1], Wilcoxon's test, SAM [2], RVM [3], limma [4], VarMixt [5] and SMVar [6]. Our comparison process relies on four steps (gene list analysis, simulations, spike-in data and re-sampling) to formulate comprehensive and robust conclusions about test performance, in terms of statistical power, false-positive rate, execution time and ease of use. Our results raise concerns about the ability of some methods to control the expected number of false positives at a desirable level. Besides, two tests (limma and VarMixt) show significant improvement compared to the t-test, in particular to deal with small sample sizes. In addition limma presents several practical advantages, so we advocate its application to analyze gene expression data. PMID:20838429

Jeanmougin, Marine; de Reynies, Aurelien; Marisa, Laetitia; Paccard, Caroline; Nuel, Gregory; Guedj, Mickael

2010-09-03

107

Correlates of Frailty Among Homeless Adults  

PubMed Central

Frailty, a relatively unexplored concept among vulnerable populations, may be a significant issue for homeless adults. This cross-sectional study assessed correlates of frailty among middle age and older homeless adults (N = 150, 40–73). A Pearson (r) bivariate correlation revealed a weak relationship between frailty and being female (r = .230, p < .01). Significant moderate negative correlations were found between frailty and resilience (r = ?.395, p < .01), social support (r = ?.377, p < .01), and nutrition (r = ?.652, p < .01). Furthermore, Spearman’s rho (rs) bivariate correlations revealed a moderate positive relationship between frailty and health care utilization (rs = .444, p < .01). A stepwise backward linear regression analysis was conducted and in the final model, age, gender, health care utilization, nutrition, and resilience were significantly related to frailty. Over the next two decades, there is an anticipated increase in the number of homeless adults which will necessitate a greater understanding of the needs of this hard-to-reach population.

Salem, Benissa E.; Nyamathi, Adeline M.; Brecht, Mary-Lynn; Phillips, Linda R.; Mentes, Janet C.; Sarkisian, Catherine; Leake, Barbara

2013-01-01

108

REMOVING AN EXTRANEOUS EFFECT IN MEASURING CORRELATION COEFFICIENT  

Microsoft Academic Search

Pearson correlation coecient is a measure for the linearity degree between two con- tinuous variables (X,Y ). When this measure is spurious from an extraneous variable eect rPR, rGM and rGR are proposed and investigated through simulation technique. And, the results show that rGR , rPR perform very well in simulation I, and rGR still performs very well in simulation

Chong-Yau Fu; Min-Hsun Tsai

109

Influence of Radiopacity of Dental Composites on the Diagnosis of Secondary Caries: The Correlation Between Objective and Subjective Analyses.  

PubMed

SUMMARY This study aimed to objectively evaluate the radiopacity of different dental composites and their subjective influence on diagnosing secondary caries-like lesions and how these results correlate. For objective analysis, three resin specimens (1 mm thick, with a 4-mm internal diameter) were made with four composites: 1) Charisma; 2) Filtek Z250; 3) Prisma AP.H; and 4) Glacier. Three human teeth were selected and then mesio-distally sectioned (1 mm thick) to make the dental specimens. An aluminum (Al) wedge (12 steps, 1 mm thick, 99.8% purity) was used as an internal standard to calculate the radiopacity. For subjective analysis, 20 human teeth were selected and then prepared with a mesio-occluso-distal (MOD) inlay cavity, with half the teeth receiving a round cavity to simulate the carious lesion. The MOD was restored using the composites at four different times. Standardized radiographs were acquired and then digitized (300 dpi and eight-bit TIFF) for both analyses. A histogram objectively measured the pixel intensity values of the images, which were converted into millimeters of Al using linear regressions. Eight observers subjectively evaluated the images using a five-point rating scale to diagnose the caries. The data were statistically analyzed using the Student t-test, the Kappa test, diagnostic testing, and the Pearson correlation coefficient (?=0.05). All materials showed radiopacity values compatible with dental tissues (p>0.05); Glacier was similar to dentin and Prisma AP.H was similar to enamel, while the remaining materials showed a middle radiopacity. Prisma AP.H and Glacier differed (p<0.05) in relation to their accuracy to caries diagnosis, with Glacier having greater accuracy. There was a correlation between objective and subjective analyses with negative linear dependence. An increase in the material's radiopacity could have a subjectively negative influence on the diagnosis of secondary caries; thus, an ideal radiopacity for a dental composite is closer to the dentin image and produces similar attenuation to X-rays than does dentin. PMID:23713807

Cruz, Ad; Esteves, Rg; Poiate, Iavp; Portero, Pp; Almeida, Sm

2013-05-28

110

Asymmetric correlation matrices: an analysis of financial data  

NASA Astrophysics Data System (ADS)

We analyse the spectral properties of correlation matrices between distinct statistical systems. Such matrices are intrinsically non-symmetric, and lend themselves to extend the spectral analyses usually performed on standard Pearson correlation matrices to the realm of complex eigenvalues. We employ some recent random matrix theory results on the average eigenvalue density of this type of matrix to distinguish between noise and non-trivial correlation structures, and we focus on financial data as a case study. Namely, we employ daily prices of stocks belonging to the American and British stock exchanges, and look for the emergence of correlations between two such markets in the eigenvalue spectrum of their non-symmetric correlation matrix. We find several non trivial results when considering time-lagged correlations over short lags, and we corroborate our findings by additionally studying the asymmetric correlation matrix of the principal components of our datasets.

Livan, G.; Rebecchi, L.

2012-06-01

111

A table for the rapid determination of the tetrachoric correlation coefficient  

Microsoft Academic Search

A table is developed and presented to facilitate the computation of the PearsonQ\\u000a3 (cosine method) estimate of the tetrachoric correlation coefficient. Data are presented concerning the accuracy ofQ\\u000a3 as an estimate of the tetrachoric correlation coefficient, and it is compared with the results obtainable from the Chesire, Saffir, and Thurstone tables for the same four-fold frequency tables.

Melvin D. Davidoff; Howard W. Goheen

1953-01-01

112

Calculating a robust correlation coefficient and quantifying its uncertainty  

NASA Astrophysics Data System (ADS)

Relationships between primary and secondary data are frequently quantified using the correlation coefficient; however, traditional means of calculating experimental correlation coefficients are known to be adversely affected by outlier data. A new method for calculating a robust correlation coefficient is proposed based on a weighted average correlation calculated from different combinations or subsets of the original data. The proposed robust correlation coefficient is shown to have a higher breakdown point than either Pearson's or Spearman's correlation coefficients as well as two out of three other robust correlation coefficients. The least median of squares (LMS) correlation coefficient has the highest possible breakdown point; however, it also tends to give unrealistically high or low correlation coefficients. A simulation study demonstrates the differences between the proposed robust correlation coefficient and other robust correlation coefficients. When the sample size is small, the uncertainty in the measured correlation can be very large, especially when the measured correlation is low. The uncertainty in the correlation coefficient is calculated based on the measured correlation and the number of data. This sampling distribution for the correlation coefficient requires a number of independent data; however, earth sciences data are often spatially dependent. Thus, a method for calculating an effective number of independent data using the variogram is proposed. An example is presented that applies the developed techniques to a petroleum geostatistics problem. The methodologies presented in this paper are implemented in FORTRAN code made available as part of this paper.

Niven, Eric B.; Deutsch, Clayton V.

2012-03-01

113

On the insignificance of Herschel's sunspot correlation  

NASA Astrophysics Data System (ADS)

We examine William Herschel's hypothesis that solar-cycle variation of the Sun's irradiance has a modulating effect on the Earth's climate and that this is, specifically, manifested as an anticorrelation between sunspot number and the market price of wheat. Since Herschel first proposed his hypothesis in 1801, it has been regarded with both interest and skepticism. Recently, reports have been published that either support Herschel's hypothesis or rely on its validity. As a test of Herschel's hypothesis, we seek to reject a null hypothesis of a statistically random correlation between historical sunspot numbers, wheat prices in London and the United States, and wheat farm yields in the United States. We employ binary-correlation, Pearson-correlation, and frequency-domain methods. We test our methods using a historical geomagnetic activity index, well known to be causally correlated with sunspot number. As expected, the measured correlation between sunspot number and geomagnetic activity would be an unlikely realization of random data; the correlation is "statistically significant." On the other hand, measured correlations between sunspot number and wheat price and wheat yield data would be very likely realizations of random data; these correlations are "insignificant." Therefore, Herschel's hypothesis must be regarded with skepticism. We compare and contrast our results with those of other researchers. We discuss procedures for evaluating hypotheses that are formulated from historical data.

Love, Jeffrey J.

2013-08-01

114

Mitochondrial Inverted Repeats Strongly Correlate with Lifespan: mtDNA Inversions and Aging  

PubMed Central

Mitochondrial defects are implicated in aging and in a multitude of age-related diseases, such as cancer, heart failure, Parkinson’s disease, and Huntington’s disease. However, it is still unclear how mitochondrial defects arise under normal physiological conditions. Mitochondrial DNA (mtDNA) deletions caused by direct repeats (DRs) are implicated in the formation of mitochondrial defects, however, mitochondrial DRs show relatively weak (Pearson’s r?=??0.22, p<0.002; Spearman’s ??=??0.12, p?=?0.1) correlation with maximum lifespan (MLS). Here we report a stronger correlation (Pearson’s r?=??0.55, p<10–16; Spearman’s ??=??0.52, p<10–14) between mitochondrial inverted repeats (IRs) and lifespan across 202 species of mammals. We show that, in wild type mice under normal conditions, IRs cause inversions, which arise by replication-dependent mechanism. The inversions accumulate with age in the brain and heart. Our data suggest that IR-mediated inversions are more mutagenic than DR-mediated deletions in mtDNA, and impose stronger constraint on lifespan. Our study identifies IR-induced mitochondrial genome instability during mtDNA replication as a potential cause for mitochondrial defects.

Yang, Jiang-Nan; Seluanov, Andrei; Gorbunova, Vera

2013-01-01

115

A global correlation of the step-wise consolidated crust-stripped gravity field quantities with the topography, bathymetry, and the CRUST 2.0 Moho boundary  

Microsoft Academic Search

We investigate globally the correlation of the step-wise consolidated cruststripped gravity field quantities with the topography, bathymetry, and the Moho boundary. Global correlations are quantified in terms of Pearson's correlation coefficient. The elevation and bathymetry data from the ETOPO5 are used to estimate the correlation of the gravity field quantities with the topography and bathymetry. The 2×2 arc-deg discrete data

Robert Tenzer; Hamayun; Peter Vajda

2009-01-01

116

Correlation Study on PhysicoChemical Parameters and Quality Assessment of Kosi River Water, Uttarakhand  

Microsoft Academic Search

Present work deals with the assessment of physico-chemical parameters of water samples of Kosi river at Kosi sampling station during 2004 and 2005 in pre monsoon, monsoon and post monsoon seasons. Statistical studies have been carried out by calculating correlation coefficients between different pairs of parameters and t- test applied for checking significance. The observed values of various physico-chemical parameters

NARENDRA SINGH BHANDARI; KAPIL NAYAL

117

Collective Correlations of Brodmann Areas fMRI Study with RMT-Denoising  

NASA Astrophysics Data System (ADS)

We study collective behavior of Brodmann regions of human cerebral cortex using functional Magnetic Resonance Imaging (fMRI) and Random Matrix Theory (RMT). The raw fMRI data is mapped onto the cortex regions corresponding to the Brodmann areas with the aid of the Talairach coordinates. Principal Component Analysis (PCA) of the Pearson correlation matrix for 41 different Brodmann regions is carried out to determine their collective activity in the idle state and in the active state stimulated by tapping. The collective brain activity is identified through the statistical analysis of the eigenvectors to the largest eigenvalues of the Pearson correlation matrix. The leading eigenvectors have a large participation ratio. This indicates that several Broadmann regions collectively give rise to the brain activity associated with these eigenvectors. We apply random matrix theory to interpret the underlying multivariate data.

Burda, Z.; Kornelsen, J.; Nowak, M. A.; Porebski, B.; Sboto-Frankenstein, U.; Tomanek, B.; Tyburczyk, J.

118

Effects of Different Correlation Metrics and Preprocessing Factors on Small-World Brain Functional Networks: A Resting-State Functional MRI Study  

PubMed Central

Graph theoretical analysis of brain networks based on resting-state functional MRI (R-fMRI) has attracted a great deal of attention in recent years. These analyses often involve the selection of correlation metrics and specific preprocessing steps. However, the influence of these factors on the topological properties of functional brain networks has not been systematically examined. Here, we investigated the influences of correlation metric choice (Pearson's correlation versus partial correlation), global signal presence (regressed or not) and frequency band selection [slow-5 (0.01–0.027 Hz) versus slow-4 (0.027–0.073 Hz)] on the topological properties of both binary and weighted brain networks derived from them, and we employed test-retest (TRT) analyses for further guidance on how to choose the “best” network modeling strategy from the reliability perspective. Our results show significant differences in global network metrics associated with both correlation metrics and global signals. Analysis of nodal degree revealed differing hub distributions for brain networks derived from Pearson's correlation versus partial correlation. TRT analysis revealed that the reliability of both global and local topological properties are modulated by correlation metrics and the global signal, with the highest reliability observed for Pearson's-correlation-based brain networks without global signal removal (WOGR-PEAR). The nodal reliability exhibited a spatially heterogeneous distribution wherein regions in association and limbic/paralimbic cortices showed moderate TRT reliability in Pearson's-correlation-based brain networks. Moreover, we found that there were significant frequency-related differences in topological properties of WOGR-PEAR networks, and brain networks derived in the 0.027–0.073 Hz band exhibited greater reliability than those in the 0.01–0.027 Hz band. Taken together, our results provide direct evidence regarding the influences of correlation metrics and specific preprocessing choices on both the global and nodal topological properties of functional brain networks. This study also has important implications for how to choose reliable analytical schemes in brain network studies.

Liang, Xia; Wang, Jinhui; Yan, Chaogan; Shu, Ni; Xu, Ke; Gong, Gaolang; He, Yong

2012-01-01

119

Pairwise Correlations of Eight Strong DIBs and N(H), N(H2), and EBV  

Microsoft Academic Search

We discuss the correlations between equivalent widths of eight diffuse interstellar bands (DIBs), and examine their correlations with the column densities of atomic hydrogen (N(H)) and molecular hydrogen (N(H2)), and EB-V. The DIBs are centered at lambda 5780.5, 6204.5, 6283.8, 6196.0, 6613.6, 5705.1, 5797.1, and 5487.7, in decreasing order of Pearson's correlation coefficient with N(H), which ranges from 0.94 to

Scott D. Friedman; D. G. York; B. J. McCall; J. Dahlstrom; P. Sonnentrucker; D. E. Welty; M. M. Drosback; L. M. Hobbs; B. L. Rachford; T. P. Snow

2011-01-01

120

Application of a correlation correction factor in a microarray cross-platform reproducibility study  

PubMed Central

Background Recent research examining cross-platform correlation of gene expression intensities has yielded mixed results. In this study, we demonstrate use of a correction factor for estimating cross-platform correlations. Results In this paper, three technical replicate microarrays were hybridized to each of three platforms. The three platforms were then analyzed to assess both intra- and cross-platform reproducibility. We present various methods for examining intra-platform reproducibility. We also examine cross-platform reproducibility using Pearson's correlation. Additionally, we previously developed a correction factor for Pearson's correlation which is applicable when X and Y are measured with error. Herein we demonstrate that correcting for measurement error by estimating the "disattenuated" correlation substantially improves cross-platform correlations. Conclusion When estimating cross-platform correlation, it is essential to thoroughly evaluate intra-platform reproducibility as a first step. In addition, since measurement error is present in microarray gene expression data, methods to correct for attenuation are useful in decreasing the bias in cross-platform correlation estimates.

Archer, Kellie J; Dumur, Catherine I; Taylor, G Scott; Chaplin, Michael D; Guiseppi-Elie, Anthony; Grant, Geraldine; Ferreira-Gonzalez, Andrea; Garrett, Carleton T

2007-01-01

121

Gaussian graphical modeling reveals specific lipid correlations in glioblastoma cells  

NASA Astrophysics Data System (ADS)

Advances in high-throughput measurements of biological specimens necessitate the development of biologically driven computational techniques. To understand the molecular level of many human diseases, such as cancer, lipid quantifications have been shown to offer an excellent opportunity to reveal disease-specific regulations. The data analysis of the cell lipidome, however, remains a challenging task and cannot be accomplished solely based on intuitive reasoning. We have developed a method to identify a lipid correlation network which is entirely disease-specific. A powerful method to correlate experimentally measured lipid levels across the various samples is a Gaussian Graphical Model (GGM), which is based on partial correlation coefficients. In contrast to regular Pearson correlations, partial correlations aim to identify only direct correlations while eliminating indirect associations. Conventional GGM calculations on the entire dataset can, however, not provide information on whether a correlation is truly disease-specific with respect to the disease samples and not a correlation of control samples. Thus, we implemented a novel differential GGM approach unraveling only the disease-specific correlations, and applied it to the lipidome of immortal Glioblastoma tumor cells. A large set of lipid species were measured by mass spectrometry in order to evaluate lipid remodeling as a result to a combination of perturbation of cells inducing programmed cell death, while the other perturbations served solely as biological controls. With the differential GGM, we were able to reveal Glioblastoma-specific lipid correlations to advance biomedical research on novel gene therapies.

Mueller, Nikola S.; Krumsiek, Jan; Theis, Fabian J.; Böhm, Christian; Meyer-Bäse, Anke

2011-05-01

122

Correlational analysis.  

PubMed

A common question of interest in nursing research is the relationships between variables. Correlational analysis is a statistical technique employed to investigate the magnitude and significance of such relationships. This paper presents commonly used techniques to examine bivariate relationships of interval/ratio, ordinal and nominal variables. PMID:22464607

Prematunga, Roshani K

2012-03-30

123

Pairwise Correlations Of Eight Strong DIBs And N(H), N(H2), And E(BV)  

Microsoft Academic Search

We establish correlations between equivalent widths of eight diffuse interstellar bands (DIBs), and examine their correlations with N(H), N(H2), and E(B-V). The DIBs are centered at 5780.5, 6204.5, 6283.8, 6196.0, 6613.6, 5705.1, 5797.1, and 5487.7, in decreasing order of Pearson's correlation coefficient with N(H), which range from 0.96 to 0.82. We find the equivalent width of 5780.5 is better correlated

Scott David Friedman; D. G. York; B. J. McCall; J. Dahlstrom; P. Sonnentrucker; D. E. Welty; M. M. Drosback; L. M. Hobbs; B. L. Rachford; T. P. Snow

2011-01-01

124

Correlations between blood glucose and breath components from portable gas sensors and PTR-TOF-MS.  

PubMed

Acetone is one of the most abundant volatile compounds in the human breath and might be important for monitoring diabetic patients. Here, a portable acetone sensor consisting of flame-made, nanostructured, Si-doped WO3 sensing films was used to analyse the end tidal fraction of the breath (collected in Tedlar bags) from eight healthy volunteers after overnight fasting (morning) and after lunch (afternoon). After breath sampling, the gaseous components were also analysed by proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS), and each person's blood glucose level was measured. The portable sensor accurately detected the presence of acetone with fast response/recovery times (<12 s) and a high signal-to-noise ratio. Statistical analysis of the relationship between the PTR-TOF-MS measurements of breath gases (e.g., acetone, isoprene, ethanol and methanol), sensor response and the blood glucose level was performed for both sampling periods. The best correlations were found after overnight fasting (morning): in particular, between blood glucose level and breath acetone (Pearson's 0.98 and Spearman's 0.93). Whereas the portable sensor response correlated best with the blood glucose (Pearson's 0.96 and Spearman's 0.81) and breath acetone (Pearson's 0.92 and Spearman's 0.69). PMID:23959908

Righettoni, M; Schmid, A; Amann, A; Pratsinis, S E

2013-08-20

125

Correlation of metallothionein expression with apoptosis in nasopharyngeal carcinoma  

PubMed Central

The expression of metallothionein (MT), an intracellular ubiquitous low molecular weight protein thiol with antioxidant properties, was studied in nasopharyngeal cancer (NPC) and correlated with the apoptotic index. Immunohistochemical staining of randomly selected, formalin-fixed and paraffin-embedded normal and malignant nasopharyngeal tissues were analysed for the expression of MT using the commercially available E9 antibody directed against MT I and MT II isoforms. The corresponding apoptosis labelling indices were evaluated by the TUNEL method. Localization of MT at the ultrastructural level was studied by immunogold labelling. All the tumour sections (17 specimens) showed MT-immunopositivity. A direct correlation between the percentage of MT-positive cells and the staining intensity was noted (P< 0.001; Pearson's r = 0.95). There was absence of cytoplasmic staining and only nuclear staining (with localization in the nucleoplasm) was demonstrated in the tumour cells. In normal epithelium of the nasopharynx, the basal layer was stained. An inverse relationship was observed between the level of MT expression and the apoptotic index in the NPC tissues (P = 0.0059; Pearson's r = –0.6380). The results suggest that overexpression of MT in NPC may protect the tumour cells from entering into the apoptotic process and thereby contribute to tumour expansion. Preferential localization of MT in the nuclei of NPC cells may possibly enhance radioresistance since radiotherapy is known to eradicate tumour cells by free radical-induced apoptosis. © 2000 Cancer Research Campaign

Jayasurya, A; Bay, B H; Yap, W M; Tan, N G

2000-01-01

126

Correlation spectrometer  

DOEpatents

A correlation spectrometer can detect a large number of gaseous compounds, or chemical species, with a species-specific mask wheel. In this mode, the spectrometer is optimized for the direct measurement of individual target compounds. Additionally, the spectrometer can measure the transmission spectrum from a given sample of gas. In this mode, infrared light is passed through a gas sample and the infrared transmission signature of the gasses present is recorded and measured using Hadamard encoding techniques. The spectrometer can detect the transmission or emission spectra in any system where multiple species are present in a generally known volume.

Sinclair, Michael B. (Albuquerque, NM); Pfeifer, Kent B. (Los Lunas, NM); Flemming, Jeb H. (Albuquerque, NM); Jones, Gary D. (Tijeras, NM); Tigges, Chris P. (Albuquerque, NM)

2010-04-13

127

Correlation between serum gastrin and cellular proliferation in Barrett's esophagus  

PubMed Central

Background: Patients with Barrett’s esophagus (BE) are commonly treated with proton-pump inhibitors (PPIs) to minimize the exposure of esophageal mucosa to stomach acid. However, the use of these medications can lead to significant hypergastrinemia in a subset of patients, which is concerning due to the known tumorigenic and proliferative effects of gastrin. The present pilot study aims to investigate a potential correlation between serum gastrin and cellular proliferation in BE. Methods: We performed a cross-sectional analysis of patients with nondysplastic BE on PPI therapy. Fasting serum gastrin was measured on the same day as esophageal biopsies were obtained. These biopsies were then stained with Ki-67 nuclear antibody. Pearson’s correlation coefficient was calculated to assess the relationship between Ki-67 index and ln(gastrin). Results: A total of 10 patients were included in the study. The mean age was 62.6 (±8.4) years and 5 patients were male. The median serum gastrin level was 45.2 pM (interquartile range [IQR] 33–113) and the median Ki-67 index was 49.6% (IQR 23–64). We found a statistically significant positive correlation between Ki-67 index and ln(gastrin) (r?=?0.64; p?=?0.05). Conclusions: In nondysplastic BE patients on PPI therapy, serum gastrin levels were significantly correlated with cellular proliferation. These pilot data lend support to a potential causal effect of gastrin on neoplastic progression in BE. Longitudinal studies of patients with BE are needed to determine whether hypergastrinemia is a risk factor for the development of dysplasia and adenocarcinoma or could be used as a biomarker for disease progression.

Green, Daniel A.; Mlynarczyk, Carrie M.; Vaccaro, Benjamin J.; Capiak, Kristina M.; Quante, Michael; Lightdale, Charles J.; Abrams, Julian A.

2011-01-01

128

Inferring correlation networks from genomic survey data.  

PubMed

High-throughput sequencing based techniques, such as 16S rRNA gene profiling, have the potential to elucidate the complex inner workings of natural microbial communities - be they from the world's oceans or the human gut. A key step in exploring such data is the identification of dependencies between members of these communities, which is commonly achieved by correlation analysis. However, it has been known since the days of Karl Pearson that the analysis of the type of data generated by such techniques (referred to as compositional data) can produce unreliable results since the observed data take the form of relative fractions of genes or species, rather than their absolute abundances. Using simulated and real data from the Human Microbiome Project, we show that such compositional effects can be widespread and severe: in some real data sets many of the correlations among taxa can be artifactual, and true correlations may even appear with opposite sign. Additionally, we show that community diversity is the key factor that modulates the acuteness of such compositional effects, and develop a new approach, called SparCC (available at https://bitbucket.org/yonatanf/sparcc), which is capable of estimating correlation values from compositional data. To illustrate a potential application of SparCC, we infer a rich ecological network connecting hundreds of interacting species across 18 sites on the human body. Using the SparCC network as a reference, we estimated that the standard approach yields 3 spurious species-species interactions for each true interaction and misses 60% of the true interactions in the human microbiome data, and, as predicted, most of the erroneous links are found in the samples with the lowest diversity. PMID:23028285

Friedman, Jonathan; Alm, Eric J

2012-09-20

129

Correlation functions and factorial correlator data  

SciTech Connect

The close connection between factorial moments and factorial correlators as integrals of the same underlying correlation function is explored, leading to extensions of sum rules previously suggested. Cumulants, which were previously found to be the fundamental building blocks for moments, have been analogously defined for the correlators also, revealing the true {ital n}-particle correlations. Decomposing the factorial correlators into cumulants, we find that the largest part of the correlators consists of two-particle correlations for NA22 data. The nonstationarity of the correlation function is found to affect the results to a surprisingly small degree. It is pointed out that all linking schemes for higher-order correlations must be tested not on the correlators but on the cumulants in order to claim success. Finally, applying our scheme to UA1 factorial moment data, we predict the size and shape of UA1 correlators.

Eggers, H.C.; Carruthers, P.; Lipa, P.; Sarcevic, I. (Department of Physics, University of Arizona, Tucson, Arizona (USA))

1991-10-01

130

Decline in lumbar extensor muscle strength the older adults: correlation with age, gender and spine morphology  

PubMed Central

Background Muscle morphology, age and gender may be determinants of muscle strength in older adults. However, very few research studies have directly examined such correlation in the ageing spine. The aim of the study was to examine the correlation between lumbar extensor muscle strength, its muscle fibre angles, thoracolumbar curvature, age and gender in the older and younger adults. Methods Muscle fibre angles of lumbar extensor muscles, thoracolumbar curvature and lumbar extensor muscle strength were examined in 26 young (mean age 27.9, SD 5.2) and 26 older (mean age 72.1, SD 5.9) participants. Pearson’s correlation was employed to determine the association among lumbar extensor muscle fibre angle, thoracolumbar curvature, age, gender and lumbar extensor muscle strength. Multiple stepwise linear regression analysis was used to identify significant determinants of lumbar extensor muscle strength. Results The results demonstrated a significant correlation between lumbar extensor muscle strength, muscle fibre angle, age and gender. In the step wise regression analysis, both gender and age were identified as the most robust determinant for lumbar extensor muscle strength in older adults. However, gender was the only determinant of muscle strength in the young. Conclusion These results suggest that the decline in the lumbar extensor muscle strength in older adults was more dependent on age when compared to younger adults.

2013-01-01

131

Emotional structure and commitment: implications for health care management  

Microsoft Academic Search

Purpose – This paper aims to determine if the emotional structure of direct healthcare workers was related to their commitment to the organization. Design\\/methodology\\/approach – A total of 105 direct healthcare workers completed self-report surveys to determine their emotional intelligence, emotional coping ability, and affective organizational commitment. Pearson Product Moment Correlation and independent sample t tests were used to analyze

John Humphreys; Bill Brunsen; Dale Davis

2005-01-01

132

Type II Robustness of H0: Rho=0 for Non-Normal Distributions  

ERIC Educational Resources Information Center

|Is the t test statistic for the Pearson Product Moment Correlation Coefficient robust to errors of the second kind? This investigation indirectly measured the effects of power through a type 2 error rate robustness study. The results were revealing. [The dissertation citations contained here are published with the permission of ProQuest LLC.…

Wren, Stephanie D.

2010-01-01

133

Assessing Employees Perception On Health And Safety Management In Public Hospitals  

Microsoft Academic Search

This research examined the perception of employees regarding the management of occupational health and safety (OHS) in public hospital. 418 employees from three state hospitals in the northern region of Malaysia participated in this study. Data was collected using a set of questionnaires. Data analysis was done using descriptive statistics, t-test, one-way ANOVA, Pearson correlation and multiple regressions. Findings showed

Nor Azimah Chew Abdullah; Jeffery T. Spickett; Krassi B. Rumchev; Satvinder S. Dhaliwal

134

Substance Abuse Counselors and Moral Reasoning: Hypothetical and Authentic Dilemmas  

ERIC Educational Resources Information Center

|This exploratory study examined the assumption that the level of moral reasoning (Defining Issues Test; J. R. Rest, 1986) used in solving hypothetical and authentic dilemmas is similar for substance abuse counselors (N = 188). The statistical analyses used were paired-sample t tests, Pearson product-moment correlation, and simultaneous multiple…

Sias, Shari M.

2009-01-01

135

Anthropometric and Behavioral Measures Related to Mindfulness in College Students  

Microsoft Academic Search

Objective: To determine whether mindfulness is associated with physical and behavioral measures in first semester college students. Participants: Male and female first year college students (n = 75) from the University of Rhode Island. Methods: Height, weight, waist circumference (WC), and blood pressure were assessed and online questionnaires were completed. Independent t tests and Pearson correlations were utilized for analysis.

Sarah Grinnell; Geoffrey Greene; Kathleen Melanson; Bryan Blissmer; Ingrid E. Lofgren

2011-01-01

136

Statistical approaches for assessing the relative validity of a food-frequency questionnaire: use of correlation coefficients and the kappa statistic  

Microsoft Academic Search

Objective: To compare different statistical methods for assessing the relative validity of a self-administered, 150-item, semi-quantitative food-frequency questionnaire (FFQ) with 4-day weighed diet records (WR). Design: Subjects completed the Scottish Collaborative Group FFQ and carried out a 4- day WR. Relative agreement between the FFQ and WR for energy-adjusted nutrient intakes was assessed by Pearson and Spearman rank correlation coefficients,

LF Masson; G MCNeill; JO Tomany; JA Simpson; HS Peace; L Wei; DA Grubb; C Bolton-Smith

2003-01-01

137

Image restoration through thin turbid layers by correlation with a known object.  

PubMed

A method to recover the image of an object behind thin turbid layers is developed by wavefront shaping technique. The optimized wavefront is generated by modulating the scattering light of a known object with a spatial light modulator. A Pearson Correlation Coefficient is introduced as a cost function for the optimization. A beam scanning method based on optical memory effect is proposed to further enlarge the Field-of-View (FOV). The experimental results show good fidelity and large FOV of the recovered image. PMID:23736472

He, Hexiang; Guan, Yefeng; Zhou, Jianying

2013-05-20

138

The correlation between self-reported and measured height, weight, and BMI in reproductive age women.  

PubMed

This prospective, cross-sectional study of 60 women compares self-reported height, weight, and BMI with measured values. Self-reported BMI (29.0±8.37kg/m(2)) was slightly lower than measured BMI (29.1±8.38kg/m(2)) (p=0.4). Eighty percent of participants reported a BMI in the same category in which their BMI was measured. Pearson's correlation coefficient for height (0.96, p<0.001), weight (0.99, p<0.001), and BMI (0.99, p<0.001) were high. Reproductive age women accurately reported their height and weight. PMID:23958434

Roth, Lauren W; Allshouse, Amanda A; Lesh, Jennifer; Polotsky, Alex J; Santoro, Nanette

2013-08-16

139

Academic correlates of Taiwanese senior high school students' happiness.  

PubMed

This study examined the relation between academic factors and senior high school students' general happiness using a nationally representative sample of 11,061 11th graders in Taiwan. Pearson correlation analyses indicated that English teacher-perceived academic performance, mathematics teacher-perceived academic performance, teacher academic support, classmate academic support, organizational processes, and school satisfaction were positively related to students' general happiness,while disturbance in class was negatively related. Regression analysis found that objective academic achievement, mathematics teacher-perceived academic achievement, classmate academic support, disturbance in class, organizational processes, and most importantly, students' overall appraisals of their own happiness with school helped predict students' general happiness, account for 18.4% of the total variance. Among these variables, objective academic achievement and disturbance in class were negatively associated with general happiness. Some of the study's findings are consistent with those in the literature and some extend established accounts, while others point to future research directions. PMID:20432611

Chen, Su-Yen; Lu, Luo

2009-01-01

140

Tricuspid annulus motion and mitral annulus motion: Anatomical intimacy causing a good correlation?  

PubMed Central

BACKGROUND: Echocardiographic evaluation of the heart and its function, especially left ventricular systolic function, has great clinical importance. Systolic function can be measured using several methods, such as the amplitude of motion of the left atrioventricular plane (mitral annulus motion [MAM]) toward the apex during systole. Similarly, right ventricular systolic function can be measured using the motion of the right atrioventricular plane (tricuspid annulus motion [TAM]) toward the apex during systole. OBJECTIVES: Because the mitral and tricuspid annuli are situated close to each other in the fibrous skeleton between both ventricles and atria, one might think that a decrease in the amplitude of MAM would be followed by a decrease in the amplitude of TAM. The present study was developed to determinine if this anatomical intimacy causes a good correlation between the amplitudes of TAM and MAM. METHODS: Nineteen healthy subjects and 103 consecutive patients were included in the study and examined using echocardiography. The amplitudes of TAM and MAM were measured and the correlation between the amplitudes was calculated. RESULTS: In the 103 consecutive patients, a significant but relatively weak positive correlation was found between TAM and MAM amplitudes (Pearson’s correlation coefficient [r]=0.58; P<0.001). In the 19 healthy subjects, no significant correlation was found. CONCLUSIONS: Despite the anatomical intimacy of the annuli, the correlation between the amplitudes of TAM and MAM in consecutive patients was rather weak, and there was no correlation in healthy subjects. These findings could be due to anatomical and physiological differences between the right and left ventricles.

Emilsson, K; Egerlid, R; Nygren, BM

2005-01-01

141

The t-test Tutorial: Comparing Cultures  

NSDL National Science Digital Library

This tutorial, created by Dale Berger of Claremont Graduate University, takes the learner step-by-step in applying descriptive and inferential statistics using a real world situation. The site focuses on the cultural differences in child rearing in the countries of Belize and Samoa. Overall, this is a great site for applied statistical theories.

Berger, Dale

2008-12-22

142

Filtering induces correlation in fMRI resting state data.  

PubMed

Correlation-based functional MRI connectivity methods typically impose a temporal sample independence assumption on the data. However, the conventional use of temporal filtering to address the high noise content of fMRI data may introduce sample dependence. Violation of the independence assumption has ramifications for the distribution of sample correlation which, if unaccounted for, may invalidate connectivity results. To enable the use of temporal filtering for noise suppression while maintaining the integrity of connectivity results, we derive the distribution of sample correlation between filtered timeseries as a function of the filter frequency response. Corrected distributions are also derived for statistical inference tests of sample correlation between filtered timeseries, including Fisher's z-transformation and the Student's t-test. Crucially, the proposed corrections are valid for any unknown true correlation and arbitrary filter specifications. Empirical simulations demonstrate the potential for temporal filtering to artificially induce connectivity by introducing sample dependence, and verify the utility of the proposed corrections in mitigating this effect. The importance of our corrections is exemplified in a resting state fMRI connectivity analysis: seed-voxel correlation maps generated from filtered data using uncorrected test variates yield an unfeasible number of connections to the left primary motor cortex, suggesting artificially induced connectivity, while maps acquired from filtered data using corrected test variates exhibit bilateral connectivity in the primary motor cortex, in conformance with expected results as seen in the literature. PMID:22939874

Davey, Catherine E; Grayden, David B; Egan, Gary F; Johnston, Leigh A

2012-08-25

143

Mitochondrial Inverted Repeats Strongly Correlate with Lifespan: mtDNA Inversions and Aging.  

PubMed

Mitochondrial defects are implicated in aging and in a multitude of age-related diseases, such as cancer, heart failure, Parkinson's disease, and Huntington's disease. However, it is still unclear how mitochondrial defects arise under normal physiological conditions. Mitochondrial DNA (mtDNA) deletions caused by direct repeats (DRs) are implicated in the formation of mitochondrial defects, however, mitochondrial DRs show relatively weak (Pearson's r?=?-0.22, p<0.002; Spearman's ??=?-0.12, p?=?0.1) correlation with maximum lifespan (MLS). Here we report a stronger correlation (Pearson's r?=?-0.55, p<10(-16); Spearman's ??=?-0.52, p<10(-14)) between mitochondrial inverted repeats (IRs) and lifespan across 202 species of mammals. We show that, in wild type mice under normal conditions, IRs cause inversions, which arise by replication-dependent mechanism. The inversions accumulate with age in the brain and heart. Our data suggest that IR-mediated inversions are more mutagenic than DR-mediated deletions in mtDNA, and impose stronger constraint on lifespan. Our study identifies IR-induced mitochondrial genome instability during mtDNA replication as a potential cause for mitochondrial defects. PMID:24069185

Yang, Jiang-Nan; Seluanov, Andrei; Gorbunova, Vera

2013-09-17

144

Is there an optimal substitution matrix for contact prediction with correlated mutations?  

PubMed

Correlated mutations in proteins are believed to occur in order to preserve the protein functional folding through evolution. Their values can be deduced from sequence and/or structural alignments and are indicative of residue contacts in the protein three-dimensional structure. A correlation among pairs of residues is routinely evaluated with the Pearson correlation coefficient and the MCLACHLAN similarity matrix. In literature, there is no justification for the adoption of the MCLACHLAN instead of other substitution matrices. In this paper, we approach the problem of computing the optimal similarity matrix for contact prediction with correlated mutations, i.e., the similarity matrix that maximizes the accuracy of contact prediction with correlated mutations. We describe an optimization procedure, based on the gradient descent method, for computing the optimal similarity matrix and perform an extensive number of experimental tests. Our tests show that there is a large number of optimal matrices that perform similarly to MCLACHLAN. We also obtain that the upper limit to the accuracy achievable in protein contact prediction is independent of the optimized similarity matrix. This suggests that the poor scoring of the correlated mutations approach may be due to the choice of the linear correlation function in evaluating correlated mutations. PMID:20855922

Di Lena, Pietro; Fariselli, Piero; Margara, Luciano; Vassura, Marco; Casadio, Rita

145

Some Properties of Adaptive Neyman-Pearson Detectors†  

Microsoft Academic Search

Several upper bounds have recently been derived by the present authors, and others, for the improvement in performance achievable by an optimum adaptive receiver with respect to a receiver which, although optimum for its state of a priori information, is not adaptive to other states of prior information. This earlier work has been characterized by the general Bayesian approach to

R. ESPOSITO; D. MIDDLETON; J. A. MULLEN

1966-01-01

146

Correlation of PET Images of Metabolism, Proliferation and Hypoxia to Characterize Tumor Phenotype in Patients with Cancer of the Oropharynx  

PubMed Central

Spatial organization of tumor phenotype is of great interest to radiotherapy target definition and outcome prediction. We characterized tumor phenotype in patients with cancers of the oropharynx through voxel-based correlation of PET images of metabolism, proliferation, and hypoxia. Methods Patients with oropharyngeal cancer received 18F-fluorodeoxyglucose (FDG) PET/CT, 18F-fluorothymidine (FLT) PET/CT, and 61Cu-diacetyl-bis(N4-methylthiosemicarbazone) (Cu-ATSM) PET/CT. Images were co-registered and standardized uptake values (SUV) were calculated for all modalities. Voxel-based correlation was evaluated with Pearson’s correlation coefficient in tumor regions. Additionally, sensitivity studies were performed to quantify the effects of image segmentation, registration, noise, and segmentation on R. Results On average, FDG PET and FLT PET images were most highly correlated (RFDG:FLT=0.76, range 0.53–0.85), while Cu-ATSM PET showed greater heterogeneity in correlation to other tracers (RFDG:Cu-ATSM=0.64, range 0.51–0.79; RFLT:Cu-ATSM=0.61, range 0.21–0.80). Of the tested parameters, correlation was most sensitive to image registration. Misregistration of one voxel lead to ?RFDG=0.25, ?RFLT=0.39, and ?RCu-ATSM=0.27. Image noise and reconstruction also had quantitative effects on correlation. No significant quantitative differences were found between GTV, expanded GTV, or CTV regions. Conclusions Voxel-based correlation represents a first step into understanding spatial organization of tumor phenotype. These results have implications for radiotherapy target definition and provide a framework to test outcome prediction based on pretherapy distribution of phenotype.

Nyflot, Matthew J; Harari, Paul M; Yip, Stephen; Perlman, Scott B; Jeraj, Robert

2012-01-01

147

Isotope Correlation Experiment.  

National Technical Information Service (NTIS)

The ESARDA working group on Isotopic Correlation Techniques (ICT) and Reprocessing Input Analysis performed an Isotope Correlation Experiment (ICE) to check the feasibility of the new technique. Ten input batches of the reprocessing of the KWO fuel at the...

L. Koch S. Schoof

1983-01-01

148

Correlation in business networks  

NASA Astrophysics Data System (ADS)

This paper considers business networks. Through empirical study, we show that business networks display characteristics of small-world networks and scale-free networks. In this paper, we characterize firms as sales and bankruptcy probabilities. A correlation between sales and a correlation between bankruptcy probabilities in business networks are also considered. The results reveal that the correlation between sales depends strongly on the type of network, whereas the correlation between bankruptcy probabilities does so only weakly.

Souma, Wataru; Aoyama, Hideaki; Fujiwara, Yoshi; Ikeda, Yuichi; Iyetomi, Hiroshi; Kaizoji, Taisei

2006-10-01

149

Evaluation of the construct validity of the DASH questionnaire by correlation to the SF-36.  

PubMed

The construct validity of the Disabilities of the Arm, Shoulder, and Hand (DASH) questionnaire was evaluated by examining its correlation to the Medical Outcomes Study Short Form-36 (SF-36). The study sample was 90 patients seen at the upper-extremity clinic of a university-based orthopedic practice. Patients were asked to complete a packet that included the DASH and SF-36 questionnaires. Pearson correlation coefficients of the DASH questionnaire to the SF-36 subscales ranged from -0.36 to -0.62. The DASH questionnaire had fewer ceiling and floor scores than most of the SF-36 subscales. These results support the DASH questionnaire as a valid measure of health status useful in patients with a wide variety of upper-extremity complaints. PMID:12015732

SooHoo, Nelson Fong; McDonald, Allen P; Seiler, John Gray; McGillivary, Gary R

2002-05-01

150

Investigation of the correlation between the different mechanical properties of resin composites.  

PubMed

The aim of this study was to investigate the relationship between the different mechanical properties with the filler fraction of various resin composites. Mechanical properties of eighteen different resin composites were investigated in this study; flexural strength (FS), flexural modulus (FM), fracture toughness (FT), compressive strength (CS), diametral tensile strength (DTS), Barcol hardness (BH), Vickers hardness (HV), and Knoop hardness (HK). The mean values of mechanical properties and the filler fractions (V(f )) obtained from the literature and the manufacturer were analyzed using Pearson's correlation test at p<0.01. The relationships were compared with the data retrieved from previous studies. Strong correlations between Vf and BH/HV/HK and V(f) and FM were evident in the results of the present study and these results were supported by the retrieved data from previous studies. The other relationships between mechanical properties, such as that between FS and FM and between CS and HV were not significant. PMID:23370870

Jun, Soo-Kyung; Kim, Dong-Ae; Goo, Hyo-Jin; Lee, Hae-Hyoung

2013-01-01

151

Strongly correlated electron systems  

Microsoft Academic Search

This special section is dedicated to the Strongly Correlated Electron Systems Conference (SCES) 2011, which was held from 29 August–3 September 2011, in Cambridge, UK. SCES'2011 is dedicated to 100 years of superconductivity and covers a range of topics in the area of strongly correlated systems. The correlated electronic and magnetic materials featured include f-electron based heavy fermion intermetallics and

Siddharth S Saxena; P B Littlewood

2012-01-01

152

Heterodyne optical correlation \\/HOC  

Microsoft Academic Search

A new image-correlation concept based upon optical heterodyne detection is presented. In the Heterodyne Optical Correlator System (HOC), two transparencies are relatively oriented and projected onto a common image plane where coincidence is detected. By means of heterodyne optical techniques, the normalized correlation coefficient is determined at each element of a photo diode array detector in the common image plane.

N. Balasubramanian; R. D. Leighty

1976-01-01

153

Reverse Correlation in Neurophysiology  

ERIC Educational Resources Information Center

This article presents a review of reverse correlation in neurophysiology. We discuss the basis of reverse correlation in linear transducers and in spiking neurons. The application of reverse correlation to measure the receptive fields of visual neurons using white noise and m-sequences, and classical findings about spatial and color processing in…

Ringach, Dario; Shapley, Robert

2004-01-01

154

Reverse Correlation in Neurophysiology  

ERIC Educational Resources Information Center

|This article presents a review of reverse correlation in neurophysiology. We discuss the basis of reverse correlation in linear transducers and in spiking neurons. The application of reverse correlation to measure the receptive fields of visual neurons using white noise and m-sequences, and classical findings about spatial and color processing in…

Ringach, Dario; Shapley, Robert

2004-01-01

155

Correlation between the extent of coronary atherosclerosis and lipid profile.  

PubMed

Increased concentration of low density lipoprotein (LDL) cholesterol or decreased level of high density lipoprotein (HDL) cholesterol are important risk factors for coronary atherosclerosis. However, an independent association of triglycerides (TG) with atherosclerosis is uncertain. The aim of this prospective study was to evaluate the relationship between serum lipid levels and the extent of coronary atherosclerosis in patients with suspected coronary artery disease (CAD) and no previous myocardial infarction who were not treated with lipids lowering therapy or low-lipid diet. The study was conducted in 141 patients (53.6 +/- 7.8 years old; 32 female) who underwent a routine coronary angiography for CAD diagnosis. A modified angiographic Gensini Score (GS) was used to reflect the extent of coronary atherosclerosis. Fasting serum lipid concentrations were determined using cholesterol esterase/peroxidase (CHOD/PAP) enzymatic method for total cholesterol and its fractions and lipase glycerol kinase (GPO/PAP) enzymatic method TG evaluation. The association of Gensini Score with variables characterising lipid profile was analysed with the use of Pearson correlation (r co-efficient; p value). GS was positively correlated with total cholesterol (r = 0.404; p < 0.001), LDL cholesterol (r = 0.484; p < 0.001 ) and TG (r = 0.235; p = 0.005). There was a negative correlation between Gensini Score and HDL cholesterol (r = -0.396; p < 0.001). In angina pectoris patients with no previous myocardial infarction, the extent of coronary atherosclerosis is positively correlated with pro-atherogenic lipids, i.e. total cholesterol, LDL cholesterol and TG and negatively correlated with antiatherogenic HDL cholesterol. PMID:12841339

Tarchalski, Janusz; Guzik, Przemys?aw; Wysocki, Henryk

2003-04-01

156

Quantum perfect correlations  

SciTech Connect

The notion of perfect correlations between arbitrary observables, or more generally arbitrary POVMs, is introduced in the standard formulation of quantum mechanics, and characterized by several well-established statistical conditions. The transitivity of perfect correlations is proved to generally hold, and applied to a simple articulation for the failure of Hardy's nonlocality proof for maximally entangled states. The notion of perfect correlations between observables and POVMs is used for defining the notion of a precise measurement of a given observable in a given state. A longstanding misconception on the correlation made by the measuring interaction is resolved in the light of the new theory of quantum perfect correlations.

Ozawa, Masanao [Graduate School of Information Sciences, Tohoku University, Aoba-ku, Sendai 980-8579 (Japan)]. E-mail: ozawa@math.is.tohoku.ac.jp

2006-03-15

157

Optical correlator tracking nonlinearity  

NASA Astrophysics Data System (ADS)

A limitation observed in the tracking ability of optical correlators is reported. It is shown by calculations that an inherent nonlinearity exists in many optical correlator configurations, with the problem manifesting itself in a mismatch of the input scene with the position of the correlation signal. Results indicate that some care must be given to the selection of components and their configuration in constructing an optical correlator which exhibits true translational invariance. An input test scene is shown along with the correlation spot and cross hairs from a contrast detector; the offset is apparent.

Gregory, Don A.; Kirsch, James C.; Johnson, John L.

1987-01-01

158

High-resolution correlation  

NASA Astrophysics Data System (ADS)

In the basic correlation process a sequence of time-lag-indexed correlation coefficients are computed as the inner or dot product of segments of two signals. The time-lag(s) for which the magnitude of the correlation coefficient sequence is maximized is the estimated relative time delay of the two signals. For discrete sampled signals, the delay estimated in this manner is quantized with the same relative accuracy as the clock used in sampling the signals. In addition, the correlation coefficients are real if the input signals are real. There have been many methods proposed to estimate signal delay to more accuracy than the sample interval of the digitizer clock, with some success. These methods include interpolation of the correlation coefficients, estimation of the signal delay from the group delay function, and beam forming techniques, such as the MUSIC algorithm. For spectral estimation, techniques based on phase differentiation have been popular, but these techniques have apparently not been applied to the correlation problem . We propose a phase based delay estimation method (PBDEM) based on the phase of the correlation function that provides a significant improvement of the accuracy of time delay estimation. In the process, the standard correlation function is first calculated. A time lag error function is then calculated from the correlation phase and is used to interpolate the correlation function. The signal delay is shown to be accurately estimated as the zero crossing of the correlation phase near the index of the peak correlation magnitude. This process is nearly as fast as the conventional correlation function on which it is based. For real valued signals, a simple modification is provided, which results in the same correlation accuracy as is obtained for complex valued signals.

Nelson, D. J.

2007-09-01

159

Psychological profile in burning mouth syndrome  

Microsoft Academic Search

Thirty-two patients with burning mouth syndrome and 32 matched control subjects were evaluated for their personality profile using a comprehensive, reliable, and validated inventory. All subjects were requested to complete the Neo PI-R questionnaire that measures the 5 dimensions of personality and their facets. A t-test and univariate correlations (Pearson's correlation coefficient) were used to compare the 2 groups. Results

Firas A. M. Al Quran

2004-01-01

160

Correlating Heart Rate and Perceived Exertion during Aerobic Exercise in Alzheimer's Disease  

PubMed Central

Older adults reap many health benefits from aerobic exercise training; however, little is known about how to monitor training responses in older adults with Alzheimer’s disease. The purpose of this paper was to examine the correlation of objectively measured heart rate and subjectively reported perceived exertion during aerobic exercise training in four older men with advanced Alzheimer’s disease from a pilot study that used a one-group pre- and post-test design. During training (3 times a week for 8 weeks), participant’s heart rate and perceived exertion was assessed by a trained exercise trainer every 5 minutes using Polar™ heart rate monitor and the Borg Rating of Perceived Exertion Scale respectively. There were 596 heart rate-perceived exertion data pairs. The results show that Pearson’s r for heart rate and perceived exertion was .457, significant at .01, 2-tailed, controlling for age, education, exercise session, and cognition. We conclude that the Borg scale itself might be insufficient for monitoring exercise responses in older men with advanced Alzheimer’s disease. Future studies are needed to further examine the utility of the Borg scale in this population.

Yu, Fang; Bil, Kristin

2010-01-01

161

Statistics Tutorials Based on SPSS and Minitab  

NSDL National Science Digital Library

This collection of tutorials, authored by Thomas W. MacFarland of Nova Southeastern University, demonstrates various statistical topics with data and provides SPSS and Minitab code. Topics covered: measures of central tendency, sign test, Chi-square, Mann-Whitney test, Wilcoxon matched-pairs signed-ranks test, Kruskal-Wallis one-way analysis of variance, Friedman two-way analysis of variance, Spearman rank correlation, Pearson product-moment correlation, multiple regression, t-test for independent samples, t-test for matched pairs, one and two-Way ANOVA. This is a nice collection of tutorials for anyone interested in a more in-depth study of statistics.

Macfarland, Thomas W.

2009-09-10

162

Correlation in photodetachment  

SciTech Connect

Electron correlation plays a major role in all aspects of the photodetachment of an electron from a negative ion. Photodetachment measurements are well suited to investigate the relatively short range forces associated with correlation due to the absence of the long range Coulomb interaction. Measurements of electron affinities, asymmetry parameters and cross sections are described to illustrate the influence of correlation on photodetachment. 25 refs., 4 figs.

Pegg, D.J. (Oak Ridge National Lab., TN (USA) Tennessee Univ., Knoxville, TN (USA). Dept. of Physics)

1991-01-01

163

Hadronic Fluctuations and Correlations  

Microsoft Academic Search

This document is part of Volume 23 `Relativistic Heavy Ion Physics' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms'. It contains the Section `8.1 Hadronic Fluctuations and Correlations' of the Chapter `8 The Final Expansion State of Relativistic Nuclear Collisions' with the content: 8.1 Hadronic Fluctuations and Correlations 8.1.1 Introduction 8.1.2 Fluctuations and Correlations in a thermal system

Volker Koch

2010-01-01

164

Particle Correlations at Lep  

NASA Astrophysics Data System (ADS)

Particle correlations are extensively studied to obtain information about the dynamics of hadron production. Prom 1989 to 2000 the four LEP collaborations recorded more than 16 million hadronic Z0 decays and several thousand W+W- events. In Z0 decays, two-particle correlations were analysed in detail to study Bose-Einstein and Fermi-Dirac correlations for various particle species. In fully-hadronic W+W- decays, particle correlations were used to study whether the two W bosons decay independently. A review of selected results is presented.

Kress, T. H.

2002-07-01

165

Correlation between Serum PSA and Cancer Volume in Prostate Glands of Different Sizes  

PubMed Central

OBJECTIVES Although early studies showed a strong correlation between PSA and tumor volume, it has been suggested that PSA is no longer a valid marker for PCa and only correlates with prostate size. The objective of this study was to further evaluate the relationship of PSA with prostate size and tumor volume in a contemporary surgical series. METHODS From 2003 to 2009, 1234 men with data on prostate weight and total tumor volume underwent radical prostatectomy by a single surgeon. Prostate size was classified into tertiles: small (?41.2 grams), medium (41.3–54.5 grams) and large (?54.6 grams). Pearson correlation coefficients were used to examine the relationship of PSA with prostate size and tumor volume across different prostate sizes. RESULTS Median preoperative PSA was 4.9 ng/ml (SD ± 4.6), mean prostate size was 51.7 grams, and mean tumor volume was 5.6 cc. PSA had a significant correlation with prostate size only at a prostate weight ?54.6 gm (p=0.01). Regardless of prostate size, PSA had a more robust significant correlation with tumor volume than with prostate size (all p<0.0001). CONCLUSIONS PSA was significantly correlated with prostate size only in the largest prostate glands, but was significantly associated with tumor volume in small, medium, or large prostates. Thus, PSA continues to be a better marker for tumor volume than for prostate size.

Carvalhal, Gustavo F.; Daudi, Saima N.; Kan, Donghui; Mondo, Dana; Roehl, Kimberly A.; Loeb, Stacy; Catalona, William J.

2010-01-01

166

Application of the Gini correlation coefficient to infer regulatory relationships in transcriptome analysis.  

PubMed

One of the computational challenges in plant systems biology is to accurately infer transcriptional regulation relationships based on correlation analyses of gene expression patterns. Despite several correlation methods that are applied in biology to analyze microarray data, concerns regarding the compatibility of these methods with the gene expression data profiled by high-throughput RNA transcriptome sequencing (RNA-Seq) technology have been raised. These concerns are mainly due to the fact that the distribution of read counts in RNA-Seq experiments is different from that of fluorescence intensities in microarray experiments. Therefore, a comprehensive evaluation of the existing correlation methods and, if necessary, introduction of novel methods into biology is appropriate. In this study, we compared four existing correlation methods used in microarray analysis and one novel method called the Gini correlation coefficient on previously published microarray-based and sequencing-based gene expression data in Arabidopsis (Arabidopsis thaliana) and maize (Zea mays). The comparisons were performed on more than 11,000 regulatory relationships in Arabidopsis, including 8,929 pairs of transcription factors and target genes. Our analyses pinpointed the strengths and weaknesses of each method and indicated that the Gini correlation can compensate for the shortcomings of the Pearson correlation, the Spearman correlation, the Kendall correlation, and the Tukey's biweight correlation. The Gini correlation method, with the other four evaluated methods in this study, was implemented as an R package named rsgcc that can be utilized as an alternative option for biologists to perform clustering analyses of gene expression patterns or transcriptional network analyses. PMID:22797655

Ma, Chuang; Wang, Xiangfeng

2012-07-13

167

Improved Chirp Transform Correlator.  

National Technical Information Service (NTIS)

This invention relates to a chirp transform correlator in which asynchronous operation is made possible by the use of a pair of paralleled signal processing channels to which the unknown signal to be correlated is applied. The two channels include sweepin...

H. M. Gerard

1983-01-01

168

Correlates of Academic Procrastination.  

ERIC Educational Resources Information Center

|Investigated concurrent correlates of academic procrastination in Israeli college preparatory students (n=113). Procrastination in one course of study was found to be moderately correlated with procrastination in another but not to procrastination in routine tasks of daily living. Procrastination was weakly related to emotional upset about it and…

Milgram, Norman A.; And Others

1993-01-01

169

Explorations in Statistics: Correlation  

ERIC Educational Resources Information Center

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…

Curran-Everett, Douglas

2010-01-01

170

Correlation: Pitfalls and Alternatives  

Microsoft Academic Search

This article will tell you when it is safe and unproblematic to use correlation in the way that you imagine you can use it, and when you should take care. In particular it will tell you about two fallacies that have claimed many victims. These traps are known to statisticians, but not, we suggest, to the general correlation-using public. We

Paul Embrechts; Alexander Mcneil; Daniel Straumann

1999-01-01

171

Event-plane correlators  

NASA Astrophysics Data System (ADS)

Correlators between event planes of different harmonics in relativistic heavy-ion collisions have the potential to provide crucial information on the initial state of the matter formed in these collisions. We present a new procedure for analyzing such correlators, which is less demanding in terms of detector acceptance than the one used recently by the ATLAS Collaboration to measure various two-plane and three-plane correlators in Pb-Pb collisions at the Large Hadron Collider (LHC). It can also be used unambiguously for quantitative comparison between theory and data. We use this procedure to carry out realistic simulations within a multiphase transport (AMPT) model. Our theoretical results are in excellent agreement with the ATLAS data, in contrast with previous hydrodynamic calculations which only achieved qualitative agreement. We present predictions for new correlators, in particular four-plane correlators, which can easily be analyzed with our new method.

Bhalerao, Rajeev S.; Ollitrault, Jean-Yves; Pal, Subrata

2013-08-01

172

Explorations in statistics: correlation.  

PubMed

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 two variables are true random variables: for example, if we restrict in some way the variability of one variable, then the magnitude of the correlation will decrease. Correlation cannot help us decide if changes in one variable result in changes in the second variable, if changes in the second variable result in changes in the first variable, or if changes in a third variable result in concurrent changes in the first two variables. Correlation can help provide us with evidence that study of the nature of the relationship between x and y may be warranted in an actual experiment in which one of them is controlled. PMID:21098385

Curran-Everett, Douglas

2010-12-01

173

High YKL-40 Serum Concentration Is Correlated with Prognosis of Chinese Patients with Breast Cancer  

PubMed Central

This study aimed to investigate the association between serum YKL-40 and prognosis of breast cancer in a Chinese population. Expression of YKL-40 of 120 Chinese patients with breast cancer and 30 controls (benign breast lesions) was measured in tumor tissue by immunohistochemistry and in serum by ELISA. Differences in YKL-40 positivity grouped by specific patients’ characteristics were compared using Pearson Chi-square test for rates of intratumoral staining, one-way ANOVA with a Bonferroni post-hoc comparison, or two-sample t-test for mean YKL-40 serum concentrations. Factors associated with overall survival were identified by univariate and multivariate cox-regression analyses. YKL-40 was elevated in approximately 75% of Chinese patients with breast cancer. A significantly higher percentage of patients with YKL-40 positive tumors had larger tumor size, higher TNM stage, and/or lymph node metastasis. Significantly higher mean YKL-40 serum concentrations were observed in patient subgroups with invasive lobular carcinoma (P<0.0167), higher TNM stage (P<0.001), and positive lymph node metastasis (P<0.001). The estimated mean survival time of patients with YKL-40 positive tumors was significantly shorter than for patients with YKL-40 negative tumors (55.13 months vs 65.78 months, P?=?0.017). Multivariable Cox-regression analysis identified a significant association of overall survival time with YKL-40 serum concentration. Patients with YKL-40 positive tumors had significantly shorter disease free survival times than those with YKL-40 negative tumors. We propose that the potential utility of YKL-40 intratumoral staining or serum concentration as a biomarker for breast cancer is greatest within 5 years of diagnosis.

Wang, Dong; Zhai, Bo; Hu, Fengli; Liu, Chang; Zhao, Jinpeng; Xu, Jun

2012-01-01

174

Bleed-through correction for rendering and correlation analysis in multi-colour localization microscopy  

NASA Astrophysics Data System (ADS)

Multi-colour localization microscopy has enabled sub-diffraction studies of colocalization between multiple biological species and quantification of their correlation at length scales previously inaccessible with conventional fluorescence microscopy. However, bleed-through, or misidentification of probe species, creates false colocalization and artificially increases certain types of correlation between two imaged species, affecting the reliability of information provided by colocalization and quantified correlation. Despite the potential risk of these artefacts of bleed-through, neither the effect of bleed-through on correlation nor methods for its correction in correlation analyses have been systematically studied at typical rates of bleed-through reported to affect multi-colour imaging. Here, we present a reliable method of bleed-through correction applicable to image rendering and correlation analysis of multi-colour localization microscopy. Application of our bleed-through correction shows that our method accurately corrects the artificial increase in both types of correlation studied (Pearson coefficient and pair correlation), at all rates of bleed-through tested, in all types of correlation examined. In particular, anti-correlation could not be quantified without our bleed-through correction, even at rates of bleed-through as low as 2%. While it is demonstrated with dichroic-based multi-colour FPALM here, our presented method of bleed-through correction can be applied to all types of localization microscopy (PALM, STORM, dSTORM, GSDIM, etc), including both simultaneous and sequential multi-colour modalities, provided the rate of bleed-through can be reliably determined.

Kim, Dahan; Curthoys, Nikki M.; Parent, Matthew T.; Hess, Samuel T.

2013-09-01

175

Correlates of anxiety and depression among patients with type 2 diabetes mellitus  

PubMed Central

Context: Research has established the relation between diabetes and depression. Both diabetes and anxiety/depression are independently associated with increased morbidity and mortality. Aims: The present study aims at assessing the prevalence of anxiety/depression among outpatients receiving treatment for type 2 diabetes. Settings and Design: The study was conducted in the endocrinology outpatient department of an urban tertiary care center. Materials and Methods: The instruments used included a semi-structured questionnaire, HbA1c levels, fasting blood glucose and postprandial blood glucose, Brief Patient Health Questionnaire, and Hospital Anxiety and Depression Scale (HADS). Statistical Analysis Used: Analysis was carried out using the SPSS version 16.0. Pearson's correlation coefficient was calculated to find out the correlations. ANOVA was carried out for the in between group comparisons. Results: There was a significant correlation between the HADS-Anxiety scale and Body Mass Index (BMI) with a correlation coefficient of 0.34 (P = 0.008). Also, a significant correlation existed between HADS-Depression scale and BMI (correlation coefficient, 0.36; P = 0.004). Significant correlation were observed between the duration of daily physical exercise and HADS-Anxiety (coefficient of correlation, -0.25; P = 0.04) scores. HADS-Anxiety scores were found to be related to HbA1c levels (correlation-coefficient, 0.41; P = 0.03) and postprandial blood glucose levels (correlation-coefficient, 0.51; P = 0.02). Conclusions: Monitoring of biochemical parameters like HbA1c and postprandial blood glucose levels and BMI could be a guide to development of anxiety in these patients. Also, physical exercise seems to have a protective effect on anxiety in those with type 2 diabetes mellitus.

Balhara, Yatan Pal Singh; Sagar, Rajesh

2011-01-01

176

Correlations of Interstitial Cystitis/Painful Bladder Syndrome with Female Sexual Activity  

PubMed Central

Purpose We investigated how the symptoms of interstitial cystitis/painful bladder syndrome (IC/PBS) are correlated with the sexual activity of these patients. Materials and Methods A total of 87 patients were included in this study; 18 patients were diagnosed with IC and the other 69 had PBS. The diagnosis was made on the basis of the concept of IC/PBS proposed by the ICS in 2002. Patients were asked to fill in a Bristol female lower urinary tract symptom questionnaire, and symptoms were rated on a scale of from 1 to 4 or 5. Pearson's correlation coefficient was used to analyze the correlation of pain and urinary symptoms with quality of life and sexual activity. Results The average age of the patients was 51±14.7 years (range, 28-74 years). Age and vulvodynia were positively correlated with one another (r=0.232), and there was a negative correlation between age and dyspareunia (r=-0.302). Among the items regarding IC/PBS and sexual activity, frequency showed a positive correlation with vulvodynia (r=0.258) in addition to an inhibited sex life (r=0.403). Urgency showed a positive correlation with an inhibited sex life (r=0.346). Vulvodynia showed a positive correlation with an inhibited sex life (r=0.259) and dyspareunia (r=0.401). The main symptoms of IC/PBS (frequency, urgency, and pelvic pain) showed a positive correlation with almost all items related to quality of life (p<0.05). Conclusions Frequency, urgency, and various types of pain are negatively correlated with the sexual activity of patients. This suggests that physicians should consider sexual function in the management of patients with IC/PBS.

Yoon, Hyun Suk

2010-01-01

177

Correlation reflectometry at TEXTOR.  

PubMed

In high temperature fusion plasmas the transport of energy and particles is commonly believed to be driven by turbulence. Turbulence quantities as correlation length and decorrelation time are important for the confinement properties of a plasma. Besides other diagnostics, correlation reflectometry has proven to be a suitable tool for the measurement of turbulence properties. At the medium sized Toroidal EXperiment for Technical Oriented Research (TEXTOR) the existing correlation reflectometry has been recently upgraded. A new reflectometer based on a microwave synthesizer has been developed and installed for the investigation of turbulence properties in a fusion plasma. Together with the existing reflectometer the measurement of radial correlation length and decorrelation time becomes available. Both reflectometers are computer controlled and allow to program individual frequency sequences and the duration of each frequency step. With the existing poloidal antenna array at ?=0° and on top of the vacuum vessel, the system allows the measurement of radial correlation and poloidal correlations at the same time. First experiments have been performed and the results on the radial correlation length of density fluctuations in a fusion plasma are presented. PMID:21133466

Krämer-Flecken, A; Soldatov, S; Vowinkel, B; Müller, P

2010-11-01

178

Correlation reflectometry at TEXTOR  

SciTech Connect

In high temperature fusion plasmas the transport of energy and particles is commonly believed to be driven by turbulence. Turbulence quantities as correlation length and decorrelation time are important for the confinement properties of a plasma. Besides other diagnostics, correlation reflectometry has proven to be a suitable tool for the measurement of turbulence properties. At the medium sized Toroidal EXperiment for Technical Oriented Research (TEXTOR) the existing correlation reflectometry has been recently upgraded. A new reflectometer based on a microwave synthesizer has been developed and installed for the investigation of turbulence properties in a fusion plasma. Together with the existing reflectometer the measurement of radial correlation length and decorrelation time becomes available. Both reflectometers are computer controlled and allow to program individual frequency sequences and the duration of each frequency step. With the existing poloidal antenna array at {theta}=0 deg. and on top of the vacuum vessel, the system allows the measurement of radial correlation and poloidal correlations at the same time. First experiments have been performed and the results on the radial correlation length of density fluctuations in a fusion plasma are presented.

Kraemer-Flecken, A. [Institute for Energy Research (Plasma Physics), Forschungszentrum Juelich, EURATOM Association, D-52425 Juelich (Germany); Soldatov, S. [Department of Applied Physics, Ghent University, Rozier 44, 9000 Ghent (Belgium); Vowinkel, B. [1. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Strasse 77, 50937 Koeln (Germany); Mueller, P. [Argelander-Institut fuer Astronomie, Auf dem Huegel 71, 53121 Bonn (Germany)

2010-11-15

179

Two new density correlations  

SciTech Connect

The Liquid density predicted by the Peng-Robinson (P-R) equation of state is often off by 10% or more at temperature and pressure conditions encountered in most reservoirs. To improve the density predictions, two new density correlations have been developed. The first correlation is based on the chain-of-rotators (COR) equation of state and the second is based on the three-parameter Peng-Robinson (PR3) equation of state. The COR correlation is applicable to wider pressure and temperature ranges, but is computationally expensive. It is suited for interpreting fluid-analysis data, where no extensive phase-behavior calculations are needed. On the other hand, the PR3 correlation is more limited in its application range, but is computationally more efficient. It is particularly suited for compositional reservoir simulation where many density calculations are repeatedly carried out. In general, both correlations are comparable to the Standing-Katz correlation for liquid-density calculation and comparable to the P-R equation of state for vapor-density calculation. However, they are superior to the Standing-Katz correlation for liquid mixtures near critical points or liquid mixtures at high pressures. Overall, the COR equation of state gives an average prediction error of 1.9% for liquid densities and 2.7% for vapor densities, and the PR3 gives an average prediction error of less than 2% for both liquid and vapor densities.

Chien, M.C.H.; Monroy, M.R.

1986-01-01

180

Hadronic Correlations and Fluctuations  

SciTech Connect

We will provide a review of some of the physics which can be addressed by studying fluctuations and correlations in heavy ion collisions. We will discuss Lattice QCD results on fluctuations and correlations and will put them into context with observables which have been measured in heavy-ion collisions. Special attention will be given to the QCD critical point and the first order co-existence region, and we will discuss how the measurement of fluctuations and correlations can help in an experimental search for non-trivial structures in the QCD phase diagram.

Koch, Volker

2008-10-09

181

Pairwise Correlations of Eight Strong DIBs and N(H), N(H2), and EB-V  

NASA Astrophysics Data System (ADS)

We discuss the correlations between equivalent widths of eight diffuse interstellar bands (DIBs), and examine their correlations with the column densities of atomic hydrogen (N(H)) and molecular hydrogen (N(H2)), and EB-V. The DIBs are centered at ? 5780.5, 6204.5, 6283.8, 6196.0, 6613.6, 5705.1, 5797.1, and 5487.7, in decreasing order of Pearson's correlation coefficient with N(H), which ranges from 0.94 to 0.78. The equivalent width of 5780.5 is better correlated with column density of H than with EB-V or H2, and the same is true for six of the seven other DIBs presented here. Hence, they are not preferentially located in the densest, most UV shielded parts of interstellar clouds. These eight strong DIBs are not correlated well enough with each other to suggest they come from the same carrier. However, the correlations may be useful in deriving interstellar parameters, such as N(H) from W(5780.5), when more direct methods are not available. Our future plans include mapping the distribution of DIBs in interstellar clouds, closer examination of the excellent correlation between 5705.1 and 5780.5 (almost as good as the near perfect correlation of 6613.6 with 6196.0), and precise measurements of broad DIBs.

Friedman, Scott D.; York, D. G.; McCall, B. J.; Dahlstrom, J.; Sonnentrucker, P.; Welty, D. E.; Drosback, M. M.; Hobbs, L. M.; Rachford, B. L.; Snow, T. P.

2011-10-01

182

Correlation between single limb support phase and self-evaluation questionnaires in knee osteoarthritis populations  

PubMed Central

Purpose. To investigate the correlation between single limb support (SLS) phase (% of gait cycle) and the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) questionnaire and Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36 Health Survey) in patients with knee osteoarthritis (OA). Method. A prospective observational study was employed with 125 adults with bilateral medial compartment symptomatic knee OA who underwent a physical and radiographic evaluation. Velocity, step length and SLS were assessed by a computerised mat (GAITRite). Patients completed the WOMAC and SF-36 Health Survey questionnaires. Results. Statistical analysis examined the correlations between SLS and both questionnaires, between Kellgren & Lawrence (K&L) scores and both questionnaires and between SLS correlations and K&L correlations. We found significantly stronger correlations between SLS and WOMAC-pain, WOMAC-function, the SF-36 pain sub-category, velocity and step length than between K&L scores and these parameters (Pearson's r— 0.50 vs. 0.26, 0.53 vs. 0.34, 0.50 vs. 023, 0.81 vs. 0.33, 0.77 vs. 0.37, respectively; all p 5 0.05). Significant differences in SLS were found over WOMAC-pain, WOMAC-function and SF-36 overall score quartiles (p 5 0.05 for all). Conclusion. We recommend integrating SLS as an objective parameter in the comprehensive evaluation of patients with knee OA.

DEBI, RONEN; MOR, AMIT; SEGAL, GANIT; SEGAL, OFER; AGAR, GABRIEL; DEBBI, EYTAN; HALPERIN, NAHUM; HAIM, AMIR; ELBAZ, AVI

2011-01-01

183

Expression of vimentin in breast carcinoma, its correlation with Ki67 and other histopathological parameters.  

PubMed

Context: Vimentin is a mesenchymal marker, known to express in some epithelial carcinomas. Aims: 1. To find out the expression of vimentin in infiltrating ductal carcinoma of breast (not otherwise specified), 2. To find out the correlation between expression of vimentin and prognostic markers such as tumor size, tumor grade, lymph node status, proliferation index (measured by Ki 67), and Nottingham prognostic index (NPI). Materials and Methods: Study was done at Department of Pathology; 50 cases of infiltrating ductal carcinoma (NOS) were studied for tumor grade; immunohistochemistry was done using antibodies against vimentin and Ki 67. Percentages of positive cells were documented. An immunoscore was also calculated for vimentin. Vimentin expression was correlated with tumor size, lymph node status, Nottingham prognostic index, and Ki 67. Statistical analysis used: statistical correlation was done using Pearson's chi-square test. A P value less than 0.01 was considered significant. Results: Vimentin expression was seen in 18% of cases. Its expression correlated with high tumor grade and high growth fraction (P value < 0.01). It did not correlate with lymph node status, tumor size, and NPI. Conclusions: Increased vimentin expression is associated with bad prognostic factors. Immunohistochemistry with vimentin may be helpful in knowing the prognosis in cases of infiltrating ductal carcinoma of breast (NOS). PMID:24061457

Hemalatha, A; Suresh, T N; Harendra Kumar, M L

184

Comprehensive analysis of correlation coefficients estimated from pooling heterogeneous microarray data  

PubMed Central

Background The synthesis of information across microarray studies has been performed by combining statistical results of individual studies (as in a mosaic), or by combining data from multiple studies into a large pool to be analyzed as a single data set (as in a melting pot of data). Specific issues relating to data heterogeneity across microarray studies, such as differences within and between labs or differences among experimental conditions, could lead to equivocal results in a melting pot approach. Results We applied statistical theory to determine the specific effect of different means and heteroskedasticity across 19 groups of microarray data on the sign and magnitude of gene-to-gene Pearson correlation coefficients obtained from the pool of 19 groups. We quantified the biases of the pooled coefficients and compared them to the biases of correlations estimated by an effect-size model. Mean differences across the 19 groups were the main factor determining the magnitude and sign of the pooled coefficients, which showed largest values of bias as they approached ±1. Only heteroskedasticity across the pool of 19 groups resulted in less efficient estimations of correlations than did a classical meta-analysis approach of combining correlation coefficients. These results were corroborated by simulation studies involving either mean differences or heteroskedasticity across a pool of N?>?2 groups. Conclusions The combination of statistical results is best suited for synthesizing the correlation between expression profiles of a gene pair across several microarray studies.

2013-01-01

185

Correlation between ORange® (Gen 1, pseudophakic) intraoperative refraction and 1-week postcataract surgery autorefraction  

PubMed Central

Background: This study aimed to find the strength of the correlation between ORange® (intraoperative wavefront aberrometer) objective refraction during pseudophakic cataract surgery (Gen 1) and 1-week objective autorefraction postcataract surgery in order to establish the clinical degree of confidence in the ORange. Gen 1 was used because Gen 2 was not available at the time of the study. However, Gen 1 can still be a good reference. Methods: Thirty-two consecutive eyes were included in this prospective nonrandomized study. ORange was used after phacoemulsification and intraocular lens implantation. There were no complications and no withdrawals from the study. The refraction data from the ORange were recorded in spherical equivalents and put into Excel. One week postoperatively, autorefraction was done and the data were again recorded in spherical equivalents and put into Excel. Both sets of data were then transferred to SPSS for a correlation study. Because ORange is an objective refractor, it is necessary to use another objective refractor, such as the Zeiss Autorefractor, for comparison. Measurement at 1 week postoperatively is for cornea clearance for autorefraction and is the closest time to intraoperative assessment for comparison. Results: The Pearson correlation was r = +0.56, P < 0.01, which qualifies for a moderate or good correlation (0.5–0.75). Conclusion: Intraoperative refraction using the ORange Gen 1 after cataract surgery and intraocular lens implantation is moderate to good when correlated with objective autorefraction 1 week after cataract surgery.

Chen, Ming

2011-01-01

186

Human gene correlation analysis (HGCA): A tool for the identification of transcriptionally co-expressed genes  

PubMed Central

Background Bioinformatics and high-throughput technologies such as microarray studies allow the measure of the expression levels of large numbers of genes simultaneously, thus helping us to understand the molecular mechanisms of various biological processes in a cell. Findings We calculate the Pearson Correlation Coefficient (r-value) between probe set signal values from Affymetrix Human Genome Microarray samples and cluster the human genes according to the r-value correlation matrix using the Neighbour Joining (NJ) clustering method. A hyper-geometric distribution is applied on the text annotations of the probe sets to quantify the term overrepresentations. The aim of the tool is the identification of closely correlated genes for a given gene of interest and/or the prediction of its biological function, which is based on the annotations of the respective gene cluster. Conclusion Human Gene Correlation Analysis (HGCA) is a tool to classify human genes according to their coexpression levels and to identify overrepresented annotation terms in correlated gene groups. It is available at: http://biobank-informatics.bioacademy.gr/coexpression/.

2012-01-01

187

Drug Correlation Spectroscopy.  

National Technical Information Service (NTIS)

The parameters pertinent to the development of a compact instrument to detect and reliably identify drugs and related compounds in bulk and in urine were investigated. The program was conducted with emphasis on using correlation interferometry. Studies in...

C. E. Moeller K. C. Brog R. H. Barnes R. J. Jakobsen R. P. Kenan

1973-01-01

188

Scanning image correlation spectroscopy.  

PubMed

Molecular interactions are at the origin of life. How molecules get at different locations in the cell and how they locate their partners is a major and partially unresolved question in biology that is paramount to signaling. Spatio-temporal correlations of fluctuating fluorescently tagged molecules reveal how they move, interact, and bind in the different cellular compartments. Methods based on fluctuations represent a remarkable technical advancement in biological imaging. Here we discuss image analysis methods based on spatial and temporal correlation of fluctuations, raster image correlation spectroscopy, number and brightness, and spatial cross-correlations that give us information about how individual molecules move in cells and interact with partners at the single molecule level. These methods can be implemented with a standard laser scanning microscope and produce a cellular level spatio-temporal map of molecular interactions. PMID:22415853

Digman, Michelle A; Gratton, Enrico

2012-03-13

189

About photon correlations  

NASA Astrophysics Data System (ADS)

Some general properties of photon correlations are discussed in a simple way through an analysis of the two-detector measurement scheme. It is shown that the assumption of the discreteness of the random process leads directly to the conclusion that the zero-delay value of the correlation function is only bound to be non-negative. The adopted approach allows discussing in a more intuitive way the photon correlation properties of different optical fields, including non-classical fields presenting an apparent violation of the Cauchy-Schwarz inequality. The comparison between the two- and the single-detector experiment clarifies the role of the operator ordering in the definition of the correlation function.

Degiorgio, V.

2013-10-01

190

Generalized linear correlation filters  

NASA Astrophysics Data System (ADS)

We present two generalized linear correlation filters (CFs) that encompass most of the state-of-the-art linear CFs. The common criteria that arc used in linear CF design are the mean squared error (MSE), output noise variance (ONV), and average similarity measure (ASM). We present a simple formulation that uses an optimal tradeoff among these criteria both constraining and not constraining the correlation peak value, and refer to them as generalized Constrained Correlation Filter (CCF) and Unconstrained Couelation Filter (UCF). We show that most state-of-the-art linear CFs arc subsets of these filters. We present a technique for efficient UCF computation. We also introduce the modified CCF (mCCF) that chooses a unique correlation peak value for each training image, and show that mCCF usually outperforms both UCF and CCF.

Rodriguez, Andres; Vijaya Kumar, B. V. K.

2013-05-01

191

Correlation Analysis of Electrocardiograms.  

National Technical Information Service (NTIS)

A method for the interpretation of electrocardiographic waveforms by correlation analysis has been investigated. Both the autocorrelation function and the crosscorrelation function are employed in the analysis. The electrocardiographic signals of thirty-s...

W. G. Huston

1972-01-01

192

CARMA Correlator Graphical Setup  

NASA Astrophysics Data System (ADS)

CARMA Correlator Graphical Setup (CGS) is a Java tool to help users of the Combined Array for Research in Millimeter-wave Astronomy (CARMA) plan observations. It allows users to visualize the correlator bands overlaid on frequency space and view spectral lines within each band. Bands can be click-dragged to anywhere in frequency and can have their properties (e.g., bandwidth, quantization level, rest frequency) changed interactively. Spectral lines can be filtered from the view by expected line strength to reduce visual clutter. Once the user is happy with the setup, a button click generates the Python commands needed to configure the correlator within the observing script. CGS can also read Python configurations from an observing script and reproduce the correlator setup that was used. Because the correlator hardware description is defined in an XML file, the tool can be rapidly reconfigured for changing hardware. This has been quite useful as CARMA has recently commissioned a new correlator. The tool was written in Java by high school summer interns working in UMD's Laboratory for Millimeter Astronomy and has become an essential planning tool for CARMA PIs.

Wu, D.; Shaya, B.; Pound, M. W.

2011-07-01

193

On fuzzy correlations.  

PubMed

A general framework for dealing with numerical measurements in an approximate, uncertain, or fuzzy environment is presented. A fuzzy measurement is defined. It possesses several unique properties, which arise from its physical nature and distinguish it from concepts such as the fuzzy number. These properties, which include the fuzzy correlation term and the fuzzy Equality relation, follow directly from physical considerations. The introduction of the fuzzy correlation term provides a mathematical tool for representing any correlation relations, which may exist between different fuzzy measurements. The main function of the fuzzy correlation term is to eliminate, or filter out, measurement values that are unlikely, given other fuzzy measurements. Thus, using the fuzzy correlation term, the range of possible measurement values is limited by physical realities. The information represented by the fuzzy correlation term is shown to be of great value in providing a wider picture of reality than it is possible to obtain by simply considering individual fuzzy measurements. Arithmetic operations on fuzzy measurements and functions of fuzzy measurements are also discussed, leading to the derivation of the fuzzy Riemann integral and its applications. PMID:18244801

Ramot, D; Milo, R; Friedman, M; Kandel, A

2001-01-01

194

Terrain correlation suitability  

NASA Astrophysics Data System (ADS)

Terrain-aided navigation (TAN), also referred to as terrain correlation, is a technique that has proven to be highly successful as a navigational aid for autonomous, unmanned guided missiles. Qualitatively speaking, the effectiveness of terrain correlation is a function of signal- to-noise (S/N) ratio. The signal is equivalent to terrain roughness, while the noise is the combination of reference map errors, radar altimeter errors, and INS altitude errors. However, it is not practical to use only a single parameter, such as S/N, to define the suitability of terrain correlation. This paper discusses the shortcomings of the conventional single-parameter approach to the terrain contour matching algorithm (TERCOM) used in cruise missile guidance systems scene selection. A more comprehensive technique is then presented that analyzes the terrain correlation suitability based on a Monte Carlo simulation technique. A figure-of-merit (FOM) for terrain correlation suitability, computed from sample statistics, is introduced and simulation results are provided to illustrate the feasibility of using a multi-parameter FOM technique. The preliminary results indicate that the proposed approach could provide a cost effective enhancement to the TAN-based mission planning process.

Tang, Wang; McClintock, Robert L.

1994-07-01

195

Strongly correlated materials.  

PubMed

Strongly correlated materials are profoundly affected by the repulsive electron-electron interaction. This stands in contrast to many commonly used materials such as silicon and aluminum, whose properties are comparatively unaffected by the Coulomb repulsion. Correlated materials often have remarkable properties and transitions between distinct, competing phases with dramatically different electronic and magnetic orders. These rich phenomena are fascinating from the basic science perspective and offer possibilities for technological applications. This article looks at these materials through the lens of research performed at Rice University. Topics examined include: Quantum phase transitions and quantum criticality in "heavy fermion" materials and the iron pnictide high temperature superconductors; computational ab initio methods to examine strongly correlated materials and their interface with analytical theory techniques; layered dichalcogenides as example correlated materials with rich phases (charge density waves, superconductivity, hard ferromagnetism) that may be tuned by composition, pressure, and magnetic field; and nanostructure methods applied to the correlated oxides VO? and Fe?O?, where metal-insulator transitions can be manipulated by doping at the nanoscale or driving the system out of equilibrium. We conclude with a discussion of the exciting prospects for this class of materials. PMID:22893361

Morosan, Emilia; Natelson, Douglas; Nevidomskyy, Andriy H; Si, Qimiao

2012-08-15

196

No correlation between slip reduction in low-grade spondylolisthesis or change in neuroforaminal morphology and clinical outcome  

PubMed Central

Background In instrumented posterolateral fusion reduction of a spondylolisthesis is appealing on theoretical grounds since this may lead to indirect decompression of the entrapped nerve roots. However, there is no consensus in the literature whether a beneficial effect of reduction on outcome can be expected. The objective of the current study was to evaluate whether a correlation between the extent of listhesis reduction and clinical improvement could be established. Methods From two ongoing prospective studies 72 patients with a single-level instrumented posterolateral lumbar fusion for low-grade spondylolisthesis (isthmic/degenerative 51/21) were evaluated. Radiographs and clinical outcome scores were available at baseline, 6 weeks and 1 year after surgery. Changes in neuroforaminal morphology were measured on calibrated radiographs. These changes in radiographic parameters were correlated to clinical outcome (Visual Analogue Score (VAS) leg pain, Oswestry Disability Index (ODI)). Fusion status was assessed on Computed Tomography-scan at one year. Results A mean spondylolisthesis of 25 percent was reduced to 15 percent at 6 weeks with some loss of reduction to 17 percent at one year. The VAS and ODI significantly improved at both time intervals after surgery (p?correlations could be established between the extent of slip reduction and improvement in VAS or ODI (Pearson’s correlation ?0.2 and 0.07 respectively at one year); this also accounted for the other radiographic parameters. A fusion rate of 64 percent was seen on CT-scan. Conclusions Clinical outcome was not related to the obtained radiographic reduction of the slipped vertebra in patients with a lumbar fusion for low grade spondylolisthesis. Loss of reduction or non-union on CT-scans had no effect on the clinical outcome. Reduction of a low-grade spondylolisthesis in spinal fusion is appealing, however, there is no evidence that it positively affects clinical outcome on the short term. Trial registration ISRCTN43648350

2013-01-01

197

Correlations in Quantum Physics  

NASA Astrophysics Data System (ADS)

We provide a historical perspective of how the notion of correlations has evolved within quantum physics. We begin by reviewing Shannon's information theory and its first application in quantum physics, due to Everett, in explaining the information conveyed during a quantum measurement. This naturally leads us to Lindblad's information theoretic analysis of quantum measurements and his emphasis of the difference between the classical and quantum mutual information. After briefly summarizing the quantification of entanglement using these ideas, we arrive at the concept of quantum discord, which naturally captures the boundary between entanglement and classical correlations. Finally we discuss possible links between discord, which the generation of correlations in thermodynamic transformations of coupled harmonic oscillators.

Dorner, Ross; Vedral, Vlatko

2013-01-01

198

Cluster correlations in multifragmentation  

NASA Astrophysics Data System (ADS)

The possibility of strong cluster correlations in multifragmentation reactions is explored based on the antisymmetrized molecular dynamics calculations. The number of emitted protons, which is smaller than predicted by usual transport models, can be explained by introducing the two-nucleon collision process to the final states in which one or both of the scattered nucleons may form clusters (such as deuterons, tritons and ? particles) with other nucleons in the system. The cluster correlation has strong impacts on the whole collision dynamics. The multifragmentation data at 50 MeV/nucleon and above are well reproduced with this strong cluster correlation if pairs of clusters with small relative velocities are assumed to form light nuclei such as Li and Be isotopes. An analysis is shown on symmetry energy effects in emission of nucleons and clusters.

Ono, Akira

2013-03-01

199

Genuine correlations of tripartite system  

NASA Astrophysics Data System (ADS)

We define genuine total, classical and quantum correlations in tripartite systems. The genuine tripartite quantum discord can be interpreted as `quantum advantage' in tripartite superdense coding. We find in a symmetrical tripartite state, for total correlation and classical correlation, the genuine tripartite correlations are no less than the pair-wise correlations. However, the genuine quantum tripartite correlation can be surpassed by the pair-wise quantum correlations. Analytical expressions for genuine tripartite correlations are obtained for pure states and rank-2 symmetrical states. The genuine correlations in both entangled and separable states are calculated.

Zhao, Liming; Hu, Xueyuan; Yue, R.-H.; Fan, Heng

2013-07-01

200

Correlation of free-response and receiver-operating-characteristic area-under-the-curve estimates: Results from independently conducted FROC/ROC studies in mammography  

PubMed Central

Purpose: From independently conducted free-response receiver operating characteristic (FROC) and receiver operating characteristic (ROC) experiments, to study fixed-reader associations between three estimators: the area under the alternative FROC (AFROC) curve computed from FROC data, the area under the ROC curve computed from FROC highest rating data, and the area under the ROC curve computed from confidence-of-disease ratings. Methods: Two hundred mammograms, 100 of which were abnormal, were processed by two image-processing algorithms and interpreted by four radiologists under the FROC paradigm. From the FROC data, inferred-ROC data were derived, using the highest rating assumption. Eighteen months afterwards, the images were interpreted by the same radiologists under the conventional ROC paradigm; conventional-ROC data (in contrast to inferred-ROC data) were obtained. FROC and ROC (inferred, conventional) data were analyzed using the nonparametric area-under-the-curve (AUC), (AFROC and ROC curve, respectively). Pearson correlation was used to quantify the degree of association between the modality-specific AUC indices and standard errors were computed using the bootstrap-after-bootstrap method. The magnitude of the correlations was assessed by comparison with computed Obuchowski-Rockette fixed reader correlations. Results: Average Pearson correlations (with 95% confidence intervals in square brackets) were: Corr(FROC, inferred ROC) = 0.76[0.64, 0.84] > Corr(inferred ROC, conventional ROC) = 0.40[0.18, 0.58] > Corr (FROC, conventional ROC) = 0.32[0.16, 0.46]. Conclusions: Correlation between FROC and inferred-ROC data AUC estimates was high. Correlation between inferred- and conventional-ROC AUC was similar to the correlation between two modalities for a single reader using one estimation method, suggesting that the highest rating assumption might be questionable.

Zanca, Federica; Hillis, Stephen L.; Claus, Filip; Van Ongeval, Chantal; Celis, Valerie; Provoost, Veerle; Yoon, Hong-Jun; Bosmans, Hilde

2012-01-01

201

Investigation of teacher trainees’ psychological well-being in terms of time management  

Microsoft Academic Search

This study is on teacher trainees’ well-being in terms of time management, gender, family relationships, incomes, parents’ education levels, residence and grade averages. The participants were 186 students between the ages of 20 and 25. The data were collected with a personal information form, time management inventory and psychological well-being scale and analyzed with Pearson correlation technique, t-test and one-way

Jale Eldeleklio?lu; Aynur Y?lmaz; Filiz Gültekin

2010-01-01

202

How employees' perception of information technology application and their knowledge management capacity influence organisational performance  

Microsoft Academic Search

This study investigates how workers' gender, work experience, designated division, and appointment affect (i) their perception of information technology (IT) within the organisation, (ii) their self-perceived capacity in knowledge management (KM), and (iii) their perception of organisational performance (OP). Furthermore, the study also examines the correlation among the above three dimensions by using t-test, one-way Analysis of Variance (ANOVA), Pearson

Yen-Ku Kuo; Kung-Don Ye

2010-01-01

203

Correlation ion mobility spectroscopy  

SciTech Connect

Correlation ion mobility spectrometry (CIMS) uses gating modulation and correlation signal processing to improve IMS instrument performance. Closely spaced ion peaks can be resolved by adding discriminating codes to the gate and matched filtering for the received ion current signal, thereby improving sensitivity and resolution of an ion mobility spectrometer. CIMS can be used to improve the signal-to-noise ratio even for transient chemical samples. CIMS is especially advantageous for small geometry IMS drift tubes that can otherwise have poor resolution due to their small size.

Pfeifer, Kent B. (Los Lunas, NM); Rohde, Steven B. (Corrales, NM)

2008-08-26

204

Spinning conformal correlators  

NASA Astrophysics Data System (ADS)

We develop the embedding formalism for conformal field theories, aimed at doing computations with symmetric traceless operators of arbitrary spin. We use an indexfree notation where tensors are encoded by polynomials in auxiliary polarization vectors. The efficiency of the formalism is demonstrated by computing the tensor structures allowed in n-point conformal correlation functions of tensors operators. Constraints due to tensor conservation also take a simple form in this formalism. Finally, we obtain a perfect match between the number of independent tensor structures of conformal correlators in d dimensions and the number of independent structures in scattering amplitudes of spinning particles in ( d + 1)-dimensional Minkowski space.

Costa, Miguel S.; Penedones, João; Poland, David; Rychkov, Slava

2011-11-01

205

Scatter Plots and Correlation  

NSDL National Science Digital Library

This webpage will be helpful for students learning to analyze data and create scatter plots. Specifically, these examples demonstrate how to determine correlations, or relationships, between sets of data. The slope of the line created by the data will show if there is a positive, negative, or no correlation between the sets of data. At the bottom of the page, a link is included for students who would like to learn how to create scatter plots with a graphing calculator. These examples are explained clearly and include useful graphics.

Roberts, Donna

2012-01-01

206

A maximum entropy test for evaluating higher-order correlations in spike counts.  

PubMed

Evaluating the importance of higher-order correlations of neural spike counts has been notoriously hard. A large number of samples are typically required in order to estimate higher-order correlations and resulting information theoretic quantities. In typical electrophysiology data sets with many experimental conditions, however, the number of samples in each condition is rather small. Here we describe a method that allows to quantify evidence for higher-order correlations in exactly these cases. We construct a family of reference distributions: maximum entropy distributions, which are constrained only by marginals and by linear correlations as quantified by the Pearson correlation coefficient. We devise a Monte Carlo goodness-of-fit test, which tests--for a given divergence measure of interest--whether the experimental data lead to the rejection of the null hypothesis that it was generated by one of the reference distributions. Applying our test to artificial data shows that the effects of higher-order correlations on these divergence measures can be detected even when the number of samples is small. Subsequently, we apply our method to spike count data which were recorded with multielectrode arrays from the primary visual cortex of anesthetized cat during an adaptation experiment. Using mutual information as a divergence measure we find that there are spike count bin sizes at which the maximum entropy hypothesis can be rejected for a substantial number of neuronal pairs. These results demonstrate that higher-order correlations can matter when estimating information theoretic quantities in V1. They also show that our test is able to detect their presence in typical in-vivo data sets, where the number of samples is too small to estimate higher-order correlations directly. PMID:22685392

Onken, Arno; Dragoi, Valentin; Obermayer, Klaus

2012-06-07

207

A Maximum Entropy Test for Evaluating Higher-Order Correlations in Spike Counts  

PubMed Central

Evaluating the importance of higher-order correlations of neural spike counts has been notoriously hard. A large number of samples are typically required in order to estimate higher-order correlations and resulting information theoretic quantities. In typical electrophysiology data sets with many experimental conditions, however, the number of samples in each condition is rather small. Here we describe a method that allows to quantify evidence for higher-order correlations in exactly these cases. We construct a family of reference distributions: maximum entropy distributions, which are constrained only by marginals and by linear correlations as quantified by the Pearson correlation coefficient. We devise a Monte Carlo goodness-of-fit test, which tests - for a given divergence measure of interest - whether the experimental data lead to the rejection of the null hypothesis that it was generated by one of the reference distributions. Applying our test to artificial data shows that the effects of higher-order correlations on these divergence measures can be detected even when the number of samples is small. Subsequently, we apply our method to spike count data which were recorded with multielectrode arrays from the primary visual cortex of anesthetized cat during an adaptation experiment. Using mutual information as a divergence measure we find that there are spike count bin sizes at which the maximum entropy hypothesis can be rejected for a substantial number of neuronal pairs. These results demonstrate that higher-order correlations can matter when estimating information theoretic quantities in V1. They also show that our test is able to detect their presence in typical in-vivo data sets, where the number of samples is too small to estimate higher-order correlations directly.

Onken, Arno; Dragoi, Valentin; Obermayer, Klaus

2012-01-01

208

Skid Tester Correlation Study.  

National Technical Information Service (NTIS)

A correlation study was conducted between the California Skid Tester and an ASTM Skid Tester. Coefficients of friction were obtained with the California unit at the standard test conditions of locked wheel, smooth tire, wet pavement and a speed of 50 mile...

G. B. Sherman M. H. Johnson G. W. Mann R. R. Svetich

1971-01-01

209

Sensory Correlations in Autism  

ERIC Educational Resources Information Center

|This study examined the relationship between auditory, visual, touch, and oral sensory dysfunction in autism and their relationship to multisensory dysfunction and severity of autism. The Sensory Profile was completed on 104 persons with a diagnosis of autism, 3 to 56 years of age. Analysis showed a significant correlation between the different…

Kern, Janet K.; Trivedi, Madhukar H.; Grannemann, Bruce D.; Garver, Carolyn R.; Johnson, Danny G.; Andrews, Alonzo A.; Savla, Jayshree S.; Mehta, Jyutika A.; Schroeder, Jennifer L.

2007-01-01

210

Trend in correlated proportions  

Microsoft Academic Search

A random effects probit model is developed for the case in which the same units are sampled repeatedly at each level of an independent variable. Because the observed proportions may be correlated under these conditions, estimating their trend with respect to the independent variable is no longer a standard problem for probit, logit or loglinear analysis. Using a qualitative analogue

Robert D. Gibbons; R. Darrell Bock

1987-01-01

211

Correlates of School Stress.  

ERIC Educational Resources Information Center

As part of a continuing series of research studies on stress in schools, this study examined the construct validity of peripheral temperature at the fingertips as a measure of school stress. Measurements were made in classes selected at random from 11 volunteer schools in South Carolina. Three types of correlational studies were undertaken: (1)…

Matthews, Doris B.

212

Sensory Correlations in Autism  

ERIC Educational Resources Information Center

This study examined the relationship between auditory, visual, touch, and oral sensory dysfunction in autism and their relationship to multisensory dysfunction and severity of autism. The Sensory Profile was completed on 104 persons with a diagnosis of autism, 3 to 56 years of age. Analysis showed a significant correlation between the different…

Kern, Janet K.; Trivedi, Madhukar H.; Grannemann, Bruce D.; Garver, Carolyn R.; Johnson, Danny G.; Andrews, Alonzo A.; Savla, Jayshree S.; Mehta, Jyutika A.; Schroeder, Jennifer L.

2007-01-01

213

Sensory correlations in autism  

Microsoft Academic Search

This study examined the relationship between auditory, visual, touch, and oral sensory dysfunction in autism and their relationship to multisensory dysfunction and severity of autism. The Sensory Profile was completed on 104 persons with a diagnosis of autism, 3 to 56 years of age. Analysis showed a significant correlation between the different processing modalities using total scores. Analysis also showed

Janet K. Kern; Madhukar H. Trivedi; Bruce D. Grannemann; Carolyn R. Garver; Danny G. Johnson; Alonzo A. Andrews; Jayshree S. Savla; Jyutika A. Mehta; Jennifer L. Schroeder

2007-01-01

214

Correlation-Capability Studies  

Microsoft Academic Search

In missile production, a recurring problem is the measurement of derived parameters. Unlike volts, amperes, and ohms, these parameters do not lend themselves to standard black-box test equipment. Nevertheless, whatever test equipment is used for their measurement still must be closely correlated to yield consistent and reliable measures. The Span Plan, which has been successful largely because it uses range

Howard L. Berke

1961-01-01

215

Correlation and Regression  

NSDL National Science Digital Library

This applet allows the user to explore basic principles of correlation and regression. The user can manipulate points on a scatterplot. The user can then place a regression line on the plot and evaluate the resulting sums of squares error. An interesting feature of this applet is that it allows viewing of the sum of squares error as squares.

Berger, Dale

2008-12-24

216

Graphic Correlation Exercise  

NSDL National Science Digital Library

This is a graphic correlation lab exercise. It uses real data from a peer-reviewed journal publication by Lucy Edwards (1989). (I have manipulated the data set a little bit.) Students can finish the activity in two hours or less.

Stephen, Dan

217

Informationally optimal correlation  

Microsoft Academic Search

This papers studies how to decompose a correlated distribution of actions, as a convex combination of indepedent distribution, in a way that is optimal for an information theory criterion. A characterization of optimal solutions is provided for 2?2 sets of actions. Then we give an application to the exact computation of maxmin values in some repeted games.

Olivier Gossner; Rida Laraki; Tristan Tomala

2009-01-01

218

Affective correlates of trichotillomania  

Microsoft Academic Search

Affective correlates of hair pulling were investigated in a sample of 44 participants diagnosed with trichotillomania (TM). Participants completed the Hair Pulling Survey on which they rated the intensity of ten different affective states across three different phases of hair pulling (before, during and after). Repeated measures analysis of variance was used to examine the change of emotional experience across

G. J Diefenbach; S Mouton-Odum; M. A Stanley

2002-01-01

219

Correlation functions on cylinders  

SciTech Connect

We have obtained the complete finite-size structure of energy-density correlation functions at all temperatures defined for two-dimensional Ising models on cylindrical lattices, extending the original results of Hecht. This reveals novel structure in terms of winding numbers and confirms predictions from conformal invariance theory to leading order.

Abraham, D.B. (Department of Physics, Theoretical Physics, 1 Keble Road, Oxford OX1 3NP (United Kingdom)); O'Connor, D. (Dublin Institute for Advanced Studies, 10 Burlington Road, Dublin 4 (Ireland)); Parry, A.O. (Department of Mathematics, Imperial College of Science, Technology and Medicine, 180 Queen's Gate, London SW7 2BZ (United Kingdom)); Upton, P.J. (Department of Physics, Theoretical Physics, 1 Keble Roade, Oxford OX1 3NP (United Kingdom) Dublin Institute for Advanced Studies, 10 Burlington Road, Dublin 4 (Ireland))

1994-09-26

220

Temperament correlates with training success in adult rhesus macaques.  

PubMed

In recent years there has been a marked increase in awareness of issues involving the psychological well-being of nonhuman primates (NHPs) used in biomedical research. As a result, many facilities are starting to train primates to voluntarily cooperate with veterinary, husbandry, and research procedures, such as remaining still for blood draws or injections. Such training generally reduces the stress associated with these procedures, resulting in calmer animals and, ultimately, better research models. However, such training requires great investments in time, and there can be vast individual differences in training success. Some animals learn tasks quickly, while others make slower progress in training. In this study, we examined whether temperament, as measured by response to a novel food object, correlated with the amount of time it took to train 20 adult female rhesus macaques to perform a simple task. The monkeys were categorized as "exploratory" (i.e., inspected a novel object placed in the home cage within 10 sec), "moderate" (i.e., inspected the object within 10-180 sec), or "inhibited" (i.e., did not inspect the object within 3 min). We utilized positive reinforcement techniques to train the monkeys to touch a target (PVC pipe shaped like an elbow) hung on their cage. Temperament correlated with training success in this study (Pearson chi2=7.22, df=2, P=0.03). We easily trained over 75% of the animals that inspected the novel food (i.e., exploratory or moderate individuals) to touch the target. However, only 22% of the inhibited monkeys performed the task. By knowing which animals may not respond to conventional training methods, we may be able to develop alternate training techniques to address their specific needs. In addition, these results will allow us to screen monkeys to be assigned to research projects in which they will be trained, with the goal of obtaining the best candidates for those studies. PMID:15645460

Coleman, Kristine; Tully, Leigh Ann; McMillan, Jennifer L

2005-01-01

221

Correlation between Chronological Age, Dental Age and Skeletal Age among Monozygoyic and Dizygotic Twins  

PubMed Central

Introduction: Chronological age, dental development, height and weight measurements, sexual maturation characteristics and skeletal age are some biological indicators that have been used to identify time of growth. Many researchers have agreed that skeletal maturity is closely related to the craniofacial growth, and bones of hand and wrist are reliable parameters in assessing it. The complete hand and wrist radiograph involves 30 bones and assessment of these bones is one elaborate task. The present study is therefore, undertaken to assess the correlation between the chronological age, dental age and skeletal ages among different types of twins. Materials and Methods: The study consisted of 60 subjects (30 twins) aged 8 to 16 years, divided into group of 10 monozygotic, 10 dizygotic and 10 mixed sex twins. The sample was selected from Twin Survey- 2008 conducted by Department of Orthodontics and Dentofacial Orthopaedics, Sree Balaji Dental College and Hospital, Chennai. Their zygosity was determined by sex, blood groups and by the parent. The chronological age was measured by the date of birth given by the parents. Panoramic and hand wrist x-rays were taken. Dental age was assessed by Demerjian et al method and skeletal age by Greulich and Pyle method. The correlation among twins in dental and skeletal ages with the chronological age was assessed using Correlation Coefficient and Student's't' Test. Results: The obtained data was fed into the computer and statistical analysis was done for the same using the SPSS version 10.0. Statistical significance was tested at P<0.05 level. Mean and Standard Deviation, Correlation Coefficient, Student's't' Test statistical methods were employed. The result showed highly significant 'p' value as <0.001 in all the correlations except for mixed pairs. Descriptive statistics in most of the areas demonstrated a non-significant result between zygosity groups. Conclusion: There is a correlation existing between the individual’s chronological age, dental age and skeletal age and correlation also exists in the twin pairs of the same zygosity and among each pair but no correlation exists between different zygotic twins. How to cite this article: Gupta M, Divyashree R, Abhilash P R, Bijle M N A, Murali K V. Correlation between Chronological Age, Dental Age and Skeletal Age among Monozygoyic and Dizygotic Twins. J Int Oral Health 2013; 3(1):16-22.

Gupta, Mohit; Divyashree, R; Abhilash, PR; A Bijle, Mohammed Nadeem; Murali, KV

2013-01-01

222

Correlation between Chronological Age, Dental Age and Skeletal Age among Monozygoyic and Dizygotic Twins.  

PubMed

Introduction: Chronological age, dental development, height and weight measurements, sexual maturation characteristics and skeletal age are some biological indicators that have been used to identify time of growth. Many researchers have agreed that skeletal maturity is closely related to the craniofacial growth, and bones of hand and wrist are reliable parameters in assessing it. The complete hand and wrist radiograph involves 30 bones and assessment of these bones is one elaborate task. The present study is therefore, undertaken to assess the correlation between the chronological age, dental age and skeletal ages among different types of twins. Materials and Methods: The study consisted of 60 subjects (30 twins) aged 8 to 16 years, divided into group of 10 monozygotic, 10 dizygotic and 10 mixed sex twins. The sample was selected from Twin Survey- 2008 conducted by Department of Orthodontics and Dentofacial Orthopaedics, Sree Balaji Dental College and Hospital, Chennai. Their zygosity was determined by sex, blood groups and by the parent. The chronological age was measured by the date of birth given by the parents. Panoramic and hand wrist x-rays were taken. Dental age was assessed by Demerjian et al method and skeletal age by Greulich and Pyle method. The correlation among twins in dental and skeletal ages with the chronological age was assessed using Correlation Coefficient and Student's't' Test. Results: The obtained data was fed into the computer and statistical analysis was done for the same using the SPSS version 10.0. Statistical significance was tested at P<0.05 level. Mean and Standard Deviation, Correlation Coefficient, Student's't' Test statistical methods were employed. The result showed highly significant 'p' value as <0.001 in all the correlations except for mixed pairs. Descriptive statistics in most of the areas demonstrated a non-significant result between zygosity groups. Conclusion: There is a correlation existing between the individual's chronological age, dental age and skeletal age and correlation also exists in the twin pairs of the same zygosity and among each pair but no correlation exists between different zygotic twins. How to cite this article: Gupta M, Divyashree R, Abhilash P R, Bijle M N A, Murali K V. Correlation between Chronological Age, Dental Age and Skeletal Age among Monozygoyic and Dizygotic Twins. J Int Oral Health 2013; 3(1):16-22. PMID:24155573

Gupta, Mohit; Divyashree, R; Abhilash, Pr; A Bijle, Mohammed Nadeem; Murali, Kv

2013-02-26

223

High accurate volume holographic correlator with 4000 parallel correlation channels  

Microsoft Academic Search

Volume holographic correlator allows simultaneously calculate the two-dimensional inner product between the input image and each stored image. We have recently experimentally implemented in VHC 4000 parallel correlation channels with better than 98% output accuracy in a single location in a crystal. The speckle modulation is used to suppress the sidelobes of the correlation patterns, allowing more correlation spots to

Kai Ni; Zongyao Qu; Liangcai Cao; Ping Su; Qingsheng He; Guofan Jin

2008-01-01

224

Correlators in nontrivial backgrounds  

SciTech Connect

Operators in N=4 super Yang-Mills theory with an R-charge of O(N{sup 2}) are dual to backgrounds which are asymtotically AdS{sub 5}xS{sup 5}. In this article we develop efficient techniques that allow the computation of correlation functions in these backgrounds. We find that (i) contractions between fields in the string words and fields in the operator creating the background are the field theory accounting of the new geometry, (ii) correlation functions of probes in these backgrounds are given by the free field theory contractions but with rescaled propagators and (iii) in these backgrounds there are no open string excitations with their special end point interactions; we have only closed string excitations.

Mello Koch, Robert de [National Institute for Theoretical Physics, Department of Physics and Centre for Theoretical Physics, University of the Witwatersrand, Wits, 2050 (South Africa); Stellenbosch Institute for Advanced Studies, Stellenbosch (South Africa); Ives, Norman; Stephanou, Michael [National Institute for Theoretical Physics, Department of Physics and Centre for Theoretical Physics, University of the Witwatersrand, Wits, 2050 (South Africa)

2009-01-15

225

CORRELATES OF AVOWED HAPPINESS  

Microsoft Academic Search

DATA ON AVOWED HAPPINESS ARE SUMMARIZED UNDER THE HEADINGS OF (1) MEASUREMENT, RELIABILITY, AND VALIDITY; (2) DIMENSIONS; AND (3) CORRELATES. THE HAPPY PERSON EMERGES AS A YOUNG, HEALTHY, WELL-EDUCATED, WELL-PAID, EXTRAVERTED, OPTIMISTIC, WORRY-FREE, RELIGIOUS, MARRIED PERSON WITH HIGH SELF-ESTEEM, HIGH JOB MORALE, MODEST ASPIRATIONS, OF EITHER SEX, AND OF A WIDE RANGE OF INTELLIGENCE. (2 P. REF.)

WARNER R. WILSON

1967-01-01

226

Relative Age Correlation  

NSDL National Science Digital Library

The purpose of this exercise is to introduce students to how simple relative age correlation principles can be used to reliable determine the relative ages of rock units and other geologic features. Students will apply the principles of original horizontality, superposition, cross-cutting relationships and inclusion to determine the relative ages of sedimentary rocks, igneous rocks and metamorphic rocks, as well as unconformities and faults.

Daley, Gwen

227

Variable angle correlation spectroscopy  

SciTech Connect

In this dissertation, a novel nuclear magnetic resonance (NMR) technique, variable angle correlation spectroscopy (VACSY) is described and demonstrated with {sup 13}C nuclei in rapidly rotating samples. These experiments focus on one of the basic problems in solid state NMR: how to extract the wealth of information contained in the anisotropic component of the NMR signal while still maintaining spectral resolution. Analysis of the anisotropic spectral patterns from poly-crystalline systems reveal information concerning molecular structure and dynamics, yet in all but the simplest of systems, the overlap of spectral patterns from chemically distinct sites renders the spectral analysis difficult if not impossible. One solution to this problem is to perform multi-dimensional experiments where the high-resolution, isotropic spectrum in one dimension is correlated with the anisotropic spectral patterns in the other dimensions. The VACSY technique incorporates the angle between the spinner axis and the static magnetic field as an experimental parameter that may be incremented during the course of the experiment to help correlate the isotropic and anisotropic components of the spectrum. The two-dimensional version of the VACSY experiments is used to extract the chemical shift anisotropy tensor values from multi-site organic molecules, study molecular dynamics in the intermediate time regime, and to examine the ordering properties of partially oriented samples. The VACSY technique is then extended to three-dimensional experiments to study slow molecular reorientations in a multi-site polymer system.

Lee, Y.K. [Univ. of California, Berkeley, CA (United States)]|[Lawrence Berkeley Lab., CA (United States). Chemical Biodynamics Div.

1994-05-01

228

Geometry of quantum correlations  

NASA Astrophysics Data System (ADS)

We consider the set Q of quantum correlation vectors for two observers, each with two possible binary measurements. Quadric (hyperbolic) inequalities which are satisfied by every q?Q are proved, and equality holds on a two-dimensional manifold consisting of the local boxes and all quantum correlation vectors that maximally violate the Clauser-Horne-Shimony-Holt (CHSH) inequality. The quadric inequalities are tightly related to the CHSH inequality; they are their iterated versions. Consequently, it is proved that Q is contained in a hyperbolic cube whose axes lie along the nonlocal (Popescu-Rohrlich) boxes. As an application, a tight constraint on the rate of local boxes that must be present in every quantum correlation is derived. The inequalities allow one to test the validity of quantum mechanics on the basis of data available from experiments which test the violation of the CHSH inequality. It is noted how these results can be generalized to the case of n sites, each with two possible binary measurements.

Pitowsky, Itamar

2008-06-01

229

[Vector-echocardiographic correlations in type B right ventricular hypertrophy].  

PubMed

The correlation between the right posterior surface of the QRS complex in the horizontal plane and the various parameters characterizing the right ventricle on TM and 2D echocardiography on left parasternal longitudinal sections and subcostal sections was investigated by the Chi-square independence test and Student's t test in 185 cases of heart disease due to various aetiologies. The right posterior surface (Octant III) of the QRS complex in the horizontal plane is independent of the diastolic thickness of the right ventricular posterior wall (RVPW); the diastolic thickness of the right ventricular anterior wall (RVAW); the right ventricular ejection fraction (RVEF); the systolic diameter and diastolic diameter of the right ventricle; the percentage thickening of the RVPW and the RVAW; and, finally, there is no significant relationship between the diastolic thickness of the RVPW and that of the RVAW. Its variance according to the presence or absence and the nature of an associated conduction disorder (RBBB, RIBBB, RBBB + LAHB, LAHB, LBBB, LIBBB or Kent) was not significant for a risk of error of 5% and 1%. The right posterior surface (Octant III) of the QRS complex in the horizontal plane is significantly correlated with the right ventricular mass (RVM), calculated from the diastolic thickness of the right ventricular posterior wall (RVPW): alpha < 0.001; according to a simplified formula: RVM g/m2 = (RVDD + 2 RVPW)3. The correlation between these last two quantitative parameters is borderline significant r = 0.11 t = 1.25, 0.20 < alpha < 0.30 according to a linear regression equation: y = 55.15-34.71 x; Po = 549 t = 1.48, increasing from 0 to 0.137 and decreasing beyond 0.137, linearity hypothesis: admissible, p = 0.04. PMID:8763647

Hayat, J C

1996-05-01

230

``A Desideratum in Spectrology'': an Editor's Lament in the Great Correlation Era  

NASA Astrophysics Data System (ADS)

Of all the known observable characteristics of the stars in the late 19th Century, classification by the appearance of their spectra was by far the most problematic. In 1904, Edwin Frost lamented that some 23 distinct classification systems had been created, yet none were universally accepted. In 1908, the applied mathematician Karl Pearson and a student evaluated correlations between spectra and other characteristics of the stars, hoping to ``look upon the stellar universe as an orderly whole ... by which we pass from chaos to an organised and locally differentiated cosmos.'' None of the major spectral systems, however, allowed them to draw any conclusions, other than state a high correlation with color. Yet, by 1917, astronomers were making correlations, and applying them, to make some pretty strong statements about the nature and history of the sidereal system as well as the lives of the stars. One of the strongest was the technique of spectroscopic parallaxes. But even its discoverer, Walter Sydney Adams, worried about what it all meant. Writing to Eddington in 1917, Adams wished that ``we had more physical knowledge regarding the interpretations of stellar spectra.'' And as E. A. Milne observed some years later, in retrospect, ``[t]here was a gap in the logical argument.'' My talk will address some historiographical issues arising from this phase in the development of modern astrophysics that hopefully will illuminate why the gap was closed in the way it was closed, and the effect it had on the continuing process of spectral classification.

DeVorkin, David

2012-09-01

231

Correlation of pain relief with physical function in hand osteoarthritis: randomized controlled trial post hoc analysis  

PubMed Central

Introduction Nonsteroidal anti-inflammatory drugs are recommended for the relief of pain associated with hand osteoarthritis (OA) but do not alter the underlying structural changes that contribute to impaired physical function. The current analysis examined the relationship of pain relief with measures of function and global rating of disease in patients with hand OA. Methods This was a combined analysis of 2 prospective, randomized, double-blind, 8-week, multicenter, parallel-group studies comparing diclofenac sodium 1% gel with placebo gel (vehicle) in patients with radiographically confirmed mild to moderate hand OA. Patients (n = 783) aged ? 40 years applied diclofenac sodium 1% gel (2 g) or vehicle to each hand 4 times daily for 8 weeks. Outcome measures included pain intensity assessed on a 100-mm Visual Analog Scale (VAS); the Australian/Canadian Osteoarthritis Hand Index (AUSCAN) subscales for pain, stiffness, and physical function (100-mm VAS); and a global rating of disease (100-mm VAS). Change in VAS pain intensity from baseline to week 8 was categorized (<0%, 0%-<15%, 15%-<30%, 30%-<50%, 50%-<70%, and ? 70%) without regard to treatment and compared in each category with the mean change from baseline in each AUSCAN subindex and the global rating of disease. Pearson correlations between changes in outcome measures from baseline to week 8 were calculated. Results Changes in VAS pain intensity were accompanied by similar changes in AUSCAN scores and global rating of disease. Pearson correlations confirmed significant associations (P < 0.001) between change in VAS pain intensity and changes in AUSCAN pain (correlation coefficient [r] = 0.81), AUSCAN function (r = 0.75), AUSCAN stiffness (r = 0.66), and global rating of disease (r = 0.76). Conclusions Pain relief correlated with improvements in physical function, stiffness, and global rating of disease in patients with hand OA, irrespective of treatment. This suggests that pain or anticipation of pain inhibits physical function and influences patient perception of disease severity in hand OA. These results also suggest that any intervention to relieve the pain of hand OA may improve function and patient perception of disease severity, despite the absence of a disease-modifying mechanism of action. Trial registration Clinicaltrials.gov NCT00171652, NCT00171665.

2010-01-01

232

Asthma severity: histopathologic correlations.  

PubMed

Asthma is a disorder characterized by inflammation of the airways which leads to variable airflow obstruction and symptoms of wheezing, chest tightness, cough, and dyspnea. Decisions concerning the type and intensity of therapy for asthma are generally based on the severity of the disease in a given individual. Guidelines for asthma management classify disease severity on the basis of symptom frequency and intensity as well as the degree of physiological impairment. Because treatment decisions are currently not based on markers of airway inflammation, it is important to know how well the underlying inflammatory pathology correlates with clinical and physiological variables and whether airway inflammation, if undertreated, leads to longer term adverse outcomes such as chronic persistent airway obstruction. Studies of asthma pathology reveal an inflammatory response characterized by infiltration of the airways with eosinophils, mast cells and lymphocytes; disruption of the epithelium; thickening of the reticular basement membrane; and increases in smooth muscle mass. These findings are qualitatively found in mild as well as severe asthmatics, and attempts to draw quantitative correlations between severity and intensity of inflammation have yielded discordant results. Although antiinflammatory therapy with corticosteroids decreases the intensity of the inflammation in association with improved clinical variables, the association is circumstantial and it is unclear which marker of inflammation correlates best with the severity of acute episodes or the severity of the disease in patients who are stable. Problems in relating the underlying pathology to disease severity are largely due to inadequate tissue sampling as bronchoscopically obtained specimens do not permit an evaluation of the outer airway wall or small airways and their surrounding parenchyma. PMID:12973422

Fish, J E; Peters, S P

1999-08-01

233

Fluorescence correlation spectroscopy.  

PubMed

Fluorescence correlation spectroscopy (FCS) is a powerful technique to measure concentrations, mobilities, and interactions of fluorescent biomolecules. It can be applied to various biological systems such as simple homogeneous solutions, cells, artificial, or cellular membranes and whole organisms. Here, we introduce the basic principle of FCS, discuss its application to biological questions as well as its limitations and challenges, present an overview of novel technical developments to overcome those challenges, and conclude with speculations about the future applications of fluorescence fluctuation spectroscopy. PMID:22415816

Ries, Jonas; Schwille, Petra

2012-03-13

234

Psychiatric symptoms correlate with metabolic indices in the hippocampus and cingulate in patients with mitochondrial disorders  

PubMed Central

There is increasing recognition that mitochondrial dysfunction may have a critical role in the pathophysiology of major psychiatric illnesses. Patients with mitochondrial disorders offer a unique window through which we can begin to understand the association between psychiatric symptoms and mitochondrial dysfunction in vivo. Using proton magnetic resonance spectroscopy (1H-MRS), we investigated metabolic indices in mitochondrial patients in regions of the brain that have been implicated in psychiatric illness: the caudate, cingulate cortex and hippocampus. In all, 15 patients with mitochondrial disorders and 15 age- and sex-matched controls underwent a comprehensive psychiatric assessment, including the administration of standardized psychiatric rating scales, followed by single voxel 1H-MRS of the caudate, cingulate cortex and hippocampus to measure N-acetyl aspartate (NAA), creatine (Cr), glycerophosphocholine (GPC), myoinositol and glutamate+glutamine (Glx). Pearson's correlation coefficients were used to determine correlations between metabolites and the psychiatric rating scales. Anxiety symptoms in these patients correlated with higher GPC, Glx, myoinositol and Cr in the hippocampus. Impaired level of function as a result of psychiatric symptoms correlated with higher Glx and GPC in the cingulate cortex. In summary, we found remarkably consistent, and statistically significant, correlations between anxiety and metabolic indices in the hippocampus in patients with mitochondrial disorders, while overall impairment of functioning due to psychiatric symptoms correlated with metabolic markers in the cingulate cortex. These findings lend support to the notion that mitochondrial dysfunction in specific brain regions can give rise to psychiatric symptoms. In particular, they suggest that metabolic processes in the hippocampus may have an important role in the neurobiology of anxiety.

Anglin, R E; Rosebush, P I; Noseworthy, M D; Tarnopolsky, M; Mazurek, M F

2012-01-01

235

Correlation of age and HRT use with breast density as assessed by Quantra™.  

PubMed

Breast density is a significant predictor in the risk of developing breast cancer. Several methods are available for assessing breast density, but most are subject to intra-observer variability and are unable to assess the breast as a three-dimensional structure. Using Quantra(™) to quantify breast density, we have correlated this with risk factors to determine what impact these variables have on breast density. Women attending for full field digital mammography at the South West London Breast Screening Unit between December 2008 and March 2009 were invited to participate in the study by questionnaire. Consenting women returned the questionnaire allowing further data collection including demographics, menopausal status and hormone replacement therapy (HRT) use. Data were correlated against breast density measurements to determine the degree of association. Mammograms were assessed on a Hologic(™) workstation and breast density calculated using Quantra(™). Quantra(™) is an automated algorithm for volumetric assessment of breast tissue composition from digital mammograms. Six-hundred and eighty-three women were invited to participate. Those with implants or mastectomy were excluded. Three-hundred and twenty questionnaires were fully completed and able to be assessed. The mean age of participants was 59 years (range 49-81). Mean density was 19.7% (range 8.5-48.5%). There was a decrease in density with age (Pearson product-moment correlation coefficient -0.17). Correlation between density and HRT use showed a significant positive result (correlation coefficient 0.07). Quantra(™) has shown to be an accurate, reproducible tool for quantifying breast density, demonstrated by its correlation with lifestyle and demographic data. Given its ease of acquisition this may be the future of breast density quantification in the digital age. PMID:23230974

Skippage, Philippa; Wilkinson, Louise; Allen, Steven; Roche, Nicola; Dowsett, Mitch; A'hern, Roger

2012-12-10

236

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

NASA Astrophysics Data System (ADS)

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 |?| < 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.

Takeuchi, Tsutomu T.

2010-08-01

237

Correlation analysis of alveolar bone loss in buccal/palatal and proximal surfaces in rats.  

PubMed

The aim was to correlate alveolar bone loss in the buccal/palatal and the mesial/distal surfaces of upper molars in rats. Thirty-three, 60-day-old, male Wistar rats were divided in two groups, one treated with alcohol and the other not treated with alcohol. All rats received silk ligatures on the right upper second molars for 4 weeks. The rats were then euthanized and their maxillae were split and defleshed with sodium hypochlorite (9%). The cemento-enamel junction (CEJ) was stained with 1% methylene blue and the alveolar bone loss in the buccal/palatal surfaces was measured linearly in 5 points on standardized digital photographs. Measurement of the proximal sites was performed by sectioning the hemimaxillae, restaining the CEJ and measuring the alveolar bone loss linearly in 3 points. A calibrated and blinded examiner performed all the measurements. Intraclass Correlation Coefficient revealed values of 0.96 and 0.89 for buccal/lingual and proximal surfaces, respectively. The Pearson Correlation Coefficient (r) between measurements in buccal/palatal and proximal surfaces was 0.35 and 0.05 for the group treated with alcohol, with and without ligatures, respectively. The best correlations between buccal/palatal and proximal surfaces were observed in animals not treated with alcohol, in sites both with and without ligatures (r = 0.59 and 0.65, respectively). A positive correlation was found between alveolar bone loss in buccal/palatal and proximal surfaces. The correlation is stronger in animals that were not treated with alcohol, in sites without ligatures. Areas with and without ligature-induced periodontal destruction allow detection of alveolar bone loss in buccal/palatal and proximal surfaces. PMID:23184169

Azambuja, Carolina Barrera de; Cavagni, Juliano; Wagner, Marcius Comparsi; Gaio, Eduardo José; Rösing, Cassiano Kuchenbecker

238

Psychiatric symptoms correlate with metabolic indices in the hippocampus and cingulate in patients with mitochondrial disorders.  

PubMed

There is increasing recognition that mitochondrial dysfunction may have a critical role in the pathophysiology of major psychiatric illnesses. Patients with mitochondrial disorders offer a unique window through which we can begin to understand the association between psychiatric symptoms and mitochondrial dysfunction in vivo. Using proton magnetic resonance spectroscopy ((1)H-MRS), we investigated metabolic indices in mitochondrial patients in regions of the brain that have been implicated in psychiatric illness: the caudate, cingulate cortex and hippocampus. In all, 15 patients with mitochondrial disorders and 15 age- and sex-matched controls underwent a comprehensive psychiatric assessment, including the administration of standardized psychiatric rating scales, followed by single voxel (1)H-MRS of the caudate, cingulate cortex and hippocampus to measure N-acetyl aspartate (NAA), creatine (Cr), glycerophosphocholine (GPC), myoinositol and glutamate+glutamine (Glx). Pearson's correlation coefficients were used to determine correlations between metabolites and the psychiatric rating scales. Anxiety symptoms in these patients correlated with higher GPC, Glx, myoinositol and Cr in the hippocampus. Impaired level of function as a result of psychiatric symptoms correlated with higher Glx and GPC in the cingulate cortex. In summary, we found remarkably consistent, and statistically significant, correlations between anxiety and metabolic indices in the hippocampus in patients with mitochondrial disorders, while overall impairment of functioning due to psychiatric symptoms correlated with metabolic markers in the cingulate cortex. These findings lend support to the notion that mitochondrial dysfunction in specific brain regions can give rise to psychiatric symptoms. In particular, they suggest that metabolic processes in the hippocampus may have an important role in the neurobiology of anxiety. PMID:23149451

Anglin, R E; Rosebush, P I; Noseworthy, M D; Tarnopolsky, M; Mazurek, M F

2012-11-13

239

Solar feature correlation tracker  

NASA Astrophysics Data System (ADS)

We present a tracking system that stabilizes atmospheric and instrumental image motion in vacuum tower telescopes. The system is designed to lock on low contrast features, such as solar granulation or other small scale structure. A matrix diode array rapidly scans the scene of interest, usually with a field of 5 arcsec. Images are cross-correlated in real time with a previously recorded reference image of the same area. The drive signal for the image motion corrector, a small, articulated mirror, is generated by measuring the position of the cross correlation maximum. Reference pictures are updated every 30 s in order to adapt to the changing small scale solar features. Performance tests show that the residual image motion in the tracked image is 0.05 arcsec rms compared to a typical 0.5 arcsec rms for the untracked image. The system locks on any small scale structure anywhere on the sun. The bandwidth of the servo system is 40 Hz, or sufficient to stabilize image motion on a meter-class solar telescope.

Rimmele, Th.; von der Luehe, O.; Wiborg, P. H.; Widener, A. L.; Dunn, R. B.; Spence, G.

1991-12-01

240

Confinement from correlation functions  

NASA Astrophysics Data System (ADS)

We compute the Polyakov loop potential in Yang-Mills theory from the fully dressed primitively divergent correlation functions only. This is done in a variety of functional approaches ranging from functional renormalization group equations over Dyson-Schwinger equations to two-particle irreducible functionals. We present a confinement criterion that links the infrared behavior of propagators and vertices to the Polyakov loop expectation value. The present work extends the works of [J. Braun , Phys. Lett. B 684, 262 (2010)PYLBAJ0370-2693; F. Marhauser and J. M. Pawlowski, arXiv:0812.1144; J. Braun , Eur. Phys. J. C 70, 689 (2010)EPCFFB1434-6044] to general functional methods and sharpens the confinement criterion presented there. The computations are based on the thermal correlation functions in the Landau gauge calculated in [L. Fister and J. M. Pawlowski, arXiv:1112.5440; L. Fister and J. M. Pawlowski, arXiv:1112.5429; L. Fister, Ph.D. thesis, Heidelberg University, 2012].

Fister, Leonard; Pawlowski, Jan M.

2013-08-01

241

PREFACE: Correlated Electrons (Japan)  

NASA Astrophysics Data System (ADS)

This issue of Journal of Physics: Condensed Matter is dedicated to results in the field of strongly correlated electron systems under multiple-environment. The physics of strongly correlated electron systems (SCES) has attracted much attention since the discovery of superconductivity in CeCu_2 Si_2 by Steglich and his co-workers a quater-century ago. Its interest has been intensified by the discovery of high-Tc superconductivity in a series of cuprates with layered perovskite structure which are still under active debate. The present issue of Journal of Physics: Condensed Matter present some aspects of SCES physics on the basis of activities of a late project "Centre-Of-Excellence" supported by MEXT (Ministry of Education, Sports, Science, Culture and Technology of the Japanese Government). This project has been performed by a condensed matter physics group in the faculties of science and engineering science of Osaka University. Although this project also covers correlated phenomena in optics and nano-scale systems, we focus here on the issues of SCES related to superconductivity, mainly unconventional. The present issue covers the discussions on a new mechanism of superconductivity with electronic origin (critical valence fluctuation mechanism), interplay and unification of magnetism and superconductivity in SCES based on a systematic study of NQR under pressure, varieties of Fermi surface of Ce- and U-based SCES probed by the de Haas-van Alphen effect, electronic states probed by a bulk sensitive photoemission spectroscopy with soft X-ray, pressure induced superconductivity of heavy electron materials, pressure dependence of superconducting transition temperature based on a first-principle calculation, and new superconductors under very high-pressure. Some papers offer readers' reviews of the relevant fields and/or include new developments of this intriguing research field of SCES. Altogether, the papers within this issue outline some aspects of electronic states and superconductivity of SCES and related research fields, and the prospects of SCES physics. I hope that it will give an insight into the fascination of SCES research and a feeling for the advances made in the past years.

Miyake, Kazumasa

2007-03-01

242

Plasmatic nitric oxide correlates with weight and red cell distribution width in exercised rats supplemented with quercetin.  

PubMed

Abstract Quercetin is suggested as a nitric oxide regulator which may in turn influence blood parameters and weight gain. Wistar rats were classified as: quercetin-exercise training, QT; placebo-exercise training, PT; quercetin-sedentary, QS; and placebo sedentary, PS. After 6 weeks of treatment with quercetin and/or exercise, an incremental test was run to measure oxygen consumption. QT had lower levels of NO compared with PS (p?=?0.029) and QS (p?=?0.002). Red cell distribution width increased in both exercised groups, especially in the QT group (p?Pearson correlation analysis showed that nitric oxide levels were associated with weight (r?=?0.675) and red distribution width (r?=?-0814) in the QT group. Quercetin effect on NO production seems to be more powerful when it is supplemented during exercise training. Moreover, RDW relationship with NO production need to be further investigated in regards to health. PMID:23763647

Casuso, Rafael A; Martínez-Amat, Antonio; Martínez-Romero, Rubén; Camiletti-Moiron, Daniel; Hita-Contreras, Fidel; Martínez-López, Emilio

2013-06-14

243

Correlates of Desistance  

NSDL National Science Digital Library

Research has shown that marital status and employment are correlates of desistance. That is, adolescents involved with crime were more likely to discontinue offending in adulthood if they were married and had a good job. Most of what criminologists know about the process of desistance from crime is based on a sample of adult males in the 1950's. There is no question that life in America has changed drastically in the past fifty years. Given the importance of examining historical change inherent in the life course perspective, it is important to determine how changes in the social structure over time impact individuals. Therefore, the goals of this data analysis exercise are to examine changes in marriage and employment over the last fifty years. The purposes are to identify the changes that have taken place, and to hypothesize how these changes may affect the process of desistance from crime today.

Ford, Jason

2009-08-17

244

Correlated motions in DNA  

SciTech Connect

The furanose ring of nucleic acids plays a key role in detrmining the conformations of nucleic acids because it shares a common bond C3'-C4'(psi') with the sugar-phosphate backbone. This structural feature enables the transmission of conformational changes between the side-chain base and the backbone through conformational correlations between the base and sugar. Thermally-induced local fluctuations of P can be transmitted along the backbone through psi', particularly when the sugar is in the C2'-endo domain. The sugar pucker-dependent flexibility of DNA is further exemplified by studies that have shown that due to steric interactions, absence of the 2'-OH group in deoxyribose tends to increase the conformational flexibility about the internucleotide phosphodiester (..omega.., ..omega..') especially when the sugar assumes the C2'-endo pucker.

Sundaralingam, M.; Westhof, E.

1980-10-01

245

Thermopower in Correlated Systems  

NASA Astrophysics Data System (ADS)

Novel correlated materials discussed recently such as sodium cobaltate Na x CoO 2and iron antimonide FeSb 2show considerable promise for attaining high values of thermopower. These extend the limits set by standard semiconducting materials such as bismuth telluride Bi 2 Te 3. Understanding the scale of thermopower and its dependence on material properties is a difficult task, since the Kubo formulas are somewhat opaque. We have developed two alternative approximate formulas that are easier to interpret, while capturing the many body enhancements of thermopower. These are the "high frequency" Seebeck coefficient S ?and the Kelvin formula S Kelvin published recently. This article provides a brief guide to these alternate formulas together with a delineation of their domain of usefulness.

Shastry, B. Sriram

246

Strongly correlated electronic materials  

SciTech Connect

This is the final report of a 3-year project. Novel electronic materials characterized by strong electronic correlations display a number of unexpected, often extraordinary, properties. These are likely to play a major role in purpose-specific high-technology electronic materials of the future developed for electronic, magnetic, and optical applications. This project sought to develop predictive control of the novel properties by formulating, solving and applying many-body models for the underlying microscopic physics. This predictive control required the development of new analytical and numerical many-body techniques and strategies for materials of varying strengths of interactions, dimensionality and geometry. Results are compared with experiment on classes of novel materials, and the robust techniques are used to predict additional properties and motivate key additional experiments.

Bedell, K.; Albers, R.; Balatsky, A.; Bishop, A.; Bonca, J.; Gubernatis, J.; Gulasci, M.; Silver, R.; Trugman, S.

1996-04-01

247

Pairwise Correlations Of Eight Strong DIBs And N(H), N(H2), And E(B-V)  

NASA Astrophysics Data System (ADS)

We establish correlations between equivalent widths of eight diffuse interstellar bands (DIBs), and examine their correlations with N(H), N(H2), and E(B-V). The DIBs are centered at 5780.5, 6204.5, 6283.8, 6196.0, 6613.6, 5705.1, 5797.1, and 5487.7, in decreasing order of Pearson's correlation coefficient with N(H), which range from 0.96 to 0.82. We find the equivalent width of 5780.5 is better correlated with column densities of H than with E(B-V) or H2, confirming earlier results, and the same is true for six of the seven other DIBs presented here. Despite this similarity, the eight strong DIBs chosen are not correlated well enough with each other to suggest they come from the same carrier. These DIBs are more likely to be associated with H than with H2, and hence are not preferentially located in the densest, most UV shielded parts of interstellar clouds. The correlations may be useful in deriving interstellar parameters, such as N(H) from W(5780.5), when more direct methods are not available. Our future plans include closer examination the excellent correlation between 5705.1 and 5780.5 (almost as good as the near perfect correlation of 6613.6 with 6196.0), and on precise measurements of broad DIBS (e.g. 4428.83, 4881.06) and inclusion of these better measurements in correlation studies with the main DIBs noted in this poster.

Friedman, Scott David; York, D. G.; McCall, B. J.; Dahlstrom, J.; Sonnentrucker, P.; Welty, D. E.; Drosback, M. M.; Hobbs, L. M.; Rachford, B. L.; Snow, T. P.

2011-05-01

248

Generation of correlated spike trains.  

PubMed

Neuronal spike trains display correlations at diverse timescales throughout the nervous system. The functional significance of these correlations is largely unknown, and computational investigations can help us understand their role. In order to generate correlated spike trains with given statistics, several case-specific methods have been described in the litterature. This letter presents two general methods to generate sets of spike trains with given firing rates and pairwise correlation functions, along with efficient simulation algorithms. PMID:19431282

Brette, Romain

2009-01-01

249

Interaural correlation discrimination from diffuse field reference correlations.  

PubMed

Just noticeable differences in interaural correlation (?-jnds) from diffuse sound field reference correlations are obtained. In a three-interval, three-alternative forced-choice procedure, ?-jnds are measured for positive and negative deviations from nine narrowband reference conditions. Stimuli are 1 equivalent rectangular bandwidth wide noise bursts with center frequencies between 165 and 1500 Hz. The frequency dependent reference correlation (?ref) is determined by the simulated interaural correlation under ideal diffuse sound field conditions. Results show that the interaural correlation at threshold for deviation toward the positive correlation range follows the reference curve in a nonlinear fashion. For deviation toward the negative correlation range the interaural correlation at threshold is further afar the reference curve and does not markedly resemble its trend. The results indicate that the previously found asymmetry for correlation discrimination from uncorrelated broadband stimuli to the positive and negative correlation range becomes less pronounced for narrowband stimuli. For positive deviation, the highest jnds are found for the region where the reference curve occupies the global minimum in ?ref; despite that, the interaural correlation at threshold for positive deviation exhibits its lowest value at that point. PMID:23464020

Walther, Andreas; Faller, Christof

2013-03-01

250

Interregional Correlations in Parkinson Disease and Parkinson-related Dementia with Resting Functional MR Imaging  

PubMed Central

Purpose: To apply a recently developed native-space (or native-surface) method to compare resting functional magnetic resonance (MR) imaging correlations (functional connectivity) measured in patients with Parkinson-related dementia (PRD) to those measured in cognitively unimpaired, age-matched control subjects with or without Parkinson disease (PD). Materials and Methods: The study was approved by the institutional review board and complied with HIPAA regulations. Participants included cognitively unimpaired elderly individuals (n = 19), cognitively unimpaired patients with PD (n = 19), and patients with PRD (n = 18). Resting functional MR data were assessed by calculating correlation coefficients between blood oxygen level–dependent time series of a seed region and of other regions of interest selected a priori. Two seeds were used: a medial parietal region that contributes to the default network affected in Alzheimer disease and the caudate, which is affected by loss of dopaminergic inputs in PD. Correlation analyses were performed in the native space of individual subjects to avoid confounds from transformation to an average brain. Two-sample t tests were applied to data from each native-surface region of interest, and vertex-wise comparisons were made by using two-sample t tests at each vertex on the group surface; statistical results were corrected for multiple comparisons. Cortical thickness and striatal volumes were also compared across groups for the regions of interest. Results: Corticostriatal functional correlations were decreased in PRD patients relative to elderly control subjects in bilateral prefrontal regions; largest difference was observed in the right caudal middle frontal region (r = 0.48 in PRD patients and 0.81 in elderly control subjects, uncorrected P = .001). Conversely, there was no significant difference across groups in the strength of default-network correlations. There was also no significant difference across groups in cortical thickness or striatal volume. Conclusion: PRD was associated with selective disruption of corticostriatal resting functional MR imaging correlations, which suggests that resting functional MR imaging analyzed in subject-native space may be a useful biomarker in this disease. Additionally, at least in the present cohort, this technique was more sensitive to PRD changes than was quantitative structural MR imaging. © RSNA, 2012

Seibert, Tyler M.; Murphy, Elizabeth A.; Kaestner, Erik J.

2012-01-01

251

Set Correlation and Contingency Tables  

Microsoft Academic Search

Set correlation is a realization of the general multi variate linear model, can be viewed as a multivariate generalization of multiple correlation analysis, and may be employed in the analysis of multivariate data in any form. Set correlation supplements the four methods for analyzing two-way contingency tables de scribed by Zwick and Cramer (1986), and its applica tion to their

Jacob Cohen

1988-01-01

252

QUADRUPOLE CORRELATIONS IN LIGHT NUCLEI  

Microsoft Academic Search

Interactions leading to quadrupole correlations of alpha -particle ; type nuclei are investigated. Certain regularities in the bond energies of ; nucleons in light nuclei are analyzed by the shell model, with considerations for ; pair and quadrupole correlations. The quadrupole correlations disappear with ; neutron numbers exceeding the number of protons, explaining the variation in ; alpha -particle property

Solovev

1960-01-01

253

CORRELATION AS A DEPENDENT VARIABLE  

Microsoft Academic Search

THE CORRELATION BETWEEN 2 DEPENDENT VARIABLES IS SUBJECT TO THE SAME EFFECTS AS ARE THE MEANS ON 1 VARIABLE. FOR EXAMPLE, THE CORRELATION BETWEEN THE 1ST AND LAST TRIALS MAY VARY WITH CONDITIONS OF PRACTICE, JUST AS THE TRIAL MEANS MAY. THE DEPENDENCE, MOREOVER, OF A CORRELATION UPON SOME EXPERIMENTAL CONDITIONS AND ITS INDEPENDENCE OF OTHERS MAY BE RELEVANT INFORMATION.

MARSHALL B. JONES

1968-01-01

254

Correlational Analysis of Challenging Behaviours.  

ERIC Educational Resources Information Center

|It is argued that challenging behavior can be better understood if a correlational analysis (looking for correlations between behavior occurrence and other variables) is used in addition to functional analysis. A case example is provided of a man whose aggressive outbursts were negatively correlated with trips out of his unit. (Contains…

Whitaker, Simon; Hirst, Daniel

2002-01-01

255

Volume holographic wavelet correlation processor  

Microsoft Academic Search

A volume holographic wavelet correlation processor is proposed and constructed for correlation identification. It is based on the theory of wavelet transforms and the mechanism of angle-multiplexing volume holographic associative storage in a photorefractive crystal. High parallelism and discrimination are achieved with the system. Our research shows that cross-talk noise is significantly reduced with wavelet filtering preprocessing. Correlation outputs can

Wenyi Feng; Yingbai Yan; Guofan Jin; Minxian Wu; Qingsheng He

2000-01-01

256

New Generalized Cross-Correlator.  

National Technical Information Service (NTIS)

A new Generalized Cross-Correlator (GCC) for the passive time delay estimation problem is presented. The interpretation of this GCC is that of estimating the cross-correlation function by cross-correlating the least mean square estimates of the signal com...

A. Hero S. C. Schwartz

1983-01-01

257

Correlation between Duffy blood group phenotype and breast cancer incidence  

PubMed Central

Background Different ethnicities have different distribution of Duffy blood group (DBG) phenotypes and different breast cancer morbidity. A study in our lab demonstrated that Duffy antigen/receptor for chemokines (DARC, also known as DBGP, the Duffy protein phenotype), led to the inhibition of tumorigenesis. Therefore, we tested the hypothesis that DBGP is correlated with breast cancer occurrence. Methods DBGP proteins were examined by indirect antiglobulin testing with anti-FYa and anti-FYb antibodies. The phenotypes were classified into four groups according to the agglutination reactions: FYa + FYb+, FYa + FYb-, FYa-FYb + and FYa-FYb-. The phenotypes and pathological diagnosis of consecutively hospitalized female patients (n = 5,022) suffering from breast cancer at the Shanghai Cancer Hospital and Henan Province Cancer Hospital were investigated. The relationships between DBGP expression with breast cancer occurrence, axillary lymph status, histological subtype, tumor size pathological grade and overall survival were analyzed. Results The incidence of breast cancer was significantly different between FYa + FYb + (29.8%), FYa + FYb- (33.2%), FYa-FYb + (45.6%) and FYa-FYb- (59.1%; P = 0.001). Significant different numbers of breast cancer patients had metastases to the axillary lymph nodes in the FYa + FYb + group (25.1%), FYa + FYb- (36.9%), FYa-FYb + (41.0%) and FYa-FYb- (50.0%, (P = 0.005). There was a statistical significance (p = 0.022) of the overall survival difference between patients with difference phenotypes. No significant difference was observed in cancer size (t-test, p > 0.05), histological cancer type (Fisher's exact test, p > 0.05) or histological grade (Fisher's exact test, p > 0.05) between every each DBGP group. Conclusions DBGP is correlated with breast cancer incidence and axillary lymph node metastasis and overall survival. Further investigations are required to determine the underlying mechanism of Duffy blood group phenotype on breast cancer risk.

2012-01-01

258

Are secular correlations between sunspots, geomagnetic activity, and global temperature significant?  

USGS Publications Warehouse

Recent studies have led to speculation that solar-terrestrial interaction, measured by sunspot number and geomagnetic activity, has played an important role in global temperature change over the past century or so. We treat this possibility as an hypothesis for testing. We examine the statistical significance of cross-correlations between sunspot number, geomagnetic activity, and global surface temperature for the years 1868-2008, solar cycles 11-23. The data contain substantial autocorrelation and nonstationarity, properties that are incompatible with standard measures of cross-correlational significance, but which can be largely removed by averaging over solar cycles and first-difference detrending. Treated data show an expected statistically- significant correlation between sunspot number and geomagnetic activity, Pearson p < 10-4, but correlations between global temperature and sunspot number (geomagnetic activity) are not significant, p = 0.9954, (p = 0.8171). In other words, straightforward analysis does not support widely-cited suggestions that these data record a prominent role for solar-terrestrial interaction in global climate change. With respect to the sunspot-number, geomagnetic-activity, and global-temperature data, three alternative hypotheses remain difficult to reject: (1) the role of solar-terrestrial interaction in recent climate change is contained wholly in long-term trends and not in any shorter-term secular variation, or, (2) an anthropogenic signal is hiding correlation between solar-terrestrial variables and global temperature, or, (3) the null hypothesis, recent climate change has not been influenced by solar-terrestrial interaction. ?? 2011 by the American Geophysical Union.

Love, J. J.; Mursula, K.; Tsai, V. C.; Perkins, D. M.

2011-01-01

259

Correlations Among Multiple Measures of Functional and Mechanical Instability in Subjects With Chronic Ankle Instability  

PubMed Central

Context: Although dozens of individual mechanical and functional insufficiencies have been reported in those with chronic ankle instability (CAI), no authors to date have examined the relationship of the insufficiencies to each other. Therefore, studying both the functional and mechanical insufficiencies in the same experimental design will provide valuable information. Objective: To determine the relationships among the numerous functional and mechanical insufficiencies purported to cause CAI. Design: Descriptive study with a correlational design. Setting: Medical center and research laboratory. Patients or Other Participants: Thirty subjects with unilateral CAI (15 males and 15 females: age = 20.3 ± 1.3 years; height = 172.5 ± 10.7 cm; mass = 72.9 ± 15.8 kg). Main Outcome Measure(s): Twenty-six measures of mechanical insufficiencies (ankle laxity and hypomobility) and functional insufficiencies (subjective level of function, static and dynamic balance, ankle and hip strength) were taken on both limbs of all subjects. Bivariate correlations using Pearson product moment coefficients were calculated between all dependent variables measured in the unstable ankles. The level of significance was set a priori at P ? .05 for all analyses. Results: A number (35) of significant bivariate correlations were identified. Most (32) of these significant relationships were found between functional instability measures ( r = .38 to .96). Three significant relationships were noted between measures of functional (balance, strength) and mechanical (laxity, hypomobility) instability ( r = .47 to .52). No significant relationships were found between the different mechanical instability measures. Conclusions: Certain measures of functional instability were significantly correlated and may be redundant. Additionally, the significant correlations between measures of functional (balance, strength) and mechanical instability (laxity, hypomobility) demonstrate that the 2 factors are not completely dichotomous and need to be examined together.

Hubbard, Tricia J; Kramer, Lauren C; Denegar, Craig R; Hertel, Jay

2007-01-01

260

Direct measure of quantum correlation  

SciTech Connect

The quantumness of the correlation known as quantum correlation is usually measured by quantum discord. So far various quantum discords can be roughly understood as indirect measure by some special discrepancy of two quantities. We present a direct measure of quantum correlation by revealing the difference between the structures of classically and quantum correlated states. Our measure explicitly includes the contributions of the inseparability and local nonorthogonality of the eigenvectors of a density matrix. Besides its relatively easy computability, our measure can provide a unified understanding of quantum correlation of all the present versions.

Yu, Chang-shui [School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024 (China); H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Zhao, Haiqing [School of Science, Dalian Jiaotong University, Dalian 116028 (China)

2011-12-15

261

Correlates of lymphoproliferative responses to measles, mumps, and rubella (MMR) virus vaccines following MMR-II vaccination in healthy children.  

PubMed

Cell-mediated immunity (CMI) to measles, mumps, and rubella viral antigens plays a critical role in providing long-term protection against these infectious diseases. We examined CMI by measuring lymphoproliferative response induced in response to stimulation with the above three antigens following two doses of measles, mumps, and rubella-II (MMR-II) vaccine in a randomly selected, population-based cohort of healthy children. We determined if a correlative and predictive intraclass relationship exists between CMI to the three components of MMR-II. We detected positive lymphoproliferative responses to measles, mumps, and rubella vaccines. Mumps vaccine used as an antigen had the highest median stimulation index followed by measles and rubella vaccines. The overall intraclass correlation value for lymphoproliferative response to measles, mumps, and rubella using Pearson's correlation was 0.61 (95% confidence interval = 0.56, 0.66). We observed a significant pairwise association to individual vaccine components between subjects in the upper and lower 10th percentile of immune response. This study demonstrates recall CMI post-MMR-II vaccination with significant intraclass correlation among the CMI responses to the three vaccine components. PMID:15885638

Dhiman, Neelam; Ovsyannikova, Inna G; Jacobson, Robert M; Vierkant, Robert A; Pankratz, V Shane; Jacobsen, Steven J; Poland, Gregory A

2005-05-01

262

Arterial input function derived from pairwise correlations between PET-image voxels.  

PubMed

A metabolite corrected arterial input function is a prerequisite for quantification of positron emission tomography (PET) data by compartmental analysis. This quantitative approach is also necessary for radioligands without suitable reference regions in brain. The measurement is laborious and requires cannulation of a peripheral artery, a procedure that can be associated with patient discomfort and potential adverse events. A non invasive procedure for obtaining the arterial input function is thus preferable. In this study, we present a novel method to obtain image-derived input functions (IDIFs). The method is based on calculation of the Pearson correlation coefficient between the time-activity curves of voxel pairs in the PET image to localize voxels displaying blood-like behavior. The method was evaluated using data obtained in human studies with the radioligands [(11)C]flumazenil and [(11)C]AZ10419369, and its performance was compared with three previously published methods. The distribution volumes (VT) obtained using IDIFs were compared with those obtained using traditional arterial measurements. Overall, the agreement in VT was good (?3% difference) for input functions obtained using the pairwise correlation approach. This approach performed similarly or even better than the other methods, and could be considered in applied clinical studies. Applications to other radioligands are needed for further verification. PMID:23571279

Schain, Martin; Benjaminsson, Simon; Varnäs, Katarina; Forsberg, Anton; Halldin, Christer; Lansner, Anders; Farde, Lars; Varrone, Andrea

2013-04-10

263

Plasma 1,8-cineole correlates with cognitive performance following exposure to rosemary essential oil aroma  

PubMed Central

Objective The mode of influence of the aromas of plant essential oils on human behaviour is largely unclear. This study was designed to assess the potential pharmacological relationships between absorbed 1,8-cineole following exposure to rosemary aroma, cognitive performance and mood. Methods Twenty healthy volunteers performed serial subtraction and visual information processing tasks in a cubicle diffused with the aroma of rosemary. Mood assessments were made pre and post testing, and venous blood was sampled at the end of the session. Pearson correlations were carried out between serum levels of 1,8-cineole, cognitive performance measures and change in mood scores. Results Here we show for the first time that performance on cognitive tasks is significantly related to concentration of absorbed 1,8-cineole following exposure to rosemary aroma, with improved performance at higher concentrations. Furthermore, these effects were found for speed and accuracy outcomes, indicating that the relationship is not describing a speed–accuracy trade off. The relationships between 1,8-cineole levels and mood were less pronounced, but did reveal a significant negative correlation between change in contentment and plasma 1,8-cineole levels. Conclusion These findings suggest that compounds absorbed from rosemary aroma affect cognition and subjective state independently through different neurochemical pathways.

Oliver, Lorraine

2012-01-01

264

Measuring and interpreting neuronal correlations  

PubMed Central

Mounting evidence suggests that understanding how the brain encodes information and performs computations will require studying correlations between neurons. The recent advent of recording techniques such as multielectrode arrays and two-photon imaging has made it easier to measure correlations, opening the door to detailed exploration of their properties and contributions to cortical processing. Studies to date, however, have reported discrepant findings, providing a confusing picture. Here, we briefly review these studies and conduct simulations to explore the influence of several experimental and physiological factors on correlation measurements. Differences in response strength, the time window over which spikes are counted, spike sorting conventions, and internal states can all dramatically affect measured correlations and systematically bias estimates. Given these complicating factors, we offer guidelines for interpreting correlation data and a discussion of how best to evaluate the impact of correlations on cortical processing.

Cohen, Marlene R.; Kohn, Adam

2013-01-01

265

Dealing with circular correlation effects  

NASA Astrophysics Data System (ADS)

Discrete Fourier transforms (DFTs) are typically used to compute correlations and implementing correlation filters (CFs). Because of the properties of DFTs, resulting correlations are actually circular (also known as periodic) correlations. Using current CF design techniques, it is not possible to design a CF that produces exactly the desired linear correlation output. There are several techniques that may be used to reduce the effects of circular correlation. In this paper, we describe these techniques and provide some experimental results that compare these techniques. This work is sponsored by the Air Force Research Laboratory (AFRL). The views and conclusions contained in this document are those of the authors and should not be interpreted as representing offcial policies, either expressed or implied, of AFRL, or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein. This document is approved for public released via PA#: 88ABW-2013-1359.

Rodriguez, Andres; Vijaya Kumar, B. V. K.

2013-05-01

266

The syntax of correlative adverbs  

Microsoft Academic Search

The status of words like either, both and neither, here referred to as'correlative adverbs'or'correlatives'', is controversial. Using relevant data from Germanic languages, I shall show that the analyses of Schwarz (1999) and Larson (1985) are inadequate. Instead, I will suggest an analysis based on the assumptions in Hendriks (2001a,b, 2002): that correlatives are focus particles. Their syntactic position is discussed

Janne Bondi Johannessen

2005-01-01

267

Methods for correlated electron systems  

NASA Astrophysics Data System (ADS)

Three different approaches to correlated electron systems are presented. (i) The single impurity Anderson model is solved by a semi-analytical approach based on the flow equation method. (ii) A numerically implementable Multi-scale Many-Body approach to strongly correlated electron systems is introduced. An extension to quantum cluster methods, it approximates correlations on any given length-scale commensurate with the strength of the correlations on the respective scale. (iii) The spectral properties of the one-dimensional Holstein and breathing polaron models using the self-consistent Born approximation are presented.

Slezak, Cyrill Branko

268

Closed sets of nonlocal correlations  

SciTech Connect

We present a fundamental concept - closed sets of correlations - for studying nonlocal correlations. We argue that sets of correlations corresponding to information-theoretic principles, or more generally to consistent physical theories, must be closed under a natural set of operations. Hence, studying the closure of sets of correlations gives insight into which information-theoretic principles are genuinely different, and which are ultimately equivalent. This concept also has implications for understanding why quantum nonlocality is limited, and for finding constraints on physical theories beyond quantum mechanics.

Allcock, Jonathan; Linden, Noah [Department of Mathematics, University of Bristol, Bristol BS8 1TW (United Kingdom); Brunner, Nicolas; Popescu, Sandu; Skrzypczyk, Paul [H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Vertesi, Tamas [Institute of Nuclear Research, Hungarian Academy of Sciences, P.O. Box 51, H-4001 Debrecen (Hungary)

2009-12-15

269

Producing and Detecting Correlated Atoms  

SciTech Connect

We discuss experiments to produce and detect atom correlations in a degenerate or nearly degenerate gas of neutral atoms. First we treat the atomic analog of the celebrated Hanbury Brown Twiss experiment, in which atom correlations result simply from interference effects without any atom interactions. We have performed this experiment for both bosons and fermions. Next we show how atom interactions produce correlated atoms using the atomic analog of spontaneous four-wave mixing. Finally, we briefly mention experiments on a one dimensional gas on an atom chip in which correlation effects due to both interference and interactions have been observed.

Westbrook, C. I.; Schellekens, M.; Perrin, A.; Krachmalnicoff, V.; Viana Gomes, J.; Trebbia, J.-B.; Esteve, J.; Chang, H.; Bouchoule, I.; Boiron, D.; Aspect, A. [Laboratoire Charles Fabry de l'Institut d'Optique, Orsay (France); Jeltes, T.; McNamara, J.; Hogervorst, W.; Vassen, W. [Laser Center Vrije Universiteit, Amsterdam (Netherlands)

2006-11-07

270

Inter-Subject Correlation in fMRI: Method Validation against Stimulus-Model Based Analysis  

PubMed Central

Within functional magnetic resonance imaging (fMRI), the use of the traditional general linear model (GLM) based analysis methods is often restricted to strictly controlled research setups requiring a parametric activation model. Instead, Inter-Subject Correlation (ISC) method is based on voxel-wise correlation between the time series of the subjects, which makes it completely non-parametric and thus suitable for naturalistic stimulus paradigms such as movie watching. In this study, we compared an ISC based analysis results with those of a GLM based in five distinct controlled research setups. We used International Consortium for Brain Mapping functional reference battery (FRB) fMRI data available from the Laboratory of Neuro Imaging image data archive. The selected data included measurements from 37 right-handed subjects, who all had performed the same five tasks from FRB. The GLM was expected to locate activations accurately in FRB data and thus provide good grounds for investigating relationship between ISC and stimulus induced fMRI activation. The statistical maps of ISC and GLM were compared with two measures. The first measure was the Pearson's correlation between the non-thresholded ISC test-statistics and absolute values of the GLM Z-statistics. The average correlation value over five tasks was 0.74. The second was the Dice index between the activation regions of the methods. The average Dice value over the tasks and three threshold levels was 0.73. The results of this study indicated how the data driven ISC analysis found the same foci as the model-based GLM analysis. The agreement of the results is highly interesting, because ISC is applicable in situations where GLM is not suitable, for example, when analyzing data from a naturalistic stimuli experiment.

Pajula, Juha; Kauppi, Jukka-Pekka; Tohka, Jussi

2012-01-01

271

Correlations between trans-membrane pressure (TMP) and sludge properties in submerged membrane electro-bioreactor (SMEBR) and conventional membrane bioreactor (MBR).  

PubMed

The influence of sludge properties in SMEBR and conventional MBR pilot systems on membrane fouling was investigated. Generated data were analyzed using statistical analysis Pearson's product momentum correlation coefficient (r(p)). Analysis showed that TMP had strong direct (r(p)=0.9182) and inverse (r(p)=-0.9205) correlations to mean particle size diameter in MBR and SMEBR, respectively. TMP in SMEBR had a strong direct correlation to the sludge mixed liquor suspended solids concentration (MLSS) (r(p)=0.7757) while a weak direct correlation (r(p)=0.1940) was observed in MBR. SMEBR showed a moderate inverse correlation (r(p)=-0.6118) between TMP and soluble carbohydrates (EPS(c)) and a very weak direct correlation (r(p)=0.3448) to soluble proteins (EPS(p)). Conversely, EPS(p) in MBR had more significant impact (r(p)=0.4856) on membrane fouling than EPS(c) (r(p)=0.3051). The results provide insight into optimization of operational conditions in SMEBR system to overcome membrane fouling. PMID:22797086

Hasan, Shadi W; Elektorowicz, Maria; Oleszkiewicz, Jan A

2012-06-21

272

Characterization of spatiotemporally complex gait patterns using cross-correlation signatures.  

PubMed

We hypothesize that spatiotemporal joint coupling patterns during gait are closely associated with musculoskeletal injury mechanics. Previous studies examining joint coupling, have primarily focused on coupling between single pairs of neighboring body segments or joints; thus falling short of characterizing the full spatiotemporal complexity across the entire gait apparatus. This study proposes the reliance on properties of the temporal cross-correlation of distinct joint variables as a means to characterize and detect differences in multiple segmental coupling pairs and to quantify how these couplings change between different gait conditions or test groups. In particular, for each subject, a characteristic diagram array is obtained whose entries include the maximum values of the cross-correlation between all pairs of joint variables as well as the associated phase shifts at which these maxima are recorded. Paired t-tests are then used to highlight significant differences in the corresponding entries between two gait conditions. In the present study, this technique was applied to angular displacement and velocity histories across 12 lower extremity joint variables, for healthy subjects with and without a brace on the right knee. As expected, the statistical analysis indicated that the temporal cross-correlations associated with the right knee-angle variables differed the most between the two gait conditions. In addition, significant differences (p<0.01) were found in the coupling between other pairs of joint variables, establishing a characteristic spatiotemporal signature for the changes from normative gait that result from reduced mobility at the knee. PMID:22390962

Park, Kiwon; Dankowicz, Harry; Hsiao-Wecksler, Elizabeth T

2012-03-03

273

Elliptocytes and tailed poikilocytes correlate with severity of iron-deficiency anemia.  

PubMed

This study examines the relationships between abnormal RBC morphology, RBC indices measured with an automated hematology analyzer, serum iron studies, and severity of anemia in patients with findings indicative of iron-deficiency anemia. Counts and morphologic classification of 1,000 RBCs from each of 22 patients were performed, and correlations were determined between parameters. The Student t test was used to determine the level of significance for correlations between parameters. Several significant relationships were found. As the percentage of elliptocytes increased, hemoglobin concentration, hematocrit, RBC concentration, and mean corpuscular hemoglobin level decreased (r = .48, .44, .40, and .49, respectively; P < .05). As the percentage of tailed poikilocytes increased, hemoglobin concentration, hematocrit, and RBC concentration decreased (r = .70, .77, and .71, respectively; P < .01) and RBC distribution width increased (r = .73; P < .01). Of significance, serum ferritin levels, long considered the best single indicator of iron deficiency, showed no correlation with the morphologic abnormalities assessed, severity of anemia, or any of the analyzer-generated indices. Our results indicate that microscopic evaluation of RBC morphology remains an important tool for the pathologist to evaluate the severity of anemia in patients with iron deficiency. PMID:10230358

Rodgers, M S; Chang, C C; Kass, L

1999-05-01

274

Changes in nasal airflow and heat transfer correlate with symptom improvement after surgery for nasal obstruction.  

PubMed

Surgeries to correct nasal airway obstruction (NAO) often have less than desirable outcomes, partly due to the absence of an objective tool to select the most appropriate surgical approach for each patient. Computational fluid dynamics (CFD) models can be used to investigate nasal airflow, but variables need to be identified that can detect surgical changes and correlate with patient symptoms. CFD models were constructed from pre- and post-surgery computed tomography scans for 10 NAO patients showing no evidence of nasal cycling. Steady-state inspiratory airflow, nasal resistance, wall shear stress, and heat flux were computed for the main nasal cavity from nostrils to posterior nasal septum both bilaterally and unilaterally. Paired t-tests indicated that all CFD variables were significantly changed by surgery when calculated on the most obstructed side, and that airflow, nasal resistance, and heat flux were significantly changed bilaterally as well. Moderate linear correlations with patient-reported symptoms were found for airflow, heat flux, unilateral allocation of airflow, and unilateral nasal resistance as a fraction of bilateral nasal resistance when calculated on the most obstructed nasal side, suggesting that these variables may be useful for evaluating the efficacy of nasal surgery objectively. Similarity in the strengths of these correlations suggests that patient-reported symptoms may represent a constellation of effects and that these variables should be tracked concurrently during future virtual surgery planning. PMID:24063885

Kimbell, J S; Frank, D O; Laud, Purushottam; Garcia, G J M; Rhee, J S

2013-08-26

275

Correlation of neurocognitive function and brain parenchyma volumes in children surviving cancer  

NASA Astrophysics Data System (ADS)

This research builds on our hypothesis that white matter damage and associated neurocognitive symptoms, in children treated for cancer with cranial spinal irradiation, spans a continuum of severity that can be reliably probed using non-invasive MR technology. Quantitative volumetric assessments of MR imaging and psychological assessments were obtained in 40 long-term survivors of malignant brain tumors treated with cranial irradiation. Neurocognitive assessments included a test of intellect (Wechsler Intelligence Test for Children, Wechsler Adult Intelligence Scale), attention (Conner's Continuous Performance Test), and memory (California Verbal Learning Test). One-sample t-tests were conducted to evaluate test performance of survivors against age-adjusted scores from the test norms; these analyses revealed significant impairments in all apriori selected measures of intelligence, attention, and memory. Partial correlation analyses were performed to assess the relationships between brain tissues volumes (normal appearing white matter (NAWM), gray matter, and CSF) and neurocognitive function. Global intelligence (r = 0.32, p = 0.05) and global attentional (r = 0.49, p < 0.01) were significantly positively correlated with NAWM volumes, whereas global memory was significantly positively correlated with overall brain parenchyma (r = 0.38, p = 0.04). We conclude that quantitative assessment of MR examinations in survivors of childhood cancer treated with cranial irradiation reveal that loss of NAWM is associated with decreased intellectual and attentional deficits, whereas overall parenchyma loss, as reflected by increased CSF and decreased white matter, is associated with memory-related deficits.

Reddick, Wilburn E.; White, Holly A.; Glass, John O.; Mulhern, Raymond K.

2002-04-01

276

My Child Doesn't Test Well. Carnegie Perspectives  

ERIC Educational Resources Information Center

|The writer examines a variety of reasons why test performance may not always be a valid measure of a person's competence or potential. Citing that a sizable percentage of students perform well in their schoolwork but poorly on standardized, multiple-choice tests, Bond defines and discusses four candidates as source factors for the phenomenon: (1)…

Bond, Lloyd

2007-01-01

277

Correlation femtoscopy of small systems  

NASA Astrophysics Data System (ADS)

The basic principles of the correlation femtoscopy, including its correspondence to the Hanbury Brown and Twiss intensity interferometry, are reexamined. The main subject of the paper is an analysis of the correlation femtoscopy when the source size is as small as the order of the uncertainty limit. It is about 1 fm for the current high energy experiments. Then the standard femtoscopy model of random sources is inapplicable. The uncertainty principle leads to the partial indistinguishability and coherence of closely located emitters that affect the observed femtoscopy scales. In thermal systems the role of corresponding coherent length is taken by the thermal de Broglie wavelength that also defines the size of a single emitter. The formalism of partially coherent phases in the amplitudes of closely located individual emitters is used for the quantitative analysis. The general approach is illustrated analytically for the case of the Gaussian approximation for emitting sources. A reduction of the interferometry radii and a suppression of the Bose-Einstein correlation functions for small sources due to the uncertainty principle are found. There is a positive correlation between the source size and the intercept of the correlation function. The peculiarities of the nonfemtoscopic correlations caused by minijets and fluctuations of the initial states of the systems formed in pp and e+e- collisions are also analyzed. The factorization property for the contributions of femtoscopic and nonfemtoscopic correlations into complete correlation function is observed in numerical calculations in a wide range of the model parameters.

Sinyukov, Yu. M.; Shapoval, V. M.

2013-05-01

278

Object Localization by Bayesian Correlation  

Microsoft Academic Search

Maximisation of cross-correlation is a commonly used prin- ciple for intensity-based object localization that gives a sin- gle estimate of location. However, to facilitate sequential inference (eg over time or scale) and to allow the representa- tion of ambiguity, it is desirable to represent an entire prob- ability distribution for object location. Although the cross- correlation itself (or some function

Josephine Sullivan; Andrew Blake; Michael Isard; John Maccormick

1999-01-01

279

A GENERAL CANONICAL CORRELATION INDEX  

Microsoft Academic Search

BECAUSE A CANONICAL CORRELATION IS THE CORRELATION BETWEEN 2 LINEAR COMPOSITES, IT PRESENTS SOME INTERPRETIVE PROBLEMS. NO MEASURE OF THE REDUNDANCY IN 1 SET OF VARIABLES, GIVEN ANOTHER SET OF VARIABLES, HAS BEEN AVAILABLE. A NONSYMMETRIC INDEX OF REDUNDANCY IS PROPOSED WHICH REPRESENTS THE AMOUNT OF PREDICTED VARIANCE IN A SET OF VARIABLES.

DOUGLAS STEWART; WILLIAM LOVE

1968-01-01

280

Correlation Weights in Multiple Regression  

ERIC Educational Resources Information Center

A general theory on the use of correlation weights in linear prediction has yet to be proposed. In this paper we take initial steps in developing such a theory by describing the conditions under which correlation weights perform well in population regression models. Using OLS weights as a comparison, we define cases in which the two weighting…

Waller, Niels G.; Jones, Jeff A.

2010-01-01

281

Alignment effects in correlation spectra  

SciTech Connect

The structure of nuclei at very high spins can be studied by measuring correlations between ..gamma..-ray energies in the unresolved spectrum emitted. Collective rotations have been shown to produce characteristic features in such correlation spectra. The features produced by the noncollective alignment effects in some high spin Er nuclei are shown here.

Ellegaard, C.; Deleplanque, M.A.; Andersen, O.; Herskind, B.; Stephens, F.S.; Diamond, R.M.; Kluge, H.; Schuck, C.; Shih, S.; Draper, J.E.

1982-03-08

282

Electron correlation in the continuum  

SciTech Connect

We consider a class of problems, notably double ionization, which require accurate descriptions of correlation in both the initial and final states. Methods are presented for representing correlated wavefunctions on a basis spline lattice, and for calculating bound-continuum transition probabilities. 13 refs.

Bottcher, C.; Strayer, M.R.

1989-07-24

283

GSP auctions with correlated types  

Microsoft Academic Search

The Generalized Second Price (GSP) auction is the primary method by which sponsered search advertisements are sold. We study the performance of this auction in the Bayesian setting for players with correlated types. Correlation arises very naturally in the context of sponsored search auctions, especially as a result of uncertainty inherent in the behaviour of the underlying ad allocation algorithm.

Brendan Lucier; Renato Paes Leme

2011-01-01

284

On Inferring Causation from Correlation.  

ERIC Educational Resources Information Center

|Discusses linear structural relations, Two Stage Least Squares, and path analysis as statistical procedures that sometimes permit causal inferences from correlational findings. Even though two variables cannot be interpreted causally due to a possible but unknown third variable, these methods are appropriate for handling models with correlated

Shedler, Johnathan

1995-01-01

285

Polarization correlations of Dirac particles  

SciTech Connect

We calculate the polarization correlation function in the Einstein-Podolsky-Rosen-type experiments with relativistic spin-1/2 particles. This function depends monotonically on the particle momenta. Moreover, we also show that the polarization correlation function violates the Clauser-Horn-Shimony-Holt inequality and the degree of this violation can depend on the particle momenta and the motion of observers.

Caban, Pawel; Dziegielewska, Agnieszka; Karmazyn, Anna; Okrasa, Malgorzata [Department of Theoretical Physics, University of Lodz, Pomorska 149/153, 90-236 Lodz (Poland)

2010-03-15

286

Noise cascades and Lévy correlations  

NASA Astrophysics Data System (ADS)

We explore a general model of stochastic noise cascades which can be illustrated by the example of rain dropping down on the earth and then seeping through layers of ground—pouring down layer by layer. The rain represents an input noise that is assumed to be spatially uncorrelated, and each ground layer represents a stochastic convolution filter. As the input noise percolates through the layered filters spatial correlations—which are initially nonexistent—build up. We study this build-up of correlations and focus on the following question: are there universally emergent forms of spatial correlations? The answer is proved affirmative, and is shown to be uniquely characterized by power spectra that coincide with the Fourier transform of the spherically symmetric Lévy distribution. We term these universally emergent spatial correlations ‘Lévy correlations’.

Eliazar, Iddo I.; Shlesinger, Michael F.

2013-10-01

287

Squeezed Particle-Antiparticle Correlations  

NASA Astrophysics Data System (ADS)

A novel type of correlation involving particle-antiparticle pairs was found out in the 1990's. Currently known as squeezed or Back-to-Back Correlations (BBC), they should be present if the hadronic masses are modified in the hot and dense medium formed in high energy heavy ion collisions. Although well-established theoretically, such hadronic correlations have not yet been observed experimentally. In this phenomenological study we suggest a promising way to search for the BBC signal, by looking into the squeezed correlation function of phi phi and K+ K- pairs at RHIC energies, as function of the pair average momentum, K12=(@BOLD@ k1+@BOLD@ k2)/2. The effects of in-medium mass-shift on the identical particle correlations (Hanbury-Brown and Twiss effect) are also discussed.

Padula, S. S.; Dudek, D. M.; Socolowski, O., Jr.

2009-04-01

288

CORRELATIONS BETWEEN PLANETARY MICROLENSING PARAMETERS  

SciTech Connect

Characterization of microlensing planets requires modeling of observed light curves including many parameters. Studying the dependency of the pattern of light curves on the lensing parameters and the correlations between the parameters is important to understand how the uncertainties of the planetary parameters are propagated from other parameters. In this paper, we show that despite the apparent complexity of the pattern of light curves of planetary lensing events, the correlations between the lensing parameters can be understood by studying how the parameters affect the characteristics of lensing light curves such as the height and width, the caustic-crossing time scale, and the location and duration of planetary perturbations. Based on analytic arguments about the dependency of light curve features on the parameters, we obtain the correlations for the two representative cases of planetary events. We also demonstrate the applicability of the correlations to general planetary events by actually obtaining the correlations from modelings of light curves produced by simulations.

Han, Cheongho; Hwang, Kyu-Ha; Ryu, Yoon-Hyun, E-mail: cheongho@astroph.chungbuk.ac.k, E-mail: kyuha@astroph.chungbuk.ac.k, E-mail: yhryu@astroph.chungbuk.ac.k [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of)

2010-09-01

289

Neural correlations, decisions and actions  

PubMed Central

4. Summary of recent advances Multielectrode recording experiments let us measure correlations between the activity of individual neurons and the neural circuits in which they are embedded. Recently, multielectrode studies have been emphasizing how correlated neuronal activity is linked with behavior. Decisions are fundamental to voluntary behavior. Here, we discuss computations necessary to turn a decision into an action and review progress in studying correlated neural activity in areas of the brain which link sensory and motor representations. The themes that emerge are that correlated patterns of activity in populations of neurons can be revealed by measurements of field potential fluctuations and that these measurements can relate the activity of individual neurons to the activity of populations of neurons distributed across different regions of the brain. Investigations into patterns of neuronal correlation are helping us to understand how decisions and other cognitive processes result from the interactions between different brain systems that are responsible for controlling and regulating our behavior.

Pesaran, Bijan

2010-01-01

290

[Antimicrobial use and its correlations with the frequency of carbapenem-resistant Pseudomonas aeruginosa strains in a hospital setting].  

PubMed

One of the major causes leading to increased antibiotic resistance is excess antimicrobial consumption. We have analysed the correlation between antibiotic use and frequency of carbapenem-resistant Pseudomonas aeruginosa (CRPA) strains in the general intensive care unit of a university hospital Antibiotic use was expressed as number DDD (daily defined doses)/100 occupied hospital bed-days (BD). CRPA incidence rates were determined by number of unique isolates reported to 100,000 BD. The average use of antibiotics between January and August 2008 was 174 DDD/100 BD. The first four most frequently prescribed antibiotics were as follows: first and second generation cephalosporins (47 DDD/100 BD), carbapenemns (29 DDD/100 BD), fluoroquinolones (26 DDD/100 BD) and glycopeptids (20 DDD/100 BD). Average monthly incidence rate of CRPA was 546/100,000 BD (319-773/100,000 BD. CI 95%). There was a correlation between CRPA incidence rate and carbapenem plus fluoroquinolone use (Pearson coefficient of correlation r = 0.7, p < 0.05). Our data showed that the evolution of CRPA incidence rates was related to carbapenem and fluoroquinolone use. PMID:21553483

Székely, Edit; Bucur, Gabriela; Vass, Levente; Butiurca, Manuela; Bilca, Doina; Foldes, Annamaria; Lorinczi, Lilla

291

Spinocerebellar ataxias - genotype-phenotype correlations in 104 Brazilian families  

PubMed Central

OBJECTIVE: Spinocerebellar ataxias are neurodegenerative disorders involving the cerebellum and its connections. There are more than 30 distinct subtypes, 16 of which are associated with an identified gene. The aim of the current study was to evaluate a large group of patients from 104 Brazilian families with spinocerebellar ataxias. METHODS: We studied 150 patients from 104 families with spinocerebellar ataxias who had received molecular genetic testing for spinocerebellar ataxia types 1, 2, 3, 6, 7, 8, 10, 12, 17, and dentatorubral-pallidoluysian atrophy. A statistical analysis of the results was performed using basic descriptive statistics and the correlation coefficient (r), Student's t-test, chi-square test, and Yates' correction. The statistical significance level was established for p-values <0.05. RESULTS: The results show that the most common subtype was spinocerebellar ataxia 3, which was followed by spinocerebellar ataxia 10. Moreover, the comparison between patients with spinocerebellar ataxia 3, spinocerebellar ataxia 10, and other types of spinocerebellar ataxia revealed distinct clinical features for each type. In patients with spinocerebellar ataxia 3, the phenotype was highly pleomorphic, although the most common signs of disease included cerebellar ataxia (CA), ophthalmoplegia, diplopia, eyelid retraction, facial fasciculation, pyramidal signs, and peripheral neuropathy. In patients with spinocerebellar ataxia 10, the phenotype was also rather distinct and consisted of pure cerebellar ataxia and abnormal saccadic eye movement as well as ocular dysmetria. Patients with spinocerebellar ataxias 2 and 7 presented highly suggestive features of cerebellar ataxia, including slow saccadic ocular movements and areflexia in spinocerebellar ataxia 2 and visual loss in spinocerebellar ataxia 7. CONCLUSIONS: Spinocerebellar ataxia 3 was the most common subtype examined, followed by spinocerebellar ataxia 10. Patients with spinocerebellar ataxia 2 and 7 demonstrated highly suggestive features, whereas the phenotype of spinocerebellar ataxia 3 patients was highly pleomorphic and spinocerebellar ataxia 10 patients exhibited pure cerebellar ataxia. Epilepsy was absent in all of the patients with spinocerebellar ataxia 10 in this series.

Teive, Helio A. G.; Munhoz, Renato P.; Arruda, Walter O.; Lopes-Cendes, Iscia; Raskin, Salmo; Werneck, Lineu C.; Ashizawa, Tetsuo

2012-01-01

292

Autocorrelation and cross-correlation between hCG? and PAPP-A in repeated sampling during first trimester of pregnancy.  

PubMed

Abstract Background: Theoretically, repeated sampling of free ?-human chorionic gonadotropin (hCG?) and pregnancy associated plasma protein-A (PAPP-A) in the first trimester of pregnancy might improve performance of risk assessment of trisomy 21 (T21). To assess the performance of a screening test involving repeated measures of biochemical markers, correlations between markers must be estimated. The aims of this study were to calculate the autocorrelation and cross-correlation between hCG? and PAPP-A in the first trimester of pregnancy and to investigate the possible impact of gestational age at the first sample and time between sampling on the correlation. Methods: A prospective study was conducted including 3891 unaffected singleton pregnancies. Two measurements of hCG? and PAPP-A were obtained during the first trimester in each pregnancy. Correlations between the four parameters, hCG? first, hCG? second, PAPP-A first and PAPP-A second, were estimated and presented in terms of Pearson's r coefficients. Furthermore, the correlation between paired samples as a function of time between samples was investigated. Results: The study demonstrated high correlation between first and second samples of hCG? and PAPP-A with a correlation coefficient of 0.80 and 0.79, respectively. By contrast, the correlations between hCG? and PAPP-A were low. In addition, the study demonstrated that the correlation between paired samples of hCG? and PAPP-A decreases with earlier gestational age at the first sample and with increasing time between samples. Conclusions: We have developed a parameter set in terms of correlations between biochemical markers, which can be incorporated into a T21 screening algorithm based on repeated measures within the first trimester. PMID:23612665

Nørgaard, Pernille; Wright, Dave; Ball, Susan; Newell, Paul; Kirkegaard, Ida; Petersen, Olav Bjørn; Uldbjerg, Niels; Tørring, Niels; Jørgensen, Finn Stener; Friis-Hansen, Lennart; Ekelund, Charlotte; Tabor, Ann; Sørensen, Steen

2013-09-01

293

Clinical Correlates to Laboratory Measures for use in Non-Contact Anterior Cruciate Ligament Injury Risk Prediction Algorithm  

PubMed Central

Background Prospective measures of high knee abduction moment during landing identify female athletes at high risk for non-contact anterior cruciate ligament injury. Biomechanical laboratory measurements predict high knee abduction moment landing mechanics with high sensitivity (85%) and specificity (93%). The purpose of this study was to identify correlates to laboratory-based predictors of high knee abduction moment for use in a clinic-based anterior cruciate ligament injury risk prediction algorithm. The hypothesis was that clinically obtainable correlates derived from the highly predictive laboratory-based models would demonstrate high accuracy to determine high knee abduction moment status. Methods Female basketball and soccer players (N=744) were tested for anthropometrics, strength and landing biomechanics. Pearson correlation was used to identify clinically feasible correlates and logistic regression to obtain optimal models for high knee abduction moment prediction. Findings Clinical correlates to laboratory-based measures were identified and predicted high knee abduction moment status with 73% sensitivity and 70% specificity. The clinic-based prediction algorithm, including (Odds Ratio: 95% confidence interval) knee valgus motion (1.43:1.30–1.59 cm), knee flexion range of motion (.98:0.96–1.01 deg), body mass (1.04:1.02–1.06 kg), tibia length (1.38:1.25–1.52 cm) and quadriceps to hamstring ratio (1.70:1.06–2.70) predicted high knee abduction moment status with C statistic 0.81. Interpretation The combined correlates of increased knee valgus motion, knee flexion range of motion, body mass, tibia length and quadriceps to hamstrings ratio predict high knee abduction moment status in female athletes with high sensitivity and specificity.

Myer, Gregory D.; Ford, Kevin R.; Khoury, Jane; Succop, Paul; Hewett, Timothy E.

2010-01-01

294

Randomized controlled trial of desloratadine for persistent allergic rhinitis: correlations between symptom improvement and quality of life.  

PubMed

Allergic rhinitis (AR) symptoms can impart emotional, quality of life (QOL), and work productivity burdens, especially in persistent AR (PER). Desloratadine, an H1-receptor antagonist, has been shown to be effective against nasal and nonnasal AR symptoms and to improve QOL. Exploratory analyses were conducted to evaluate whether desloratadine-mediated symptom improvement correlated with improvements in QOL and productivity. The Aerius Control: Clinical and Evaluative Profile of Treatment 2 (NCT00405964) study was a 12-week, multinational, randomized, placebo-controlled prospective study of once-daily desloratadine at 5 mg in subjects with moderate-to-severe PER. Assessments included twice-daily symptom severity ratings (0 = none to 3 = severe; total and individual symptoms), sleep interference (morning [A.M.]), interference with activities of daily living (ADL; evening [P.M.]), the Rhinoconjunctivitis Quality of Life Questionnaire-Standardized version (baseline and days 29 and 85), and the Work Productivity and Activity Impairment-Allergy-Specific questionnaire (baseline and weekly). Pearson product-moment correlation statistics (r) were determined to assess correlations between symptom score improvements and QOL factors. All desloratadine-treated patients (n = 360) were included in this exploratory analysis. In the desloratadine-treated patients, all correlations tested were positive (all p < 0.0001). The highest coefficients were seen for the correlations between A.M./P.M. PRIOR total five-symptom score and interference with ADL (r = 0.72) and between A.M. NOW congestion and ADL interference (r = 0.69). Continuous daily treatment of moderate-to-severe PER with desloratadine at 5 mg/day significantly improved symptoms, which correlated positively, albeit moderately, with QOL benefits and reversal of functional impairments caused by PER. PMID:23676577

Bousquet, Jean; Zuberbier, Torsten; Canonica, G Walter; Fokkens, Wytske J; Gopalan, Gokul; Shekar, Tulin

295

High accurate volume holographic correlator with 4000 parallel correlation channels  

NASA Astrophysics Data System (ADS)

Volume holographic correlator allows simultaneously calculate the two-dimensional inner product between the input image and each stored image. We have recently experimentally implemented in VHC 4000 parallel correlation channels with better than 98% output accuracy in a single location in a crystal. The speckle modulation is used to suppress the sidelobes of the correlation patterns, allowing more correlation spots to be contained in the output plane. A modified exposure schedule is designed to ensure the hologram in each channel with unity diffraction efficiency. In this schedule, a restricted coefficient was introduced into the original exposure schedule to solve the problem that the sensitivity and time constant of the crystal will change as a time function when in high-capacity storage. An interleaving method is proposed to improve the output accuracy. By unifying the distribution of the input and stored image patterns without changing the inner products between them, this method could eliminate the impact of correlation pattern variety on calculated inner product values. Moreover, by using this method, the maximum correlation spot size is reduced, which decreases the required minimum safe clearance between neighboring spots in the output plane, allowing more spots to be parallely detected without crosstalk. The experimental results are given and analyzed.

Ni, Kai; Qu, Zongyao; Cao, Liangcai; Su, Ping; He, Qingsheng; Jin, Guofan

2008-03-01

296

Pseudopotentials for correlated electron systems  

NASA Astrophysics Data System (ADS)

A scheme is developed for creating pseudopotentials for use in correlated-electron calculations. Pseudopotentials for the light elements H, Li, Be, B, C, N, O, and F, are reported, based on data from high-level quantum chemical calculations. Results obtained with these correlated electron pseudopotentials (CEPPs) are compared with data for atomic energy levels and the dissociation energies, molecular geometries, and zero-point vibrational energies of small molecules obtained from coupled cluster single double triple calculations with large basis sets. The CEPPs give better results in correlated-electron calculations than Hartree-Fock-based pseudopotentials available in the literature.

Trail, J. R.; Needs, R. J.

2013-07-01

297

Correlated domains in spin glasses  

NASA Astrophysics Data System (ADS)

We study the 3D Edwards-Anderson spin glasses, by analyzing spin-spin correlation functions in thermalized spin configurations at low T on lattices of sizes up to 323. We consider individual disorder samples and analyze connected clusters of very correlated sites: we analyze how the volume and the surface of these clusters increase with the lattice size. We qualify the important excitations of the system by checking how large they are, and we define a correlation length by measuring their gyration radius. We find that the clusters have a very dense interface, compatible with being space filling.

Billoire, Alain; Maiorano, Andrea; Marinari, Enzo

2012-12-01

298

Precordial R Wave Height Does Not Correlate with Echocardiographic Findings in Boys with Duchenne Muscular Dystrophy.  

PubMed

OBJECTIVES.: Cardiomyopathy (CM) is an inevitable consequence of Duchenne muscular dystrophy, and electrocardiographic changes, right ventricular hypertrophy in particular, have been proposed to serve as an early marker for CM. To evaluate this concept, we assessed the correlation between R wave height in lead V1 and echocardiographic findings in boys with Duchenne muscular dystrophy. METHODS.: Serial echocardiograms and electrocardiograms (n = 800) were performed during each clinic visit in a cohort of 155 boys with Duchenne muscular dystrophy. Precordial R wave height in lead V1 was measured. Echocardiographic parameters included ejection fraction (EF), shortening fraction, and left ventricular end-diastolic dimension. Data were analyzed using Pearson correlation and linear regression. RESULTS.: Ages ranged from 1.8 to 37.2 years (mean 14.7 ± 5.9 years). Seventy-one patients had CM and 318/800 echocardiograms had an EF < 55%. Older patients tended to have a lower EF, but there was no correlation between age and left ventricular end-diastolic dimension. R wave height in lead V1 correlated poorly with both left ventricular end-diastolic dimension (r = 0.096, P =.0078) and EF (r = 0.096, P =.0088) for the whole cohort as well as those studies demonstrating an EF <55% (left ventricular end-diastolic dimension r = 0.089, P =.12 and EF?r = -0.044, P =.94). No individual patient demonstrated significant correlation between R wave height in lead V1 and left ventricular end-diastolic dimension or EF. Left ventricular end-diastolic dimension showed a moderate negative correlation with EF for the whole cohort (r = -0.394, P <.001) as well as those with an EF < 55% (r = -0.376, P <.001). CONCLUSIONS.: The precordial R wave height in V1 correlates poorly with the presence of depressed left ventricular function and is not prognostic for the development of CM. While not predictive for CM, the electrocardiogram remains vital to cardiac screening for boys with Duchenne muscular dystrophy due to risk for other cardiac manifestations such as arrhythmias. PMID:23510265

Thrush, Philip T; Edward, Neeraj; Flanigan, Kevin M; Mendell, Jerry R; Allen, Hugh D

2013-03-20

299

Correlation of histone methyl marks with circulating nucleosomes in blood plasma of cancer patients.  

PubMed

Circulating DNA is present in plasma/serum, mainly complexed with histones as nucleosomes. The detection of circulating nucleosomes (cNUCs) in the peripheral blood may be a diagnostic modality for cancer-associated changes of modified histone tails in blood circulation. In the present study, we investigated the correlation between the trimethylation of H3 lysine 9 (H3K9me3) and H4 lysine 20 (H4K20me3), which are hallmarks of pericentric heterochromatin, and cNUCs in healthy subjects and patients with colorectal cancer (CRC) and multiple myeloma (MM). The plasma concentration of cNUCs was measured using the Cell-Death Detection ELISA kit. Histone methylation marks were detected using chromatin immunoprecipitation (ChIP), followed by quantitative PCR with pericentric satellite 2 as the target sequence. The results showed a high variation in the concentrations of cNUCs, with healthy subjects exhibiting the lowest levels (median 0.194), the CRC patients intermediate (median 0.25) and the MM patients the highest levels (median 0.648). However, the differences between the groups did not reach statistical significance (p>0.05). Analysis using the Pearson's correlation test revealed a significant positive correlation between the concentration of cNUCs and H3K9me3 and H4K20me3 in the whole study group (N=57, p<0.001 for both histone marks). A study of the correlation between cNUCs and histone marks in the individual study groups demonstrated the correlation between cNUCs and H3K9me3 in CRC patients to be weak (p=0.046), indicating that circulating H3K9me3 may be modified in CRC patients. The histone marks were normalized using the values of cNUCs. In agreement with the weak correlation between cNUCs and H3K9me3 in CRC patients, H3K9me3 levels (median 0.047) were lowest in this group compared with the other two groups (0.06 in healthy subjects, 0.2 in MM patients, p = not significant). For H4K20me3, the median values were 0.022 in healthy subjects, 0.052 in CRC patients and 0.056 in MM patients. In conclusion, our findings indicate a marked correlation between cNUCs and histone methyl marks. PMID:22783398

Gezer, Ugur; Mert, Ufuk; Ozgür, Emre; Yörüker, Ebru E; Holdenrieder, Stefan; Dalay, Nejat

2012-02-10

300

A Correlational Study of Scoliosis and Trunk Balance in Adult Patients with Mandibular Deviation  

PubMed Central

Previous studies have confirmed that patients with mandibular deviation often have abnormal morphology of their cervical vertebrae. However, the relationship between mandibular deviation, scoliosis, and trunk balance has not been studied. Currently, mandibular deviation is usually treated as a single pathology, which leads to poor clinical efficiency. We investigated the relationship of spine coronal morphology and trunk balance in adult patients with mandibular deviation, and compared the finding to those in healthy volunteers. 35 adult patients with skeletal mandibular deviation and 10 healthy volunteers underwent anterior X-ray films of the head and posteroanterior X-ray films of the spine. Landmarks and lines were drawn and measured on these films. The axis distance method was used to measure the degree of scoliosis and the balance angle method was used to measure trunk balance. The relationship of mandibular deviation, spine coronal morphology and trunk balance was evaluated with the Pearson correlation method. The spine coronal morphology of patients with mandibular deviation demonstrated an “S” type curve, while a straight line parallel with the gravity line was found in the control group (significant difference, p<0.01). The trunk balance of patients with mandibular deviation was disturbed (imbalance angle >1°), while the control group had a normal trunk balance (imbalance angle <1°). There was a significant difference between the two groups (p<0.01). The degree of scoliosis and shoulder imbalance correlated with the degree of mandibular deviation, and presented a linear trend. The direction of mandibular deviation was the same as that of the lateral bending of thoracolumbar vertebrae, which was opposite to the direction of lateral bending of cervical vertebrae. Our study shows the degree of mandibular deviation has a high correlation with the degree of scoliosis and trunk imbalance, all the three deformities should be clinically evaluated in the management of mandibular deviation.

Yang, Yang; Wang, Na; Wang, Wenyong; Ding, Yin; Sun, Shiyao

2013-01-01

301

Morphometry of the suprascapular notch: correlation with scapular dimensions and clinical relevance  

PubMed Central

Background Better knowledge of the suprascapular notch anatomy may help to prevent and to assess more accurately suprascapular nerve entrapment syndrome. Our purposes were to verify the reliability of the existing data, to assess the differences between the two genders, to verify the correlation between the dimensions of the scapula and the suprascapular notch, and to investigate the relationship between the suprascapular notch and the postero-superior limit of the safe zone for the suprascapular nerve. Methods We examined 500 dried scapulae, measuring seven distances related to the scapular body and suprascapular notch; they were also catalogued according to gender, age and side. Suprascapular notch was classified in accordance with Rengachary’s method. For each class, we also took into consideration the width/depth ratio. Furthermore, Pearson's correlation was calculated. Results The frequencies were: Type I 12.4%, Type II 19.8%, Type III 22.8%, Type IV 31.1%, Type V 10.2%, Type VI 3.6%. Width and depth did not demonstrate a statistical significant difference when analyzed according to gender and side; however, a significant difference was found between the depth means elaborated according to median age (73 y.o.). Correlation indexes were weak or not statistically significant. The differences among the postero-superior limits of the safe zone in the six types of notches was not statistically significant. Conclusions Patient’s characteristics (gender, age and scapular dimensions) are not related to the characteristics of the suprascapular notch (dimensions and Type); our data suggest that the entrapment syndrome is more likely to be associated with a Type III notch because of its specific features.

2013-01-01

302

Socioeconomic Status Correlates with the Prevalence of Advanced Coronary Artery Disease in the United States  

PubMed Central

Background Increasingly studies have identified socioeconomic factors adversely affecting healthcare outcomes for a multitude of diseases. To date, however, there has not been a study correlating socioeconomic details from nationwide databases on the prevalence of advanced coronary artery disease. We seek to identify whether socioeconomic factors contribute to advanced coronary artery disease prevalence in the United States. Methods and Findings State specific prevalence data was queried form the United States Nationwide Inpatient Sample for 2009. Patients undergoing percutaneous coronary angioplasty and coronary artery bypass graft were identified as principal procedures. Non-cardiac related procedures, lung lobectomy and hip replacement (partial and total) were identified and used as control groups. Information regarding prevalence was then merged with data from the Behavioral Risk Factor Surveillance System, the largest, on-going telephone health survey system tracking health conditions and risk behaviors in the United States. Pearson's correlation coefficient was calculated for individual socioeconomic variables including employment status, level of education, and household income. Household income and education level were inversely correlated with the prevalence of percutaneous coronary angioplasty (?0.717; ?0.787) and coronary artery bypass graft surgery (?0.541; ?0.618). This phenomenon was not seen in the non-cardiac procedure control groups. In multiple linear regression analysis, socioeconomic factors were significant predictors of coronary artery bypass graft and percutaneous transluminal coronary angioplasty (p<0.001 and p?=?0.005, respectively). Conclusions Socioeconomic status is related to the prevalence of advanced coronary artery disease as measured by the prevalence of percutaneous coronary angioplasty and coronary artery bypass graft surgery.

Bashinskaya, Bronislava; Nahed, Brian V.; Walcott, Brian P.; Coumans, Jean-Valery C. E.; Onuma, Oyere K.

2012-01-01

303

Psychosocial and sociocultural correlates of depressive symptoms among diverse African American women.  

PubMed

African American women are faced with many challenges regarding their historical, cultural, and social structural position in the United States that may heighten their vulnerability for depression, one of the most prevalent disorders that can engender poor functionality. The purpose of this cross-sectional pilot study was to foster greater understanding about the occurrence and correlates of depressive symptoms among a diverse convenience sample of 63 African American women recruited from a comprehensive primary health care clinic (n = 23), a small private academic institution (n = 25), and an urban community setting (n = 15). Self-report data concerning selected psychological, sociocultural, and biological factors were collected. Descriptive statistics, Pearson product moment correlation, and analysis of variance were used to analyze data. Results indicated several similarities and differences among the 3 groups of women concerning levels of depressive symptoms and their correlates. Among the total sample, symptoms of depression were mild among 65% of the women. Depressive symptoms were significant and positively associated with negative and ruminative thinking (r = 0.79, p < .01), low self-esteem (r = 0.58, p < .01), stressful life events (r = 0.43, p < .05), low social support (r = 0.46, p <.01), depression stigma (r = 0.36, p < 01), and indication of chronic diseases (r = 0.34, p < .01). Depressive symptoms were significant and negatively associated with resiliency (r = -0.48, p < .01) and spiritual well-being (r = -.47, p < .01). This research adds to the empirical data concerning contributors to depressive symptoms for African American women. PMID:23560351

Holden, Kisha B; Hall, Stephanie P; Robinson, Maryam; Triplett, Sharra; Babalola, Dolapo; Plummer, Valens; Treadwell, Henrie; Bradford, L DiAnne

304

Prognostic value of ornithine decarboxylase and polyamines in human breast cancer: correlation with clinicopathologic parameters.  

PubMed

The polyamines putrescine, spermidine, and spermine and ornithine decarboxylase (ODC), the rate-limiting enzyme in their biosynthetic pathway, play an important role in cell proliferation, differentiation, and transformation. In the present study, we have analyzed polyamine concentrations and ODC activity in samples from benign breast diseases (n = 36), benign breast tissue adjacent to the primary carcinoma (n = 19), and breast carcinoma (n = 104). ODC activity in primary carcinoma was significantly higher (2.42 +/- 0.22 nmol CO2/h g; P < 0.001) than that found in benign breast (0.62 +/- 0.15 nmol CO2/h g) or in breast tissue adjacent to the primary carcinoma (0.52 +/- 0.16 nmol CO2/h g). The total polyamine content of breast cancer tissues was higher than in benign breast diseases (704.3 +/- 38.3 nmol/g wet weight versus 295.8 +/- 27.4 nmol/g wet weight) and correlated well with ODC activity (Pearson, r = 0.42; P < 0.001). ODC activity correlated with histological grade, peritumoral lymphatic or blood vessel invasion, S-phase fraction, and cathepsin D. Total polyamine concentration increased with S-phase fraction, cathepsin D, and aneuploidy. No significant correlation was found between ODC or polyamines and tumor size, lymph node involvement, or steroid receptor status. A major finding in our study was that ODC activity was an independent prognostic factor for recurrence and death. The results indicate that the estimation of ODC activity and polyamines in human breast carcinoma might be useful to determine tumor aggressiveness and suggest that ODC may have a potential value as both a prognostic factor and a chemoprevention target in human breast cancer. PMID:10473083

Cañizares, F; Salinas, J; de las Heras, M; Diaz, J; Tovar, I; Martinez, P; Peñafiel, R

1999-08-01

305

Psychosocial and Sociocultural Correlates of Depressive Symptoms Among Diverse African American Women  

PubMed Central

African American women are faced with many challenges regarding their historical, cultural, and social structural position in the United States that may heighten their vulnerability for depression, one of the most prevalent disorders that can engender poor functionality. The purpose of this cross-sectional pilot study was to foster greater understanding about the occurrence and correlates of depressive symptoms among a diverse convenience sample of 63 African American women recruited from a comprehensive primary health care clinic (n = 23), a small private academic institution (n = 25), and an urban community setting (n = 15). Self-report data concerning selected psychological, sociocultural, and biological factors were collected. Descriptive statistics, Pearson product moment correlation, and analysis of variance were used to analyze data. Results indicated several similarities and differences among the 3 groups of women concerning levels of depressive symptoms and their correlates. Among the total sample, symptoms of depression were mild among 65% of the women. Depressive symptoms were significant and positively associated with negative and ruminative thinking (r = 0.79, p < .01), low self-esteem (r = 0.58, p < .01), stressful life events (r = 0.43, p < .05), low social support (r = 0.46, p < .01), depression stigma (r= 0.36, p < 01), and indication of chronic diseases (r = 0.34, p <.01). Depressive symptoms were significant and negatively associated with resiliency (r = ?0.48, p < .01) and spiritual well-being [r = ?.47, p < .01). This research adds to the empirical data concerning contributors to depressive symptoms for African American women.

Holden, Kisha B.; Hall, Stephanie P.; Robinson, Maryam; Triplett, Sharra; Babalola, Dolapo; Plummer, Valens; Treadwell, Henrie; Bradford, L. DiAnne

2013-01-01

306

Correlates of alcohol use in adults with ADHD and comorbid alcohol use disorders: exploratory analysis of a placebo-controlled trial of atomoxetine  

PubMed Central

Background Attention-deficit/hyperactivity disorder (ADHD) and substance use disorder are often comorbid in adults. The effects of ADHD treatment on comorbid alcohol use disorder have not been extensively studied. Objective To assess correlates of ADHD and alcohol use outcomes in ADHD with comorbid alcohol use disorders, via a post-hoc exploratory subgroup analysis of a previously conducted, randomized, double-blind, placebo controlled study of recently abstinent adults. Methods Adults who had ADHD and alcohol use disorders and were abstinent for 4–30 days were randomized to daily atomoxetine 25–100 mg (mean final dose=89.9 mg) or placebo for 12 weeks. Changes in ADHD symptoms from baseline to endpoint were assessed using the ADHD Investigator Symptom Rating Scale (AISRS) total score, alcohol use by the timeline followback method, and alcohol cravings by the Obsessive Compulsive Drinking Scale. Results Of 147 subjects receiving atomoxetine (n=72) or placebo (n=75) in the primary study, 80 (54%) completed 12 weeks (n=32 atomoxetine; n=48 placebo). Improvements in ADHD symptoms on the AISRS correlated significantly with decreases in alcohol cravings (Pearson’s r=0.28; 95% confidence interval [CI]=0.11–0.43; p=0.002), and the correlation was most notable with atomoxetine (r=0.29; CI [0.04 – 0.51]; p=0.023) rather than with placebo (r=0.24; CI [0.00–0.46]; p=0.055). On-treatment drinking levels correlated with AISRS scores (r=0.12; CI [0.05 –0.19]; p=0.001). Relapse to alcohol abuse significantly correlated with worse ADHD symptoms on 15 of 18 items of the AISRS in the placebo group (p<0.05 for each). Conclusions No baseline predictor (other than degree of sobriety) of alcohol use or ADHD outcomes emerged. ADHD symptom improvements correlated significantly with reductions in alcohol cravings, and relapse to alcohol abuse correlated significantly with worsening of most ADHD symptoms in the placebo group, but not in the atomoxetine group. This post-hoc subgroup analysis is of a hypothesis-generating nature, and the generalizability of the findings may be limited by exclusion of adults with common ADHD comorbidities from the base study. Further, prospective clinical trials in larger and more heterogeneous patient populations are warranted to confirm or reject these preliminary associations.

Wilens, Timothy E.; Adler, Lenard A.; Tanaka, Yoko; Xiao, Feng; D'Souza, Deborah N.; Gutkin, Stephen W.; Upadhyaya, Himanshu P.

2013-01-01

307

Random Variables and Correlational Overkill  

ERIC Educational Resources Information Center

|Research findings may be more publishable if significant results are reported. This type of publication bias would increase the likelihood of "chance" relationships being disseminated. The implications of these assumptions are empirically investigated in a correlational analogue study. (Author)|

Kunce, Joseph T.; And Others

1975-01-01

308

Surface Wave Chirp Transform Correlator.  

National Technical Information Service (NTIS)

The feasibility of developing a surface wave chirp transform correlator (CTC) is evaluated. A comprehensive characterization of chirp transform (CT) signal processing is presented. A computer model for simulating CT processors is described, with numerous ...

H. M. Gerard O. W. Otto

1976-01-01

309

Transverse correlations in multiphoton entanglement  

SciTech Connect

We have analyzed the transverse correlation in multiphoton entanglement. The generalization of quantum ghost imaging is extended to the N-photon state. The Klyshko's two-photon advanced-wave picture is generalized to the N-photon case.

Wen Jianming; Rubin, Morton H.; Shih Yanhua [Physics Department, University of Maryland, Baltimore County, Baltimore, Maryland 21250 (United States)

2007-10-15

310

Multiple Correlation versus Multiple Regression.  

ERIC Educational Resources Information Center

|Describes differences between multiple correlation analysis (MCA) and multiple regression analysis (MRA), showing how these approaches involve different research questions and study designs, different inferential approaches, different analysis strategies, and different reported information. (SLD)|

Huberty, Carl J.

2003-01-01

311

Electronic correlations in the ironpnictides  

SciTech Connect

In correlated metals derived from Mott insulators, the motion of an electron is impeded by Coulomb repulsion due to other electrons. This phenomenon causes a substantial reduction in the electron's kinetic energy, leading to remarkable experimental manifestations in optical spectroscopy. The high-transition-temperature (Tc) superconducting cuprates are perhaps the most studied examples of such correlated metals. The occurrence of high-Tc superconductivity in the iron pnictides puts a spotlight on the relevance of correlation effects in these materials. Here, we present an infrared and optical study on single crystals of the iron pnictide superconductor LaFePO. We find clear evidence of electronic correlations in metallic LaFePO with the kinetic energy of the electrons reduced to half of that predicted by band theory of nearly free electrons. We deduce that electronic many-body effects are important in the iron pnictides despite the absence of a Mott transition.

Qazilbash, M. M. [University of California, San Diego; Hamlin, J. J. [University of California, San Diego; Baumbach, R. E. [University of California, San Diego; Zhang, Lijun [ORNL; Singh, David J [ORNL; Maple, M. B. [University of California, San Diego; Basov, D. N. [University of California, San Diego

2009-01-01

312

Plasma with Two Particle Correlation.  

National Technical Information Service (NTIS)

This is a fundamental investigation in the theory of the two particle correlation function in the BBGKY approximation hierarchy to the Lionville equation. It introduces one significant new method which in some cases, reduces the integer-differential equat...

E. Pinney

1966-01-01

313

Subpixel registration with gradient correlation.  

PubMed

We address the problem of subpixel registration of images assumed to be related by a pure translation. We present a method which extends gradient correlation to achieve subpixel accuracy. Our scheme is based on modeling the dominant singular vectors of the 2-D gradient correlation matrix with a generic kernel which we derive by studying the structure of gradient correlation assuming natural image statistics. Our kernel has a parametric form which offers flexibility in modeling the functions obtained from various types of image data. We estimate the kernel parameters, including the unknown subpixel shifts, using the Levenberg-Marquardt algorithm. Experiments with LANDSAT and MRI data show that our scheme outperforms recently proposed state-of-the-art phase correlation methods. PMID:21118776

Tzimiropoulos, Georgios; Argyriou, Vasileios; Stathaki, Tania

2010-11-29

314

Transverse correlations in multiphoton entanglement  

Microsoft Academic Search

We have analyzed the transverse correlation in multiphoton entanglement. The generalization of quantum ghost imaging is extended to the N -photon state. The Klyshko's two-photon advanced-wave picture is generalized to the N -photon case.

Jianming Wen; Morton H. Rubin; Yanhua Shih

2007-01-01

315

Transverse correlations in multiphoton entanglement  

NASA Astrophysics Data System (ADS)

We have analyzed the transverse correlation in multiphoton entanglement. The generalization of quantum ghost imaging is extended to the N -photon state. The Klyshko’s two-photon advanced-wave picture is generalized to the N -photon case.

Wen, Jianming; Rubin, Morton H.; Shih, Yanhua

2007-10-01

316

Transverse correlations in multiphoton entanglement  

Microsoft Academic Search

We have analyzed the transverse correlation in multiphoton entanglement. The generalization of quantum ghost imaging is extended to the N-photon state. The Klyshko's two-photon advanced-wave picture is generalized to the N-photon case.

Wen Jianming; Morton H. Rubin; Shih Yanhua

2007-01-01

317

Statistical Applets: Correlation and Regression  

NSDL National Science Digital Library

Created for W.H. Freeman and Co., this applet is designed to help students see correlations in data and see how outliers can affect the correlation and least-squares line. Users can input their own data points and then try to fit a line to the data and see how the sum of squares changed. The user can then also see what the lest-square line is for that set of data.

2009-02-24

318

Correlated imaging through atmospheric turbulence  

SciTech Connect

Correlated imaging through atmospheric turbulence is studied, and the analytical expressions describing turbulence effects on image resolution are derived. Compared with direct imaging, correlated imaging can reduce the influence of turbulence to a certain extent and reconstruct high-resolution images. The result is backed up by numerical simulations, in which turbulence-induced phase perturbations are simulated by random-phase screens inserted into propagation paths.

Zhang Pengli; Gong Wenlin; Shen Xia; Han Shensheng [Key Laboratory for Quantum Optics and Center for Cold Atom Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)

2010-09-15

319

Gluon correlations in the glasma  

NASA Astrophysics Data System (ADS)

The physics of the initial conditions of heavy ion collisions is dominated by the nonlinear gluonic interactions of QCD. These lead to the concepts of parton saturation and the Color Glass Condensate (CGC). We discuss recent progress in calculating multi-gluon correlations in this framework, prompted by the observation that these correlations are in fact easier to compute in a dense system (nucleus-nucleus) than a dilute one (proton-proton).

Lappi, T.

2011-01-01

320

Gluon Correlations in the Glasma  

NASA Astrophysics Data System (ADS)

The physics of the initial conditions of heavy ion collisions isdominated by the nonlinear gluonic interactions of QCD. These lead to the concepts of parton saturation and the Color Glass Condensate (CGC). We discuss recent progress in calculating multi-gluon correlations in this framework, prompted by the observation that these correlations are in fact easier to compute in a dense system (nucleus-nucleus) than a dilute one (proton-proton).

Lappi, T.

321

Distributing fully optomechanical quantum correlations  

SciTech Connect

We present a scheme to prepare quantum correlated states of two mechanical systems based on the pouring of preavailable all-optical entanglement into the state of two micromirrors belonging to remote and noninteracting optomechanical cavities. We show that, under realistic experimental conditions, the protocol allows for the preparation of a genuine quantum state of a composite mesoscopic system whose nonclassical features extend beyond the occurrence of entanglement. We finally discuss a way to access such mechanical correlations.

Mazzola, L. [Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, FI-20014 Turun Yliopisto (Finland); Centre for Theoretical Atomic, Molecular and Optical Physics, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN (United Kingdom); Paternostro, M. [Centre for Theoretical Atomic, Molecular and Optical Physics, School of Mathematics and Physics, Queen's University Belfast, Belfast BT7 1NN (United Kingdom)

2011-06-15

322

Fatty acid correlates of temperament in adolescent boys with attention deficit hyperactivity disorder.  

PubMed

Atypical fatty acid metabolism has been reported in attention deficit hyperactivity disorder (ADHD), however, its relationship with temperament in this population is unclear. The current study investigated the association between blood levels of fatty acids implicated in brain structure and function (omega-3, omega-6, omega-9) and personality traits of stability (neuroticism, conscientiousness and agreeableness) and plasticity (extraversion and openness). Twenty right-handed adolescent boys with ADHD completed a self-report NEO-FFI personality questionnaire, and had fatty acid content assessed from red blood using gas chromatography. Pearson's correlations showed no significant associations between omega-3 levels and personality. After correction for multiple comparisons, Adrenic Acid (C22:4n6) was inversely associated with stability. Oleic acid (C18:1n9) was positively associated with plasticity. Results are in line with a role of fatty acids in brain function. They suggest that those fatty acids that are involved in myelination (Adrenic, Oleic) have the strongest associations with temperament in adolescents with ADHD. PMID:23566869

Sumich, Alex L; Matsudaira, Toshiko; Heasman, Bryony; Gow, Rachel V; Ibrahimovic, Almira; Ghebremeskel, Kebreab; Crawford, Michael A; Taylor, Eric

2013-04-06

323

Robustness of joint transform correlator versus Vander Lugt correlator  

NASA Astrophysics Data System (ADS)

The robustness of the joint transform correlator (JTC) versus the VanderLugt correlator (VLC) are evaluated based on the transversal and the longitudinal misalignment. We show that the VLC is very sensitive to the transversal misalignment, while the JTC is not. Although the VLC performs better in terms of longitudinal alignment, the tolerable misalignment in recording the joint transform power spectrum is in the order of a millimeter, which can be easily adjusted in practice. In short, we conclude that the JTC is far more robust than the VLC.

Purwosumarto, Purwadi; Yu, Francis T.

1997-10-01

324

Correlation of the clinical and physical image quality in chest radiography for average adults with a computed radiography imaging system.  

PubMed

Objective: The purpose of this study was to examine the correlation between the quality of visually graded patient (clinical) chest images and a quantitative assessment of chest phantom (physical) images acquired with a computed radiography (CR) imaging system. Methods: The results of a previously published study, in which four experienced image evaluators graded computer-simulated postero-anterior chest images using a visual grading analysis scoring (VGAS) scheme, were used for the clinical image quality measurement. Contrast-to-noise ratio (CNR) and effective dose efficiency (eDE) were used as physical image quality metrics measured in a uniform chest phantom. Although optimal values of these physical metrics for chest radiography were not derived in this work, their correlation with VGAS in images acquired without an antiscatter grid across the diagnostic range of X-ray tube voltages was determined using Pearson's correlation coefficient. Results: Clinical and physical image quality metrics increased with decreasing tube voltage. Statistically significant correlations between VGAS and CNR (R=0.87, p<0.033) and eDE (R=0.77, p<0.008) were observed. Conclusion: Medical physics experts may use the physical image quality metrics described here in quality assurance programmes and optimisation studies with a degree of confidence that they reflect the clinical image quality in chest CR images acquired without an antiscatter grid. Advances in knowledge: A statistically significant correlation has been found between the clinical and physical image quality in CR chest imaging. The results support the value of using CNR and eDE in the evaluation of quality in clinical thorax radiography. PMID:23568362

Moore, C S; Wood, T J; Beavis, A W; Saunderson, J R

2013-04-08

325

Correlation between carotid bifurcation calcium burden on non-enhanced CT and percentage stenosis, as confirmed by digital subtraction angiography  

PubMed Central

Objectives Previous evidence supports a direct relationship between the calcium burden (volume) on post-contrast CT with the percent internal carotid artery (ICA) stenosis at the carotid bifurcation. We sought to further investigate this relationship by comparing non-enhanced CT (NECT) and digital subtraction angiography (DSA). Methods 50 patients (aged 41–82 years) were retrospectively identified who had undergone cervical NECT and DSA. A 64-multidetector array CT (MDCT) scanner was utilised and the images reviewed using preset window widths/levels (30/300) optimised to calcium, with the volumes measured via three-dimensional reconstructive software. Stenosis measurements were performed on DSA and luminal diameter stenoses >40% were considered “significant”. Volume thresholds of 0.01, 0.03, 0.06, 0.09 and 0.12 cm3 were utilised and Pearson'S correlation coefficient (r) was calculated to correlate the calcium volume with percent stenosis. Results Of 100 carotid bifurcations, 88 were available and of these 7 were significantly stenotic. The NECT calcium volume moderately correlated with percent stenosis on DSA r=0.53 (p<0.01). A moderate–strong correlation was found between the square root of calcium volume on NECT with percent stenosis on DSA (r=0.60, p<0.01). Via a receiver operating characteristic curve, 0.06 cm3 was determined to be the best threshold (sensitivity 100%, specificity 90.1%, negative predictive value 100% and positive predictive value 46.7%) for detecting significant stenoses. Conclusion This preliminary investigation confirms a correlation between carotid bifurcation calcium volume and percent ICA stenosis and is promising for the optimal threshold for stenosis detection. Future studies could utilise calcium volumes to create a “score” that could predict high grade stenosis.

Sarikaya, B; Lohman, B; Mckinney, A M; Gadani, S; Irfan, M; Lucato, L

2012-01-01

326

Serum trace elements levels in preeclampsia and eclampsia: correlation with the pregnancy disorder.  

PubMed

Preeclampsia and eclampsia are fatal medical complications of pregnancy accounting for 20-80 % of increased maternal death in developing countries. Their aetiologies are still under investigation. Serum trace elements have been suggested to be involved in the pathogenesis of preeclampsia. Aim of this study was to address the correlation of serum trace elements with preeclampsia and eclampsia. It was a comparative cross-sectional study conducted on conveniently recruited 44 preeclampsia, 33 eclampsia and 27 normotensive pregnant patients. Atomic absorption spectrometry was employed to analyse serum concentrations of Ca, Mg, Cu, Zn and Fe. Data were analysed by Student's t test, one-way analysis of variance and multinomial logistic and binary regression analyses. p?correlations of Mg with Zn in eclampsia and Mg with Fe in preeclampsia and eclampsia were predicted. Significant changes in serum trace element levels were present in preeclampsia and eclampsia that may have a link with the pathogenesis of pregnancy disorder. PMID:23526144

Ahsan, Touhida; Banu, Salina; Nahar, Quamrun; Ahsan, Monira; Khan, Md Nazrul Islam; Islam, Sheikh Nazrul

2013-03-23

327

Correlation between the Condyle Position and Intra-Extraarticular Clinical Findings of Temporomandibular Dysfunction  

PubMed Central

Objectives: To investigate the relationship between different clinical findings and condyle position. Methods: Tenderness on masseter (MM), temporal (TM), lateral pyterigoid (LPM), medial pyterigoid (MPM) and posterior cervical (PSM) muscles, limitation, deviation and deflection in opening of mouth, clicking, crepitating, tenderness on lateral palpation of temporomandibular joint (TMJ) area for each side of 85 patients were evaluated. Each side of patients was categorized into the clinical findings: no sign and/or symptom of temporomandibular dysfunctions (TMDs), only extraarticular findings and only intraarticular findings, extra and intraarticular findings. Condyle positions of 170 TMJs were determined the narrowest anterior (a) and posterior interarticular distance (p) on mid-sagittal MRIs of condyles and expressed as p/a ratio and these ratio were transformed into logarithmic base e. Spearman’s Correlation was used to investigate the relationship between the condyle position and the clinical findings. The difference between the condyle positions of different groups was tested by T test. Reliability statistic was used to determine intra-observer concordance of two measurements of condylar position. Results: A significant relationship was found between the condyle position and tenderness of PSM. There was no significant difference between the groups in aspect of the condyle position. Occlusion and condyle position correlated with significantly. Conclusions: The inclination of the upper cervical spine and craniocervical angulations can cause the signs and symptoms of TMD and condyle position is not main cause of TMDs alone but it may be effective together with other possible etiological factors synergistically.

Sener, Sevgi; Akgunlu, Faruk

2011-01-01

328

Recirculating cross-correlation detector  

DOEpatents

A digital cross-correlation detector is provided in which two time-varying signals are correlated by repetitively comparing data samples stored in digital form to detect correlation between the two signals. The signals are sampled at a selected rate converted to digital form, and stored in separate locations in separate memories. When the memories are filled, the data samples from each memory are first fed word-by-word through a multiplier and summing circuit and each result is compared to the last in a peak memory circuit and if larger than the last is retained in the peak memory. Then the address line to leading signal memory is offset by one byte to affect one sample period delay of a known amount in that memory and the data in the two memories are then multiplied word-by-word once again and summed. If a new result is larger than a former sum, it is saved in the peak memory together with the time delay. The recirculating process continues with the address of the one memory being offset one additional byte each cycle until the address is shifted through the length of the memory. The correlation between the two signals is indicated by the peak signal stored in the peak memory together with the delay time at which the peak occurred. The circuit is faster and considerably less expensive than comparable accuracy correlation detectors.

Andrews, W.H. Jr.; Roberts, M.J.

1985-01-18

329

Inverting the angular correlation function  

NASA Astrophysics Data System (ADS)

The two point angular correlation function is an excellent measure of structure in the Universe. To extract from it the three-dimensional power spectrum, one must invert Limber's equation. Here we perform this inversion using a Bayesian prior constraining the smoothness of the power spectrum. Among other virtues, this technique allows for the possibility that the estimates of the angular correlation function are correlated from bin to bin. The outputs of this technique are estimators for the binned power spectrum and a full covariance matrix. Angular correlations mix small and large scales but after the inversion, small-scale data can be trivially eliminated, thereby allowing for realistic constraints on theories of large-scale structure. We analyse the automated plate measurement (APM) catalogue as an example, comparing our results with previous results. As a by-product of these tests, we find - in rough agreement with previous work - that APM places stringent constraints on cold dark matter inspired models, with the shape parameter constrained to be 0.25+/-0.04 (using data with wavenumber k<=0.1hMpc-1). This range of allowed values uses the full power spectrum covariance matrix, but assumes negligible covariance in the off-diagonal angular correlation error matrix, which is estimated with a large angular resolution of 0.5 deg (in the range 0.5 deg and 20 deg).

Dodelson, Scott; Gaztañaga, Enrique

2000-03-01

330

Screening correlators with chiral fermions  

SciTech Connect

We study screening correlators of quark-antiquark composites at T=2T{sub c}, where T{sub c} is the QCD phase transition temperature, using overlap quarks in the quenched approximation of lattice QCD. As the lattice spacing is changed from 1/4T to a=1/6T and 1/8T, we find that screening correlators change little, in contrast with the situation for other types of lattice fermions. All correlators are close to the ideal gas prediction at small separations. The long distance falloff is clearly exponential, showing that a parametrization by a single screening length is possible at distances z{>=}1/T. The correlator corresponding to the thermal vector is close to the ideal gas value at all distances, whereas that for the thermal scalar deviates at large distances. This is examined through the screening lengths and momentum space correlators. There is strong evidence that the screening transfer matrix does not have reflection positivity.

Gavai, R. V.; Gupta, Sourendu; Lacaze, R. [Department of Theoretical Physics, Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India); Service de Physique Theorique, CEA Saclay, F-91191 Gif-sur-Yvette Cedex (France)

2008-07-01

331

Local critical stress correlates better than global maximum stress with plaque morphological features linked to atherosclerotic plaque vulnerability: an in vivo multi-patient study  

PubMed Central

Background It is believed that mechanical stresses play an important role in atherosclerotic plaque rupture process and may be used for better plaque vulnerability assessment and rupture risk predictions. Image-based plaque models have been introduced in recent years to perform mechanical stress analysis and identify critical stress indicators which may be linked to rupture risk. However, large-scale studies based on in vivo patient data combining mechanical stress analysis, plaque morphology and composition for carotid plaque vulnerability assessment are lacking in the current literature. Methods 206 slices of in vivo magnetic resonance image (MRI) of carotid atherosclerotic plaques from 20 patients (age: 49–71, mean: 67.4; all male) were acquired for model construction. Modified Mooney-Rivlin models were used for vessel wall and all plaque components with parameter values chosen to match available data. A morphological plaque severity index (MPSI) was introduced based on in vivo plaque morphological characteristics known to correlate with plaque vulnerability. Critical stress, defined as the maximum of maximum- principal-stress (Stress-P1) values from all possible vulnerable sites, was determined for each slice for analysis. A computational plaque stress index (CPSI, with 5 grades 0–4, 4 being most vulnerable) was defined for each slice using its critical stress value and stress interval for each CPSI grade was optimized to reach best agreement with MPSI. Correlations between CPSI and MPSI, plaque cap thickness, and lipid core size were analyzed. Results Critical stress values correlated positively with lipid core size (r = 0.3879) and negatively with cap thickness (r = -0.3953). CPSI classifications had 71.4% agreement with MPSI classifications. The Pearson correlation coefficient between CPSI and MPSI was 0.849 (p < 0.0001). Using global maximum Stress-P1 value for each slice to define a global maximum stress-based CPSI (G-CPSI), the agreement rate with MPSI was only 34.0%. The Pearson correlation coefficient between G-CPSI and MPSI was 0.209. Conclusion Results from this in vivo study demonstrated that localized critical stress values had much better correlation with plaque morphological features known to be linked to plaque rupture risk, compared to global maximum stress conditions. Critical stress indicators have the potential to improve image-based screening and plaque vulnerability assessment schemes.

Tang, Dalin; Teng, Zhongzhao; Canton, Gador; Hatsukami, Thomas S; Dong, Li; Huang, Xueying; Yuan, Chun

2009-01-01

332

The BRCA1 Ashkenazi founder mutations occur on common haplotypes and are not highly correlated with anonymous single nucleotide polymorphisms likely to be used in genome-wide case-control association studies  

PubMed Central

Background We studied linkage disequilibrium (LD) patterns at the BRCA1 locus, a susceptibility gene for breast and ovarian cancer, using a dense set of 114 single nucleotide polymorphisms in 5 population groups. We focused on Ashkenazi Jews in whom there are known founder mutations, to address the question of whether we would have been able to identify the 185delAG mutation in a case-control association study (should one have been done) using anonymous genetic markers. This mutation is present in approximately 1% of the general Ashkenazi population and 4% of Ashkenazi breast cancer cases. We evaluated LD using pairwise and haplotype-based methods, and assessed correlation of SNPs with the founder mutations using Pearson's correlation coefficient. Results BRCA1 is characterized by very high linkage disequilibrium in all populations spanning several hundred kilobases. Overall, haplotype blocks and pair-wise LD bins were highly correlated, with lower LD in African versus non-African populations. The 185delAG and 5382insC founder mutations occur on the two most common haplotypes among Ashkenazim. Because these mutations are rare, even though they are in strong LD with many other SNPs in the region as measured by D-prime, there were no strong associations when assessed by Pearson's correlation coefficient, r (maximum of 0.04 for the 185delAG). Conclusion Since the required sample size is related to the inverse of r, this suggests that it would have been difficult to map BRCA1 in an Ashkenazi case-unrelated control association study using anonymous markers that were linked to the founder mutations.

Pereira, Lutecia H Mateus; Pineda, Marbin A; Rowe, William H; Fonseca, Libia R; Greene, Mark H; Offit, Kenneth; Ellis, Nathan A; Zhang, Jinghui; Collins, Andrew; Struewing, Jeffery P

2007-01-01

333

Thermodynamics of Correlated Nuclear Matter  

NASA Astrophysics Data System (ADS)

The Self-Consistent Green's Function's (SCGF) method at the level of the ladder approximation is used to calculate the free-energy of symmetric nuclear matter. The ladder approximation considers the propagation of particles and holes which translates into the incorporation of significant correlations in the wave function. These correlations are reflected in the shape of the single-particle spectral functions. An essential ingredient of the free energy is the entropy, which is calculated with the Luttinger-Ward formalism. In this approach, the finite width of the quasi-particle states is explicitly taken into account. It turns out that the entropy measures thermal effects and the effect of dynamical correlations, already present at zero temperature, is not so relevant for the calculation of the entropy. Preliminary results for the liquid-gas phase transition are also presented.

Polls, A.; Ramos, A.; Rios, A.; Müther, H.

2008-02-01

334

Electron correlation in real time.  

PubMed

Electron correlation, caused by the interaction among electrons in a multielectron system, manifests itself in all states of matter. A complete theoretical description of interacting electrons is challenging; different approximations have been developed to describe the fundamental aspects of the correlation that drives the evolution of simple (few-electron systems in atoms/molecules) as well as complex (multielectron wave functions in atoms, molecules, and solids) systems. Electron correlation plays a key role in the relaxation mechanisms that characterize excited states of neutral or ionized atoms and molecules populated by absorption of extreme ultraviolet (XUV) or X-ray radiation. The dynamics of these states can lead to different processes such as Fano resonance and Auger decay in atoms or interatomic Coulombic decay or charge migration in molecules and clusters. Many of these relaxation mechanisms are ubiquitous in nature and characterize the interaction of complex systems, such as biomolecules, adsorbates on surfaces, and hydrogen-bonded clusters, with XUV light. These mechanisms evolve typically on the femtosecond (1 fs=10(-15) s) or sub-femtosecond timescale. The experimental availability of few-femtosecond and attosecond (1 as=10(-18) s) XUV pulses achieved in the last 10 years offers, for the first time, the opportunity to excite and probe in time these dynamics giving the possibility to trace and control multielectron processes. The generation of ultrashort XUV radiation has triggered the development and application of spectroscopy techniques that can achieve time resolution well into the attosecond domain, thereby offering information on the correlated electronic motion and on the correlation between electron and nuclear motion. A deeper understanding of how electron correlation works could have a large impact in several research fields, such as biochemistry and biology, and trigger important developments in the design and optimization of electronic devices. PMID:22162320

Sansone, Giuseppe; Pfeifer, Thomas; Simeonidis, Konstantinos; Kuleff, Alexander I

2011-12-08

335

Cultural correlates of youth suicide.  

PubMed

Youth suicide has risen in most developed nations over the past 50 years, especially among males, but the increase remains to be explained. Statistical analyses were used to examine associations between youth suicide rates in 11-21 mainly Western, developed nations and 32 socio-economic and cultural variables. The central hypothesis was that suicide rates would be correlated with various cultural measures of social attachment and integration, especially individualism. Socio-economic variables were included in the analysis to demonstrate the relative strength of the cultural associations. The study found a strong positive correlation between male youth suicide rates and subjective measures of health, optimism, and several indices of individualism, including personal freedom and control. Correlations between female youth suicide and individualism were smaller, attaining significance in only one instance. Male youth suicide and individualism were negatively correlated with older people's sense of parental duty. Correlations between suicide and other possibly relevant cultural variables--tolerance of suicide, belief in God and national pride--were not significant. The analysis of socio-economic variables yielded only one significant, but doubtful, correlation. The findings can be interpreted as supporting two very different hypotheses: that youth suicide represents "an island of misery in an ocean of happiness" or "the tip of an iceberg of suffering". In favouring the latter interpretation, and consistent with Durkheim's theories on suicide, it is argued that increased youth suicide reflects a failure of Western societies to provide appropriate sites or sources of social identity and attachment, and, conversely, a tendency to promote unrealistic or inappropriate expectations of individual freedom and autonomy. PMID:12406459

Eckersley, Richard; Dear, Keith

2002-12-01

336

Recent advances in fluorescence correlation spectroscopy  

Microsoft Academic Search

Fluorescence correlation spectroscopy is a method in which fluctuations in the fluorescence arising from a very small sample volume are correlated to obtain information about the processes giving rise to the fluctuations. Recent progress has been made in methodologies such as two-photon excitation, photon counting histogram analysis, cross-correlation, image correlation and evanescent excitation. Fluorescence correlation spectroscopy techniques have been applied

Nancy L Thompson; Alena M Lieto; Noah W Allen

2002-01-01

337

Performance measures for correlation filters  

SciTech Connect

Several performance criteria are described to enable a fair comparison among the various correlation filter designs: signal-to-noise ratio, peak sharpness, peak location, light efficiency, discriminability, and distortion invariance. The trade-offs resulting between some of these criteria are illustrated with the help of a new family of filters called fractional power filters (FPFs). The classical matched filter, phase-only filter (POF), and inverse filter are special cases of FPFs. Using examples, we show that the POF appears to provide a good compromise between noise tolerance and peak sharpness. Keywords: Correlators, performance criteria, matched filters, phase-only filters, fractional power filters.

Vijaya Kumar, B.V.K.; Hassebrook, L. (Carnegie Mellon University, Department of Electrical Computer Engineering, Center for Excellence in Optical Data Processing, Pittsburgh, PA (USA))

1990-07-10

338

Quantum optical correlation through metamaterials  

NASA Astrophysics Data System (ADS)

Based on the quantization scheme of the radiation fields in the dispersive and absorptive magnetic media, the normally ordered correlation functions of the outgoing field through a metamaterial plate are obtained. Then the relative photon-number densities of the transmitted field, the reflected field and the absorbed field are gotten through the correlation functions. Furthermore, the contributions of the relative permittivity and permeability of the metamaterials to the transmission are analyzed. Our results show that the permittivity and permeability reinforce the transmission for frequencies that are big compared with the magnetic resonance frequency.

Dong, Yun-Xia; Cui, Xiao-Hua

2012-10-01

339

Global correlation of tectonic movements  

SciTech Connect

Papers bear on one of the most important problems of geotectonics: that of the existence and role of global tectonic movements, or impulses of tectonic and magmatic activity, in the process of tectogenesis. Main lines of the investigations delineate the succession of tectonic and magmatic events in given regions, revealing the correlations between tectonic and magmatic events, and discovered interregional correlations which show the distinction between global and regional phases of tectogenesis. Topics covered include paleogene volcanism, cenozoic olistrosomes, synchronism and heterochronism of compressive tectogenesis. Himalayan orogeny, and self-excited oscillations in geological systems.

Leonov, Y.G.

1987-01-01

340

Anisotropic diffusion and correlation analysis.  

PubMed

A method of statistical analysis of the correlation between two given scale invariant sequences is proposed. The relation between the fractal dimension of a two-dimensional random walk, generated with jumps derived from the signals, and the scaling exponents of the sequences is investigated, and a well-defined relation is found in the case of statistically independent signals. The method of analysis, whose performance is described for the case of an intermittent map, might represent a new tool for the study of the correlation between coupled complex systems. PMID:12241145

Bellazzini, Jacopo

2002-08-09

341

Pairing correlations and effective mass  

SciTech Connect

We study the effect of effective mass on pairing correlations in the ground states of superfluid nuclei {sup 124}Sn and {sup 136}Sn. Various parameter sets of Skyrme interactions and relativistic Lagrangians are adopted to study pairing correlations across a wide range of effective mass. It is shown that surface-type pairing interaction gives an almost constant pairing gap as a function of the effective mass, while volume-type pairing interaction shows rather strong dependence of the pairing gap upon the effective mass. The local pair potentials of various effective interactions are also examined in relation to the effective mass.

Yoshida, Satoshi [Science Research Center, Hosei University, 2-17-1 Fujimi, Chiyoda, Tokyo 102-8160 (Japan); Sagawa, Hiroyuki [Center for Mathematical Sciences, University of Aizu Aizu-Wakamatsu, Fukushima 965-8580 (Japan)

2008-05-15

342

Universal Fluctuations in Correlated Systems  

NASA Astrophysics Data System (ADS)

The probability density function (PDF) of a global measure in a large class of highly correlated systems has been suggested to be of the same functional form. Here, we identify the analytical form of the PDF of one such measure, the order parameter in the low temperature phase of the 2D XY model. We demonstrate that this function describes the fluctuations of global quantities in other correlated equilibrium and nonequilibrium systems. These include a coupled rotor model, Ising and percolation models, models of forest fires, sandpiles, avalanches, and granular media in a self-organized critical state. We discuss the relationship with both Gaussian and extremal statistics.

Bramwell, S. T.; Christensen, K.; Fortin, J.-Y.; Holdsworth, P. C. W.; Jensen, H. J.; Lise, S.; López, J. M.; Nicodemi, M.; Pinton, J.-F.; Sellitto, M.

2000-04-01

343

Correlation between bone mineral density of jaws and skeletal sites in an Iranian population using dual X-ray energy absorptiometry  

PubMed Central

Background: The aim of the present study was to evaluate the relationship between the bone density of various regions of jaws and skeletal bones. Materials and Methods: A total of 110 patients with a mean age of 55.01 ± 10.77 years were selected for the purpose of the present descriptive study. Dual X-ray Energy Absorptiometry (DXA) was carried out to determine bone mineral density (BMD) of the femur and lumbar vertebrae. Then all the subjects underwent DXA of the jaw bones and BMD values were determined at four jaw regions. Data were analyzed by SPSS 16 statistical software, and the correlation between the various BMD values was determined by Pearson's correlation coefficient. Results: The results showed that 42.7% of females had normal BMD values in the femur, and in vertebrae, 20% were osteopenic and 37.3% suffered from osteoporosis, with statistically significant differences in the BMD values of the jaws between the three above-mentioned groups (P < 0.001). There was an increasing tendency toward osteopenia and osteoporosis with age. There was a positive correlation between BMD values of the femur and lumbar vertebrae and those of all the jaw regions under study (P < 0.005). There was a negative correlation (P < 0.01) between age and the BMD values of the femur, lumbar vertebrae and anterior maxilla. Conclusion: The bone density of the maxilla and mandible and presence of osteoporosis or osteopenia in these bones might reflect the same problem in skeletal bones.

Esfahanizadeh, Nasrin; Davaie, Sotoudeh; Rokn, A. R.; Daneshparvar, Hamid Reza; Bayat, Noushin; Khondi, Nasrin; Ajvadi, Sara; Ghandi, Mostafa

2013-01-01

344

On the lack of correlation between self-report and urine loss measured with standing provocation test in older stress-incontinent women.  

PubMed

This study examined the association between the measured amount of urine lost during a standardized series of coughs in clinic (paper towel test) and questionnaire estimates of stress-related urine loss in 51 older women with mild to moderate urinary incontinence. It also examined the relationship between these questionnaire estimates and a 6-day urinary diary self-report of incontinence frequency and voiding episodes. Pearson's correlation coefficient and percent agreement were used to analyze the relationship between the variables. No significant correlations were found between the paper towel test results and questionnaire items reporting volume of urine loss. The relationship between urinary diary results and questionnaire items regarding the number of incontinence occurrences was weak but significant (r = 0.33, p = 0.045), with agreement in 53% of cases. Agreement was achieved in 68% of cases for number of voids per day recorded by urinary diary and reported by questionnaire (r = 0.65, p = 0.000). This study has quantified a weak correlation between objective and subjective measures of urine loss. These weak correlations could arise from either methodologic limitations in quantifying incontinence or the degree to which differences arise because different phenomena are being measured. PMID:10100129

Miller, J M; Ashton-Miller, J A; Carchidi, L T; DeLancey, J O

1999-03-01

345

Correlation between high-risk pregnancy and developmental delay in children aged 4-60 months  

PubMed Central

Background The future development of children is considered more than ever now due to the advances in medical knowledge and thus the increase in survival rates of high-risk infants. This study investigated the correlation between high-risk pregnancy and developmental delay in children aged 4–60 months. Methods This descriptive study was conducted on 401 mothers and their children (4–60 months) who visited health service centers affiliated to Isfahan University of Medical Sciences, Iran, in 2011. Sampling was carried out in several stages, and the Ages and Stage Questionnaire was completed by the participants. Data were analyzed with SPSS 18 software and independent t-test; Mann-Whitney and logistic-regression tests were used. Results The average age of children in the low-risk pregnancy group was 22±16 months, and that in the high-risk pregnancy group was 18.9±14.8 months. The majority of children were female (53.1%). The prevalence of high-risk pregnancies was 80.5%, and the prevalence of developmental delay was 18.7%. Multiple pregnancies, low birth weight, habitual abortions, maternal medical disorders in pregnancy, and gestational diabetes had significant correlations with developmental delay in children (P<0.04). In the logistic model, male gender, low birth weight, family marriage, and maternal medical disorders during pregnancy showed significant correlations with developmental delay in children (P<0.05). Additionally, abnormal body mass index (BMI) and social and economic status showed probability values close to the significance level (P = 0.05), whereas other high-risk pregnancy variables had no correlation with developmental delay in children. A correlation between high-risk pregnancy and developmental delay (P = 0.002) and fine motor delay was observed (P = 0.02), but no correlation was observed between high-risk pregnancy and other developmental domains. Conclusion This study showed that some high-risk pregnancy variables had a significant correlation with developmental delay. Moreover, a significant correlation was observed between high-risk pregnancy and fine motor developmental delay.

Torabi, Fatemeh; Akbari, Sedigheh Amir Ali; Amiri, Saba; Soleimani, Farin; Majd, Hamid Alavi

2012-01-01

346

PREFACE: Strongly correlated electron systems Strongly correlated electron systems  

NASA Astrophysics Data System (ADS)

This special section is dedicated to the Strongly Correlated Electron Systems Conference (SCES) 2011, which was held from 29 August-3 September 2011, in Cambridge, UK. SCES'2011 is dedicated to 100 years of superconductivity and covers a range of topics in the area of strongly correlated systems. The correlated electronic and magnetic materials featured include f-electron based heavy fermion intermetallics and d-electron based transition metal compounds. The selected papers derived from invited presentations seek to deepen our understanding of the rich physical phenomena that arise from correlation effects. The focus is on quantum phase transitions, non-Fermi liquid phenomena, quantum magnetism, unconventional superconductivity and metal-insulator transitions. Both experimental and theoretical work is presented. Based on fundamental advances in the understanding of electronic materials, much of 20th century materials physics was driven by miniaturisation and integration in the electronics industry to the current generation of nanometre scale devices. The achievements of this industry have brought unprecedented advances to society and well-being, and no doubt there is much further to go—note that this progress is founded on investments and studies in the fundamentals of condensed matter physics from more than 50 years ago. Nevertheless, the defining challenges for the 21st century will lie in the discovery in science, and deployment through engineering, of technologies that can deliver the scale needed to have an impact on the sustainability agenda. Thus the big developments in nanotechnology may lie not in the pursuit of yet smaller transistors, but in the design of new structures that can revolutionise the performance of solar cells, batteries, fuel cells, light-weight structural materials, refrigeration, water purification, etc. The science presented in the papers of this special section also highlights the underlying interest in energy-dense materials, which make use of 'small' electrons packed to the highest possible density. These are by definition 'strongly correlated'. For example: good photovoltaics must be efficient optical absorbers, which means that photons will generate tightly bound electron-hole pairs (excitons) that must then be ionised at a heterointerface and transported to contacts; efficient solid state refrigeration depends on substantial entropy changes in a unit cell, with large local electrical or magnetic moments; efficient lighting is in a real sense the inverse of photovoltaics; the limit of an efficient battery is a supercapacitor employing mixed valent ions; fuel cells and solar to fuel conversion require us to understand electrochemistry on the scale of a single atom; and we already know that the only prospect for effective high temperature superconductivity involves strongly correlated materials. Even novel IT technologies are now seen to have value not just for novel function but also for efficiency. While strongly correlated electron systems continue to excite researchers and the public alike due to the fundamental science issues involved, it seems increasingly likely that support for the science will be leveraged by its impact on energy and sustainability. Strongly correlated electron systems contents Strongly correlated electron systemsSiddharth S Saxena and P B Littlewood Magnetism, f-electron localization and superconductivity in 122-type heavy-fermion metalsF Steglich, J Arndt, O Stockert, S Friedemann, M Brando, C Klingner, C Krellner, C Geibel, S Wirth, S Kirchner and Q Si High energy pseudogap and its evolution with doping in Fe-based superconductors as revealed by optical spectroscopyN L Wang, W Z Hu, Z G Chen, R H Yuan, G Li, G F Chen and T Xiang Structural investigations on YbRh2Si2: from the atomic to the macroscopic length scaleS Wirth, S Ernst, R Cardoso-Gil, H Borrmann, S Seiro, C Krellner, C Geibel, S Kirchner, U Burkhardt, Y Grin and F Steglich Confinement of chiral magnetic modulations in the precursor region of FeGeH Wilhelm, M Baenitz, M Schmidt, C Naylor, R Lortz, U

Saxena, Siddharth S.; Littlewood, P. B.

2012-07-01

347

Correlation Between Standardized Uptake Value and Apparent Diffusion Coefficient of Neoplastic Lesions Evaluated With Whole-Body Simultaneous Hybrid PET/MRI.  

PubMed

OBJECTIVE. The purpose of this study was to assess the correlation between standardized uptake value (SUV) and apparent diffusion coefficient (ADC) of neoplastic lesions in the use of a simultaneous PET/MRI hybrid system. SUBJECTS AND METHODS. Twenty-four patients with known primary malignancies underwent FDG PET/CT. They then underwent whole-body PET/MRI. Diffusion-weighted imaging was performed with free breathing and a single-shot spin-echo echo-planar imaging sequence with b values of 0, 350, and 750 s/mm(2). Regions of interest were manually drawn along the contours of neoplastic lesions larger than 1 cm, which were clearly identified on PET and diffusion-weighted images. Maximum SUV (SUVmax) on PET/MRI and PET/CT images, mean SUV (SUVmean), minimum ADC (ADCmin), and mean ADC (ADCmean) were recorded on PET/MR images for each FDG-avid neoplastic soft-tissue lesion with a maximum of three lesions per patient. Pearson correlation coefficient was used to asses the following relations: SUVmax versus ADCmin on PET/MR and PET/CT images, SUVmean versus ADCmean, and ratio of SUVmax to mean liver SUV (SUV ratio) versus ADCmin. A subanalysis of patients with progressive disease versus partial treatment response was performed with the ratio of SUVmax to ADCmin for the most metabolically active lesion. RESULTS. Sixty-nine neoplastic lesions (52 nonosseous lesions, 17 bone metastatic lesions) were evaluated. The mean SUVmax from PET/MRI was 7.0 ± 6.0; SUVmean, 5.6 ± 4.6; mean ADCmin, 1.10 ± 0.58; and mean ADCmean, 1.48 ± 0.72. A significant inverse Pearson correlation coefficient was found between PET/MRI SUVmax and ADCmin (r = -0.21, p = 0.04), between SUVmean and ADCmean (r = -0.18, p = 0.07), and between SUV ratio and ADCmin (r = -0.27, p = 0.01). A similar inverse Pearson correlation coefficient was found between the PET/CT SUVmax and ADCmin. Twenty of 24 patients had previously undergone PET/CT; five patients had a partial treatment response, and six had progressive disease according to Response Evaluation Criteria in Solid Tumors 1.1. The ratio between SUVmax and ADCmin was higher among patients with progressive disease than those with a partial treatment response. CONCLUSION. Simultaneous PET/MRI is a promising technology for the detection of neoplastic disease. There are inverse correlations between SUVmax and ADCmin and between SUV ratio and ADCmin. Correlation coefficients between SUVmax and ADCmin from PET/MRI were similar to values obtained with SUVmax from the same-day PET/CT. Given that both SUV and ADC are related to malignancy and that the correlation between the two biomarkers is relatively weak, SUV and ADC values may offer complementary information to aid in determination of prognosis and treatment response. The combined tumoral biomarker, ratio between SUVmax and ADCmin, may be useful for assessing progressive disease versus partial treatment response. PMID:24147485

Rakheja, Rajan; Chandarana, Hersh; Demello, Linda; Jackson, Kimberly; Geppert, Christian; Faul, David; Glielmi, Christopher; Friedman, Kent P

2013-11-01

348

The Physiological Correlates of Learning.  

ERIC Educational Resources Information Center

|The author reviews the literature and makes tentative conclusions concerning the physiological correlates of learning and memory. Particular attention is given to the issues of spinal cord learning, subcortical learning, cerebral cortex learning, localization of learning within the brain (specificity vs. non-specificity), and association areas…

Davis, Mary

349

Clutter Effects on Optical Correlators.  

National Technical Information Service (NTIS)

We examine the effect of varying ground clutter on the performance of optical correlators. We compare the classical matched (CMF), phase-only (POF), and binary phase-only (BPOF) filters. A new definitions of the signal-to-clutter ratio (SCR) in the input ...

J. L. Horner K. H. Fielding

1990-01-01

350

Myological correlates of prosimian leaping  

Microsoft Academic Search

Although the skeletal correlates of vertical clinging and leaping behavior in primates have been studied in great detail, myological information on this locomotor group is not readily available. We here provide relative muscle mass data for the hindlimb of four prosimian leapers, representing indriids as well as the small-bodied tarsiers and galagos. Wet weights of all hindlimb muscles, with the

B Demes; J. G Fleagle; P Lemelin

1998-01-01

351

Correlation Energy of Atomic Fluorine.  

National Technical Information Service (NTIS)

The linked-cluster many-body perturbation theory of Brueckner and Goldstone has been applied to calculate the correlation energy of atomic fluorine in its doublet P ground state. Approximate results using complete orthonormal HFV(N-1), HFV(N)OAO and HFSV(...

D. F. Scofield D. M. Dutta N. C. Dutta

1972-01-01

352

Correlation and Integration in English.  

ERIC Educational Resources Information Center

Correlation, fusion, integration, and core in the English program originated in the 1930's and have been found to increase the student's breadth of knowledge and appreciation of literature. Basically, such curriculum structuring utilizes three approaches--the joint study of two or more subjects (often literature and history), the use of a broad…

Mersand, Joseph

1969-01-01

353

Negative correlation in incremental learning  

Microsoft Academic Search

Negative Correlation Learning (NCL) has been successfully applied to con- struct neural network ensembles. It encourages the neural networks that compose the ensemble to be different from each other and, at the same time, accurate. The difference among the neural networks that compose an ensemble is a desirable feature to perform incremental learning, for some of the neural networks can

Fernanda Li Minku; Hirotaka Inoue; Xin Yao

2009-01-01

354

Correlation effects in molecular conductors.  

PubMed

The source-sink potential (SSP) model introduced previously [F. Goyer, M. Ernzerhof, and M. Zhuang, J. Chem. Phys. 126, 144104 (2007)] enables one to eliminate the semi-infinite contacts in molecular electronic devices (MEDs) in favor of complex potentials. SSP has originally been derived for independent electrons and extended to interacting two-electron systems subsequently [A. Goker, F. Goyer, and M. Ernzerhof, J. Chem. Phys. 129, 194901 (2008)]. Here we generalize SSP to N-electron systems and consider the impact of electron correlation on the transmission probability. In our correlated method for molecular conductors, the molecular part of the Hu?ckel Hamiltonian of the original SSP is replaced by the Hubbard Hamiltonian. For the contacts, however, the single-electron picture is retained and they are assumed to be spin polarized. Using our method, we study electron transmission in molecular wires, cross-conjugated chains, as well as aromatic systems. We find that, for realistic values of the electron-electron repulsion parameter, correlation effects modify the transmission probability quantitatively, the qualitative features remain. However, we find subtle new effects in correlated MEDs, such as Coulomb drag, that are absent in uncorrelated systems. PMID:21548667

Goyer, Francois; Ernzerhof, Matthias

2011-05-01

355

Sample Size and Correlational Inference  

ERIC Educational Resources Information Center

|In 4 studies, the authors examined the hypothesis that the structure of the informational environment makes small samples more informative than large ones for drawing inferences about population correlations. The specific purpose of the studies was to test predictions arising from the signal detection simulations of R. B. Anderson, M. E. Doherty,…

Anderson, Richard B.; Doherty, Michael E.; Friedrich, Jeff C.

2008-01-01

356

Tetrachoric Correlation: A Permutation Alternative  

ERIC Educational Resources Information Center

|An exact permutation test is provided for the tetrachoric correlation coefficient. Comparisons with the conventional test employing Student's t distribution demonstrate the necessity of using the permutation approach for small sample sizes and/or disproportionate marginal frequency totals. (Contains 4 tables.)|

Long, Michael A.; Berry, Kenneth J.; Mielke, Paul W., Jr.

2009-01-01

357

Pairing correlations in exotic nuclei  

NASA Astrophysics Data System (ADS)

The BCS and HFB theories which can accommodate the pairing correlations in the ground states of atomic nuclei are presented. As an application of the pairing theories, we investigate the spatial extension of weakly bound Ne and C isotopes by taking into account the pairing correlation with the Hartree-Fock-Bogoliubov (HFB) method and a 3-body model, respectively. We show that the odd-even staggering in the reaction cross sections of 30,31,32Ne and 14,15,16C are successfully reproduced, and thus the staggering can be attributed to the unique role of pairing correlations in nuclei far from the stability line. A correlation between a one-neutron separation energy and the anti-halo effect is demonstrated for s- and p-waves using the HFB wave functions. We also propose effective density-dependent pairing interactions which reproduce both the neutron-neutron (nn) scattering length at zero density and the neutron pairing gap in uniform matter. Then, we apply these interactions to study pairing gaps in semi-magic finite nuclei, such as Ca, Ni, Sn and Pb isotopic chains.

Sagawa, H.; Hagino, K.

2013-02-01

358

CCD Correlated Quadruple Sampling Processor.  

National Technical Information Service (NTIS)

A correlated quadruple sampling processor for improved signal-to-noise ratio in the output of a charge-coupled device (CCD) is comprised of: (1) switching means for momentarily clamping a CCD signal line at a first reference level A before a CCD data puls...

S. D. Gaalema

1979-01-01

359

Correlation effects and bound states  

SciTech Connect

Bound states in a simple quark model that are due to correlation effects are analyzed. The confining properties of this model in meson (quark-antiquark and diquark) channels manifest themselves at any quark momenta, and an extra potential field may only enhance the confining effect.

Zinovjev, G. M. [National Academy of Sciences of Ukraine, Bogolyubov Institute for Theoretical Physics (Ukraine); Molodtsov, S. V., E-mail: molodtsov@itep.ru [Joint Institute for Nuclear Research (Russian Federation)

2012-11-15

360

Clinical correlates with diaper dermatitis.  

PubMed

Three types of clinical studies were carried out to better understand diaper dermatitis in a general infant population. In 'snapshot' clinical studies, skin condition under the diaper was evaluated at a given point in time across a large base of infants. Correlations were sought between diaper dermatitis incidence and severity and a number of factors, including sex, diet, maturity, type of diaper, history of allergy, contact with fecal matter, presence of Candida albicans, and diaper change frequency. Severe diaper rash correlated strongly with the presence of C. albicans, and the frequency of rash correlated with duration of contact with feces and inversely with diaper change frequency. Diaper rash peaked at ages 9-12 months and was lower for breast-fed than for formula-fed infants. Exclusive use of disposable diapers correlated with lower rash levels than when some or all cloth diapers were used. In a longitudinal study, infants were observed daily for 50 days in order to determine the frequency and duration of rash episodes. In this study, the tendency for some infants to be rash-prone was clearly indicated. In a third type of study, over 10,000 infant visits to physicians' offices were used to record skin condition. Results showed a three-to fourfold increase in diaper rash if the child had diarrhea during the previous 48 h. PMID:3299331

Benjamin, L

1987-01-01

361

Correlates of Senior Center Utilization.  

ERIC Educational Resources Information Center

Gerontological research appears to indicate that a relatively small percentage of the elderly population of the United States attends any of the nation's senior centers. In order to identify the correlates of senior center participation for a sample of elderly living in a small urban community, elderly male and female center users (N=97) and…

Krout, John A.

362

Correlation Algorithm: the Conceptual Framework.  

National Technical Information Service (NTIS)

The lack of a utilitarian solution to the frame-to-frame correlation problem poses insurmountable difficulties for the successful passive observation of a collection of co-moving, nearly co-located objects. This is exactly the task faced in a scenario wit...

L. G. Taff

1988-01-01

363

Correlated Tunneling in Hydrogen Bonds  

NASA Astrophysics Data System (ADS)

We study the quantum nature of the protons participating in hydrogen bonds in several ice structures by analyzing the one particle density matrix. We find that in all cases, including ice Ih, the most common form of ice, and the high pressure phases, ice VIII, VII, and X, the system is ground-state dominated. However, while the dynamics is uncorrelated in the structures with standard asymmetric hydrogen bonds, such as ice Ih and VIII, local correlations among the protons characterize ice VII and, to a lesser extent, ice X in the so-called low barrier hydrogen bond regime. The correlations appear along the path to hydrogen bond symmetrization, when quantum fluctuations delocalize the proton on the two bond sides. The correlations derive from a strong requirement for local charge neutrality that favors concerted motion along the bonds. The resulting behavior deviates substantially from mean field theory, which would predict in ice VII coherent tunneling of the proton between the two bond sides, thereby causing an ionization catastrophe. Due to the correlations, the quantum state of the proton is entangled.

Lin, Lin; Morrone, Joseph A.; Car, Roberto

2011-10-01

364

Resolution of Fluorescence Correlation Measurements  

Microsoft Academic Search

The resolution limit of fluorescence correlation spectroscopy for two-component solutions is investigated theoretically and experimentally. The autocorrelation function for two different particles in solution were computed, statistical noise was added, and the resulting curve was fitted with a least squares fit. These simulations show that the ability to distinguish between two different molecular species in solution depends strongly on the

Ulrich Meseth; Thorsten Wohland; Rudolf Rigler; Horst Vogel

1999-01-01

365

Echoes in correlated neural systems  

NASA Astrophysics Data System (ADS)

Correlations are employed in modern physics to explain microscopic and macroscopic phenomena, like the fractional quantum Hall effect and the Mott insulator state in high temperature superconductors and ultracold atoms. Simultaneously probed neurons in the intact brain reveal correlations between their activity, an important measure to study information processing in the brain that also influences the macroscopic signals of neural activity, like the electroencephalogram (EEG). Networks of spiking neurons differ from most physical systems: the interaction between elements is directed, time delayed, mediated by short pulses and each neuron receives events from thousands of neurons. Even the stationary state of the network cannot be described by equilibrium statistical mechanics. Here we develop a quantitative theory of pairwise correlations in finite-sized random networks of spiking neurons. We derive explicit analytic expressions for the population-averaged cross correlation functions. Our theory explains why the intuitive mean field description fails, how the echo of single action potentials causes an apparent lag of inhibition with respect to excitation and how the size of the network can be scaled while maintaining its dynamical state. Finally, we derive a new criterion for the emergence of collective oscillations from the spectrum of the time-evolution propagator.

Helias, M.; Tetzlaff, T.; Diesmann, M.

2013-02-01

366

Enamel lesion parameter correlations between polychromatic micro-CT and TMR.  

PubMed

Transverse microradiography (TMR) is considered as the gold standard technique for the evaluation of enamel lesions. Micro-computed tomography (µCT) has the advantage of non-destructive measurements, but the beam-hardening effect with polychromatic x-rays is a major drawback. To date, no study has validated µCT against TMR. The objective of this study was to validate µCT measurements of enamel lesions under various x-ray conditions and software beam-hardening correction (BHC) against TMR. Human molars with natural white-spot lesions were scanned for 5 min by µCT at 100 kV in different conditions: 50 µA (0.5-mm Al filter), 165 µA (0.5-mm Al/0.3-mm Cu), and 200 µA (0.5-mm Al/0.4-mm Cu), with or without BHC. Grayscale values were converted into mineral density values using phantoms. Thin sections at the same positions were then prepared for TMR. Lesion depth (LD; µm) and mineral loss (?Z; vol%µm) were compared between µCT and TMR by Pearson's correlations. µCT measurements correlated well with TMR under all conditions (p < 0.001, r > 0.86 for LD and ?Z), except for 0.5-mm Al without BHC (p > 0.05). Even without BHC, combined Al/Cu filters successfully reduced the beam-hardening effect. µCT can be used as a non-destructive alternative to TMR with comparable parameters for the study of enamel lesions. PMID:22476867

Hamba, H; Nikaido, T; Sadr, A; Nakashima, S; Tagami, J

2012-04-03

367

Correlation of C-reactive protein to severity of symptoms in acute influenza A infection  

PubMed Central

Background: Currently there is no objective measure to determine disease severity in patients with acute influenza infection. During acute viral infections, C-reactive protein (CRP) has been shown to be elevated. Aim: To study the relationship between the symptoms of acute influenza A infection and correlate them with the level of inflammation as measured by serum CRP levels. Settings and Design: Prospective study. Materials and Methods: We enrolled a convenience sample of adults presenting to an urban academic emergency department (ED), who had positive Enzyme-linked immunosorbent assay detection of the influenza A antigen. The subjects were excluded if they had immunosuppression, liver disease or were currently taking antiviral medication. A previously validated severity of symptom (SOS) score was calculated by asking the participants to record the severity of seven symptoms associated with influenza infection. The subjects had the serum C-reactive protein (CRP) levels tested during their ED visit. Statistical Analysis: A linear regression model was used with CRP as a predictor of the SOS score. Pearson's product-moment coefficient was used to measure the dependence between the two quantities. Results: Thirty-two subjects were enrolled from January through March 2009, and of those, eight patients were excluded from the analysis, leaving 24 study subjects: 58% were women, of ages 18 to 63 years, with a mean age of 31 years (95% CI 25, 37). The mean SOS score was 14.1 ranging from 6 to 21 (95% CI 12.6, 26.4). The mean CRP score was 24.6 ranging from 0 to 64.7 (95% CI 15.8, 33.4). The correlation coefficient between the SOS score and CRP levels was r = 0.65 (P=0.00056). Conclusion: The severity of symptoms associated with acute influenza A infection correlateswith the serum CRP levels.

Haran, John P; Suner, Selim; Gardiner, Fenwick

2012-01-01

368

Poor correlation between intracranial pressure and intraocular pressure by hand-held tonometry  

PubMed Central

Purpose The aim of this study is to provide data on the controversial issue of whether handheld measurements of intraocular pressure (IOP) are capable of accurately predicting elevated intracranial pressure (ICP) in patients undergoing lumbar puncture (LP). Methods All patients over the age of 18 years who underwent an LP in the emergency or neurological departments at the Tel Aviv Medical Center for any reason between October 2007 and July 2010 were eligible to participate in this prospective observational pilot study. IOP was measured with the Tono-Pen XL while patients were in the supine position before undergoing LP. ICP was measured in the lateral recumbent position. ICP and bilateral IOP were measured, and the mean and maximum values of IOP were calculated. The association between ICP and each one of the four IOP measures was evaluated by the Pearson correlation coefficient. Results Twenty-four patients (mean age 37.8 ± 15.8 years, ten males and 14 females) were enrolled. The reasons for their requiring an LP were headache (19/24 patients), evaluation for hemiparesis (2/24), cognitive deterioration (1/24), and seizures (2/24). Nine had elevated mean opening pressure (>20 cm H2O), six had an elevated mean IOP (>20 mmHg), and four of these six also had an elevated opening pressure. There was no significant correlation between the ICP measurements and any of the IOP measurements. Conclusion Handheld ocular tonometry has poor sensitivity and specificity for the prediction of increased ICP and is not an effective tool for screening for ICP in the ED or in the neurology department.

Golan, Shani; Kurtz, Shimon; Mezad-Koursh, Daphna; Waisbourd, Michael; Kesler, Anat; Halpern, Pinchas

2013-01-01

369

Dynamics of electricity market correlations  

NASA Astrophysics Data System (ADS)

Electricity market participants rely on demand and price forecasts to decide their bidding strategies, allocate assets, negotiate bilateral contracts, hedge risks, and plan facility investments. However, forecasting is hampered by the non-linear and stochastic nature of price time series. Diverse modeling strategies, from neural networks to traditional transfer functions, have been explored. These approaches are based on the assumption that price series contain correlations that can be exploited for model-based prediction purposes. While many works have been devoted to the demand and price modeling, a limited number of reports on the nature and dynamics of electricity market correlations are available. This paper uses detrended fluctuation analysis to study correlations in the demand and price time series and takes the Australian market as a case study. The results show the existence of correlations in both demand and prices over three orders of magnitude in time ranging from hours to months. However, the Hurst exponent is not constant over time, and its time evolution was computed over a subsample moving window of 250 observations. The computations, also made for two Canadian markets, show that the correlations present important fluctuations over a seasonal one-year cycle. Interestingly, non-linearities (measured in terms of a multifractality index) and reduced price predictability are found for the June-July periods, while the converse behavior is displayed during the December-January period. In terms of forecasting models, our results suggest that non-linear recursive models should be considered for accurate day-ahead price estimation. On the other hand, linear models seem to suffice for demand forecasting purposes.

Alvarez-Ramirez, J.; Escarela-Perez, R.; Espinosa-Perez, G.; Urrea, R.

2009-06-01

370

Double parton correlations in the bag model  

NASA Astrophysics Data System (ADS)

Double parton scattering is sensitive to correlations between the two partons in the hadron, including correlations in flavor, spin, color, momentum fractions and transverse separation. We obtain a first estimate of the size of these correlations by calculating the corresponding double parton distribution functions in a bag model of the proton. We find significant correlations between momentum fractions, spin and flavor, but negligible correlations with transverse separation. The model estimates of the relative importance of these correlations will help experimental studies disentangle them.

Chang, Hsi-Ming; Manohar, Aneesh V.; Waalewijn, Wouter J.

2013-02-01

371

Quantitative ultrashort echo time (UTE) MRI of human cortical bone: correlation with porosity and biomechanical properties.  

PubMed

In this study we describe the use of ultrashort echo time (UTE) magnetic resonance imaging (MRI) to evaluate short and long T2* components as well as the water content of cortical bone. Fourteen human cadaveric distal femur and proximal tibia were sectioned to produce 44 rectangular slabs of cortical bone for quantitative UTE MR imaging, microcomputed tomography (µCT), and biomechanical testing. A two-dimensional (2D) UTE pulse sequence with a minimal nominal TE of 8?µseconds was used together with bicomponent analysis to quantify the bound and free water in cortical bone using a clinical 3T scanner. Total water concentration was measured using a 3D UTE sequence together with a reference water phantom. UTE MR measures of water content (total, free, and bound), T2* (short and long), and short and long T2* fractions were compared with porosity assessed with µCT, as well as elastic (modulus, yield stress, and strain) and failure (ultimate stress, failure strain, and energy) properties, using Pearson correlation. Porosity significantly correlated positively with total (R(2) ?=?0.23; p?correlated positively with short T2* (R(2) ?=?0.29; p?correlated negatively with total (R(2) ?=?0.25; p?correlated positively with both short (R(2) ?=?0 30; p?

Bae, Won C; Chen, Peter C; Chung, Christine B; Masuda, Koichi; D'Lima, Darryl; Du, Jiang

2012-04-01

372

Fatty liver index correlates with non-alcoholic fatty liver disease, but not with newly diagnosed coronary artery atherosclerotic disease in Chinese patients  

PubMed Central

Background Fatty liver index (FLI) was recently established to predict non-alcoholic fatty liver disease (NAFLD) in general population, which is known to be associated with coronary artery atherosclerotic disease (CAD). This study aims to investigate whether FLI correlates with NAFLD and with newly diagnosed CAD in a special Chinese population who underwent coronary angiography. Methods Patients with CAD (n?=?231) and without CAD (n?=?482) as confirmed by coronary angiography were included. Among them, 574 patients underwent B-ultrosonography were divided into NAFLD group (n?=?209) and non-NAFLD group (n?=?365). Correlation between FLI and NAFLD was analyzed using pearson’s correlation. The associations between FLI and NAFLD as well as CAD were assessed using logistic regression. The predictive accuracy of FLI for NAFLD was evaluated using receiver operating characteristics (ROC) curve analysis. Results FLI was significantly higher in NAFLD group (37.10?±?1.95) than in non-NAFLD group (17.70?±?1.04), P?correlated with NAFLD (r?=?0.372, P??0.05). Conclusions FLI showed good correlation with NAFLD in patients who underwent coronary angiography, but not with newly diagnosed CAD. This might be underestimated because some patients in non-CAD group may have other underlying cardiovascular diseases.

2013-01-01

373

Incubation of selected fermentable fibres with feline faecal inoculum: correlations between in vitro fermentation characteristics and end products.  

PubMed

This study aimed to evaluate correlations between fermentation characteristics and end products of selected fermentable fibres (three types of fructans, citrus pectin, guar gum), incubated with faecal inocula from donor cats fed two diets, differing in fibre and protein sources and concentrations. Cumulative gas production was measured over 72 h, fermentation end products were analysed at 4, 8, 12, 24, 48 and 72 h post-incubation, and quantification of lactobacilli, bifidobacteria and bacteroides in fermentation liquids were performed at 4 and 48 h of incubation. Partial Pearson correlations, corrected for inoculum, were calculated to assess the interdependency of the fermentation characteristics of the soluble fibre substrates. Butyric and valeric acid concentrations increased with higher fermentation rates, whereas acetic acid declined. Concentrations of butyric acid (highest in fructans) and propionic acid were inversely correlated with protein fermentation end products at several time points, whereas concentrations of acetic acid (highest in citrus pectin) were positively correlated with these products at most time points. Remarkably, a lack of clear relationship between the counts of bacterial groups and their typically associated products after 4 h of incubation was observed. Data from this experiment suggest that differences in fibre fermentation rate in feline faecal inocula coincide with typical changes in the profile of bacterial fermentation products. The observed higher concentrations of propionic and butyric acid as a result of fibre fermentation could possibly have beneficial effects on intestinal health, and may be confounded with a concurrent decrease in the production of putrefactive compounds. In conclusion, supplementing guar gum or fructans to a feline diet might be more advantageous compared with citrus pectin. However, in vivo research is warranted to confirm these conclusions in domestic cats. PMID:23952674

Rochus, Kristel; Bosch, Guido; Vanhaecke, Lynn; Van de Velde, Hannelore; Depauw, Sarah; Xu, Jia; Fievez, Veerle; Van de Wiele, Tom; Hendriks, Wouter Hendrikus; Paul Jules Janssens, Geert; Hesta, Myriam

2013-08-19

374

Retinol-binding protein 4 correlates with triglycerides but not insulin resistance in prepubertal children with and without premature adrenarche  

PubMed Central

Background Retinol-binding protein 4 (RBP4) has been proposed as an early marker for insulin resistance (IR), but no prior studies have addressed RBP4 in an exclusively prepubertal population. Children with premature adrenarche (PA) are at increased risk for IR and metabolic syndrome (MeS), thus finding an appropriate early marker for IR in this population would allow for early intervention and prevention of morbidity related to IR and MeS. Objective To determine whether prepubertal children with PA have higher levels of RBP4 than controls and whether RBP4 correlates with comorbidities of metabolic disease in prepubertal children. Subjects This study comprised 49 prepubertal children (24 with PA and 25 control subjects), 20 boys and 29 girls, who were between the ages of 5 and 9 years. Methods This was a cross-sectional, case-control study conducted in a subspecialty ambulatory clinic based in a quaternary care center. RBP4 levels, hormonal values, lipids and response to an oral glucose tolerance test were evaluated in children with PA and controls, and body composition measures were obtained in a subset of patients (n=18). Results RBP4 correlated with triglycerides (r = 0.57, P < 0.0001) but did not correlate with IR in a body mass index z-score-adjusted Pearson correlation analysis. There was no difference in RBP4 levels between the PA and control groups. Conclusions These findings suggest that RBP4 may be an early marker of dyslipidemia, which may herald future onset of hepatic IR, polycystic ovary syndrome and MeS.

Sopher, Aviva B.; Gerken, Adrienne T.; Lee, Eun-Ju; Blaner, William E.; Deeds, Stefanie; Gallagher, Dympna; Shungu, Dikoma C.; Mao, Xiangling; Hassoun, Abeer; McMahon, Donald J.; Oberfield, Sharon E.

2013-01-01

375

Biomechanical Properties and Correlation With Collagen Solubility Profile in the Posterior Sclera of Canine Eyes With an ADAMTS10 Mutation  

PubMed Central

Purpose. We examined the biomechanical properties and correlation with the collagen solubility profile of the posterior sclera in a canine model of primary open-angle glaucoma caused by the G661R missense mutation in the ADAMTS10 gene. Methods. Scleral strips from ADAMTS10-mutant (affected) dogs and age-matched controls were collected. Viscoelastic properties (i.e., complex modulus and tan[?]) were measured using dynamic mechanical analysis (DMA) with a 0.15% sinusoidal strain at different frequencies superimposed upon different preloads. A tensile ramp was performed following DMA. The collagen solubility profile was examined using a colorimetric hydroxyproline assay to determine the amount of soluble and insoluble collagen. The viscoelastic properties were compared between groups using linear mixed models for repeated measures at different preloads and frequencies. The correlation between the biomechanical properties and collagen content were evaluated using Pearson correlations. Results. Complex modulus and tan(?) were significantly lower in the affected group (P < 0.001), and the differences were consistent at different preloads and frequencies. The B value from the tensile ramp test also was significantly lower in the affected group (P = 0.02). The insoluble collagen was significantly lower in the affected group (P < 0.05) and correlated positively with the complex modulus (R = 0.88, P < 0.005). Conclusions. An inherently weaker and biochemically distinct posterior sclera was observed in dogs with the G661R missense mutation in ADAMTS10 before clinical indications of optic nerve damage. It remains to be shown whether and how the altered scleral biomechanics may affect the rate of glaucoma progression following intraocular pressure elevation.

Palko, Joel R.; Iwabe, Simone; Pan, Xueliang; Agarwal, Gunjan; Komaromy, Andras M.; Liu, Jun

2013-01-01

376

Quantum correlations in predictive processes  

NASA Astrophysics Data System (ADS)

We consider the role of quantum correlations in the efficient use of information by a predictive quantum system, generalizing a recently proposed classical measure of nonpredictive information to the quantum regime. We show that, as a quantum system changes state, the nonpredictive information held by another correlated quantum system is exactly equal to the extractable work that is lost from the second system. We use quantum discord to quantify the quantum contribution, and demonstrate the possibility of improved thermodynamic efficiency due to a negative “quantum part” of the lost work. We also give a thermodynamic interpretation to quantum discord, as the reduction in extractable work under an optimal classical approximation of a quantum memory.

Grimsmo, Arne L.

2013-06-01

377

Coal combustion chemistry correlation aspects  

SciTech Connect

This book provides fundamental guidelines to reducing the combustion problems that inorganic impurity compounds cause in coal-fired electricity-generating plants. The compounds treated are those of eight major-abundance metal and semimetal elements - silcon, aluminum, iron, calcium, potassium, magnesium, titanium, and sodium. The book employs a combustion chemistry approach, together with a methodology that relates empirical correlations to the effects of inorganic impurity compounds on oxidation-combustion that may occur prior to ignition, at ignition, during heat-up to flame temperatures, or at flame temperatures. Why basic oxide constituents have higher chemical reactivities during coal combustion than acidic oxide chemical reactivities is shown in the introductory chapter. Other discussions cover the chemistry and coal-science backgrounds that relate to oxide constituents of the eight major-abundance elements. The book concludes with sets of empirical correlations.

Badin, E.J.

1984-01-01

378

Correlations in avalanche critical points.  

PubMed

Avalanche dynamics and related power-law statistics are ubiquitous in nature, arising in phenomena such as earthquakes, forest fires, and solar flares. Very interestingly, an analogous behavior is associated with many condensed-matter systems, such as ferromagnets and martensites. Bearing it in mind, we study the prototypical random-field Ising model at T=0. We find a finite correlation between waiting intervals and the previous avalanche size. This correlation is not found in other models for avalanches but it is experimentally found in earthquakes and in forest fires. Our study suggests that this effect occurs in critical points that are at the end of a first-order discontinuity separating two regimes: one with high activity from another with low activity. PMID:19658651

Cerruti, Benedetta; Vives, Eduard

2009-07-06

379

Ultraviolet divergences in cosmological correlations  

SciTech Connect

A method is developed for dealing with ultraviolet divergences in calculations of cosmological correlations, which does not depend on dimensional regularization. An extended version of the WKB approximation is used to analyze the divergences in these calculations, and these divergences are controlled by the introduction of Pauli-Villars regulator fields. This approach is illustrated in the theory of a scalar field with arbitrary self-interactions in a fixed flat-space Robertson-Walker metric with arbitrary scale factor a(t). Explicit formulas are given for the counterterms needed to cancel all dependence on the regulator properties, and an explicit prescription is given for calculating finite regulator-independent correlation functions. The possibility of infrared divergences in this theory is briefly considered.

Weinberg, Steven [Theory Group, Department of Physics, University of Texas Austin, Texas, 78712 (United States)

2011-03-15

380

Counterion Correlations on Condensed Biopolymers  

NASA Astrophysics Data System (ADS)

Like-charged polyelectrolytes condense into ordered phases in the presence of multivalent ions. The physical origin of the attractive interaction required for this condensation has been intensely debated, but no clear consensus has emerged, although counterion correlations appear to play a key role. In order to elucidate the nature of these interactions, we have performed structural measurements of condensed phases formed between multivalent ions and a range of rod-like polyelectrolytes, including cytoskeletal F-actin, and Fd and M13 filamentary virus particles.šDirect measurements of the counterion density and correlations in different condensed phases will be presented, along with the temperature dependence of these phases. This work was supported by NSF DMR-0071761, DOE DEFG02-91ER45439, the Beckman Young Investigator Program, and the Cystic Fibrosis Foundation.

Angelini, Tommy; Butler, John; Ho, James; Liang, Hongjun; Wong, Gerard

2002-03-01

381

Coal combustion chemistry correlation aspects  

Microsoft Academic Search

This book provides fundamental guidelines to reducing the combustion problems that inorganic impurity compounds cause in coal-fired electricity-generating plants. The compounds treated are those of eight major-abundance metal and semimetal elements - silcon, aluminum, iron, calcium, potassium, magnesium, titanium, and sodium. The book employs a combustion chemistry approach, together with a methodology that relates empirical correlations to the effects of

Badin

1984-01-01

382

Correlated Default With Incomplete Information  

Microsoft Academic Search

The recent accounting scandals at Enron, WorldCom, and Tyco were related to the misrep- resentation of liabilities. We provide a structural model of correlated multi-firm default, in which public bond investors are uncertain about the liability-dependent barrier at which indi- vidual firms default. Investors form prior beliefs on the barriers, which they update with the default status information of firms

Kay Giesecke

2002-01-01

383

Correlated default with incomplete information  

Microsoft Academic Search

The recent accounting scandals at Enron, WorldCom, and Tyco were related to the misrepresentation of liabilities. We provide a structural model of correlated multi-firm default, in which public bond investors are uncertain about the liability-dependent barrier at which individual firms default. Investors form prior beliefs on the barriers, which they update with the default status information of firms arriving over

Kay Giesecke

2004-01-01

384

Correlates of Protection Against Influenza  

Microsoft Academic Search

\\u000a Correlates of protection against influenza viruses have not been fully defined, but it is widely believed that protection\\u000a against influenza can be conferred by serum hemagglutinin (HA) antibodies. The immune responses to injected influenza vaccines\\u000a are routinely assessed by titrating serological HA antibodies. It is generally accepted that neutralizing and HA antibodies,\\u000a as well as antibodies to neuraminidase, can be

Emanuele Montomoli; Barbara Capecchi; Katja Hoschler

385

Clinical correlation of anticentromere antibodies  

Microsoft Academic Search

A retrospective survey of all patients with a positive anticentromere antibody (ACA) determination was undertaken over a 3-years period of time in a university hospital. Forty-five patients were positive for anticentromere antibodies. The analysis of the clinical characteristics and diagnoses of the patients with anticentromere antibodies were correlated and showed a diverse array of symptoms. Only 4.4% had CREST syndrome,

M. Zuber; R. Gotzen; I. Filler

1994-01-01

386

Polarization correlations in pulsed VCSELs  

Microsoft Academic Search

Summary form only given. Vertical-cavity surface-emitting lasers (VCSELs) exhibit very interesting physical properties and have great potential for use in optical communications. However, the physical mechanisms that lead to polarization selection in VCSELs are not completely understood, despite much research. We have measured polarization correlations in a pulsed VCSEL. We apply short (3-30 ns) current pulses to the laser and

D. R. Shelly; T. W. S. Garrison; M. Beck; D. H. Christensen

2000-01-01

387

Correlates of Prenatal Alcohol Use  

Microsoft Academic Search

Objectives: To identify correlates of prenatal alcohol use in a statewide population-based sample. Methods: A self-reported survey was conducted in 67 prenatal clinics in Minnesota with 4,272 women at their first prenatal visit.\\u000a Chi-squared and multivariate logistic regression analyses were conducted to identify risk markers associated with any prenatal\\u000a alcohol use. Results: Nearly 27% of the respondents were calculated as having

Laurie L. Meschke; Wendy Hellerstedt; Joyce A. Holl; Sara Messelt

2008-01-01

388

Correlates of postpartum smoking relapse  

Microsoft Academic Search

Background: Using population-based data from the Pregnancy Risk Assessment Monitoring System (PRAMS), this study examines the prevalence and intensity of smoking before, during, and after pregnancy, and identifies correlates of postpartum smoking relapse.Methods: Women who delivered live births in 1996 responded to a mailed questionnaire approximately 2 to 6 months after delivery (N =17,378). Data from 10 states participating in

Suzan L. Carmichael; Indu B. Ahluwalia

2000-01-01

389

Stable Bose-Einstein correlations  

Microsoft Academic Search

The shape of Bose-Einstein (or HBT) correlation functions is determined for\\u000athe case when particles are emitted from a stable source, obtained after\\u000aconvolutions of large number of elementary random processes. The two-particle\\u000acorrelation function is shown to have a {\\\\it stretched exponential} shape,\\u000acharacterized by the L\\\\'evy index of stability $ 0 < \\\\alpha \\\\le 2$ and the\\u000ascale

S. Hegyi; W. A. Zajc; MTA KFKI RMKI

2004-01-01

390

Empirical correlation for ejector design  

Microsoft Academic Search

In the present study, two empirical correlations from the test results of 15 ejectors are derived for the performance prediction of ejectors using R141b as the working fluid. The ratio of the hypothetical throat area of the entrained flow to the nozzle throat area Ae\\/At, the geometric design parameter of the ejector A3\\/At, and the pressure ratios Pg\\/Pe and Pc*\\/Pe

B. J Huang; J. M Chang

1999-01-01

391

Somatic correlates of functional enuresis  

Microsoft Academic Search

Functional enuresis is a heterogeneous group of syndromes with different aetiology and pathophysiology. The aim was to identify\\u000a specific somatic correlates of enuresis non-invasively in child psychiatric patients after exclusion of neurologic and structural\\u000a forms of incontinence. One hundred sixty-seven consecutive children, aged 5 to 10 years with day and\\/or night wetting were\\u000a examined prospectively with: urinalysis and bacteriology; ultrasonography,

A. von Gontard; B. Benden; K. Mauer-Mucke; G. Lehmkuhl

1999-01-01

392

Neural correlates of feeling sympathy  

Microsoft Academic Search

Positron emission tomography (PET) was used to investigate the neural correlates of feeling sympathy for someone else (i.e. the affinity, association, or relationship between persons wherein whatever affects one similarly affects the other). While undergoing PET scans, subjects were presented with a series of video-clips showing individuals (who were semi-professional stage actors) telling sad and neutral stories, as if they

Jean Decety; Thierry Chaminade

2003-01-01

393

Optical Spectroscopy of Correlated Oxides  

NASA Astrophysics Data System (ADS)

This dissertation presents optical studies of correlated oxide thin films mainly through the use of spectroscopic ellipsometry. The main focus is on exploring how electron-electron interactions shape the electronic properties of various transition metal oxides, although work on weakly correlated CrO 2 is also included. Epitaxial strain and temperature are employed as "tuning knobs" for material properties, often inducing and in one case completely suppressing a phase transition. A series of nickelate thin films of varying thickness and strain are investigated over broad energy and temperature ranges, spanning both the insulating and metallic phases. The far-infrared parts of the spectra are studied in the context of the extended Drude model. A detailed analysis is carried out to assess the energy scales associated with the transfer of electronic spectral weight across the insulator-to-metal transition and within the metallic state. These results are then compared to the predictions of the Mott-Hubbrad model for correlated electron systems. Additionally, a similar analysis is employed to study thin films of V 2O3, which exhibits and insulator-to-metal transition at ˜150 K. Finally, a study of the ferromagnetic transition in half-metallic CrO 2 is presented. The optical response of the films along various crystallographic directions is extracted from ellipsometry data and a comparison to existing band structure calculations is presented.

Stewart, Margaret K.

394

Correlated genotypes in friendship networks  

PubMed Central

It is well known that humans tend to associate with other humans who have similar characteristics, but it is unclear whether this tendency has consequences for the distribution of genotypes in a population. Although geneticists have shown that populations tend to stratify genetically, this process results from geographic sorting or assortative mating, and it is unknown whether genotypes may be correlated as a consequence of nonreproductive associations or other processes. Here, we study six available genotypes from the National Longitudinal Study of Adolescent Health to test for genetic similarity between friends. Maps of the friendship networks show clustering of genotypes and, after we apply strict controls for population stratification, the results show that one genotype is positively correlated (homophily) and one genotype is negatively correlated (heterophily). A replication study in an independent sample from the Framingham Heart Study verifies that DRD2 exhibits significant homophily and that CYP2A6 exhibits significant heterophily. These unique results show that homophily and heterophily obtain on a genetic (indeed, an allelic) level, which has implications for the study of population genetics and social behavior. In particular, the results suggest that association tests should include friends’ genes and that theories of evolution should take into account the fact that humans might, in some sense, be metagenomic with respect to the humans around them.

Fowler, James H.; Settle, Jaime E.; Christakis, Nicholas A.

2011-01-01

395

Spatial Correlations in Attribute Communities  

PubMed Central

Community detection is an important tool for exploring and classifying the properties of large complex networks and should be of great help for spatial networks. Indeed, in addition to their location, nodes in spatial networks can have attributes such as the language for individuals, or any other socio-economical feature that we would like to identify in communities. We discuss in this paper a crucial aspect which was not considered in previous studies which is the possible existence of correlations between space and attributes. Introducing a simple toy model in which both space and node attributes are considered, we discuss the effect of space-attribute correlations on the results of various community detection methods proposed for spatial networks in this paper and in previous studies. When space is irrelevant, our model is equivalent to the stochastic block model which has been shown to display a detectability-non detectability transition. In the regime where space dominates the link formation process, most methods can fail to recover the communities, an effect which is particularly marked when space-attributes correlations are strong. In this latter case, community detection methods which remove the spatial component of the network can miss a large part of the community structure and can lead to incorrect results.

Cerina, Federica; De Leo, Vincenzo; Barthelemy, Marc; Chessa, Alessandro

2012-01-01

396

Observability transitions in correlated networks  

NASA Astrophysics Data System (ADS)

Yang, Wang, and Motter [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.109.258701 109, 258701 (2012)] analyzed a model for network observability transitions in which a sensor placed on a node makes the node and the adjacent nodes observable. The size of the connected components comprising the observable nodes is a major concern of the model. We analyze this model in random heterogeneous networks with degree correlation. With numerical simulations and analytical arguments based on generating functions, we find that negative degree correlation makes networks more observable. This result holds true both when the sensors are placed on nodes one by one in a random order and when hubs preferentially receive the sensors. Finally, we numerically optimize networks with a fixed degree sequence with respect to the size of the largest observable component. Optimized networks have negative degree correlation induced by the resulting hub-repulsive structure; the largest hubs are rarely connected to each other, in contrast to the rich-club phenomenon of networks.

Hasegawa, Takehisa; Takaguchi, Taro; Masuda, Naoki

2013-10-01

397

Correlated Temporal and Spectral Variability  

NASA Astrophysics Data System (ADS)

The variability of neutron star and black hole X-ray sources has several dimensions, because of the roles played by different important time-scales. The variations on time scales of hours, weeks, and months, ranging from 50% to orders of magnitude, arise out of changes in the flow in the disk. The most important driving forces for those changes are probably various possible instabilities in the disk, though there may be effects with other dominant causes. The changes in the rate of flow appear to be associated with changes in the flow's configuration, as the accreting material approaches the compact object, for there are generally correlated changes in both the Xray spectra and the character of the faster temporal variability. There has been a lot of progress in tracking these correlations, both for Z and Atoll neutron star low-mass X-ray binaries, and for black hole binaries. I will discuss these correlations and review briefly what they tell us about the physical states of the systems.

Swank, Jean H.

2007-01-01

398

Spin correlations in bilayer manganites  

NASA Astrophysics Data System (ADS)

The lowered dimensionality in the naturally layered manganites La_2-2xSr_1+2xMn_2O_7, where x is the hole-doping in the MnO2 layers, leads to an extended temperature region over which fluctuations are important. These systems are therefore ideal to study in detail the influence of spin, charge and lattice fluctuations on the transport properties on approaching the ferromagnetic and concomitant metal-insulator transition. Here we report on our detailed neutron scattering investigation of the spin correlations in the region of optimal doping ( x ~ 0.32 - 0.4 ). In the paramagnetic region above TC ~ 120 K, the correlations obey standard two-dimensional scaling with a crossover towards three-dimensional critical behavior close to T_C, consistent with a conventional quasi two-dimensional phase transition. This suggests that conventional critical spin fluctuations drive the phase transition while simultaneously destroying the charge correlations observed in the paramagnetic region [L. Vasiliu-Doloc et al., Phys. Rev. Lett. 83, 4393 (1999)]. Work supported by US DOE BES-DMS W-31-109-ENG-38, NSF DMR 97-01339 and the Swiss NSF.

Rosenkranz, Stephan; Osborn, Ray; Vasiliu-Doloc, Lida; Mitchell, John F.; Sinha, Sunil; Lynn, Jeff W.

2001-03-01

399

Co-Overexpression of GEP100 and AMAP1 Proteins Correlates with Rapid Local Recurrence after Breast Conservative Therapy.  

PubMed

A major problem of current cancer research and therapy is prediction of tumor recurrence after initial treatment, rather than the simple biological characterization of the malignancy and proliferative properties of tumors. Breast conservation therapy (BCT) is a well-approved, standard treatment for patients with early stages of breast cancer, which consists of lumpectomy and whole-breast irradiation. In spite of extensive studies, only 'age' and 'Ki-67 positivity' have been identified to be well correlated with local recurrence after BCT. An Arf6 pathway, activated by GEP100 under receptor tyrosine kinases (RTKs) and employs AMAP1 as its effector, is crucial for invasion and metastasis of some breast cancer cells. This pathway activates ?1 integrins and perturbs E-cadherin-based adhesions, hence appears to be integral for epithelial-mesenchymal transdifferentiation (EMT). We here show that expression of the Arf6 pathway components statistically correlates with rapid local recurrence after BCT. We retrospectively analyzed four hundred seventy-nine patients who received BCT in Hokkaido University Hospital, and found 20 patients had local recurrence. We then analyzed pathological samples of patients who experienced local recurrence by use of Kaplan-Meier analysis, Stepwise regression analysis and the t-test, coupled with immunostaining, and found that co-overexpression of GEP100 and AMAP1 correlates with rapidity of the local recurrence. Their margin-status, node-positivity, and estrogen receptor (ER)- or progesterone receptor (PgR)-positivity did not correlated with the rapidity. This study is the first to show that expression of a certain set of proteins correlates with the rapidity of local recurrence. Our results are useful not only for prediction, but highlight the possibility of developing novel strategies to block local recurrence. We also discuss why mRNAs encoding these proteins have not been identified to correlate with local recurrence by previous conventional gene expression profiling analyses. PMID:24116160

Kinoshita, Rumiko; Nam, Jin-Min; Ito, Yoichi M; Hatanaka, Kanako C; Hashimoto, Ari; Handa, Haruka; Otsuka, Yutaro; Hashimoto, Shigeru; Onodera, Yasuhito; Hosoda, Mitsuchika; Onodera, Shunsuke; Shimizu, Shinichi; Tanaka, Shinya; Shirato, Hiroki; Tanino, Mishie; Sabe, Hisataka

2013-10-07

400

Co-Overexpression of GEP100 and AMAP1 Proteins Correlates with Rapid Local Recurrence after Breast Conservative Therapy  

PubMed Central

A major problem of current cancer research and therapy is prediction of tumor recurrence after initial treatment, rather than the simple biological characterization of the malignancy and proliferative properties of tumors. Breast conservation therapy (BCT) is a well-approved, standard treatment for patients with early stages of breast cancer, which consists of lumpectomy and whole-breast irradiation. In spite of extensive studies, only 'age' and 'Ki-67 positivity' have been identified to be well correlated with local recurrence after BCT. An Arf6 pathway, activated by GEP100 under receptor tyrosine kinases (RTKs) and employs AMAP1 as its effector, is crucial for invasion and metastasis of some breast cancer cells. This pathway activates ?1 integrins and perturbs E-cadherin-based adhesions, hence appears to be integral for epithelial-mesenchymal transdifferentiation (EMT). We here show that expression of the Arf6 pathway components statistically correlates with rapid local recurrence after BCT. We retrospectively analyzed four hundred seventy-nine patients who received BCT in Hokkaido University Hospital, and found 20 patients had local recurrence. We then analyzed pathological samples of patients who experienced local recurrence by use of Kaplan-Meier analysis, Stepwise regression analysis and the t-test, coupled with immunostaining, and found that co-overexpression of GEP100 and AMAP1 correlates with rapidity of the local recurrence. Their margin-status, node-positivity, and estrogen receptor (ER)- or progesterone receptor (PgR)-positivity did not correlated with the rapidity. This study is the first to show that expression of a certain set of proteins correlates with the rapidity of local recurrence. Our results are useful not only for prediction, but highlight the possibility of developing novel strategies to block local recurrence. We also discuss why mRNAs encoding these proteins have not been identified to correlate with local recurrence by previous conventional gene expression profiling analyses.

Kinoshita, Rumiko; Nam, Jin-Min; Ito, Yoichi M.; Hatanaka, Kanako C.; Hashimoto, Ari; Handa, Haruka; Otsuka, Yutaro; Hashimoto, Shigeru; Onodera, Yasuhito; Hosoda, Mitsuchika; Onodera, Shunsuke; Shimizu, Shinichi; Tanaka, Shinya; Shirato, Hiroki; Tanino, Mishie; Sabe, Hisataka

2013-01-01

401

Correlation between Serum Total Testosterone and the AMS and IIEF Questionnaires in Patients with Erectile Dysfunction with Testosterone Deficiency Syndrome  

PubMed Central

Purpose This study was conducted to investigate the relationship between serum total testosterone levels and scores on the Aging Male's Symptom (AMS) scale and the International Index of Erectile Function (IIEF) in men with erectile dysfunction with testosterone deficiency syndrome (TDS). Materials and Methods From January 2005 to July 2008, 134 patients who complained of sexual dysfunction such as erectile dysfunction or decreased libido as the main symptoms of TDS with serum total testosterone levels less than 3.5 ng/ml were evaluated by independent t-test and linear regression analysis, respectively. Patients with treated hypogonadism within 6 months, with a history of taking a PDE5 inhibitor or an antidepressant for a depressive disorder, or who had metabolic syndrome were excluded from this study. Results The AMS scale and its 3 subdomain scores were not significantly correlated with the total testosterone level. By contrast, the total IIEF score and the score of each IIEF domain except sexual desire showed a weakly significantly positive correlation with serum total testosterone. Conclusions In TDS patients with erectile dysfunction, there was a low relationship between serum total testosterone levels and the AMS scale and a weakly positive correlation between total testosterone levels and all IIEF domains except sexual desire. There was a low relationship between the AMS scale, the sexual desire domain score of the IIEF, and total testosterone. We should understand these limitations when evaluating patients with erectile dysfunction with TDS. New scales should be developed for the evaluation of erectile dysfunction in these patients.

Kang, Jae Il; Ham, Byeong Kuk; Oh, Mi Mi; Kim, Je Jong

2011-01-01

402

Correlation theory of quantized electromagnetic field I  

Microsoft Academic Search

A correlation matrix is defined which describes arbitrary order correlation effects of the electromagnetic field. Dynamical equations are derived which govern the space-time development of the correlation matrix of the quantized electromagnetic field in vacuo. With the help of these equations, propagation laws and non-linear conservation laws for the correlation matrix are obtained.

R. Horák

1969-01-01

403

Extended Length Digital Correlator Threshold Circuit.  

National Technical Information Service (NTIS)

An extended length digital correlator threshold circuit for (N . M) -bit correlation using N M-bit correlators is disclosed. For the exemplary case where N=2, the digital correlator threshold circuit comprises: a first circuit for storing a preselected co...

L. M. Leibowitz T. Mai

1992-01-01

404

Completion problem with partial correlation vines  

Microsoft Academic Search

This paper extends the results in [D. Kurowicka, R.M. Cooke, A parametrization of positive definite matrices in terms of partial correlation vines, Linear Algebra Appl. 372 (2003) 225–251]. We show that a partial correlation vine represents a factorization of the determinant of the correlation matrix. We show that the graph of an incompletely specified correlation matrix is chordal if and

D. Kurowicka; R. M. Cooke

2006-01-01

405

COMPARING THE EFFECTIVENESS OF RANK CORRELATION STATISTICS  

Microsoft Academic Search

Rank correlation is a fundamental tool to express dependence in cases in which the data are arranged in order. There are, by contrast, circumstances where the ordinal association is of a nonlinear type. In this paper we investigate the effectiveness of several measures of rank correlation. These measures have been divided into three classes: conventional rank correlations, weighted rank correlations,

Agostino Tarsitano

2009-01-01

406

Environmental Attitude - Behaviour Correlations in 21 Countries  

Microsoft Academic Search

We used data from the International Social Survey Program to investigatethe correlation between 'green' attitudes and 'green' consumption behaviours in 21 different countries. Despite avoiding the methodological problems often blamed for poor attitude-behaviour correlations, we found lower correlations than reported in a recent meta-analysis of this subject. Furthermore, the correlations varied considerably between countries, and in some countries were not

Malcolm Wright; Babs Klÿn

1998-01-01

407

Correlation, functional analysis and optical pattern recognition  

SciTech Connect

Correlation integrals have played a central role in optical pattern recognition. The success of correlation, however, has been limited. What is needed is a mathematical operation more complex than correlation. Suitably complex operations are the functionals defined on the Hilbert space of Lebesgue square integrable functions. Correlation is a linear functional of a parameter. In this paper, we develop a representation of functionals in terms of inner products or equivalently correlation functions. We also discuss the role of functionals in neutral networks. Having established a broad relation of correlation to pattern recognition, we discuss the computation of correlation functions using acousto-optics.

Dickey, F.M.; Lee, M.L.; Stalker, K.T.

1994-03-01

408

The Jomon in early agriculture discourse: issues arising from Matsui, Kanehara and Pearson  

Microsoft Academic Search

Two articles in World Archaeology (2006) raise issues regarding the long-standing classification of the Jomon as collectors and affluent foragers. Crops and food production have not played a significant role in understanding Jomon settlement systems, population density, complexity and their regional variation despite the reports of crops from numerous Jomon sites. A misunderstanding of one of my publications provides an

Gary W. Crawford

2008-01-01

409

On the Asymptotic Distribution of Pearson's X[superscript 2] in Cross-Validation Samples  

ERIC Educational Resources Information Center

In categorical data analysis, two-sample cross-validation is used not only for model selection but also to obtain a realistic impression of the overall predictive effectiveness of the model. The latter is of particular importance in the case of highly parametrized models capable of capturing every idiosyncracy of the calibrating sample. We show…

Joe, Harry; Maydeu-Olivares, Albert

2006-01-01

410

The Pearson Report--compromise or step towards effective and just compensation for disability?  

PubMed Central

The setting up of the Royal Commission on Civil Liability and Compensation for Personal Injury, its terms of reference and report are discussed. The main recommendations are detailed with brief consideration of their possible impact. The proposals are assessed and the philosophy and principles behind the reform, explicit or implicit in the Report, are considered. Finally, the extent to which the proposals can be a blueprint for later reforms dealing with compensation for disability in general is discussed.

Collinson, J M

1979-01-01

411

Finite size effects in correlated electron models  

NASA Astrophysics Data System (ADS)

Introduction -- Quantum spin- 1/2 chain with the nearest-neighbour couplings -- Co-ordinate Bethe ansatz for a Heisenber-Ising ring -- Correlated electron chains: Co-ordinate Bethe ansatz -- Algebraic Bethe ansatz -- Correlated quantum chains with open boundary conditions -- Correlated quantum chains with isolated impurities -- Correlated quantum chains with a finite concentration of impurities -- Finite size corrections in quantum correlated chains -- Beyond the integrability: Approximate methods.

Zvyagin, Andrei A.

412

Pack hike test finishing time for Australian firefighters: pass rates and correlates of performance.  

PubMed

The pack hike test (PHT, 4.83 km hike wearing a 20.4-kg load) was devised to determine the job readiness of USA wildland firefighters. This study measured PHT performance in a sample of Australian firefighters who currently perform the PHT (career land management firefighters, LMFF) and those who do not (suburban/regional volunteer firefighters, VFF). The study also investigated the relationships between firefighters' PHT performance and their performance across a range of fitness tests for both groups. Twenty LMFF and eighteen age-, body mass-, and height-matched VFF attempted the PHT, and a series of muscular endurance, power, strength and cardiorespiratory fitness tests. Bivariate correlations between the participants' PHT finishing time and their performance in a suite of different fitness tests were determined using Pearson's product moment correlation coefficient. The mean PHT finishing time for LMFF (42.2 ± 2.8 min) was 9 ± 14% faster (p = 0.001) than for VFF (46.1 ± 3.6 min). The pass rate (the percentage of participants who completed the PHT in under 45 min) for LMFF (90%) was greater than that of VFF (39%, p = 0.001). For LMFF, VO(2peak) in L min(-1)(r = -0.66, p = 0.001) and the duration they could sustain a grip 'force' of 25 kg (r = -0.69, p = 0.001) were strongly correlated with PHT finishing time. For VFF, VO(2peak) in mL kg(-1) min(-1)(r = -0.75, p = 0.002) and the duration they could hold a 1.2-m bar attached to 45.5 kg in a 'hose spray position' (r = -0.69, p = 0.004) were strongly correlated with PHT finishing time. This study shows that PHT fitness-screening could severely limit the number of VFF eligible for duty, compromising workforce numbers and highlights the need for specific and valid firefighter fitness standards. The results also demonstrate the strong relationships between PHT performance and firefighters' cardiorespiratory fitness and local muscular endurance. Those preparing for the PHT should focus their training on these fitness components in the weeks and months prior to undertaking the PHT. PMID:20888552

Phillips, M; Petersen, A; Abbiss, C R; Netto, K; Payne, W; Nichols, D; Aisbett, B

2011-03-01

413

Variable Selection through Correlation Sifting  

NASA Astrophysics Data System (ADS)

Many applications of computational biology require a variable selection procedure to sift through a large number of input variables and select some smaller number that influence a target variable of interest. For example, in virology, only some small number of viral protein fragments influence the nature of the immune response during viral infection. Due to the large number of variables to be considered, a brute-force search for the subset of variables is in general intractable. To approximate this, methods based on ?1-regularized linear regression have been proposed and have been found to be particularly successful. It is well understood however that such methods fail to choose the correct subset of variables if these are highly correlated with other "decoy" variables. We present a method for sifting through sets of highly correlated variables which leads to higher accuracy in selecting the correct variables. The main innovation is a filtering step that reduces correlations among variables to be selected, making the ?1-regularization effective for datasets on which many methods for variable selection fail. The filtering step changes both the values of the predictor variables and output values by projections onto components obtained through a computationally-inexpensive principal components analysis. In this paper we demonstrate the usefulness of our method on synthetic datasets and on novel applications in virology. These include HIV viral load analysis based on patients' HIV sequences and immune types, as well as the analysis of seasonal variation in influenza death rates based on the regions of the influenza genome that undergo diversifying selection in the previous season.

Huang, Jim C.; Jojic, Nebojsa

414

Distortion tolerant correlation filter design.  

PubMed

This paper introduces a computationally efficient algorithm for synthesis of a distortion tolerant correlation filter and associated threshold, denoted collectively as the enhanced matched filter (EMF). Application areas of EMF include imagery based automatic target detection and recognition and biometrics. The EMF is synthesized from a set of training images characterizing the target of interest within the expected distortion range. A distinguishing feature of EMF is the ascribed threshold, which is a byproduct of the filter computation process and does not rely on nontarget trainers. The EMF performance is compared to that of the synthetic discriminant function using realistic test scenarios. PMID:23669663

Heidary, Kaveh

2013-04-20

415

Correlation Dimension of Complex Networks  

NASA Astrophysics Data System (ADS)

We propose a new measure to characterize the dimension of complex networks based on the ergodic theory of dynamical systems. This measure is derived from the correlation sum of a trajectory generated by a random walker navigating the network, and extends the classical Grassberger-Procaccia algorithm to the context of complex networks. The method is validated with reliable results for both synthetic networks and real-world networks such as the world air-transportation network or urban networks, and provides a computationally fast way for estimating the dimensionality of networks which only relies on the local information provided by the walkers.

Lacasa, Lucas; Gómez-Gardeñes, Jesús

2013-04-01

416

Correlator optical wavefront sensor COWS  

NASA Astrophysics Data System (ADS)

This report documents the significant upgrades and improvements made to the correlator optical wavefront sensor (COWS) optical bench during this phase of the program. Software for the experiment was reviewed and documented. Flowcharts showing the program flow are included as well as documentation for programs which were written to calculate and display Zernike polynomials. The system was calibrated and aligned and a series of experiments to determine the optimum settings for the input and output MOSLM polarizers were conducted. In addition, design of a simple aberration generation is included.

1991-02-01

417

Correlation dimension of complex networks.  

PubMed

We propose a new measure to characterize the dimension of complex networks based on the ergodic theory of dynamical systems. This measure is derived from the correlation sum of a trajectory generated by a random walker navigating the network, and extends the classical Grassberger-Procaccia algorithm to the context of complex networks. The method is validated with reliable results for both synthetic networks and real-world networks such as the world air-transportation network or urban networks, and provides a computationally fast way for estimating the dimensionality of networks which only relies on the local information provided by the walkers. PMID:23679650

Lacasa, Lucas; Gómez-Gardeñes, Jesús

2013-04-19

418

Insulating states of correlated electrons  

SciTech Connect

The insulating states of three model systems, the two-chain Hubbard model, the two-layer two-dimensional Hubbard model, and the two-dimensional symmetric periodic Anderson model are discussed. All of these systems at half-filling have a charge gap but they can exhibit various types of spin gaps ranging from a vanishing spin gap in systems with strong antiferromagnetic correlations to a spin gap which is equal to the charge gap on the band-insulator regime. The interchain, interplane, or Anderson model f-d hybridization plays a key role in determining the spin-to-charge gap ratio and the nature of the insulating state.

Scalapino, D.J.; Sugar, R.L.; Noack, R. [Univ. of California, Santa Barbara, CA (United States)] [and others

1995-05-01

419

Concordance of Gene Expression and Functional Correlation Patterns across the NCI-60 Cell Lines and the Cancer Genome Atlas Glioblastoma Samples  

PubMed Central

Background The NCI-60 is a panel of 60 diverse human cancer cell lines used by the U.S. National Cancer Institute to screen compounds for anticancer activity. We recently clustered genes based on correlation of expression profiles across the NCI-60. Many of the resulting clusters were characterized by cancer-associated biological functions. The set of curated glioblastoma (GBM) gene expression data from the Cancer Genome Atlas (TCGA) initiative has recently become available. Thus, we are now able to determine which of the processes are robustly shared by both the immortalized cell lines and clinical cancers. Results Our central observation is that some sets of highly correlated genes in the NCI-60 expression data are also highly correlated in the GBM expression data. Furthermore, a “double fishing” strategy identified many sets of genes that show Pearson correlation ?0.60 in both the NCI-60 and the GBM data sets relative to a given “bait” gene. The number of such gene sets far exceeds the number expected by chance. Conclusion Many of the gene-gene correlations found in the NCI-60 do not reflect just the conditions of cell lines in culture; rather, they reflect processes and gene networks that also function in vivo. A number of gene network correlations co-occur in the NCI-60 and GBM data sets, but there are others that occur only in NCI-60 or only in GBM. In sum, this analysis provides an additional perspective on both the utility and the limitations of the NCI-60 in furthering our understanding of cancers in vivo.

Zeeberg, Barry R.; Kohn, Kurt W.; Kahn, Ari; Larionov, Vladimir; Weinstein, John N.; Reinhold, William; Pommier, Yves

2012-01-01

420

Body adiposity index (BAI) correlates with BMI and body fat pre- and post-bariatric surgery but is not an adequate substitute for BMI in severely obese women.  

PubMed

OBJECTIVE: Body Adiposity Index (BAI), a new surrogate measure of body fat (hip circumference/[height 1.5-18]), has been proposed as a more accurate alternative to BMI. We compared BAI with BMI and their correlations with measures of body fat, waist circumference (WC), and indirect indices of fat pre- and post-Roux-en-Y gastric bypass (RYGB). METHODS: Sixteen clinically severe obese (CSO) non-diabetic women (age = 33.9± 7.9 SD; BMI = 46.5±9.5 kg/m(2)) were assessed pre-surgery, and at 2 (n=9) and 5 mo (n=8) post-surgery. Body fat percentage (% fat) was estimated with bioimpedance analysis (BIA), air displacement plethysmography (ADP), and dual-energy x-ray absorptiometry (DXA). WC, an indicator of central fat, and both plasma leptin (ng/ml) and insulin (mU/l) concentrations were measured as indirect body fat indices. Pre- and post-surgery values were analyzed with Pearson correlations and linear regressions. RESULTS: BAI and BMI correlated significantly with each other pre-surgery and at each time point post surgery. BAI and BMI also correlated significantly with % fat from BIA and ADP; however, only BMI correlated significantly with % fat from DXA pre- and post-RYGB. BMI was the single best predictor of WC and leptin at 2 and 5 mo post-surgery and had significant longitudinal changes correlating with % fat from BIA and DXA as well as with leptin. DISCUSSION: Both BAI and BMI were good surrogates of % fat as estimated from BIA and ADP, but only BMI was a good surrogate of % fat from DXA in CSO women. Thus, BAI may not be a better alternative to BMI. PMID:23243391

Gibson, C D; Atalayer, D; Flancbaum, L; Geliebter, A

2012-01-01

421

Body adiposity index (BAI) correlates with BMI and body fat pre- and post-bariatric surgery but is not an adequate substitute for BMI in severely obese women  

PubMed Central

Objective Body Adiposity Index (BAI), a new surrogate measure of body fat (hip circumference/[height 1.5–18]), has been proposed as a more accurate alternative to BMI. We compared BAI with BMI and their correlations with measures of body fat, waist circumference (WC), and indirect indices of fat pre- and post-Roux-en-Y gastric bypass (RYGB). Methods Sixteen clinically severe obese (CSO) non-diabetic women (age = 33.9± 7.9 SD; BMI = 46.5±9.5 kg/m2) were assessed pre-surgery, and at 2 (n=9) and 5 mo (n=8) post-surgery. Body fat percentage (% fat) was estimated with bioimpedance analysis (BIA), air displacement plethysmography (ADP), and dual-energy x-ray absorptiometry (DXA). WC, an indicator of central fat, and both plasma leptin (ng/ml) and insulin (mU/l) concentrations were measured as indirect body fat indices. Pre- and post-surgery values were analyzed with Pearson correlations and linear regressions. Results BAI and BMI correlated significantly with each other pre-surgery and at each time point post surgery. BAI and BMI also correlated significantly with % fat from BIA and ADP; however, only BMI correlated significantly with % fat from DXA pre- and post-RYGB. BMI was the single best predictor of WC and leptin at 2 and 5 mo post-surgery and had significant longitudinal changes correlating with % fat from BIA and DXA as well as with leptin. Discussion Both BAI and BMI were good surrogates of % fat as estimated from BIA and ADP, but only BMI was a good surrogate of % fat from DXA in CSO women. Thus, BAI may not be a better alternative to BMI.

Gibson, C.D.; Atalayer, D.; Flancbaum, L.; Geliebter, A.

2012-01-01

422

Correlation of tinnitus loudness and onset duration with audiological profile indicating variation in prognosis.  

PubMed

Purpose. Subjective tinnitus has different forms and degrees of severity. Many studies in the literature have assessed psychoacoustic characteristics of tinnitus but hardly any of them had focused on the association of audiological profile with onset duration and loudness perception. The aim of this study was to evaluate existence of any association between tinnitus loudness/onset duration and audiological profile to explain differences in prognosis. Method. Study design was prospective. The sample consisted of 26 subjects having tinnitus, which was divided into tinnitus and nontinnitus ears. Audiological profile included pure-tone audiometry, speech audiometry, tympanometry, acoustic reflex test, and auditory evoked potentials (early and middle latency). Unpaired t-test was applied to compare two subgroups. Correlation and association between tinnitus onset duration/loudness perception and audiological profile were also assessed by calculating Spearman's coefficient and Fischer exact value. Results. The two subgroups had significant differences for pure-tone and speech audiometry hearing thresholds. A significant association was observed between the high frequency/extended high frequency and tinnitus loudness/onset duration. Conclusion. The changes in hearing thresholds and auditory pathway are associated with an increase in tinnitus loudness and its onset duration. This knowledge would be helpful to differentiate between severity and chronicity of the patients for planning therapeutic management and predicting prognosis. PMID:24078882

Gudwani, Sunita; Munjal, Sanjay K; Panda, Naresh K; Verma, Roshan K

2013-09-02

423

Correlation of Tinnitus Loudness and Onset Duration with Audiological Profile Indicating Variation in Prognosis  

PubMed Central

Purpose. Subjective tinnitus has different forms and degrees of severity. Many studies in the literature have assessed psychoacoustic characteristics of tinnitus but hardly any of them had focused on the association of audiological profile with onset duration and loudness perception. The aim of this study was to evaluate existence of any association between tinnitus loudness/onset duration and audiological profile to explain differences in prognosis. Method. Study design was prospective. The sample consisted of 26 subjects having tinnitus, which was divided into tinnitus and nontinnitus ears. Audiological profile included pure-tone audiometry, speech audiometry, tympanometry, acoustic reflex test, and auditory evoked potentials (early and middle latency). Unpaired t-test was applied to compare two subgroups. Correlation and association between tinnitus onset duration/loudness perception and audiological profile were also assessed by calculating Spearman's coefficient and Fischer exact value. Results. The two subgroups had significant differences for pure-tone and speech audiometry hearing thresholds. A significant association was observed between the high frequency/extended high frequency and tinnitus loudness/onset duration. Conclusion. The changes in hearing thresholds and auditory pathway are associated with an increase in tinnitus loudness and its onset duration. This knowledge would be helpful to differentiate between severity and chronicity of the patients for planning therapeutic management and predicting prognosis.

Munjal, Sanjay K.; Panda, Naresh K.; Verma, Roshan K.

2013-01-01

424

Extending Local Canonical Correlation Analysis to Handle General Linear Contrasts for fMRI Data  

PubMed Central

Local canonical correlation analysis (CCA) is a multivariate method that has been proposed to more accurately determine activation patterns in fMRI data. In its conventional formulation, CCA has several drawbacks that limit its usefulness in fMRI. A major drawback is that, unlike the general linear model (GLM), a test of general linear contrasts of the temporal regressors has not been incorporated into the CCA formalism. To overcome this drawback, a novel directional test statistic was derived using the equivalence of multivariate multiple regression (MVMR) and CCA. This extension will allow CCA to be used for inference of general linear contrasts in more complicated fMRI designs without reparameterization of the design matrix and without reestimating the CCA solutions for each particular contrast of interest. With the proper constraints on the spatial coefficients of CCA, this test statistic can yield a more powerful test on the inference of evoked brain regional activations from noisy fMRI data than the conventional t-test in the GLM. The quantitative results from simulated and pseudoreal data and activation maps from fMRI data were used to demonstrate the advantage of this novel test statistic.

Jin, Mingwu; Nandy, Rajesh; Curran, Tim; Cordes, Dietmar

2012-01-01

425

Extending local canonical correlation analysis to handle general linear contrasts for FMRI data.  

PubMed

Local canonical correlation analysis (CCA) is a multivariate method that has been proposed to more accurately determine activation patterns in fMRI data. In its conventional formulation, CCA has several drawbacks that limit its usefulness in fMRI. A major drawback is that, unlike the general linear model (GLM), a test of general linear contrasts of the temporal regressors has not been incorporated into the CCA formalism. To overcome this drawback, a novel directional test statistic was derived using the equivalence of multivariate multiple regression (MVMR) and CCA. This extension will allow CCA to be used for inference of general linear contrasts in more complicated fMRI designs without reparameterization of the design matrix and without reestimating the CCA solutions for each particular contrast of interest. With the proper constraints on the spatial coefficients of CCA, this test statistic can yield a more powerful test on the inference of evoked brain regional activations from noisy fMRI data than the conventional t-test in the GLM. The quantitative results from simulated and pseudoreal data and activation maps from fMRI data were used to demonstrate the advantage of this novel test statistic. PMID:22461786

Jin, Mingwu; Nandy, Rajesh; Curran, Tim; Cordes, Dietmar

2012-01-23

426

Effect of gender on correlation of anaemia with body mass index in medical students.  

PubMed

Nutritional anemia exists globally and cuts across all the sections of the population. Adolescent being formative years in life are more susceptible to nutritional anemia. Considerable changes in growth pattern, lifestyle, dietary habits & behavior are likely to influence the hemoglobin levels among male and females of high income group. Study was done to assess the level of anemia among medical students and it's relation to Body mass index (BMI) among medical students. 200 healthy medical students at the Himalayan Institute of Medical Sciences belonging to both the sexes were taken in the study. Following consent anthropometry was conducted using standard protocol. Body Mass Index of >/= 18.5 kg/m2 is used to define undernutrition. Hemoglobin was estimated in gram %. Statistical analyses was done using mean .Standard deviation, Student's t test, and was studied for effect of gender on correlation of anemia with BMI. 8% of the students of MBBS were found to be anemic (Hb <12 g%) with none of the boys having hemoglobin <12 g% .15.5% under nutrition was observed in the medical students with (25.75%) of girls having a BMI of <18.5 kg/m2. A negative association of hemoglobin was found with nutritional status (BMI) (r = -0.59; P = 0.24) in over weight and obese females students. Nutritional anemia and under nutrition exist among female medical students who are literate, and have free access to the nutritive diet in a good healthy environment. PMID:23362730

Saxena, Yogesh; Shrivastava, Abha; Saxena, Vartika

427

A correlated nickelate synaptic transistor.  

PubMed

Inspired by biological neural systems, neuromorphic devices may open up new computing paradigms to explore cognition, learning and limits of parallel computation. Here we report the demonstration of a synaptic transistor with SmNiO3, a correlated electron system with insulator-metal transition temperature at 130°C in bulk form. Non-volatile resistance and synaptic multilevel analogue states are demonstrated by control over composition in ionic liquid-gated devices on silicon platforms. The extent of the resistance modulation can be dramatically controlled by the film microstructure. By simulating the time difference between postneuron and preneuron spikes as the input parameter of a gate bias voltage pulse, synaptic spike-timing-dependent plasticity learning behaviour is realized. The extreme sensitivity of electrical properties to defects in correlated oxides may make them a particularly suitable class of materials to realize artificial biological circuits that can be operated at and above room temperature and seamlessly integrated into conventional electronic circuits. PMID:24177330

Shi, Jian; Ha, Sieu D; Zhou, You; Schoofs, Frank; Ramanathan, Shriram

2013-11-01

428

Angular correlation in ^134Pr  

NASA Astrophysics Data System (ADS)

A background subtraction method for ?-ray spectroscopic measurements with large multidetector HpGe arrays has been applied to data from the GS2K009 experiment in which the ^116Cd(^23Na,5n) reaction was employed to study ^134Pr. The method takes advantage of recently developed BLUE data storage which allows for event retrieval in their native fold. The background spectrum is constructed based on the parameters evaluated from one-dimensional spectra only; the method, therefore, is complementary to other methods applied so far which are optimized for multidimensional, symmetrized histograms. When the background subtracted spectra projected on the Gammasphere rings are summed together, the applied algorithm compare well to that in the RADWARE data analysis package. Double gated spectra projected on Gammasphere rings were analyzed for angular correlations and Doppler Shift Attenuation studies. The method allows investigation of triple-? correlations which can be used to enhance angular asymmetry. It can also be apply to DCO or angular distributions studies from doubly gated spectra if appropriate angular conditions are set for the gating ?-rays. The resulting spin/parity assignments in ^134Pr will be presented.

Starosta, Krzysztof

2004-10-01

429

Fiducial marker for correlating images  

SciTech Connect

The invention relates to a fiducial marker having a marking grid that is used to correlate and view images produced by different imaging modalities or different imaging and viewing modalities. More specifically, the invention relates to the fiducial marking grid that has a grid pattern for producing either a viewing image and/or a first analytical image that can be overlaid with at least one other second analytical image in order to view a light path or to image different imaging modalities. Depending on the analysis, the grid pattern has a single layer of a certain thickness or at least two layers of certain thicknesses. In either case, the grid pattern is imageable by each imaging or viewing modality used in the analysis. Further, when viewing a light path, the light path of the analytical modality cannot be visualized by viewing modality (e.g., a light microscope objective). By correlating these images, the ability to analyze a thin sample that is, for example, biological in nature but yet contains trace metal ions is enhanced. Specifically, it is desired to analyze both the organic matter of the biological sample and the trace metal ions contained within the biological sample without adding or using extrinsic labels or stains.

Miller, Lisa Marie (Rocky Point, NY); Smith, Randy J. (Wading River, NY); Warren, John B. (Port Jefferson, NY); Elliott, Donald (Hampton Bays, NY)

2011-06-21

430

PREFACE: Correlation Dynamics in Nuclei  

NASA Astrophysics Data System (ADS)

The International Symposium on `Correlation Dynamics in Nuclei' was held at the Sanjo Kaikan, the University of Tokyo, from the 31 January to 4 February 2005. This symposium was organized on the occasion of the 50th anniversary of the Configuration Mixing theory of Arima and Horie. The symposium was hosted by the University of Tokyo, and supported by the Inoue Foundation for Science, the Japan Atomic Energy Research Institute and the Ministry of Education, Culture, Sports, Science and Technology. The purpose of the symposium was to discuss theoretical and experimental developments and future prospects in physics of correlation dynamics in nuclei, including topics such as effective interactions, shell model studies of configuration mixing and spin-isospin modes in nuclei. It was shown in many ways and angles that the Arima-Horie theory has been a starting point of a variety of developments of the studies in these fields over many decades. The developments have been enhanced by the expansion of computational capabilities and the progress in accelerators, detectors and radioactive beam facilities. We enjoyed 28 excellent and lively invited talks and 30 oral presentations in the symposium with about 90 participants. A special session was dedicated to celebrate the 80th birthday of Professor Igal Talmi, who made invaluable and pioneering works in the shell model theory. Finally, we would like to thank all the speakers and the participants as well as the other organizers for their contributions which made the symposium very successful.

Suzuki, Toshio; Otsuka, Takaharu; Ichimura, Munetake

2005-01-01

431

Cortical Correlates of Fitts' Law  

PubMed Central

Fitts’ law describes the fundamental trade-off between movement accuracy and speed: it states that the duration of reaching movements is a function of target size (TS) and distance. While Fitts’ law has been extensively studied in ergonomics and has guided the design of human–computer interfaces, there have been few studies on its neuronal correlates. To elucidate sensorimotor cortical activity underlying Fitts’ law, we implanted two monkeys with multielectrode arrays in the primary motor (M1) and primary somatosensory (S1) cortices. The monkeys performed reaches with a joystick-controlled cursor toward targets of different size. The reaction time (RT), movement time, and movement velocity changed with TS, and M1 and S1 activity reflected these changes. Moreover, modifications of cortical activity could not be explained by changes of movement parameters alone, but required TS as an additional parameter. Neuronal representation of TS was especially prominent during the early RT period where it influenced the slope of the firing rate rise preceding movement initiation. During the movement period, cortical activity was correlated with movement velocity. Neural decoders were applied to simultaneously decode TS and motor parameters from cortical modulations. We suggest that sensorimotor cortex activity reflects the characteristics of both the movement and the target. Classifiers that extract these parameters from cortical ensembles could improve neuroprosthetic control.

Ifft, Peter J.; Lebedev, Mikhail A.; Nicolelis, Miguel A. L.

2011-01-01

432

Exact exchange for correlated electrons  

NASA Astrophysics Data System (ADS)

The cover picture is taken from the article by Pavel Novák that was chosen as Editor's Choice of this issue [1]. The figure shows the density of minority spin states in nickel oxide calculated by three commonly used approximations (LSDA, GGA, LDA+U) as well as using the newly prop