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1

Complete convergence for negatively dependent random variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we study the complete convergence for the means 1n?i=1nXi and 1n??k=1nXnk via. exponential bounds, where ?>0 and {Xn,n?1} is a sequence of negatively dependent random variables and {Xnk,1?k?n,n?1} is an array of rowwise pairwise negatively dependent random variables.

M. Amini D.; Bozorgnia, A.

2003-01-01

2

Empirical Value at Risk for Weak Dependent Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available In this work, we study the empirical estimator of the Value at Risk (VaR for short for weak dependent observations. Our approach uses the oscillation of the empirical process under hypothesis of moment's inequality. We provide general conditions which ensure the convergence of  the empirical estimator of the VaR. We also prove  a central limit theorem (CLT  for the difference. We perform some simulations for different sequences to illustrate our results. Finally, we apply the results for different sequences under assumptions of mixing or covariance.

Samir Ben Hariz

2013-01-01

3

Explicit Bounds for the Distribution Function of the Sum of Dependent Normally Distributed Random Variables  

CERN Document Server

In this paper an analytic expression is given for the bounds of the distribution function of the sum of dependent normally distributed random variables. Using the theory of copulas and the important Frechet bounds the dependence structure is not restricted to any specific type. Numerical illustrations are provided to assess the quality of the derived bounds.

Schneider, Walter

2011-01-01

4

Central limit theorem for the Banach-valued weakly dependent random variables  

International Nuclear Information System (INIS)

The central limit theorem (CLT) for the Banach-valued weakly dependent random variables is proved. In proving CLT convergence of finite-measured (i.e. cylindrical) distributions is established. A weak compactness of the family of measures generated by a certain sequence is confirmed. The continuity of the limiting field is checked

1983-01-01

5

Negatively dependent bounded random variable probability inequalities and the strong law of large numbers  

Directory of Open Access Journals (Sweden)

Full Text Available Let X1,…,Xn be negatively dependent uniformly bounded random variables with d.f. F(x. In this paper we obtain bounds for the probabilities P(|?i=1nXi|?nt and P(|?ˆpn??p|>? where ?ˆpn is the sample pth quantile and ?p is the pth quantile of F(x. Moreover, we show that ?ˆpn is a strongly consistent estimator of ?p under mild restrictions on F(x in the neighborhood of ?p. We also show that ?ˆpn converges completely to ?p.

M. Amini

2000-01-01

6

A duality approach to the worst case value at risk for a sum of dependent random variables with known covariances  

CERN Multimedia

We propose an approach to the aggregation of risks which is based on estimation of simple quantities (such as covariances) associated to a vector of dependent random variables, and which avoids the use of parametric families of copulae. Our main result demonstrates that the method leads to bounds on the worst case Value at Risk for a sum of dependent random variables. Its proof applies duality theory for infinite dimensional linear programs.

Franke, Brice

2009-01-01

7

Variable survival exponents in history-dependent random walks: hard movable reflector  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english We review recent studies demonstrating a nonuniversal (continuously variable) survival exponent for history-dependent random walks, and analyze a new example, the hard movable partial reflector. These processes serve as simplified models of infection in a medium with a history-dependent susceptibili [...] ty, and for spreading in systems with an infinite number of absorbing configurations. The memory may take the form of a historydependent step length, or be the result of a partial reflector whose position marks the maximum distance the walker has ventured from the origin. In each case, a process with memory is rendered Markovian by a suitable expansion of the state space. Asymptotic analysis of the probability generating function shows that, for large t, the survival probability decays as S(t) ~ t -d, where d varies with the parameters of the model. We report new results for a hard partial reflector, i.e., one that moves forward only when the walker does. When the walker tries to jump to the site R occupied by the reflector, it is reflected back with probability r, and stays at R with probability 1 - r; only in the latter case does the reflector move (R ® R+1). For this model, d = 1/2(1 - r), and becomes arbitrarily large as r approaches 1. This prediction is confirmed via iteration of the transition matrix, which also reveals slowly-decaying corrections to scaling.

Ronald, Dickman; Francisco Fontenele, Araujo Jr.; Daniel, ben-Avraham.

8

Wavelet random variables  

Science.gov (United States)

If G is an orthonormal system in IL2 then for any function g (epsilon) G the function g2 is a probability density. In this paper we discuss the properties of wavelet based densities and corresponding random variables.

Vidakovic, Brani

1997-10-01

9

Strong Invariance Principle for Dependent Random Fields  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A strong invariance principle is established for random fields which satisfy dependence conditions more general than positive or negative association. We use the approach of Csörg\\H{o} and Révész applied recently by Balan to associated random fields. The key step in our proof combines new moment and maximal inequalities, established by the authors for partial sums of multiindexed random variables, with the estimate of the convergence rate in the CLT for random fields under consideration.

Bulinski, Alexander; Shashkin, Alexey

2005-01-01

10

Strong invariance principle for dependent random fields  

CERN Document Server

A strong invariance principle is established for random fields which satisfy dependence conditions more general than positive or negative association. We use the approach of Cs\\"{o}rg\\H{o} and R\\'{e}v\\'{e}sz applied recently by Balan to associated random fields. The key step in our proof combines new moment and maximal inequalities, established by the authors for partial sums of multiindexed random variables, with the estimate of the convergence rate in the CLT for random fields under consideration.

Bulinski, A; Bulinski, Alexander; Shashkin, Alexey

2006-01-01

11

On the structure of Gaussian random variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study when a given Gaussian random variable on a given probability space $(\\Omega, {\\cal{F}}, P) $ is equal almost surely to $\\beta_{1}$ where $\\beta $ is a Brownian motion defined on the same (or possibly extended) probability space. As a consequences of this result, we prove that the distribution of a random variable (satisfying in addition a certain property) in a finite sum of Wiener chaoses cannot be normal. This result also allows to understand better some character...

Tudor, Ciprian

2009-01-01

12

Asymptotics for Associated Random Variables  

CERN Document Server

The book concerns the notion of association in probability and statistics. Association and some other positive dependence notions were introduced in 1966 and 1967 but received little attention from the probabilistic and statistics community. The interest in these dependence notions increased in the last 15 to 20 years, and many asymptotic results were proved and improved. Despite this increased interest, characterizations and results remained essentially scattered in the literature published in different journals. The goal of this book is to bring together the bulk of these results, presenting

Oliveira, Paulo Eduardo

2012-01-01

13

Distributions of Ratios: From Random Variables to Random Matrices  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The ratio R of two random quantities is frequently encountered in probability and statistics. But while for unidimensional statistical variables the distribution of R can be computed relatively easily, for symmetric positive definite random matrices, this ratio can take various forms and its distribution, and even its definition, can offer many challenges. However, for the distribution of its determinant, Meijer G-function often provides an effective anal...

Thu Pham-Gia; Noyan Turkkan

2011-01-01

14

Unbalanced Bidding Problem with Fuzzy Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available Unbalanced bidding problem with mixed uncertainty of fuzziness and randomness is considered in this paper, where the bidding engineering quantities of each activity are assumed to be fuzzy random variables. Two types of fuzzy random models as expected value maximization model and maximax chance-constrained model are built to satisfy different optimization requirements. Then a hybrid intelligent algorithm integrating fuzzy random simulations, neural network and genetic algorithm is designed to solve these models. Finally, a numerical experiment is given to illustrate its effectiveness of the algorithm. The results show that the algorithm is feasible and effective.

Dongran Zang

2009-02-01

15

Unbalanced Bidding Problem with Fuzzy Random Variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Unbalanced bidding problem with mixed uncertainty of fuzziness and randomness is considered in this paper, where the bidding engineering quantities of each activity are assumed to be fuzzy random variables. Two types of fuzzy random models as expected value maxim...

Dongran Zang; Liang Lin; Xingzi Liu

2009-01-01

16

Mean and Variance of Random Variables  

Science.gov (United States)

This site, created by the Department of Statistics at Yale University, gives an explanation, a definition and an example of mean and variance of random variables. Definitions and properties are also included. Overall, this is a great resource for any mathematics classroom studying statistics.

Lacey, Michelle

2008-12-23

17

Reduction of the Random Variables of the Turbulent Wind Field  

DEFF Research Database (Denmark)

Applicability of the Probability Density Evolution Method (PDEM) for realizing evolution of the probability density for the wind turbines has rather strict bounds on the basic number of the random variables involved in the model. The efficiency of most of the Advanced Monte Carlo (AMC) methods, i.e. Importance Sampling (IS) or Subset Simulation (SS), will be deteriorated on problems with many random variables. The problem with PDEM is that a multidimensional integral has to be carried out over the space defined by the random variables of the system. The numerical procedure requires discretization of the integral domain; this becomes increasingly difficult as the dimensions of the integral domain increase. On the other hand efficiency of the AMC methods is closely dependent on the design points of the problem. Presence of many random variables may increase the number of the design points, hence affects the efficiency of the AMC methods. The idea of the paper is to propose new schemes which allow reduction of the basic random variables of the turbulence such that PDEM and Advanced Monte Carlo (AMC) methods, i.e. subset simulation, are applicable on it.

Sichani, Mahdi Teimouri; Nielsen, Søren R.K.

2012-01-01

18

Quantum random walks with history dependence  

CERN Multimedia

We introduce a multi-coin discrete quantum random walk where the amplitude for a coin flip depends upon previous tosses. Although the corresponding classical random walk is unbiased, a bias can be introduced into the quantum walk by varying the history dependence. By mixing the biased random walk with an unbiased one, the direction of the bias can be reversed leading to a new quantum version of Parrondo's paradox.

Flitney, A P; Johnson, N F; Flitney, Adrian P.; Abbott, Derek; Johnson, Neil F.

2003-01-01

19

Measuring Association and Dependence Between Random Vectors  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Measures of association are suggested between two random vectors. The measures are copula-based and therefore invariant with respect to the univariate marginal distributions. The measures are able to capture positive as well as negative association. In case the random vectors are just random variables, the measures reduce to Kendall's tau or Spearman's rho. Nonparametric estimators, based on ranks, for the measures are derived. Their large-sample asymptotics are derived and their small-sample...

2013-01-01

20

Random forest automated supervised classification of Hipparcos periodic variable stars  

CERN Document Server

We present an evaluation of the performance of an automated classification of the Hipparcos periodic variable stars into 26 types. The sub-sample with the most reliable variability types available in the literature is used to train supervised algorithms to characterize the type dependencies on a number of attributes. The most useful attributes evaluated with the random forest methodology include, in decreasing order of importance, the period, the amplitude, the V-I colour index, the absolute magnitude, the residual around the folded light-curve model, the magnitude distribution skewness and the amplitude of the second harmonic of the Fourier series model relative to that of the fundamental frequency. Random forests and a multi-stage scheme involving Bayesian network and Gaussian mixture methods lead to statistically equivalent results. In standard 10-fold cross-validation experiments, the rate of correct classification is between 90 and 100%, depending on the variability type. The main mis-classification case...

Dubath, P; Süveges, M; Blomme, J; López, M; Sarro, L M; De Ridder, J; Cuypers, J; Guy, L; Lecoeur, I; Nienartowicz, K; Jan, A; Beck, M; Mowlavi, N; De Cat, P; Lebzelter, T; Eyer, L

2011-01-01

 
 
 
 
21

Inequalities for Walsh like random variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Let (Xn)n≥1 be a sequence of mean zero independent random variables. Let Wk={∏j=1kXij|1≤i10 and K>0 and let C(p,m)=16(52p2p−1)m−1plogp(Kδ)m for 1

Hajela, D.

1990-01-01

22

Theory of Dependent Hierarchical Normalized Random Measures  

CERN Document Server

This paper presents theory for Normalized Random Measures (NRMs), Normalized Generalized Gammas (NGGs), a particular kind of NRM, and Dependent Hierarchical Normalized Random Measures which have been used for time-dependent topic modelling. In this paper, we first introduce in some mathematical background of completely random measures (CRM) and their constructions from Poisson processes, as well as dependency operators in Poisson processes and the corresponding CRMs. The Normalized Generalised Gamma (NGG) is introduced. Slice sampling is also introduced to do the posterior sampling of normalized random measures. Operators on CRMs and NRMs are then given. Posterior inference on the NGGs is presented and it is shown that marginalizing the mass parameter of the NGG yields a Poisson-Dirichlet distribution. Finally, we give dependency results when applying these operators to NRMs. Proofs of related Lemmas and Theorems are given in the Appendix.

Chen, Changyou; Ding, Nan

2012-01-01

23

Uniqueness conditions for finitely dependent random fields  

International Nuclear Information System (INIS)

The authors consider a random field for which uniqueness and some additional conditions guaranteeing that the correlations between the variables of the field decrease rapidly enough with the distance between the values of the parameter occur. The main result of the paper states that in such a case uniqueness is true for any other field with transition probabilities sufficiently close to those of the original field. Then they apply this result to some ''degenerate'' classes of random fields for which one can check this condition of correlation to decay, and thus obtain some new conditions of uniqueness. (Auth.)

1979-06-30

24

Message Based Random Variable Length Key Encryption Algorithm  

Directory of Open Access Journals (Sweden)

Full Text Available Problem statement: A block ciphers provides confidentiality in cryptography but cryptanalysis of the classical block ciphers demonstrated some old weaknesses grabbing a partial key in any stage of encryption procedure leads to reconstructing the whole key. Exhaustive key search shows that key generation should be indeterminist and random for each round. Matching cipher-text attack shows that larger size of block is more secure. In order to overcome analysis mentioned above a new algorithm is designed that is based on random numbers and also can defeat time and memory constraints. Approach: Dynamic and message dependent key generator was created by producing a random number and it was selected as the size of first chunk. Residual value of second chunk divided by first chunk concatenating with first chunk forms the first cipher as an input for SP-boxes. These processes repeated until whole mesaage get involved into the last cipher. Encrypted messages are not equal under different run. Value of random number should be greater than 35 bits and plaintext must be at least 7 bits. A padding algorithm was used for small size messages or big random numbers. Results: Attack on the key generation process was prevented because of random key generation and its dependency to input message. Encryption and decryption times measured between 5 and 27 m sec in 2 GHz Pentium and java platform so time variant and fast enough key generation had been kept collision and timing attacks away due to small seized storage. Long and variable key length made key exhaustive search and differential attack impossible. None fixed size key caused avoidance of replaying and other attacks that can happen on fixed sized key algorithms. Conclusion: Random process employed in this block cipher increased confidentiality of the message and dynamic length substitution in proposed algorithm may lead to maximum cryptographic confusion and consequently makes it difficult for cryptanalysis.

Hamid Mirvaziri

2009-01-01

25

Temperature dependent resonant random phase approximation  

Energy Technology Data Exchange (ETDEWEB)

The influence of thermal fluctuations upon escape widths of giant resonances is analyzed within a thermal random phase approximation that includes the effect of the continuum through the use of resonant single-particle states in the basis set of states. It is found that those escape widths are only weakly dependent on the temperature.

Dussel, G.G.; Liotta, R.J. (Departamento de Fisica, Pabellon 1, Ciudad Universitaria, RA-1428 Buenos Aires (Argentina) Manne Siegbahn Institute, S-10405 Stockholm (Sweden)); Sofia, H. (Departamento de Fisica, Comision Nacional de Energia Atomica, Avenida del Libertador 8250, RA-1429 Buenos Aires (Argentina)); Vertse, T. (Institute of Nuclear Research, Hungarian Academy of Sciences, P.O. Box 51, H-4001 Debrecen (Hungary))

1992-08-01

26

Random Variables Fundamental in Probability and Sigma-Complete Convergence  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this paper is to study some necessary and sufficient conditions for fundamental (Cauchy in probability sequences of random variables. In this way, we will be able to deduce some relationships between certain types of convergence and these sequences of random variables characterized because in their definition the random variable limit does not appear. Finally, we introduce the concept of a Sigma-completely convergent sequence and a sufficient condition for it.

Salvador Cruz Rambaud

2014-03-01

27

Probability, random variables, and random processes theory and signal processing applications  

CERN Multimedia

Probability, Random Variables, and Random Processes is a comprehensive textbook on probability theory for engineers that provides a more rigorous mathematical framework than is usually encountered in undergraduate courses. It is intended for first-year graduate students who have some familiarity with probability and random variables, though not necessarily of random processes and systems that operate on random signals. It is also appropriate for advanced undergraduate students who have a strong mathematical background. The book has the following features: Several app

Shynk, John J

2012-01-01

28

Maximum Entropy Functions of Discrete Fuzzy Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available Due to deficiency of information, the probability distribution and membership functions of a fuzzy random variablecannot be obtained explicitly. It is a challenging work to find an appropriate probability distribution and membershipfunction when certain partial information about a fuzzy random variable is given, such as expected value or moments.This paper solves such problems for the maximum entropy of discrete fuzzy random variables with certain constraints. Agenetic algorithm is designed to solve the general maximum entropy model for discrete fuzzy random variables, which isillustrated by numerical experiment.

Lianlong Gao

2010-07-01

29

Selection for altruism through random drift in variable size populations  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Altruistic behavior is defined as helping others at a cost to oneself and a lowered fitness. The lower fitness implies that altruists should be selected against, which is in contradiction with their widespread presence is nature. Present models of selection for altruism (kin or multilevel show that altruistic behaviors can have ‘hidden’ advantages if the ‘common good’ produced by altruists is restricted to some related or unrelated groups. These models are mostly deterministic, or assume a frequency dependent fitness. Results Evolutionary dynamics is a competition between deterministic selection pressure and stochastic events due to random sampling from one generation to the next. We show here that an altruistic allele extending the carrying capacity of the habitat can win by increasing the random drift of “selfish” alleles. In other terms, the fixation probability of altruistic genes can be higher than those of a selfish ones, even though altruists have a smaller fitness. Moreover when populations are geographically structured, the altruists advantage can be highly amplified and the fixation probability of selfish genes can tend toward zero. The above results are obtained both by numerical and analytical calculations. Analytical results are obtained in the limit of large populations. Conclusions The theory we present does not involve kin or multilevel selection, but is based on the existence of random drift in variable size populations. The model is a generalization of the original Fisher-Wright and Moran models where the carrying capacity depends on the number of altruists.

Houchmandzadeh Bahram

2012-05-01

30

Continuum Random Combs and Scale Dependent Spectral Dimension  

CERN Multimedia

Numerical computations have suggested that in causal dynamical triangulation models of quantum gravity the effective dimension of spacetime in the UV is lower than in the IR. In this paper we develop a simple model based on previous work on random combs, which share some of the properties of CDT, in which this effect can be shown to occur analytically. We construct a definition for short and long distance spectral dimensions and show that the random comb models exhibit scale dependent spectral dimension defined in this way. We also observe that a hierarchy of apparent spectral dimensions may be obtained in the cross-over region between UV and IR regimes for suitable choices of the continuum variables. Our main result is valid for a wide class of tooth length distributions thereby extending previous work on random combs by Durhuus et al.

Atkin, Max R; Wheater, John F

2011-01-01

31

Continuum random combs and scale-dependent spectral dimension  

International Nuclear Information System (INIS)

Numerical computations have suggested that in causal dynamical triangulation models of quantum gravity (CDT) the effective dimension of spacetime in the ultraviolet (UV) is lower than in the infrared (IR). In this paper we develop a simple model based on the previous work on random combs, which share some of the properties of CDT, in which this effect can be shown to occur analytically. We construct a definition for short- and long-distance spectral dimensions and show that the random comb models exhibit scale-dependent spectral dimension defined in this way. We also observe that a hierarchy of apparent spectral dimensions may be obtained in the cross-over region between UV and IR regimes for suitable choices of the continuum variables. Our main result is valid for a wide class of tooth length distributions thereby extending previous work on random combs by Durhuus et al.

2011-07-01

32

Approximation and Computation of Random Variables using Finite Elements  

Directory of Open Access Journals (Sweden)

Full Text Available A method is introduced with which continuous random variables can be represented and linked with one another. The distribution functions of the random variables are approximated using a Finite Element approach in a finite interval [tmin; tmax]. As an example, two stochastically independent random variables are added by numerical computation of the convolution integral of their probability density functions.Es wird ein Verfahren vorgestellt, mit dem stetige Zufallsgrößen rechnerunterstützt dargestellt und miteinander verknüpft werden können. Die Verteilungsfunktionen der Zufallsgrößen werden mit einem Finite-Elemente-Ansatz in einem endlichen Intervall [tmin; tmax] approximiert. Die Addition zweier Zufallsgrößen wird durch numerische Berechnung des Faltungsintegrals durchgeführt.

Dr.-Ing. Helge Plehn

2005-07-01

33

Grüss-Type Bounds for the Covariance of Transformed Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available A number of problems in Economics, Finance, Information Theory, Insurance, and generally in decision making under uncertainty rely on estimates of the covariance between (transformed random variables, which can, for example, be losses, risks, incomes, financial returns, and so forth. Several avenues relying on inequalities for analyzing the covariance are available in the literature, bearing the names of Chebyshev, Grüss, Hoeffding, Kantorovich, and others. In the present paper we sharpen the upper bound of a Grüss-type covariance inequality by incorporating a notion of quadrant dependence between random variables and also utilizing the idea of constraining the means of the random variables.

Martín Egozcue

2010-01-01

34

Multivariate non-normally distributed random variables in climate research – introduction to the copula approach  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Probability distributions of multivariate random variables are generally more complex compared to their univariate counterparts which is due to a possible nonlinear dependence between the random variables. One approach to this problem is the use of copulas, which have become popular over recent years, especially in fields like econometrics, finance, risk management, or insurance. Since this newly emerging field includes various practices, a controversial discussion, and vast fi...

Scho?lzel, C.; Friederichs, P.

2008-01-01

35

General discrete random walk with variable absorbing probabilities  

CERN Document Server

We obtain expected number of arrivals, probability of arrival, absorption probabilities and expected time before absorption for a general discrete random walk with variable absorbing probabilities on a finite interval using Fibonacci numbers

van Uem, Theo

2009-01-01

36

Limit theorems for a class of identically distributed random variables  

CERN Document Server

A new type of stochastic dependence for a sequence of random variables is introduced and studied. Precisely, (X_n)_{n\\geq 1} is said to be conditionally identically distributed (c.i.d.), with respect to a filtration (G_n)_{n\\geq 0}, if it is adapted to (G_n)_{n\\geq 0} and, for each n\\geq 0, (X_k)_{k>n} is identically distributed given the past G_n. In case G_0={\\varnothing,\\Omega} and G_n=\\sigma(X_1,...,X_n), a result of Kallenberg implies that (X_n)_{n\\geq 1} is exchangeable if and only if it is stationary and c.i.d. After giving some natural examples of nonexchangeable c.i.d. sequences, it is shown that (X_n)_{n\\geq 1} is exchangeable if and only if (X_{\\tau(n)})_{n\\geq 1} is c.i.d. for any finite permutation \\tau of {1,2,...}, and that the distribution of a c.i.d. sequence agrees with an exchangeable law on a certain sub-\\sigma-field. Moreover, (1/n)\\sum_{k=1}^nX_k converges a.s. and in L^1 whenever (X_n)_{n\\geq 1} is (real-valued) c.i.d. and E[| X_1| ]<\\infty. As to the CLT, three types of random cente...

Berti, P; Rigo, P; Berti, Patrizia; Pratelli, Luca; Rigo, Pietro

2004-01-01

37

Understanding variable importances in forests of randomized trees  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Despite growing interest and practical use in various scientific areas, variable importances derived from tree-based ensemble methods are not well understood from a theoretical point of view. In this work we characterize the Mean Decrease Impurity (MDI) variable importances as measured by an ensemble of totally randomized trees in asymptotic sample and ensemble size conditions. We derive a three-level decomposition of the information jointly provided by all input variables about the output in...

Louppe, Gilles; Wehenkel, Louis; Sutera, Antonio; Geurts, Pierre

2013-01-01

38

Optical variability of quasars: a damped random walk  

CERN Multimedia

A damped random walk is a stochastic process, defined by an exponential covariance matrix that behaves as a random walk for short time scales and asymptotically achieves a finite variability amplitude at long time scales. Over the last few years, it has been demonstrated, mostly but not exclusively using SDSS data, that a damped random walk model provides a satisfactory statistical description of observed quasar variability in the optical wavelength range, for rest-frame timescales from 5 days to 2000 days. The best-fit characteristic timescale and asymptotic variability amplitude scale with the luminosity, black hole mass, and rest wavelength, and appear independent of redshift. In addition to providing insights into the physics of quasar variability, the best-fit model parameters can be used to efficiently separate quasars from stars in imaging surveys with adequate long-term multi-epoch data, such as expected from LSST.

Ivezic, Zeljko

2013-01-01

39

IS QUASAR OPTICAL VARIABILITY A DAMPED RANDOM WALK?  

Energy Technology Data Exchange (ETDEWEB)

The damped random walk (DRW) model is increasingly used to model the variability in quasar optical light curves, but it is still uncertain whether the DRW model provides an adequate description of quasar optical variability across all timescales. Using a sample of OGLE quasar light curves, we consider four modifications to the DRW model by introducing additional parameters into the covariance function to search for deviations from the DRW model on both short and long timescales. We find good agreement with the DRW model on timescales that are well sampled by the data (from a month to a few years), possibly with some intrinsic scatter in the additional parameters, but this conclusion depends on the statistical test employed and is sensitive to whether the estimates of the photometric errors are correct to within {approx}10%. On very short timescales (below a few months), we see some evidence of the existence of a cutoff below which the correlation is stronger than the DRW model, echoing the recent finding of Mushotzky et al. using quasar light curves from Kepler. On very long timescales (>a few years), the light curves do not constrain models well, but are consistent with the DRW model.

Zu Ying; Kochanek, C. S. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Kozlowski, Szymon; Udalski, Andrzej, E-mail: yingzu@astronomy.ohio-state.edu [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland)

2013-03-10

40

IS QUASAR OPTICAL VARIABILITY A DAMPED RANDOM WALK?  

International Nuclear Information System (INIS)

The damped random walk (DRW) model is increasingly used to model the variability in quasar optical light curves, but it is still uncertain whether the DRW model provides an adequate description of quasar optical variability across all timescales. Using a sample of OGLE quasar light curves, we consider four modifications to the DRW model by introducing additional parameters into the covariance function to search for deviations from the DRW model on both short and long timescales. We find good agreement with the DRW model on timescales that are well sampled by the data (from a month to a few years), possibly with some intrinsic scatter in the additional parameters, but this conclusion depends on the statistical test employed and is sensitive to whether the estimates of the photometric errors are correct to within ?10%. On very short timescales (below a few months), we see some evidence of the existence of a cutoff below which the correlation is stronger than the DRW model, echoing the recent finding of Mushotzky et al. using quasar light curves from Kepler. On very long timescales (>a few years), the light curves do not constrain models well, but are consistent with the DRW model.

2013-03-10

 
 
 
 
41

Random perturbations of stochastic chains with unbounded variable length memory  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We consider binary infinite order stochastic chains perturbed by a random noise. This means that at each time step, the value assumed by the chain can be randomly and independently flipped with a small fixed probability. We show that the transition probabilities of the perturbed chain are uniformly close to the corresponding transition probabilities of the original chain. As a consequence, in the case of stochastic chains with unbounded but otherwise finite variable length m...

Collet, Pierre; Galves, Antonio; Leonardi, Florencia G.

2007-01-01

42

Random non-response on study variable versus on study as well as auxiliary variables  

Directory of Open Access Journals (Sweden)

Full Text Available In most practical situations in sample surveys, random non-response, for some units, is present on both the study and auxiliary variables. In other situations, it may be present on study variable only since information on the auxiliary variable may be easily obtainable. In this paper, we compare the two situations by considering the usual ratio estimator for the population mean. The former is found to provide a more biased, more efficient and more non-response robust estimator in comparison to the latter whenever it is advisable to use the ratio method of estimation over simple random sampling in the absence of random non-response.

Derric Shannon Tracy

1994-06-01

43

Regularity of Digits and Significant Digits of Random Variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A random variable X is digit-regular (respectively, significant-digit-regular) if the probability that every block of k given consecutive digits (significant digits) appears in the b-adic expansion of X approaches b?k as the block moves to the right, for all integers b > 1 and k ¸ 1. Necessary and sufficient conditions are established, in terms of convergence of Fourier coefficients, and in terms of convergence in distribution modulo 1, for a random variable to be digit-regular (significant-...

2004-01-01

44

Discrete Random Contention System with Variable Packet Length  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The paper researches the random contention system in-depth using the average cycle method, then gets the formulas of the systemic throughput, free rate and collision rate with variable packet length. The simulation results verify the correctness of the theory, meanwhile, gets some conclusions that the different arrival rate G is how to affect the main source of the throughput with variable packet length. It has some researching significance.    

Yingying Guo; Hongwei Ding; Jing Nan; Qianlin Liu

2013-01-01

45

Discrete Random Contention System with Variable Packet Length  

Directory of Open Access Journals (Sweden)

Full Text Available The paper researches the random contention system in-depth using the average cycle method, then gets the formulas of the systemic throughput, free rate and collision rate with variable packet length. The simulation results verify the correctness of the theory, meanwhile, gets some conclusions that the different arrival rate G is how to affect the main source of the throughput with variable packet length. It has some researching significance.    

Yingying Guo

2013-07-01

46

The Benford phenomenon for random variables. Discussion of Feller's way  

CERN Document Server

This paper is devoted to the first digit of a random variable. We will discuss some arguments starting from Feller (1966) and rely specially on Engel-Leuenberger (2003), D\\"umbgen-Leuenberger (2008), Gauvrit-Delahaye (2008--2009), Berger (2010). Some "disaster"appears. We will not discuss papers relying on Fourier Analysis.

Valadier, Michel

2012-01-01

47

Complete Convergence for Weighted Sums of ??-Mixing Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available We obtain the complete convergence for weighted sums of ??-mixing random variables. Our result extends the result of Peligrad and Gut (1999 on unweighted average to a weighted average under a mild condition of weights. Our result also generalizes and sharpens the result of An and Yuan (2008.

Soo Hak Sung

2010-01-01

48

Complete Convergence for Weighted Sums of ??-Mixing Random Variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We obtain the complete convergence for weighted sums of ??-mixing random variables. Our result extends the result of Peligrad and Gut (1999) on unweighted average to a weighted average under a mild condition of weights. Our result also generalizes and sharpens the result of An and Yuan (2008).

Soo Hak Sung

2010-01-01

49

Partitioning loops with variable dependence distances  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new technique to parallelize loops,vith variable distance vectors is presented The method extends previous methods in two ways. First, the present method makes it possible for array subscripts to be any linear combination of all loop indices. The solutions to the linear dependence equations established from such army subscripts are characterized by a pseudo distance matrix(PDM). Second, it allows us to exploit loop parallelism from the PDM by applying unimodular and partitioning transformat...

Yu, Y.; D Hollander, Erik

2000-01-01

50

Random non-response on study variable versus on study as well as auxiliary variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In most practical situations in sample surveys, random non-response, for some units, is present on both the study and auxiliary variables. In other situations, it may be present on study variable only since information on the auxiliary variable may be easily obtainable. In this paper, we compare the two situations by considering the usual ratio estimator for the population mean. The former is found to provide a more biased, more efficient and more non-response robust estimator in comparison t...

Derric Shannon Tracy; Osahan, S. S.

1994-01-01

51

Random linear recursions with dependent coefficients  

CERN Document Server

We consider the equation R(n)=Q(n)+M(n) R(n-1), with random non-i.i.d. coefficients (Q(n),M(n)), and show that the distribution tails of the stationary solution to this equation are regularly varying at infinity.

Ghosh, A P; Hirpara, V; Rastegar, R; Roitershtein, A; Schulteis, A; Suh, J

2010-01-01

52

Use of allele scores as instrumental variables for Mendelian randomization  

Science.gov (United States)

Background An allele score is a single variable summarizing multiple genetic variants associated with a risk factor. It is calculated as the total number of risk factor-increasing alleles for an individual (unweighted score), or the sum of weights for each allele corresponding to estimated genetic effect sizes (weighted score). An allele score can be used in a Mendelian randomization analysis to estimate the causal effect of the risk factor on an outcome. Methods Data were simulated to investigate the use of allele scores in Mendelian randomization where conventional instrumental variable techniques using multiple genetic variants demonstrate ‘weak instrument’ bias. The robustness of estimates using the allele score to misspecification (for example non-linearity, effect modification) and to violations of the instrumental variable assumptions was assessed. Results Causal estimates using a correctly specified allele score were unbiased with appropriate coverage levels. The estimates were generally robust to misspecification of the allele score, but not to instrumental variable violations, even if the majority of variants in the allele score were valid instruments. Using a weighted rather than an unweighted allele score increased power, but the increase was small when genetic variants had similar effect sizes. Naive use of the data under analysis to choose which variants to include in an allele score, or for deriving weights, resulted in substantial biases. Conclusions Allele scores enable valid causal estimates with large numbers of genetic variants. The stringency of criteria for genetic variants in Mendelian randomization should be maintained for all variants in an allele score.

Burgess, Stephen; Thompson, Simon G

2013-01-01

53

Shape and distribution of Jones and Faddy's skew t random variable  

Directory of Open Access Journals (Sweden)

Full Text Available The purpose of this research is to find another way to generate Jones and Faddy's skew t random variable and to construct quantile table, coefficient of skewness, coefficient of kurtosis and coefficient of variation tables of Jones and Faddy's skew t distribution. Graphs of its probability density function and graphs of its distribution function are also presented. The results of this study show that Jones and Faddy's skew t random variable can be generated from a beta random variable on (-1,1. The coefficients of skewness and kurtosis of the distribution depend on parameters a and b. The coefficient of variation of Jones and Faddy's skew t distribution can be calculated.

Saipornchai, N.

2005-09-01

54

Random variability explains apparent global clustering of large earthquakes  

Science.gov (United States)

The occurrence of 5 Mw ? 8.5 earthquakes since 2004 has created a debate over whether or not we are in a global cluster of large earthquakes, temporarily raising risks above long-term levels. I use three classes of statistical tests to determine if the record of M ? 7 earthquakes since 1900 can reject a null hypothesis of independent random events with a constant rate plus localized aftershock sequences. The data cannot reject this null hypothesis. Thus, the temporal distribution of large global earthquakes is well-described by a random process, plus localized aftershocks, and apparent clustering is due to random variability. Therefore the risk of future events has not increased, except within ongoing aftershock sequences, and should be estimated from the longest possible record of events.

Michael, A. J.

2011-01-01

55

Utilities as Random Variables: Density Estimation and Structure Discovery  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Decision theory does not traditionally include uncertainty over utility functions. We argue that the a person's utility value for a given outcome can be treated as we treat other domain attributes: as a random variable with a density function over its possible values. We show that we can apply statistical density estimation techniques to learn such a density function from a database of partially elicited utility functions. In particular, we define a Bayesian learning framewo...

Chajewska, Urszula; Koller, Daphne

2013-01-01

56

PGA Tour Scores as a Gaussian Random Variable  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper it is demonstrated that the scoring at each PGA Tour stroke play event can be reasonably modeled as a Gaussian random variable. All 46 stroke play events in the 2007 season are analyzed. The distributions of scores are favorably compared with a Gaussian distribution using the Kolmogorov-Smirnov test. This observation suggests performance tracking on the PGA tour should be done in terms of the z-score, calculated by subtracting the mean from the raw score and di...

Grober, Robert D.

2008-01-01

57

Problems of variance reduction in the simulation of random variables  

International Nuclear Information System (INIS)

The definition of the uniform linear generator is given and some of the mostly used tests to evaluate the uniformity and the independence of the obtained determinations are listed. The problem of calculating, through simulation, some moment W of a random variable function is taken into account. The Monte Carlo method enables the moment W to be estimated and the estimator variance to be obtained. Some techniques for the construction of other estimators of W with a reduced variance are introduced

1987-01-01

58

Convexity of chance constraints with independent random variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate the convexity of chance constraints with independent random variables. It will be shown, how concavity properties of the mapping related to the decision vector have to be combined with a suitable property of decrease for the marginal densities in order to arrive at convexity of the feasible set for large enough probability levels. It turns out that the required decrease can be verified for most prominent density functions. The results are applied then, to derive convexity of ...

Henrion, Rene?; Strugarek, Cyrille

2006-01-01

59

Random Variables in Graph W*-Probability Spaces  

CERN Multimedia

In [16], we observed the graph W*-probability theory. In this paper, we will review [16] and introduce special amalgamated random variables in this amalgamated W*-probability space. In particular, we will observe the amalgamated semicircularity, amalgamated evenness and amalgamated R-diagonality. As an example, we will compute the trivial moments and trivial cumulants of the generating operator of the graph W*-algebra.

Cho, I; Cho, I Woo

2005-01-01

60

Partial summations of stationary sequences of non-Gaussian random variables  

DEFF Research Database (Denmark)

The distribution of the sum of a finite number of identically distributed random variables is in many cases easily determined given that the variables are independent. The moments of any order of the sum can always be expressed by the moments of the single term without computational problems. However, in the case of dependency between the terms even calculation of a few of the first moments of the sum presents serious computational problems. By use of computerized symbol manipulations it is practicable to obtain exact moments of partial sums of stationary sequences of mutually dependent lognormal variables or polynomials of standard Gaussian variables. The dependency structure is induced by specifying the autocorrelation structure of the sequence of standard Gaussian variables. Particularly useful polynomials are the Winterstein approximations that distributionally fit with non-Gaussian variables up to the moments of the fourth order [Winterstein, S. R. Nonlinear vibration models for extremes and fatigue. J. Engng Mech. ASCE 114 (1988) 1772-1790](1). A method to obtain the Winterstein approximation to a partial sum of a sequence of Winterstein approximations is explained and results are given for different autocorrelation functions of the generic Gaussian sequence. The primary purpose of the investigation is to provide a tool for judging the validity of the central limit theorem argument in specific applicational situations occurring in stochastic mechanics, that is, to judge the speed of convergence of the distribution of a sum (or an integral) of mutually dependent random variables to the Gaussian distribution. The paper is closely related to the work in Ditlevsen el al. [Ditlevsen, O., Mohr, G. & Hoffmeyer, P. Integration of non-Gaussian fields. Prob. Engng Mech 11 (1996) 15-23](2).

Mohr, Gunnar; Ditlevsen, Ove Dalager

1996-01-01

 
 
 
 
61

Generating Correlated QPSK Waveforms By Exploiting Real Gaussian Random Variables  

The design of waveforms with specified auto- and cross-correlation properties has a number of applications in multiple-input multiple-output (MIMO) radar, one of them is the desired transmit beampattern design. In this work, an algorithm is proposed to generate quadrature phase shift- keying (QPSK) waveforms with required cross-correlation properties using real Gaussian random-variables (RV’s). This work can be considered as the extension of what was presented in [1] to generate BPSK waveforms. This work will be extended for the generation of correlated higher-order phase shift-keying (PSK) and quadrature amplitude modulation (QAM) schemes that can better approximate the desired beampattern.

Jardak, Seifallah

2012-11-01

62

Automatic Probabilistic Program Verification through Random Variable Abstraction  

CERN Document Server

The weakest pre-expectation calculus has been proved to be a mature theory to analyze quantitative properties of probabilistic and nondeterministic programs. We present an automatic method for proving quantitative linear properties on any denumerable state space using iterative backwards fixed point calculation in the general framework of abstract interpretation. In order to accomplish this task we present the technique of random variable abstraction (RVA) and we also postulate a sufficient condition to achieve exact fixed point computation in the abstract domain. The feasibility of our approach is shown with two examples, one obtaining the expected running time of a probabilistic program, and the other the expected gain of a gambling strategy. Our method works on general guarded probabilistic and nondeterministic transition systems instead of plain pGCL programs, allowing us to easily model a wide range of systems including distributed ones and unstructured programs. We present the operational and weakest pr...

Barsotti, Damián; 10.4204/EPTCS.28.3

2010-01-01

63

Inference in Probabilistic Logic Programs with Continuous Random Variables  

CERN Document Server

Probabilistic Logic Programming (PLP), exemplified by Sato and Kameya's PRISM, Poole's ICL, Raedt et al's ProbLog and Vennekens et al's LPAD, is aimed at combining statistical and logical knowledge representation and inference. A key characteristic of PLP frameworks is that they are conservative extensions to non-probabilistic logic programs which have been widely used for knowledge representation. PLP frameworks extend traditional logic programming semantics to a distribution semantics, where the semantics of a probabilistic logic program is given in terms of a distribution over possible models of the program. However, the inference techniques used in these works rely on enumerating sets of explanations for a query answer. Consequently, these languages permit very limited use of random variables with continuous distributions. In this paper, we present a symbolic inference procedure that uses constraints and represents sets of explanations without enumeration. This permits us to reason over PLPs with Gaussian...

Islam, Muhammad Asiful; Ramakrishnan, I V

2011-01-01

64

???????????????????? On Small Deviation Theorems for Moving Averages of Dependent Integer-Valued Random Sequence  

Digital Repository Infrastructure Vision for European Research (DRIVER)

??????????????????????????????????????????????????????????????????????????????????????????????????????????????? In this paper, the notion of moving likelihood ratio, as a measure of the deviation of a sequence of integer-valued random variables from an independent random...

2011-01-01

65

Likelihood Ratio and Strong Limit Theorems for the Discrete Random Variable  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This in virtue of the notion of likelihood ratio and the tool of moment generating function, the limit properties of the sequences of random discrete random variables are studied, and a class of strong deviation theorems which represented by inequalities between random variables and their expectation are obtained. As a result, we obtain some strong deviation theorems for Poisson distribution and binomial distribution.

Wenhan Li; Wei Wang; Zhiqiang Liu

2012-01-01

66

Residuals for limited dependent variable models  

Directory of Open Access Journals (Sweden)

Full Text Available General residual expressions based on likelihood equations are given for regression models with censoring or truncation on the endogenous variable. Using nonparametric density estimation such general expressions may be used to obtain residuals for models estimated by, e.g., semiparametric estimators. The suggested approach is illustrated by numerical examples.

Kurt Brännäs

1992-06-01

67

Wavelength Dependence of Polarization. XII. Red Variables.  

Science.gov (United States)

Twenty-three red variable stars were observed for polarization in several spectral regions in the range 0.3-1.0 micrometers. The polarization rises steeply into the ultraviolet, attaining, in some cases, 8% or more. The carbon stars differ from the M-type...

A. Kruszewski T. Gehrels K. Serkowski

1968-01-01

68

Rates of profit as correlated sums of random variables  

Science.gov (United States)

Profit realization is the dominant feature of market-based economic systems, determining their dynamics to a large extent. Rather than attaining an equilibrium, profit rates vary widely across firms, and the variation persists over time. Differing definitions of profit result in differing empirical distributions. To study the statistical properties of profit rates, I used data from a publicly available database for the US Economy for 2009-2010 (Risk Management Association). For each of three profit rate measures, the sample space consists of 771 points. Each point represents aggregate data from a small number of US manufacturing firms of similar size and type (NAICS code of principal product). When comparing the empirical distributions of profit rates, significant ‘heavy tails’ were observed, corresponding principally to a number of firms with larger profit rates than would be expected from simple models. An apparently novel correlated sum of random variables statistical model was used to model the data. In the case of operating and net profit rates, a number of firms show negative profits (losses), ruling out simple gamma or lognormal distributions as complete models for these data.

Greenblatt, R. E.

2013-10-01

69

Maximum Entropy Functions of Discrete Random Fuzzy Variables and Genetic Algorithm  

Directory of Open Access Journals (Sweden)

Full Text Available Due to deficiency of information, the membership functions and probability distribution of a random fuzzy variable cannot be obtainedexplicitly. It is a challenging work to find an appropriate membership function and an appropriate probability distribution when certain partial information about a random fuzzy variable is given, such as expected value or moments. This paper solves such problems for the maximum entropy of discrete random fuzzy variables with certain constraints. A genetic algorithm is designed to solve the general maximum entropy model for discrete random fuzzy variables, which is illustrated by some numerical experiments.

Lianlong Gao

2010-10-01

70

Regime Dependant Microphysical Variability in Darwin, Australia  

Science.gov (United States)

Of utmost importance for global precipitation estimates from satellites such as TRMM and the upcoming Global Precipitation Measurement (GPM) is to understand processes that lead to variability in precipitation on sub-seasonal, seasonal, and climatological scales. Many studies have linked differences in rainfall characteristics such as mean diameter (D0) to sub-seasonal regime variability forced by large scale wind shifts, topography, and continental and maritime convection, across various regions of the globe. Several analyses have tied differences between regimes to differing microphysical processes that drive changes in the drop-size distributions occurring in convective rainfall. For example, decreased ice mass aloft and smaller mean diameters are indicative of warm rain processes, while vigorous ice formation leads to large, melting ice to create large drops. If the microphysical variability in different regimes is characterized and understood, the results could be used to improve satellite precipitation algorithms. The polarimetric, Doppler C-band radar, CPOL, located near Darwin, Australia provides a unique platform to study differences in microphysics between land and ocean, as well as variability between monsoon and break periods. The focus of this study is to examine the microphysical processes occurring in four distinct regimes around Darwin (monsoon-land, monsoon-ocean, break-land, break-ocean), using polarimetric data from CPOL. Analyses such as contoured frequency by altitude (CFADs) diagrams, cumulative distribution functions, and mean profiles of precipitation water mass, precipitation ice mass, reflectivity, differential reflectivity and specific differential phase will aide in understanding the physics of precipitation in these regimes. The formation of precipitation ice aloft, warm rain processes, and the contributions of warm rain and cold cloud processes including melting of ice into large drops, will be linked to differences in D0, rain intensity and rain volume. The results of this study will be extrapolated to comparisons with TRMM Precipitation Radar (PR) climatological observations with the eventual goal of improving satellite-based precipitation estimation.

Dolan, B.; Rutledge, S. A.; Lang, T. J.

2010-12-01

71

A new Hedging algorithm and its application to inferring latent random variables  

CERN Document Server

We present a new online learning algorithm for cumulative discounted gain. This learning algorithm does not use exponential weights on the experts. Instead, it uses a weighting scheme that depends on the regret of the master algorithm relative to the experts. In particular, experts whose discounted cumulative gain is smaller (worse) than that of the master algorithm receive zero weight. We also sketch how a regret-based algorithm can be used as an alternative to Bayesian averaging in the context of inferring latent random variables.

Freund, Yoav

2008-01-01

72

Variable Voltage Source Inverter with controlled frequency spectrum based on Random Pulse Width Modulation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper presents a new method for single phase variable voltage inverter based on Random Pulse Width Modulation. In Random Pulse Width Modulation based inverter, the frequency spectrum of the output current and voltage waveforms becomes continuous because of the randomization of the switching function of the devices controlling the output voltages. This paper establishes a theory that if the distributions of the random numbers generated by the random source are kept within certai...

Muhammad Farrukh Yaqub; Muhammad Safian Adeel; Tahir Izhar

2012-01-01

73

Development of a localized probabilistic sensitivity method to determine random variable regional importance  

International Nuclear Information System (INIS)

There are many methods to identify the important variable out of a set of random variables, i.e., “inter-variable” importance; however, to date there are no comparable methods to identify the “region” of importance within a random variable, i.e., “intra-variable” importance. Knowledge of the critical region of an input random variable (tail, near-tail, and central region) can provide valuable information towards characterizing, understanding, and improving a model through additional modeling or testing. As a result, an intra-variable probabilistic sensitivity method was developed and demonstrated for independent random variables that computes the partial derivative of a probabilistic response with respect to a localized perturbation in the CDF values of each random variable. These sensitivities are then normalized in absolute value with respect to the largest sensitivity within a distribution to indicate the region of importance. The methodology is implemented using the Score Function kernel-based method such that existing samples can be used to compute sensitivities for negligible cost. Numerical examples demonstrate the accuracy of the method through comparisons with finite difference and numerical integration quadrature estimates. - Highlights: ? Probabilistic sensitivity methodology. ? Determines the “region” of importance within random variables such as left tail, near tail, center, right tail, etc. ? Uses the Score Function approach to reuse the samples, hence, negligible cost. ? No restrictions on the random variable types or limit states.

2012-11-01

74

Phase Dependent Spectroscopy of Mira Variable Stars  

CERN Document Server

Spectroscopic measurements of Mira variable stars, as a function of phase, probe the stellar atmospheres and underlying pulsation mechanisms. For example, measuring variations in TiO, VO, and ZrO with phase can be used to help determine whether these molecular species are produced in an extended region above the layers where Balmer line emission occurs or below this shocked region. Using the same methods, the Balmer-line increment, where the strongest Balmer line at phase zero is H-delta and not H-alpha can be measured and explanations tested, along with another peculiarity, the absence of the H-epsilon line in the spectra of Miras when other Balmer lines are strong. We present new spectra covering the spectral range from 6200 Angstroms to 9000 Angstroms of 20 Mira variables. A relationship between variations in the CaII IR triplet and H-alpha as a function of phase support the hypothesis that H-epsilon's observational characteristics result from an interaction of H-epsilon photons with the CaII H line. New p...

Castelaz, M W; Caton, D B; Piontek, R A; Castelaz, Michael W.; Luttermoser, Donald G.; Caton, Daniel B.; Piontek, Robert A.

2000-01-01

75

IS ACTIVE REGION CORE VARIABILITY AGE DEPENDENT?  

Energy Technology Data Exchange (ETDEWEB)

The presence of both steady and transient loops in active region cores has been reported from soft X-ray and extreme-ultraviolet observations of the solar corona. The relationship between the different loop populations, however, remains an open question. We present an investigation of the short-term variability of loops in the core of two active regions in the context of their long-term evolution. We take advantage of the nearly full Sun observations of STEREO and Solar Dynamics Observatory spacecraft to track these active regions as they rotate around the Sun multiple times. We then diagnose the variability of the active region cores at several instances of their lifetime using EIS/Hinode spectral capabilities. We inspect a broad range of temperatures, including for the first time spatially and temporally resolved images of Ca XIV and Ca XV lines. We find that the active region cores become fainter and steadier with time. The significant emission measure at high temperatures that is not correlated with a comparable increase at low temperatures suggests that high-frequency heating is viable. The presence, however, during the early stages, of an enhanced emission measure in the ''hot'' (3.0-4.5 MK) and ''cool'' (0.6-0.9 MK) components suggests that low-frequency heating also plays a significant role. Our results explain why there have been recent studies supporting both heating scenarios.

Ugarte-Urra, Ignacio [College of Science, George Mason University, 4400 University Drive, Fairfax, VA 22030 (United States); Warren, Harry P. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States)

2012-12-10

76

Wavelet regression in random design with heteroscedastic dependent errors  

CERN Multimedia

We investigate function estimation in nonparametric regression models with random design and heteroscedastic correlated noise. Adaptive properties of warped wavelet nonlinear approximations are studied over a wide range of Besov scales, $f\\in\\mathcal{B}^s_{\\pi,r}$, and for a variety of $L^p$ error measures. We consider error distributions with Long-Range-Dependence parameter $\\alpha,02$, it is seen that there are three rate phases, namely the dense, sparse and long range dependence phase, depending on the relative values of $s,p,\\pi$ and $\\alpha$. Furthermore, we show that long range dependence does not come into play for shape estimation $f-\\int f$. The theory is illustrated with some numerical examples.

Kulik, Rafa?; 10.1214/09-AOS684

2009-01-01

77

CONVERGENCE OF THE FRACTIONAL PARTS OF THE RANDOM VARIABLES TO THE TRUNCATED EXPONENTIAL DISTRIBUTION  

Directory of Open Access Journals (Sweden)

Full Text Available Using the stochastic approximations, in this paper it was studiedthe convergence in distribution of the fractional parts of the sum of random variables to the truncated exponential distribution with parameter lambda. This fact is feasible by means of the Fourier-Stieltjes sequence (FSS of the random variable.

Bogdan Gheorghe Munteanu

2013-01-01

78

The Energy of Convolution of 2-Dimension Exponential Random Variables Base on HaarWavelet  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, through wavelet methods, we obtain the energy of convolution of two-dimension exponential random variables and analyze its some properties of wavelet alternation, and we obtain some new results.

Key words: Exponential random variables; Wavelet alternation; Convolution; Energy

Xia, Xuewen; Dai, Ting

2012-01-01

79

The Fitting of Pearson Curves to Sums of Independent Random Variables.  

Science.gov (United States)

It is shown that the distribution of a sum of independent beta random variables is often well approximated by a properly scaled beta distribution. The relationship between the type of Pearson curve which best fits a sum of independent random variables and...

T. Sellke

1983-01-01

80

The impact of random frequency-dependent mutations on the average population fitness  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background In addition to selection, the process of evolution is accompanied by stochastic effects, such as changing environmental conditions, genetic drift and mutations. Commonly it is believed that without genetic drift, advantageous mutations quickly fixate in a halpoid population due to strong selection and lead to a continuous increase of the average fitness. This conclusion is based on the assumption of constant fitness. However, for frequency dependent fitness, where the fitness of an individual depends on the interactions with other individuals in the population, this does not hold. Results We propose a mathematical model that allows to understand the consequences of random frequency dependent mutations on the dynamics of an infinite large population. The frequencies of different types change according to the replicator equations and the fitness of a mutant is random and frequency dependent. To capture the interactions of different types, we employ a payoff matrix of variable size and thus are able to accommodate an arbitrary number of mutations. We assume that at most one mutant type arises at a time. The payoff entries to describe the mutant type are random variables obeying a probability distribution which is related to the fitness of the parent type. Conclusions We show that a random mutant can decrease the average fitness under frequency dependent selection, based on analytical results for two types and simulations for n types. Interestingly, in the case of at most two types the probabilities to increase or decrease the average fitness are independent of the concrete probability density function. Instead, they only depend on the probability that the payoff entries of the mutant are larger than the payoff entries of the parent type.

Huang Weini

2012-08-01

 
 
 
 
81

Fractional calculus approach to the statistical characterization of random variables and vectors  

Science.gov (United States)

Fractional moments have been investigated by many authors to represent the density of univariate and bivariate random variables in different contexts. Fractional moments are indeed important when the density of the random variable has inverse power-law tails and, consequently, it lacks integer order moments. In this paper, starting from the Mellin transform of the characteristic function and by fractional calculus method we present a new perspective on the statistics of random variables. Introducing the class of complex moments, that include both integer and fractional moments, we show that every random variable can be represented within this approach, even if its integer moments diverge. Applications to the statistical characterization of raw data and in the representation of both random variables and vectors are provided, showing that the good numerical convergence makes the proposed approach a good and reliable tool also for practical data analysis.

Cottone, Giulio; Di Paola, Mario; Metzler, Ralf

2010-03-01

82

Testing dependence among serially correlated multi-category variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The contingency table literature on tests for dependence among discrete multi-category variables is extensive. Existing tests assume, however, that draws are independent, and there are no tests that account for serial dependencies - a problem that is particularly important in economics and finance. This paper proposes a new test of independence based on the maximum canonical correlation between pairs of discrete variables. We also propose a trace canonical correlation test using dynamically a...

Pesaran, Mohammad Hashem; Timmermann, Allan

2006-01-01

83

Variable Voltage Source Inverter with controlled frequency spectrum based on Random Pulse Width Modulation  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a new method for single phase variable voltage inverter based on Random Pulse Width Modulation. In Random Pulse Width Modulation based inverter, the frequency spectrum of the output current and voltage waveforms becomes continuous because of the randomization of the switching function of the devices controlling the output voltages. This paper establishes a theory that if the distributions of the random numbers generated by the random source are kept within certain limit with respect to the peak value of reference sinusoidal waveform, the frequency spectrum can be controlled. On the basis of the results, a novel drive using variable tap changing transformer (optional and adaptive random number generator, to control the ratio between the numbers generated by the random source and the reference waveform has been suggested that will guarantee a better power quality profile for a broad range of output voltages.

Muhammad Farrukh Yaqub

2012-01-01

84

Message Based Random Variable Length Key Encryption Algorithm  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Problem statement: A block ciphers provides confidentiality in cryptography but cryptanalysis of the classical block ciphers demonstrated some old weaknesses grabbing a partial key in any stage of encryption procedure leads to reconstructing the whole key. Exhaustive key search shows that key generation should be indeterminist and random for each round. Matching cipher-text attack shows that larger size of block is more secure. In order to overcome analysis mentioned above a new algori...

Hamid Mirvaziri; Ismail, Kasmiran J. M.; Hanapi, Zurina M.

2009-01-01

85

A preliminary, randomized trial of aerobic exercise for alcohol dependence.  

Science.gov (United States)

Interventions targeting physical activity may be valuable as an adjunct to alcohol treatment, but have been relatively untested. In the current study, alcohol dependent, physically sedentary patients were randomized to: a 12-week moderate-intensity, group aerobic exercise intervention (AE; n=25) or a brief advice to exercise intervention (BA-E; n=23). Results showed that individuals in AE reported significantly fewer drinking and heavy drinking days, relative to BA-E during treatment. Furthermore adherence to AE strengthened the beneficial effect of intervention on alcohol use outcomes. While high levels of moderate-intensity exercise appeared to facilitate alcohol recovery regardless of intervention arm, attending the group-based AE intervention seemed to further enhance the positive effects of exercise on alcohol use. Study findings indicate that a moderate intensity, group aerobic exercise intervention is an efficacious adjunct to alcohol treatment. Improving adherence to the intervention may enhance its beneficial effects on alcohol use. PMID:24666811

Brown, Richard A; Abrantes, Ana M; Minami, Haruka; Read, Jennifer P; Marcus, Bess H; Jakicic, John M; Strong, David R; Dubreuil, Mary Ella; Gordon, Alan A; Ramsey, Susan E; Kahler, Christopher W; Stuart, Gregory L

2014-07-01

86

Correlations between record events in sequences of random variables with a linear trend  

CERN Multimedia

The statistics of records in sequences of independent, identically distributed random variables is a classic subject of study. One of the earliest results concerns the stochastic independence of record events. Recently, records statistics beyond the case of i.i.d. random variables have received much attention, but the question of independence of record events has not been addressed systematically. In this paper, we study this question in detail for the case of independent, non-identically distributed random variables, specifically, for random variables with a linearly moving mean. We find a rich pattern of positive and negative correlations, and show how their asymptotics is determined by the universality classes of extreme value statistics.

Wergen, Gregor; Krug, Joachim

2011-01-01

87

Conditional Value-at-Risk for Random Immediate Reward Variables in Markov Decision Processes  

Directory of Open Access Journals (Sweden)

Full Text Available We consider risk minimization problems for Markov decision processes. From a standpoint of making the risk of random reward variable at each time as small as possible, a risk measure is introduced using conditional value-at-risk for random immediate reward variables in Markov decision processes, under whose risk measure criteria the risk-optimal policies are characterized by the optimality equations for the discounted or average case. As an application, the inventory models are considered.

Masayuki Kageyama

2011-09-01

88

Random recurrence equations and ruin in a Markov-dependent stochastic economic environment  

CERN Document Server

We develop sharp large deviation asymptotics for the probability of ruin in a Markov-dependent stochastic economic environment and study the extremes for some related Markovian processes which arise in financial and insurance mathematics, related to perpetuities and the $\\operatorname {ARCH}(1)$ and $\\operatorname {GARCH}(1,1)$ time series models. Our results build upon work of Goldie [Ann. Appl. Probab. 1 (1991) 126--166], who has developed tail asymptotics applicable for independent sequences of random variables subject to a random recurrence equation. In contrast, we adopt a general approach based on the theory of Harris recurrent Markov chains and the associated theory of nonnegative operators, and meanwhile develop certain recurrence properties for these operators under a nonstandard "G\\"artner--Ellis" assumption on the driving process.

Collamore, Jeffrey F

2009-01-01

89

Random variable approach to dissipative spin dynamics and Landau-Zener transitions  

Science.gov (United States)

We present a random variable approach to solve for the dynamics of a dissipative two-state system. Based on an exact functional integral description, our method reformulates the problem as that of non-unitary time evolution of a quantum state vector under a Hamiltonian containing random noise fields. This non-perturbative formalism goes beyond the frequently used Non-Interacting Blip Approximation (NIBA) and is particularly well suited to treat an explicitly time-dependent Hamiltonian. As an example, we consider the renowned Landau-Zener problem in the presence of an Ohmic bath with a large bath cutoff frequency ?c. We identify an intermediate time regime where the energy separation of the two spin states is much larger than their tunneling coupling ?, but still smaller than ?c such that bath mediated spin transitions still occur. Such a situation can for example be realized with a cold atomic quantum dot setup. We also derive an approximate analytical expression for the decay of the upper spin state population in this regime, which agrees well with our numerical results.

Orth, Peter P.; Le Hur, Karyn; Imambekov, Adilet

2010-03-01

90

Danger: High Power! – Exploring the Statistical Properties of a Test for Random Forest Variable Importance  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Random forests have become a widely-used predictive model in many scientific disciplines within the past few years. Additionally, they are increasingly popular for assessing variable importance, e.g., in genetics and bioinformatics. We highlight both advantages and limitations of different variable importance scores and associated testing procedures, especially in the context of correlated predictor variables. For the test of Breiman and Cutler (2008), we investigate the statistical propertie...

Strobl, Carolin; Zeileis, Achim

2008-01-01

91

The expected sample variance of uncorrelated random variables with a common mean and applications in unbalanced random effects models  

Digital Repository Infrastructure Vision for European Research (DRIVER)

There is a little-known but very simple generalization of the standard result that for uncorrelated variables with a common mean and variance, the expected sample variance is the marginal variance. The generalization justifies the use of the usual standard error of the sample mean in possibly heteroscedastic situations and motivates some simple estimators for unbalanced linear random effects models. The latter is illustrated for the simple one-way context.

Vardeman, Stephen B.; Wendelberger, Joanne R.

2004-01-01

92

Detection of Gauss-Markov Random Fields with Nearest-Neighbor Dependency.  

Science.gov (United States)

The problem of hypothesis testing against independence for a Gauss- Markov random field (GMRF) is analyzed. Assuming an acyclic dependency graph, an expression for the log-likelihood ratio of detection is derived. Assuming random placement of nodes over a...

A. Anandkumar A. Swami L. Tong

2010-01-01

93

On the Efficient Calculation of a Linear Combination of Chi-Square Random Variables with an Application in Counting String Vacua  

CERN Multimedia

As a first result, an explicit analytic expression for the density of the sum of two Gamma random variables is derived. Then a computationally efficient algorithm to numerically calculate the linear combination of an even number of chi^2_r random variables is developed. An explicit expression for the error bound is obtained. As an application, the exponential dependence of the eigenvalue fluctuation probability of a random matrix model for 4d supergravity with N scalar fields is found to be of the asymptotic form exp(-0.35N).

Bausch, Johannes

2012-01-01

94

On the use of fractional calculus for the probabilistic characterization of random variables  

CERN Document Server

In this paper, the classical problem of the probabilistic characterization of a random variable is re-examined. A random variable is usually described by the probability density function (PDF) or by its Fourier transform, namely the characteristic function (CF). The CF can be further expressed by a Taylor series involving the moments of the random variable. However, in some circumstances, the moments do not exist and the Taylor expansion of the CF is useless. This happens for example in the case of $\\alpha$--stable random variables. Here, the problem of representing the CF or the PDF of random variables (r.vs) is examined by introducing fractional calculus. Two very remarkable results are obtained. Firstly, it is shown that the fractional derivatives of the CF in zero coincide with fractional moments. This is true also in case of CF not derivable in zero (like the CF of $\\alpha$--stable r.vs). Moreover, it is shown that the CF may be represented by a generalized Taylor expansion involving fractional moments. ...

Cottone, Giulio; 10.1016/j.probengmech.2008.08.002

2013-01-01

95

Convergence properties of polynomial chaos approximations for L2 random variables.  

Energy Technology Data Exchange (ETDEWEB)

Polynomial chaos (PC) representations for non-Gaussian random variables are infinite series of Hermite polynomials of standard Gaussian random variables with deterministic coefficients. For calculations, the PC representations are truncated, creating what are herein referred to as PC approximations. We study some convergence properties of PC approximations for L{sub 2} random variables. The well-known property of mean-square convergence is reviewed. Mathematical proof is then provided to show that higher-order moments (i.e., greater than two) of PC approximations may or may not converge as the number of terms retained in the series, denoted by n, grows large. In particular, it is shown that the third absolute moment of the PC approximation for a lognormal random variable does converge, while moments of order four and higher of PC approximations for uniform random variables do not converge. It has been previously demonstrated through numerical study that this lack of convergence in the higher-order moments can have a profound effect on the rate of convergence of the tails of the distribution of the PC approximation. As a result, reliability estimates based on PC approximations can exhibit large errors, even when n is large. The purpose of this report is not to criticize the use of polynomial chaos for probabilistic analysis but, rather, to motivate the need for further study of the efficacy of the method.

Field, Richard V., Jr. (.,; .); Grigoriu, Mircea (Cornell University, Ithaca, NY)

2007-03-01

96

The Discovery of Timescale-Dependent Color Variability of Quasars  

CERN Document Server

Quasars are variable on timescales from days to years in UV/optical, and generally appear bluer while they brighten. The physics behind the variations in fluxes and colors remains unclear. Using SDSS g and r band photometric monitoring data of quasars in Stripe 82, we find that although the flux variation amplitude increases with timescale, the color variability exhibits opposite behavior. The color variability of quasars is prominent at timescales as short as ~ 10 days, but gradually reduces toward timescales up to years. In other words, the variable emission at shorter timescales is bluer than that at longer timescales. This timescale dependence is clearly and consistently detected at all redshifts from z = 0 to 3.5, thus can not be due to contaminations to broadband photometry from emission lines which do not respond to fast continuum variations. The discovery directly rules out the possibility that simply attributes the color variability to contamination from a non-variable redder component, such as the h...

Sun, Yu-Han; Chen, Xiao-Yang; Zheng, Zhen-Ya

2014-01-01

97

Modelado con variables aleatorias en simulink utilizando simulación montercarlo / Modeling with random variables in simulink using montecarlo simulations  

Scientific Electronic Library Online (English)

Full Text Available SciELO Venezuela | Language: Spanish Abstract in spanish Este artículo presenta el Modelado Con Variables Aleatorias En Simulink Utilizando Simulación Montecarlo, muchos modelos de sistemas reales contienen elementos que precisan o admiten un modelado estadístico, Sistemas de comunicaciones, Sistemas de conmutación, Sistemas sensores, Modelado toma forma [...] definiendo, Variables aleatorias que rigen ciertos comportamientos del sistema Procesos estocásticos para modelar variación de entradas en el tiempo, como lo son las fluctuaciones en la bolsa de valores e ciertos productos. Se deben definir métodos para generar muestras de variables aleatorias y muestras de procesos estocásticos. Entre ellos está el método de Montecarlo, el modelo implementado mostro la capacidad proponer precios optativos al precio de mercado ante cambios en el precio de un producto. Las simulaciones permitieron conocer con mayor exactitud la versatilidad del Método ante otros Métodos usados, prediciendo con gran exactitud las fluctuaciones de precios ocurridas en el producto de prueba. Abstract in english This article presents the model with random variables in Monte CarloSimulation Using Simulink, many models of real systems contain elements that require or permit a statistical modeling, communication systems,switching systems, sensor systems, modeling takes definite shape, random variables governin [...] g certain stochastic processes system behavior modelinginputs change over time, as are the fluctiaciones in the stock market andsome products. You must define methods to generate samples of random variables and stochastic samples. Among them is the Monte Carlo method, the implemented model showed the ability to propose optional pricing to the market price to changes in the price of a product. The simulations allowed to know more precisely the versatility of the method to other methods used, predicting with great accuracy the price fluctuations that occurred in the trial product.

Sergio, Velásquez; Ronny, Velásquez.

98

Structural Fatigue Reliability Based on Extension of Random Loads into Interval Variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

According to the problem that for a structure under random loads, the structural fatigue life cant be directly calculated out by S-N curves and linear Miner cumulative damage rule. Owing to the uncertainty of loads, and the problem of the inaccuracy of calculated structural reliability index for the existence of deviation between measured data in projects and real data, the research method for structural fatigue reliability based on extension of random loads into interval variables is propose...

Qiangfeng Wang; Jianjun Li; Shengli Zhang

2013-01-01

99

On the Decrease Rate of the Non-Gaussianness of the Sum of Independent Random Variables  

CERN Document Server

Several proofs of the monotonicity of the non-Gaussianness (divergence with respect to a Gaussian random variable with identical second order statistics) of the sum of n independent and identically distributed (i.i.d.) random variables were published. We give an upper bound on the decrease rate of the non-Gaussianness which is proportional to the inverse of n, for large n. The proof is based on the relationship between non-Gaussianness and minimum mean-square error (MMSE) and causal minimum mean-square error (CMMSE) in the time-continuous Gaussian channel.

Binia, J

2006-01-01

100

Exact Distribution of the Ratio of Gamma and Rayleigh Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available The distributions of the ratio of two independent random variables arise in many applied problems and have been extensively studied by many researchers. This article derives the distributions of the ratio Z=|x/y| , when x and y are gamma and Rayleigh random variables respectively and are distributed independently of each other. The associated pdf, cdf, and moments have been given in terms of different special functions, for examples, confluent hypergeometric function, parabolic-cylinder function and beta functions. Some plots for the cdf and pdf associated with the distribution of the ratio have been provided.

M. Shakil

2006-07-01

 
 
 
 
101

Some results on the span of families of Banach valued independent, random variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Let E be a Banach space, and let (Ω,ℱ,P) be a probability space. If L1(Ω) contains an isomorphic copy of L1[0,1] then in LEP(Ω)(1≤P<∞), the closed linear span of every sequence of independent, E valued mean zero random variables has infinite codimension. If E is reflexive or B-convex and 1random variables is super...

Rohan Hemasinha

1991-01-01

102

Random walk approximation for the radial dose dependence  

International Nuclear Information System (INIS)

We investigate the properties of the radial distribution of energy deposited by ions, calculated using a random walk approach, which is an important analytical tool for solving transport problems. This investigation is motivated by the desire to understand the range of applicability of the random walk approximation for problems related to radiation damage assessment. We study the radial dose at small and moderate distances and compare our results to the results of Monte Carlo simulations. (authors)

2012-08-01

103

Approximation to Distribution of Product of Random Variables Using Orthogonal Polynomials for Lognormal Density  

CERN Document Server

We derive a closed-form expression for the orthogonal polynomials associated with the general lognormal density. The result can be utilized to construct easily computable approximations for probability density function of a product of random variables. As an example, we have calculated the approximative distribution for the product of correlated Nakagami-m variables. Simulations indicate that accuracy of the proposed approximation is good.

Zheng, Zhong; Hämäläinen, Jyri; Tirkkonen, Olav

2012-01-01

104

Statistical Analysis for Multisite Trials Using Instrumental Variables with Random Coefficients  

Science.gov (United States)

Multisite trials can clarify the average impact of a new program and the heterogeneity of impacts across sites. Unfortunately, in many applications, compliance with treatment assignment is imperfect. For these applications, we propose an instrumental variable (IV) model with person-specific and site-specific random coefficients. Site-specific IV…

Raudenbush, Stephen W.; Reardon, Sean F.; Nomi, Takako

2012-01-01

105

Convolutions of Heavy Tailed Random Variables and Applications to Portfolio Diversification and MA(1) Time Series  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The paper characterizes first and second order tail behavior of convolutions of i.i.d. heavy tailed random variables with support on the real line. The result is applied to the problem of risk diversification in portfolio analysis and to the estimation of the parameter in a MA(1) model.

Geluk, J. L.; Peng, L.; Vries, C. G.

1999-01-01

106

Asymptotic expansions for distributions of compound sums of light subexponential random variables  

CERN Multimedia

We derive an asymptotic expansion for the distribution of a compound sum of independent random variables, all having the same light-tailed subexponential distribution. The examples of a Poisson and geometric number of summands serve as an illustration of the main result. Complete calculations are done for a Weibull distribution, with which we derive, as examples and without any difficulties, 7 terms expansions.

Barbe, P; Zhang, C; Barbe, Ph .

2006-01-01

107

Model Building with Multiple Dependent Variables and Constraints  

CERN Document Server

The most widely used method for finding relationships between several quantities is multiple regression. This however is restricted to a single dependent variable. We present a more general method which allows models to be constructed with multiple variables on both sides of an equation and which can be computed easily using a spreadsheet program. The underlying principle (originating from canonical correlation analysis) is that of maximising the correlation between the two sides of the model equation. This paper presents a fitting procedure which makes it possible to force the estimated model to satisfy constraint conditions which it is required to possess, these may arise from theory, prior knowledge or be intuitively obvious. We also show that the least squares approach to the problem is inadequate as it produces models which are not scale invariant.

Tofallis, Chris

2011-01-01

108

Efficient Design for Mendelian Randomization Studies: Subsample and 2-Sample Instrumental Variable Estimators  

Science.gov (United States)

Mendelian randomization (MR) is a method for estimating the causal relationship between an exposure and an outcome using a genetic factor as an instrumental variable (IV) for the exposure. In the traditional MR setting, data on the IV, exposure, and outcome are available for all participants. However, obtaining complete exposure data may be difficult in some settings, due to high measurement costs or lack of appropriate biospecimens. We used simulated data sets to assess statistical power and bias for MR when exposure data are available for a subset (or an independent set) of participants. We show that obtaining exposure data for a subset of participants is a cost-efficient strategy, often having negligible effects on power in comparison with a traditional complete-data analysis. The size of the subset needed to achieve maximum power depends on IV strength, and maximum power is approximately equal to the power of traditional IV estimators. Weak IVs are shown to lead to bias towards the null when the subsample is small and towards the confounded association when the subset is relatively large. Various approaches for confidence interval calculation are considered. These results have important implications for reducing the costs and increasing the feasibility of MR studies.

Pierce, Brandon L.; Burgess, Stephen

2013-01-01

109

Model Checking with Program Slicing Based on Variable Dependence Graphs  

Directory of Open Access Journals (Sweden)

Full Text Available In embedded control systems, the potential risks of software defects have been increasing because of software complexity which leads to, for example, timing related problems. These defects are rarely found by tests or simulations. To detect such defects, we propose a modeling method which can generate software models for model checking with a program slicing technique based on a variable dependence graph. We have applied the proposed method to one case in automotive control software and demonstrated the effectiveness of the method. Furthermore, we developed a software tool to automate model generation and achieved a 35% decrease in total verification time on model checking.

Masahiro Matsubara

2012-12-01

110

???????????????????? On Small Deviation Theorems for Moving Averages of Dependent Integer-Valued Random Sequence  

Directory of Open Access Journals (Sweden)

Full Text Available ??????????????????????????????????????????????????????????????????????????????????????????????????????????????? In this paper, the notion of moving likelihood ratio, as a measure of the deviation of a sequence of integer-valued random variables from an independent random sequence with geometric distribution, is intro-duced. By restricting the moving likelihood ratio, a certain subset of the sample space is given, and on this subset, a class of strong laws, represented by inequalities, are obtained. These strong laws contain some limit properties of the sequence of integer-valued random variables, concerning relative entropy density and the entropy function of geometric distribution.

??

2011-07-01

111

Event-controlled constructions of random fields of maxima with non-max-stable dependence  

CERN Document Server

Max-stable random fields can be constructed according to Schlather (2002) with a random function or a stationary process and a kind of random event magnitude. These are applied for the modelling of natural hazards. We simply extend these event-controlled constructions to random fields of maxima with non-max-stable dependence structure (copula). The theory for the variant with a stationary process is obvious; the parameter(s) of its correlation function is/are determined by the event magnitude. The introduced variant with random functions can only be researched numerically. The scaling of the random function is exponentially determined by the event magnitude. The location parameter of the Gumbel margins depends only on this exponential function in the researched examples; the scale parameter of the margins is normalized. In addition, we propose a method for the parameter estimation for such constructions by using Kendall's tau. The spatial dependence in relation to the block size is considered therein. Finally...

Raschke, Mathias

2014-01-01

112

Strain-Dependent Creep Damage in Random Inhomogeneous Materials.  

Science.gov (United States)

Employing a recent homogeneous strain-dependent creep damage theory, the propagation of a failure front in a beam under pure bending is studied. A local inhomogeneous strain-dependent creep damage theory is then postulated, based on creep damage data obta...

C. Lee F. A. Cozzarelli

1980-01-01

113

Modelling the statistical dependence of rainfall event variables through copula functions  

Directory of Open Access Journals (Sweden)

Full Text Available In many hydrological models, such as those derived by analytical probabilistic methods, the precipitation stochastic process is represented by means of individual storm random variables which are supposed to be independent of each other. However, several proposals were advanced to develop joint probability distributions able to account for the observed statistical dependence. The traditional technique of the multivariate statistics is nevertheless affected by several drawbacks, whose most evident issue is the unavoidable subordination of the dependence structure assessment to the marginal distribution fitting. Conversely, the copula approach can overcome this limitation, by dividing the problem in two distinct parts. Furthermore, goodness-of-fit tests were recently made available and a significant improvement in the function selection reliability has been achieved. Herein the dependence structure of the rainfall event volume, the wet weather duration and the interevent time is assessed and verified by test statistics with respect to three long time series recorded in different Italian climates. Paired analyses revealed a non negligible dependence between volume and duration, while the interevent period proved to be substantially independent of the other variables. A unique copula model seems to be suitable for representing this dependence structure, despite the sensitivity demonstrated by its parameter towards the threshold utilized in the procedure for extracting the independent events. The joint probability function was finally developed by adopting a Weibull model for the marginal distributions.

M. Balistrocchi

2011-06-01

114

Modelling the statistical dependence of rainfall event variables through copula functions  

Science.gov (United States)

In many hydrological models, such as those derived by analytical probabilistic methods, the precipitation stochastic process is represented by means of individual storm random variables which are supposed to be independent of each other. However, several proposals were advanced to develop joint probability distributions able to account for the observed statistical dependence. The traditional technique of the multivariate statistics is nevertheless affected by several drawbacks, whose most evident issue is the unavoidable subordination of the dependence structure assessment to the marginal distribution fitting. Conversely, the copula approach can overcome this limitation, by dividing the problem in two distinct parts. Furthermore, goodness-of-fit tests were recently made available and a significant improvement in the function selection reliability has been achieved. Herein the dependence structure of the rainfall event volume, the wet weather duration and the interevent time is assessed and verified by test statistics with respect to three long time series recorded in different Italian climates. Paired analyses revealed a non negligible dependence between volume and duration, while the interevent period proved to be substantially independent of the other variables. A unique copula model seems to be suitable for representing this dependence structure, despite the sensitivity demonstrated by its parameter towards the threshold utilized in the procedure for extracting the independent events. The joint probability function was finally developed by adopting a Weibull model for the marginal distributions.

Balistrocchi, M.; Bacchi, B.

2011-06-01

115

Survival probabilities of history-dependent random walks.  

Science.gov (United States)

We analyze the dynamics of random walks with long-term memory (binary chains with long-range correlations) in the presence of an absorbing boundary. An analytically solvable model is presented, in which a dynamical phase transition occurs when the correlation strength parameter mu reaches a critical value mu(c). For strong positive correlations, mu > mu(c), the survival probability is asymptotically finite, whereas for mu < mu(c) it decays as a power law in time (chain length). PMID:16383505

Keshet, Uri; Hod, Shahar

2005-10-01

116

Randomly charged polymers excess charge dependence of spatial configurations  

CERN Multimedia

Spatial configurations of randomly charged polymers, known as polyampholytes (PAs), are very sensitive to the overall excess charge Q. Analytical arguments, supported by Monte Carlo simulations and exact enumeration studies, lead to the following picture: For Q Q_c the polymer stretches with decreasing T. At low T, the dense states are described by Debye-Huckel theory, while the expanded states resemble a necklace of globules connected by strings. At such temperatures, the transition between the dense and the expanded states with increasing Q, is reminiscent of the breakup of a charged drop.

Kantor, Ya; Kantor, Yacov; Kardar, Mehran

1995-01-01

117

[Scale-dependency of spatial variability of soil available nutrients].  

Science.gov (United States)

With the support of GIS and by using classical statistics and geostatistics methods, the spatial variability of soil available P (AP) and available K (AK) in cultivated lands in Yucheng City of Shandong Province was approached at county and township scales. The results showed that both the soil AP and AK followed the logarithmic normal distribution, with the coefficient of variation (CV) at the two scales being 26.5% - 36.6% and presenting a moderate variation. With the decrease of the scale, the CV of the soil AP and AK increased. Both the soil AP and AK were spatially correlated with scale. At county scale, the soil AP and AK had a larger spatial correlation distance, being 9.0 km and 26.5 km, respectively; while at township scale, the soil AP and AK had a smaller spatial correlation distance, being 1.7 km and 2.8 km, respectively. The spatial distribution of the soil AP and AK at the two scales was obviously different, which was mainly affected by structural factors and random factors. PMID:21608258

Yang, Qi-Yong; Yang, Jing-Song; Liu, Guang-Ming

2011-02-01

118

Rigorous mean field model for CPA Anderson model with free random variables  

CERN Multimedia

A model of a randomly disordered system with site-diagonal random energy fluctuations is introduced. It is an extension of Wegner's n-orbital model to arbitrary eigenvalue distribution in the electronic level space. The new feature is that the random energy values are not assumed to be independent at different sites but free. Freeness of random variables is an analogue of the concept of independence for non-commuting random operators. A possible realization is the ensemble of at different lattice-sites randomly rotated matrices. The one- and two-particle Green functions of the proposed hamiltonian are calculated exactly. The eigenstates are extended and the conductivity is nonvanishing everywhere inside the band. The long-range behaviour and the zero-frequency limit of the two-particle Green function are universal with respect to the eigenvalue distribution in the electronic level space. The solutions solve the CPA-equation for the one- and two-particle Green function of the corresponding Anderson model. Thus...

Neu, P; Neu, Peter; Speicher, Roland

1994-01-01

119

The exact distribution of the sample variance from bounded continuous random variables  

CERN Document Server

For a sample of absolutely bounded i.i.d. random variables with a continuous density the cumulative distribution function of the sample variance is represented by a univariate integral over a Fourier series. If the density is a polynomial or a trigonometrical polynomial the coefficients of this series are simple finite terms containing only the error function, the exponential function and powers. In more general cases - e.g. for all beta densities - the coefficients are given by some series expansions. The method is generalized to positive semi-definite quadratic forms of bounded independent but not necessarily identically distributed random variables if the form matrix differs from a diagonal matrix D > 0 only by a matrix of rank 1

Royen, T

2008-01-01

120

Some results on the span of families of Banach valued independent, random variables  

Directory of Open Access Journals (Sweden)

Full Text Available Let E be a Banach space, and let (Ω,ℱ,P be a probability space. If L1(Ω contains an isomorphic copy of L1[0,1] then in LEP(Ω(1≤P<∞, the closed linear span of every sequence of independent, E valued mean zero random variables has infinite codimension. If E is reflexive or B-convex and 1random variables is super-reflexive.

Rohan Hemasinha

1991-06-01

 
 
 
 
121

Discovery of Fourier-dependent time lags in cataclysmic variables  

CERN Document Server

We report the first study of Fourier-frequency-dependent coherence and phase/time lags at optical wavelengths of cataclysmic variables (MV Lyr and LU Cam) displaying typical flickering variability in white light. Observations were performed on the William Herschel Telescope using ULTRACAM. Lightcurves for both systems have been obtained with the SDSS filters $u'$, $g'$ and $r'$ simultaneously with cadences between $\\approx0.5-2$ seconds, and allow us to probe temporal frequencies between ~10^{-3} Hz and ~1 Hz. We find high levels of coherence between the u', g' and r' lightcurves up to at least ~10^{-2} Hz. Furthermore we detect red/negative lags where the redder bands lag the bluer ones at the lowest observed frequencies. For MV Lyr time lags up to ~3 seconds are observed, whilst LU Cam displays larger time lags of ~10 seconds. Mechanisms which seek to explain red/negative lags observed in X-ray binaries and Active Galactic Nuclei involve reflection of photons generated close to the compact object onto the s...

Scaringi, S; Groot, P J; Uttley, P; Marsh, T; Knigge, C; Maccarone, T; Dhillon, V S

2013-01-01

122

A comparison of response patterns on fixed-, variable-, and random-ratio schedules  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The behavior of individual pigeons on fixed-ratio, variable-ratio, and random-ratio schedules was examined. Within each type of ratio schedule the size of the ratio was varied in an irregular sequence. At various ratio sizes (5, 10, 40, 80) no differences were found among overall response rates (postreinforcement pause plus running response rate) as a function of ratio type. This similarity in overall response rates held despite noticeable differences in the microstructure of performance both...

Crossman, Edward K.; Bonem, Elliott J.; Phelps, Brady J.

1987-01-01

123

A saturation property of structures obtained by forcing with a compact family of random variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A method how to construct Boolean-valued models of some fragments of arithmetic was developed in Krajicek (2011), with the intended applications in bounded arithmetic and proof complexity. Such a model is formed by a family of random variables defined on a pseudo-finite sample space. We show that under a fairly natural condition on the family (called compactness in K.(2011)) the resulting structure has a property that is naturally interpreted as saturation for existential ty...

Krajicek, Jan

2012-01-01

124

Intraspecific Variability within Globodera tabacum solanacearum Using Random Amplified Polymorphic DNA  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Random amplified polymorphic DNA (RAPDs) were used to investigate the intraspecific variability among 19 geographic isolates of Globodera tabacum solanacearum from eight counties in Virginia and one county in North Carolina. Globodera tabacum tabacum, G. t. virginiae, and the Mexican cyst nematode (MCN) were included as outgroups. Six primers were used and 119 amplification products were observed. Each primer yielded reproducible differences in fragment patterns that differentiated the isolat...

Syracuse, A. J.; Johnson, C. S.; Eisenback, J. D.; Nessler, C. L.; Smith, E. P.

2004-01-01

125

Dependence of NAO variability on coupling with sea ice  

Energy Technology Data Exchange (ETDEWEB)

The variance of the North Atlantic Oscillation index (denoted N) is shown to depend on its coupling with area-averaged sea ice concentration anomalies in and around the Barents Sea (index denoted B). The observed form of this coupling is a negative feedback whereby positive N tends to produce negative B, which in turn forces negative N. The effects of this feedback in the system are examined by modifying the feedback in two modeling frameworks: a statistical vector autoregressive model (F{sub VAR}) and an atmospheric global climate model (F{sub CAM}) customized so that sea ice anomalies on the lower boundary are stochastic with adjustable sensitivity to the model's evolving N. Experiments show that the variance of N decreases nearly linearly with the sensitivity of B to N, where the sensitivity is a measure of the negative feedback strength. Given that the sea ice concentration field has anomalies, the variance of N goes down as these anomalies become more sensitive to N. If the sea ice concentration anomalies are entirely absent, the variance of N is even smaller than the experiment with the most sensitive anomalies. Quantifying how the variance of N depends on the presence and sensitivity of sea ice anomalies to N has implications for the simulation of N in global climate models. In the physical system, projected changes in sea ice thickness or extent could alter the sensitivity of B to N, impacting the within-season variability and hence predictability of N. (orig.)

Strong, Courtenay [University of Utah, Salt Lake City, Utah (United States); Magnusdottir, Gudrun [University of California, Irvine, Irvine, CA (United States)

2011-05-15

126

Detection of Gauss-Markov Random Fields with Nearest-Neighbor Dependency  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The problem of hypothesis testing against independence for a Gauss-Markov random field (GMRF) is analyzed. Assuming an acyclic dependency graph, an expression for the log-likelihood ratio of detection is derived. Assuming random placement of nodes over a large region according to the Poisson or uniform distribution and nearest-neighbor dependency graph, the error exponent of the Neyman-Pearson detector is derived using large-deviations theory. The error exponent is expressed...

Anandkumar, Animashree; Tong, Lang; Swami, Ananthram

2007-01-01

127

On the Amount of Dependence in the Prime Factorization of a Uniform Random Integer  

Digital Repository Infrastructure Vision for European Research (DRIVER)

How much dependence is there in the prime factorization of a random integer distributed uniformly from 1 to n? How much dependence is there in the decomposition into cycles of a random permutation of n points? What is the relation between the Poisson-Dirichlet process and the scale invariant Poisson process? These three questions have essentially the same answers, with respect to total variation distance, considering only small components, and with respect to a Wasserstein d...

Arratia, Richard

2013-01-01

128

Human phoneme recognition depending on speech-intrinsic variability.  

Science.gov (United States)

The influence of different sources of speech-intrinsic variation (speaking rate, effort, style and dialect or accent) on human speech perception was investigated. In listening experiments with 16 listeners, confusions of consonant-vowel-consonant (CVC) and vowel-consonant-vowel (VCV) sounds in speech-weighted noise were analyzed. Experiments were based on the OLLO logatome speech database, which was designed for a man-machine comparison. It contains utterances spoken by 50 speakers from five dialect/accent regions and covers several intrinsic variations. By comparing results depending on intrinsic and extrinsic variations (i.e., different levels of masking noise), the degradation induced by variabilities can be expressed in terms of the SNR. The spectral level distance between the respective speech segment and the long-term spectrum of the masking noise was found to be a good predictor for recognition rates, while phoneme confusions were influenced by the distance to spectrally close phonemes. An analysis based on transmitted information of articulatory features showed that voicing and manner of articulation are comparatively robust cues in the presence of intrinsic variations, whereas the coding of place is more degraded. The database and detailed results have been made available for comparisons between human speech recognition (HSR) and automatic speech recognizers (ASR). PMID:21110608

Meyer, Bernd T; Jürgens, Tim; Wesker, Thorsten; Brand, Thomas; Kollmeier, Birger

2010-11-01

129

Epoch-dependent absorption line profile variability in ? Cep  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in spanish Reportamos el análisis de una campaña de monitoreo espectroscópico multiépoca de la estrella O6 Ief ? Cep. Observaciones previas habían reportado la existencia de dos modos de pulsaciones no-radiales en esta estrella. Nuestros datos revelan una situación considerablemente más compleja. Las frequenci [...] as contenidas en el espectro de potencia cambian considerablemente de una época a otra. No encontramos ninguna frecuencia estable que pueda ser atribuida inequívocamente a pulsaciones. La dependencia temporal de las frequencias y los patrones devariabilidad son similares a los observados en las líneas de emisión del viento en esta y otras estrellas Oef, lo cual sugiere que ambos fenómenos tienen probablemente el mismo origen, aunque éste siga todavía sin conocerse. Abstract in english We present the analysis of a multi-epoch spectroscopic monitoring campaign of the O6Iefstar ? Cep. Previous observations reported the existence of two modes of non-radial pulsations in this star. Our data reveal a much more complex situation. The frequency content of the power spectrum considerably [...] changes from one epoch to the other. We find no stable frequency that can unambiguously be attributed to pulsations. The epoch-dependence of the frequencies and variability patterns are similar to what is seen in the wind emission lines of this and other Oef stars, suggesting that both phenomena likely have the same, currently still unknown, origin.

J.M., Uuh-Sonda; G., Rauw; P., Eenens; L., Mahy; M., Palate; E., Gosset; C.A., Flores.

130

Beneficial Changes in Random Variables via Copulas: An Application to Insurance  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A risk-averse agent does not necessarily decrease the optimal insurance whenever a beneficial change in the distribution of final wealth occurs. This paper provides sufficient conditions to guarantee such a decrease. Beneficial changes can be induced by either a beneficial loss-distribution shift, by a modification of the dependence structure between the randomness sources, or by both of these. Conditions for each case are stated. Hadar-Seo and Meyer results turn out as special cases.

Tibiletti, Luisa

1995-01-01

131

Blind estimation of statistical properties of non-stationary random variables  

Science.gov (United States)

To identify or equalize wireless transmission channels, or alternatively to evaluate the performance of many wireless communication algorithms, coefficients or statistical properties of the used transmission channels are often assumed to be known or can be estimated at the receiver end. For most of the proposed algorithms, the knowledge of transmission channel statistical properties is essential to detect signals and retrieve data. To the best of our knowledge, most proposed approaches assume that transmission channels are static and can be modeled by stationary random variables (uniform, Gaussian, exponential, Weilbul, Rayleigh, etc.). In the majority of sensor networks or cellular systems applications, transmitters and/or receivers are in motion. Therefore, the validity of static transmission channels and the underlying assumptions may not be valid. In this case, coefficients and statistical properties change and therefore the stationary model falls short of making an accurate representation. In order to estimate the statistical properties (represented by the high-order statistics and probability density function, PDF) of dynamic channels, we firstly assume that the dynamic channels can be modeled by short-term stationary but long-term non-stationary random variable (RV), i.e., the RVs are stationary within unknown successive periods but they may suddenly change their statistical properties between two successive periods. Therefore, this manuscript proposes an algorithm to detect the transition phases of non-stationary random variables and introduces an indicator based on high-order statistics for non-stationary transmission which can be used to alter channel properties and initiate the estimation process. Additionally, PDF estimators based on kernel functions are also developed. The first part of the manuscript provides a brief introduction for unbiased estimators of the second and fourth-order cumulants. Then, the non-stationary indicators are formulated. Finally, simulation results are presented and conclusions are derived.

Mansour, Ali; Mesleh, Raed; Aggoune, el-Hadi M.

2014-12-01

132

Aleatoriedade e variabilidade produtiva de feijão-de-vagem / Randomness and variability productive of bean pod  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Com o objetivo de estudar a aleatoriedade e a variabilidade produtiva de feijão-de-vagem, foram realizados os seguintes experimentos em branco: 1) em estufa no outono-inverno; 2) em túnel no outono-inverno; 3) em ambiente não protegido no outono-inverno; 4) em túnel na primavera-verão; e 5) em ambie [...] nte não protegido na primavera-verão. A variável mensurada foi a fitomassa fresca de vagens. Foram realizados estudos por colheita e por agrupamentos de colheitas. Foram planejados diferentes tamanhos de parcela e, para cada um, foram realizados testes de homogeneidade de variâncias entre as fileiras de cultivo e entre as colheitas, e testes de aleatoriedade em cada fileira de cultivo. A não aleatoriedade e a variabilidade da produção de fitomassa fresca de vagens são maiores em condições meteorológicas adversas a cultura do feijão-de-vagem e diminuem com o aumento do tamanho de parcela. O uso de parcelas constituídas por seis unidades básicas (12 plantas), em ambiente protegido ou não protegido, torna a produção de fitomassa fresca de vagens aleatória e proporciona menor variabilidade entre fileiras de cultivo e entre colheitas. Abstract in english With the aim of studying the randomness and variability of productive bean pod, the following experiments were performed on white: 1) in greenhouse in autumn-winter, 2) in tunnel in autumn-winter, 3) in unprotected environment in autumn-winter, 4) in tunnel in spring-summer and 5) in unprotected env [...] ironment in spring-summer. The variable measured was the fresh weight of pods. Studies were conducted by harvest and harvest groupings. Were planned different plot sizes, and for each, were conducted tests of homogeneity of variances between crop row and between harvests, and tests of randomness in each crop row. The non-randomness and variability in production of fresh pods are larger in adverse weather conditions the culture of the bean pod and decrease with increasing plot size. The use of plots consisting of six basic units (12 plants) in protected or unprotected makes the production of fresh pods random and provides lower variability between rows and between harvests.

Daniel, Santos; Fernando Machado, Haesbaert; Alessandro Dal' Col, Lúcio; Sidinei José, Lopes; Alberto, Cargnelutti Filho; Vilson, Benz.

133

Rearrangement Invariant Norms of Symmetric Sequence Norms of Independent Sequences of Random Variables  

CERN Multimedia

Let X_1, X_2,..., X_n be a sequence of independent random variables, let M be a rearrangement invariant space on the underlying probability space, and let N be a symmetric sequence space. This paper gives an approximate formula for the quantity || ||(X_i)||_N ||_M whenever L_q embeds into M for some 1 le q < infty. This extends work of Johnson and Schechtman who tackled the cases when N = l_1 or N = l_2, and recent work of Gordon, Litvak, Schuett and Werner who obtained similar results for Orlicz spaces.

Montgomery-Smith, S J

2001-01-01

134

Order-distance and other metric-like functions on jointly distributed random variables  

CERN Document Server

We construct a class of real-valued nonnegative binary functions on a set of jointly distributed random variables, which satisfy the triangle inequality and vanish at identical arguments (pseudo-quasi-metrics). These functions are useful in dealing with the problem of selective probabilistic causality encountered in behavioral sciences and in quantum physics. The problem reduces to that of ascertaining the existence of a joint distribution for a set of variables with known distributions of certain subsets of this set. Any violation of the triangle inequality or its consequences by one of our functions when applied to such a set rules out the existence of this joint distribution. We focus on an especially versatile and widely applicable pseudo-quasi-metric called an order-distance and its special case called a classification distance.

Dzhafarov, Ehtibar N

2011-01-01

135

Gametocytes infectiousness to mosquitoes: variable selection using random forests, and zero inflated models  

CERN Document Server

Malaria control strategies aiming at reducing disease transmission intensity may impact both oocyst intensity and infection prevalence in the mosquito vector. Thus far, mathematical models failed to identify a clear relationship between Plasmodium falciparum gametocytes and their infectiousness to mosquitoes. Natural isolates of gametocytes are genetically diverse and biologically complex. Infectiousness to mosquitoes relies on multiple parameters such as density, sex-ratio, maturity, parasite genotypes and host immune factors. In this article, we investigated how density and genetic diversity of gametocytes impact on the success of transmission in the mosquito vector. We analyzed data for which the number of covariates plus attendant interactions is at least of order of the sample size, precluding usage of classical models such as general linear models. We then considered the variable importance from random forests to address the problem of selecting the most influent variables. The selected covariates were ...

Genuer, Robin; Toussile, Wilson

2011-01-01

136

An uncertainty conserving probability/possibility transformation for the combined treatment of random and fuzzy variables  

International Nuclear Information System (INIS)

Different formalisms can be applied to decision-making problems with uncertain quantities. If the information is given by a large number of statistical data, the corresponding parameters can be interpreted as random variables and the results can be calculated by the rules of the probability theory. If the information consists however of subjective expert knowledge, the parameters can be interpreted as fuzzy variables and the results can be calculated by the rules of possibility theory. If both kinds of information appear in a problem with several parameters, transformations between probability and possibility distributions are necessary to make the problem treatable within one formalism. A probability/possibility transformation that fulfills simultaneously the consistency principle and conserves uncertainty is presented. For the implementation of expert knowledge into a probablistic framework, it is an alternative to the method of unbiased guess

1994-09-14

137

Frequency and temperature dependent mobility of a charged carrier and randomly interrupted strand  

International Nuclear Information System (INIS)

Randomly interrupted strand model of a one-dimensional conductor is considered. Exact analytical expression is obtained for the temperature dependent as mobility for a finite segment drawn at random, taking into account the reflecting barriers at the two open ends. The real part of mobility shows a broad resonance as a function of both frequency and tempeature, and vanishes quadratically in the dc limit. The frequency (temperature) maximum shifts to higher values for higher temperatures (frequencies). (author)

1981-01-01

138

Producto de variables aleatorias independentes que involucran variables con función hipergeométrica invertida de tipo I Product of independent random variables involving inverted hypergeometric function type I variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

La distribución de función hipergeométrica invertida tipo I tiene la función de densidad de probabilidad proporcional a [fórmula] donde 2F1 es la función hipergeométrica de Gauss. En este artículo se deriva la función de densidad de probabilidad del producto de dos variables aleatorias independientes que se distribuyen según la función hipergeométrica inversa tipo I. También se consideran otros productos entre variables aleatorias con distribución beta tipo I, beta tipo II, beta...

Edwin Zarrazola; Nagar, Daya K.

2009-01-01

139

A functional CLT for the occupation time of state-dependent branching random walk  

CERN Document Server

We show that the centred occupation time process of the origin of a system of critical binary branching random walks in dimension $d \\ge 3$, started off either from a Poisson field or in equilibrium, when suitably normalised, converges to a Brownian motion in $d \\ge 4$. In $d=3$, the limit process is fractional Brownian motion with Hurst parameter 3/4 when starting in equilibrium, and a related Gaussian process when starting from a Poisson field. For (dependent) branching random walks with state dependent branching rate we obtain convergence in f.d.d. to the same limit process, and for $d=3$ also a functional limit theorem.

Birkner, M; Birkner, Matthias; Z\\"ahle, Iljana

2007-01-01

140

Multivariant logit models for ordinal scale-dependent variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In dieser Arbeit wird gezeigt, wie multivariate Modelle geschätzt werden können, bei denen die abhängige Variable auf Ordinalskalenniveau vorliegt. Solche Variablen kommen in soziologischen Untersuchungen relativ häufig vor, manche Autoren vertreten sogar die Meinung, daß ein höheres Skalenniveau bei sozialwissenschaftlichen Messungen kaum erreichbar ist. Während Prüfverfahren für bivariate Zusammenhänge bzw. für Gruppenvergleiche mit ordinalskalierten Variablen seit langem im sozi...

1990-01-01

 
 
 
 
141

Diffusion of a quantum particle in time-dependent random potential  

Digital Repository Infrastructure Vision for European Research (DRIVER)

For Schrödinger equation for a particle moving in random, time-dependent potential with white noise correlation, we prove that perturbation theory result for mean square displacement X?t3/2 is asymptotically exact for a large time t. This is in contrast with the same equation with imaginary time.

Lebedev, N.; Sokoloff, D.; Kaganovich, A.

1991-01-01

142

Renormalization flow for extreme value statistics of random variables raised to a varying power  

CERN Multimedia

Using a renormalization approach, we study the asymptotic limit distribution of the maximum value in a set of independent and identically distributed random variables raised to a power q(n) that varies monotonically with the sample size n. Under these conditions, a non-standard class of max-stable limit distributions, which mirror the classical ones, emerges. Furthermore a transition mechanism between the classical and the non-standard limit distributions is brought to light. If q(n) grows slower than a characteristic function q*(n), the standard limit distributions are recovered, while if q(n) behaves asymptotically as k.q*(n), non-standard limit distributions emerge.

Angeletti, Florian; Abry, Patrice

2011-01-01

143

Convergence Rates for Probabilities of Moderate Deviations for Multidimensionally Indexed Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available Let {X,Xn¯;n¯?Z+d} be a sequence of i.i.d. real-valued random variables, and Sn¯=?k¯?n¯Xk¯, n¯?Z+d. Convergence rates of moderate deviations are derived; that is, the rates of convergence to zero of certain tail probabilities of the partial sums are determined. For example, we obtain equivalent conditions for the convergence of the series ?n¯b(n¯?2(a(n¯P{|Sn¯|?a(n¯?(a(n¯}, where a(n¯=n11/?1?nd1/?d, b(n¯=n1?1?nd?d, ? and ? are taken from a broad class of functions. These results generalize and improve some results of Li et al. (1992 and some previous work of Gut (1980.

Dianliang Deng

2009-01-01

144

Asymptotic expansions for the Laplace approximations of sums of Banach space-valued random variables  

CERN Document Server

Let X_i, i\\in N, be i.i.d. B-valued random variables, where B is a real separable Banach space. Let \\Phi be a smooth enough mapping from B into R. An asymptotic evaluation of Z_n=E(\\exp (n\\Phi (\\sum_{i=1}^nX_i/n))), up to a factor (1+o(1)), has been gotten in Bolthausen [Probab. Theory Related Fields 72 (1986) 305-318] and Kusuoka and Liang [Probab. Theory Related Fields 116 (2000) 221-238]. In this paper, a detailed asymptotic expansion of Z_n as n\\to \\infty is given, valid to all orders, and with control on remainders. The results are new even in finite dimensions.

Albeverio, S; Albeverio, Sergio; Liang, Song

2005-01-01

145

A Methodological Note on the Convergence of Sequences of Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this note is to present a new point of view for introducing all well-known modes of convergence of sequences of random variables. In the one hand, we start from two noteworthy sets in convergence viz $T_{j,\\epsilon}$ and $S_{j,\\epsilon}$. The consideration of certain progressive assumptions on both $T_{j,\\epsilon}$ and $S_{j,\\epsilon}$ gives rise to a part of convergence concepts going from uniform convergence to convergence in probability. On the other hand, some key inequalities implies the rest of convergence concepts whose link with the former scheme lies in uniform and in probability convergence which end the circle of convergence modes. Moreover, all these steps are illustrated with their respective methodological charts.

Salvador Cruz Rambaud

2012-10-01

146

Marcinkiewicz-type strong law of large numbers for double arrays of pairwise independent random variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Let {Xij} be a double sequence of pairwise independent random variables. If P{|Xmn|≥t}≤P{|X|≥t} for all nonnegative real numbers t and E|X|p(log+|X|)3<∞, for 1

1999-01-01

147

Mean convergence theorems and weak laws of large numbers for double arrays of random variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

For a double array of random variables {Xmn, m ≥ 1, n ≥ 1}, mean convergence theorems and weak laws of large numbers are established. For the mean convergence results, conditions are provided under which ∑i=1km∑j=1lnamnij(Xij−EXij)→Lr0(0

Le Van Thanh

2006-01-01

148

Instance-Dependent Verifiable Random Functions and Their Application to Simultaneous Resettability  

Science.gov (United States)

We introduce a notion of instance-dependent verifiable random functions (InstD-VRFs for short). Informally, an InstD-VRF is, in some sense, a verifiable random function [23] with a special public key, which is generated via a (possibly)interactive protocol and contains an instance y ? L ? {0,1}* for a specific NP language L, but the security requirements on such a function are relaxed: we only require the pseudorandomness property when y ? L and only require the uniqueness property when y ? L, instead of requiring both pseudorandomness and uniqueness to hold simultaneously. We show that this notion can be realized under standard assumption.

Deng, Yi; Lin, Dongdai

149

The Distribution of Minimum of Ratios of Two Random Variables and Its Application in Analysis of Multi-hop Systems  

Directory of Open Access Journals (Sweden)

Full Text Available The distributions of random variables are of interest in many areas of science. In this paper, ascertaining on the importance of multi-hop transmission in contemporary wireless communications systems operating over fading channels in the presence of cochannel interference, the probability density functions (PDFs of minimum of arbitrary number of ratios of Rayleigh, Rician, Nakagami-m, Weibull and ?-µ random variables are derived. These expressions can be used to study the outage probability as an important multi-hop system performance measure. Various numerical results complement the proposed mathematical analysis.

A. Stankovic

2012-12-01

150

Advantages of joint modeling of component HIV risk behaviors and non-response: application to randomized trials in cocaine-dependent and methamphetamine-dependent populations  

Directory of Open Access Journals (Sweden)

Full Text Available The HIV risk-taking behavior scale (HRBS is an 11-item instrument designed to assess the risks of HIV infection due self-reported injection drug use and sexual behavior. A retrospective analysis was performed on HRBS data collected from approximately 1,000 participants pooled across seven clinical trials of pharmacotherapies for either the treatment of cocaine-dependence or methamphetamine-dependence. Analysis faced three important challenges. The sample contained a high proportion of missing assessments after randomization. Also, the HRBS scale consists of two distinct behavioral components which may or may not coincide in response patterns. In addition, distributions of responses on the subscales were highly concentrated at just a few values (e.g., 0, 6. To address these challenges, a single probit regression model was fit to three outcomes variables simultaneously—the two subscale totals plus an indicator variable for assessments not obtained (non-response. This joint-outcome regression model was able to identify that those who left assessment early had higher self-reported risk of injection-drug use and lower self-reported risky sexual behavior because the model was able to draw on information on associations among the three outcomes collectively. These findings were not identified in analyses performed on each outcome separately. No evidence for an effect of pharmacotherapies was observed, except to reduce missing assessments. Univariate-outcome modeling is not recommended for the HRBS.

TysonHHolmes

2011-07-01

151

Marcinkiewicz-type strong law of large numbers for double arrays of pairwise independent random variables  

Directory of Open Access Journals (Sweden)

Full Text Available Let {Xij} be a double sequence of pairwise independent random variables. If P{|Xmn|≥t}≤P{|X|≥t} for all nonnegative real numbers t and E|X|p(log+|X|3<∞, for 1random variables under the conditions E|X|p(log+|X|r+1<∞,E|X|p(log+|X|r−1<∞, respectively, thus, extending Choi and Sung's result [1] of the one-dimensional case.

Seok Yoon Hwang

1999-03-01

152

Dopant size dependent variable range hopping conduction in polyaniline nanorods  

Science.gov (United States)

The present work investigates the electrical transport and dielectric relaxation of polyaniline (PAni) nanorods doped with organic camphorsulfonic acid (CSA) and inorganic hydrochloric acid (HCl) synthesized by interfacial polymerization technique. High resolution transmission electron micrographs (HRTEM) depict that initially spherical nuclei directionally grow into nanorods and CSA doped PAni produces more uniform and aligned structures. The electrical transport studies reveal that the CSA doped nanorods follow 1D Mott variable-range hopping (VRH), whereas the HCl doped nanorods exhibit 2D VRH conduction mechanism. The value of interchain charge transfer integral is found to be higher for smaller size HCl doped PAni than that for larger size CSA doped PAni. The resistivity measurements exhibit semiconducting behavior for both organic and inorganic dopants and the resistivity of the CSA doped nanorods is found to be smaller than that of the HCl doped nanorods. The dielectric relaxation studies suggest Debye type relaxation with a single relaxation peak for both the dopants and the relaxation time of the carriers of the CSA doped PAni nanorods is smaller than that of the HCl doped nanorods.

Chutia, P.; Nath, Chandrani; Kumar, A.

2014-06-01

153

Ergodic properties of continuous-time random walks: finite-size effects and ensemble dependences  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effects of spatial confinements and smooth cutoffs of the waiting time distribution in continuous-time random walks (CTRWs) are studied analytically. We also investigate dependences of ergodic properties on initial ensembles (i.e., distributions of the first waiting time). Here, we consider two ensembles: the equilibrium and a typical non-equilibrium ensembles. For both ensembles, it is shown that the time-averaged mean square displacement (TAMSD) exhibits a crossover fr...

Miyaguchi, Tomoshige; Akimoto, Takuma

2012-01-01

154

On Rates of Convergence for Markov Chins under Random Time State Dependent Drift Criteria  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Many applications in networked control require intermittent access of a controller to a system, as in event-triggered systems or information constrained control applications. Motivated by such applications and extending the literature on Lyapunov-theoretic drift criteria, we establish both subgeometric and geometric rates rates of convergence for Markov chains under state dependent random time drift criteria. We quantify how the rate of ergodicity, nature of Lyapunov functio...

Zurkowski, Ramiro; Yu?ksel, Serdar; Linder, Tama?s

2013-01-01

155

Energy absorption in time-dependent unitary random matrix ensembles: dynamic vs Anderson localization  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We consider energy absorption in an externally driven complex system of noninteracting fermions with the chaotic underlying dynamics described by the unitary random matrices. In the absence of quantum interference the energy absorption rate W(t) can be calculated with the help of the linear-response Kubo formula. We calculate the leading two-loop interference correction to the semiclassical absorption rate for an arbitrary time dependence of the external perturbation. Based ...

Skvortsov, M. A.; Basko, D. M.; Kravtsov, V. E.

2004-01-01

156

The limit distribution of the maximum increment of a random walk with dependent regularly varying jump sizes  

DEFF Research Database (Denmark)

We investigate the maximum increment of a random walk with heavy-tailed jump size distribution. Here heavy-tailedness is understood as regular variation of the finite-dimensional distributions. The jump sizes constitute a strictly stationary sequence. Using a continuous mapping argument acting on the point processes of the normalized jump sizes, we prove that the maximum increment of the random walk converges in distribution to a Fréchet distributed random variable.

Mikosch, Thomas Valentin; Moser, Martin

2013-01-01

157

Bell-Boole Inequality: Nonlocality or Probabilistic Incompatibility of Random Variables?  

Directory of Open Access Journals (Sweden)

Full Text Available The main aim of this report is to inform the quantum information community about investigations on the problem of probabilistic compatibility of a family of random variables: a possibility to realize such a family on the basis of a single probability measure (to construct a single Kolmogorov probability space. These investigations were started hundred of years ago by J. Boole (who invented Boolean algebras. The complete solution of the problem was obtained by Soviet mathematician Vorobjev in 60th. Surprisingly probabilists and statisticians obtained inequalities for probabilities and correlations among which one can find the famous Bell’s inequality and its generalizations. Such inequalities appeared simply as constraints for probabilistic compatibility. In this framework one can not see a priori any link to such problems as nonlocality and “death of reality” which are typically linked to Bell’s type inequalities in physical literature. We analyze the difference between positions of mathematicians and quantum physicists. In particular, we found that one of the most reasonable explanations of probabilistic incompatibility is mixing in Bell’s type inequalities statistical data from a number of experiments performed under different experimental contexts.

Andrei Khrennikov

2008-03-01

158

High confidence estimates of the mean of heavy-tailed real random variables  

CERN Document Server

We present new estimators of the mean of a real valued random variable, based on PAC-Bayesian iterative truncation. We analyze the non-asymptotic minimax properties of the deviations of estimators for distributions having either a bounded variance or a bounded kurtosis. It turns out that these minimax deviations are of the same order as the deviations of the empirical mean estimator of a Gaussian distribution. Nevertheless, the empirical mean itself performs poorly at high confidence levels for the worst distribution with a given variance or kurtosis (which turns out to be heavy tailed). To obtain (nearly) minimax deviations in these broad class of distributions, it is necessary to use some more robust estimator, and we describe an iterated truncation scheme whose deviations are close to minimax. In order to calibrate the truncation and obtain explicit confidence intervals, it is necessary to dispose of a prior bound either on the variance or the kurtosis. When a prior bound on the kurtosis is available, we o...

Catoni, Olivier

2009-01-01

159

Reliability estimation of buried gas pipelines in terms of various types of random variable distribution  

International Nuclear Information System (INIS)

This paper presents the effects of corrosion environments of failure pressure model for buried pipelines on failure prediction by using a failure probability. The FORM(First Order Reliability Method) is used in order to estimate the failure probability in the buried pipelines with corrosion defects. The effects of varying distribution types of random variables such as normal, longnormal and Weibull distributions on the failure probability of buried pipelines are systematically investigated. It is found that the failure probability for the MB31G model is larger than that for the B31G model. And the failure probability is estimated as the largest for the Weibull distribution and the smallest for the normal distribution. The effect of data scattering in corrosion environments on failure probability is also investigated and it is recognized that the scattering of wall thickness and yield strength of pipeline affects the failure probability significantly. The normalized margin is defined and estimated. Furthermore, the normalized margin is used to predict the failure probability using the fitting lines between failure probability and normalized margin

2005-06-01

160

A ratio-cum-product estimator of population mean in stratified random sampling using two auxiliary variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper proposes a ratio-cum-product estimator of finite population mean in stratified random sampling using information on population means of two auxiliary variables. The bias and mean squared error expressions are derived under large sample approximations. Proposed estimator has been compared with usual unbiased estimator in stratified sampling, combined ratio estimator and combined product estimator theoretically as well as empirically.

Rajesh Tailor; Sunil Chouhan; Ritesh Tailor; Neha Garg

2012-01-01

 
 
 
 
161

Detection of Genetic Variability using Random Amplified Polymorphic DNA Markers in Some Accessions of Moringa oleifera Lam. from Northern Nigeria  

Directory of Open Access Journals (Sweden)

Full Text Available To investigate genetic variability in Moringa oleifera Lam., 75 accessions from the Sudan and Guinea savanna zones in Nigeria were taxonomically analysed using Random Amplified polymorphic DNA (RAPD markers. The electrophoresis bands were analysed using NTSYSpc software and the result of their matrices indicated different variability in the accessions. High degrees of polymorphism (74% among the accessions were observed in terms of genetic relationship and were grouped into five clusters. This high variability can be utilised for mapping out breeding strategies in the production of cultivars with better yield of M. oleifera to meet the pressing needs of these multi-purpose crop to our growing populations.

A.U. Khan

2011-01-01

162

Generalized Hoeffding-Sobol Decomposition for Dependent Variables -Application to Sensitivity Analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we consider a regression model built on dependent variables. This regression modelizes an input output relationship. Under boundedness assumptions on the joint distribution function of the input variables, we show that a generalized Hoeffding-Sobol decomposition is available. This leads to new indices measuring the sensitivity of the output with respect to the input variables. We also study and discuss the estimation of these new indices.

Chastaing, Gae?lle; Gamboa, Fabrice; Prieur, Cle?mentine

2011-01-01

163

Fault-Tolerant Facility Location: a randomized dependent LP-rounding algorithm  

CERN Document Server

We give a new randomized LP-rounding 1.725-approximation algorithm for the metric Fault-Tolerant Uncapacitated Facility Location problem. This improves on the previously best known 2.076-approximation algorithm of Swamy & Shmoys. To the best of our knowledge, our work provides the first application of a dependent-rounding technique in the domain of facility location. The analysis of our algorithm benefits from, and extends, methods developed for Uncapacitated Facility Location; it also helps uncover new properties of the dependent-rounding approach. An important concept that we develop is a novel, hierarchical clustering scheme. Typically, LP-rounding approximation algorithms for facility location problems are based on partitioning facilities into disjoint clusters and opening at least one facility in each cluster. We extend this approach and construct a laminar family of clusters, which then guides the rounding procedure. It allows to exploit properties of dependent rounding, and provides a quite tight a...

Byrka, Jaroslaw; Swamy, Chaitanya

2010-01-01

164

Randomness Effect on the Temperature Dependence of the Finite Field Magnetization of a One-Dimensional Spin Gapped System  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate the temperature dependence of the finite-field magnetization of the S=1/2 bond-alternating XY model in the Random magnetic field along the z-direction having the Lorentzian distribution. The random-averaged free energy can be exactly calculated, which enables us to obtain the thermodynamical quantities. The temperature dependence of the finite-field magnetization shows various behaviors depending on the parameters $\\delta$ and $\\Gamma$, where $\\delta$ and $\\Ga...

Okamoto, Kiyomi

2013-01-01

165

Genetic variability of Amorphophallus muelleri Blume in Java based on Random Amplified Polymorphic DNA  

Directory of Open Access Journals (Sweden)

Full Text Available Amorphophallus muelleri Blume (Araceae is valued for its glucomanan content for use in food industry (healthy diet food, paper industry, pharmacy and cosmetics. The species is triploid (2n=3x=39 and the seed is developed apomictically. The present research is aimed to identify genetic variability of six population of A. muelleri from Java (consisted of 50 accessions using random amplified polymorphic DNA (RAPD. The six populations of the species are: East Java: (1 Silo-Jember, (2 Saradan-Madiun, (3 IPB (cultivated, from Saradan-Madiun, (4 Panti-Jember, (5 Probolinggo; and Central Java: (6 Cilacap. The results showed that five RAPD primers generated 42 scorable bands of which 29 (69.05% were polymorphic. Size of the bands varied from 300bp to 1.5kbp. The 50 accessions of A. muelleri were divided into two main clusters, some of them were grouped based on their populations, and some others were not. The range of individual genetic dissimilarity was from 0.02 to 0.36. The results showed that among six populations investigated, Saradan population showed the highest levels of genetic variation with mean values of na = 1.500+ 0.5061, ne = 1.3174 + 0.3841, PLP = 50% and He = 0, 0.1832+0.2054, whereas Silo-Jember population showed the lowest levels of genetic variation with mean values na = 1.2619+ 0.4450, ne = 1.1890 + 0.3507, PLP = 26.19% and He = 0.1048+0.1887. Efforts to conserve, domesticate, cultivate and improve genetically should be based on the genetic properties of each population and individual within population, especially Saradan population which has the highest levels of genetic variation, need more attention for its conservation.

DIYAH MARTANTI

2008-10-01

166

Variable versus conventional lung protective mechanical ventilation during open abdominal surgery: study protocol for a randomized controlled trial  

Science.gov (United States)

Background General anesthesia usually requires mechanical ventilation, which is traditionally accomplished with constant tidal volumes in volume- or pressure-controlled modes. Experimental studies suggest that the use of variable tidal volumes (variable ventilation) recruits lung tissue, improves pulmonary function and reduces systemic inflammatory response. However, it is currently not known whether patients undergoing open abdominal surgery might benefit from intraoperative variable ventilation. Methods/Design The PROtective VARiable ventilation trial (‘PROVAR’) is a single center, randomized controlled trial enrolling 50 patients who are planning for open abdominal surgery expected to last longer than 3 hours. PROVAR compares conventional (non-variable) lung protective ventilation (CV) with variable lung protective ventilation (VV) regarding pulmonary function and inflammatory response. The primary endpoint of the study is the forced vital capacity on the first postoperative day. Secondary endpoints include further lung function tests, plasma cytokine levels, spatial distribution of ventilation assessed by means of electrical impedance tomography and postoperative pulmonary complications. Discussion We hypothesize that VV improves lung function and reduces systemic inflammatory response compared to CV in patients receiving mechanical ventilation during general anesthesia for open abdominal surgery longer than 3 hours. PROVAR is the first randomized controlled trial aiming at intra- and postoperative effects of VV on lung function. This study may help to define the role of VV during general anesthesia requiring mechanical ventilation. Trial registration Clinicaltrials.gov NCT01683578 (registered on September 3 3012).

2014-01-01

167

Genetic variability in the NMDA-dependent AMPA trafficking cascade is associated with alcohol dependence.  

Science.gov (United States)

Model studies in mice indicate that the severity of alcohol withdrawal is associated with polymorphic variation and expression of the MPDZ gene. Current knowledge about variation in the human MPDZ gene is limited; however, our data indicate its potential association with alcohol dependence. The multi-PDZ protein is an important part of the N-methyl-D-aspartate (NMDA)-dependent ?-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor trafficking cascade that controls glutamate-related excitatory neurotransmission. To investigate association of variation in the NMDA-dependent AMPA trafficking cascade with alcohol dependence, we performed a gene-set (pathway) analysis using single nucleotide polymorphism (SNP) data from the Study of Addiction: Genetic and Environment. Rather than testing for association with each SNP individually, which typically has low power to detect small effects of multiple SNPs, gene-set analysis applies a single statistical test to evaluate whether variation in a set of genes is associated with the phenotype of interest. Gene-set analysis of 988 SNPs in 13 genes in the pathway demonstrated a significant association with alcohol dependence, with P < 0.01 for the global effect of variation in this pathway. The statistically significant association of alcohol dependence with genetic variation in the NMDA-dependent AMPA receptor trafficking cascade indicates a need for further investigation of the role of this pathway in alcohol dependence. PMID:21762291

Karpyak, Victor M; Geske, Jennifer R; Colby, Colin L; Mrazek, David A; Biernacka, Joanna M

2012-07-01

168

Genetic variability in the NMDA-dependent AMPA trafficking cascade is associated with alcohol dependence  

Science.gov (United States)

Model studies in mice indicate that the severity of alcohol withdrawal is associated with polymorphic variation and expression of the MPDZ gene. Current knowledge about variation in the human MPDZ gene is limited; however, our data indicate its potential association with alcohol dependence. The MPDZ protein is an important part of the NMDA-dependent AMPA receptor trafficking cascade that controls glutamate-related excitatory neurotransmission. To investigate association of variation in the NMDA-dependent AMPA trafficking cascade with alcohol dependence, we performed a gene-set (pathway) analysis using single nucleotide polymorphism (SNP) data from the Study of Addiction: Genetic and Environment (SAGE). Rather than testing for association with each SNP individually, which typically has low power to detect small effects of multiple SNPs, gene set analysis applies a single statistical test to evaluate whether variation in a set of genes is associated with the phenotype of interest. Gene-set analysis of 988 SNPs in 13 genes in the pathway demonstrated a significant association with alcohol dependence, with p<0.01 for the global effect of variation in this pathway. The statistically significant association of alcohol dependence with genetic variation in the NMDA-dependent AMPA receptor trafficking cascade indicates a need for further investigation of the role of this pathway in alcohol dependence.

Karpyak, V.M.; Geske, J.R.; Colby, C.L.; Mrazek, D.A.; Biernacka, J.M.

2011-01-01

169

Application of the random ball test for calibrating slope-dependent errors in profilometry measurements.  

Science.gov (United States)

Optical profilometers such as scanning white light interferometers and confocal microscopes provide high-resolution measurements and are widely utilized in many fields for measuring surface topography. Slope-dependent systematic errors can be present in the measurement and can be the same order of magnitude as features on the surface to be measured. We propose a self-calibration technique, the random ball test (RBT), for calibrating slope-dependent errors of such instruments. The calibration result can be used to compensate future measurements of similar spherical geometries such as profiles of refractive microlenses. A simulation study validates the approach and shows that the RBT is effective in practical limits. We demonstrate the calibration on a 50× confocal microscope and find a surface slope-dependent bias that increases monotonically with the magnitude of the surface slope and is as large as ?800??nm at a surface slope of 12°. The uncertainty of the calibration is smaller than the observed measurement bias and is dominated by residual random noise. Effects such as drift and ball radius uncertainty were investigated to understand their contribution to the calibration uncertainty. PMID:24084993

Zhou, Yue; Ghim, Young-Sik; Fard, Ali; Davies, Angela

2013-08-20

170

Genetic variability in the NMDA-dependent AMPA trafficking cascade is associated with alcohol dependence  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Model studies in mice indicate that the severity of alcohol withdrawal is associated with polymorphic variation and expression of the MPDZ gene. Current knowledge about variation in the human MPDZ gene is limited; however, our data indicate its potential association with alcohol dependence. The MPDZ protein is an important part of the NMDA-dependent AMPA receptor trafficking cascade that controls glutamate-related excitatory neurotransmission. To investigate association of variation in the NM...

Karpyak, V. M.; Geske, J. R.; Colby, C. L.; Mrazek, D. A.; Biernacka, J. M.

2012-01-01

171

Cryptography based on chaotic random maps with position dependent weighting probabilities  

International Nuclear Information System (INIS)

Chaotic cryptology has been widely investigated recently. A common feature in the most recent developments of chaotic cryptosystems is the use of a single dynamical rule in the encoding-decoding process. The main objective of this paper is to provide a set of chaotic systems instead of a single one for cryptography. In this paper, we introduce a chaotic cryptosystem based on the symbolic dynamics of random maps with position dependent weighting probabilities. The random maps model is a deterministic dynamical system in a finite phase space with n points. The maps that establish the dynamics of the system are chosen randomly for every point. The essential idea of this paper is that, given two dynamical systems that behave in a certain way, it is possible to combine them (by composing) into a new dynamical system. This dynamically composed system behaves in a completely different way compared to the constituent systems. The proposed scheme exploits the symbolic dynamics of a set of chaotic maps in order to encode the binary information. The performance of the new cryptosystem based on chaotic dynamical systems properties is examined. Both theoretical and experimental results demonstrate that the proposed algorithm using symbolic dynamics achieves the optimal security criteria.

2009-04-15

172

Emergence of context-dependent variability across a basal ganglia network.  

Science.gov (United States)

Context dependence is a key feature of cortical-basal ganglia circuit activity, and in songbirds the cortical outflow of a basal ganglia circuit specialized for song, LMAN, shows striking increases in trial-by-trial variability and bursting when birds sing alone rather than to females. To reveal where this variability and its social regulation emerge, we recorded stepwise from corticostriatal (HVC) neurons and their target spiny and pallidal neurons in Area X. We find that corticostriatal and spiny neurons both show precise singing-related firing across both social settings. Pallidal neurons, in contrast, exhibit markedly increased trial-by-trial variation when birds sing alone, created by highly variable pauses in firing. This variability persists even when recurrent inputs from LMAN are ablated. These data indicate that variability and its context sensitivity emerge within the basal ganglia network, suggest a network mechanism for this emergence, and highlight variability generation and regulation as basal ganglia functions. PMID:24698276

Woolley, Sarah C; Rajan, Raghav; Joshua, Mati; Doupe, Allison J

2014-04-01

173

A double-blind randomized controlled trial of N-acetylcysteine in cannabis-dependent adolescents  

Science.gov (United States)

Objective Preclinical findings suggest that the over-the-counter supplement N-acetylcysteine, via glutamate modulation in the nucleus accumbens, holds promise as a pharmacotherapy targeting substance dependence. We sought to investigate N-acetylcysteine as a novel cannabis cessation treatment in adolescents, a vulnerable group for whom existing treatments have limited efficacy. Method In this 8-week double-blind randomized placebo-controlled trial, treatment-seeking cannabis-dependent adolescents (age 15-21, N = 116) received N-acetylcysteine (1200 mg) or placebo twice daily, each added to a contingency management intervention and brief (?10 minute) weekly cessation counseling. The primary efficacy measure was the odds of negative weekly urine cannabinoid tests during treatment among participants receiving N-acetylcysteine versus placebo, via intent-to-treat analysis. The primary tolerability measure was frequency of adverse events, compared by treatment group. Results N-acetylcysteine was well tolerated with minimal adverse events. N-acetylcysteine participants had more than twice the odds, compared to placebo participants, of submitting negative urine cannabinoid tests during treatment (odds ratio = 2.4, [95% CI: 1.1-5.2], p = 0.029). Exploratory secondary abstinence outcomes numerically favored N-acetylcysteine, but were not statistically significant. Conclusions This is the first randomized trial of pharmacotherapy for cannabis dependence in any age group yielding a positive primary cessation outcome via intent-to-treat analysis. Findings support N-acetylcysteine as a pharmacotherapy to complement psychosocial treatment for cannabis dependence in adolescents. Further research is needed to replicate these findings and explore the efficacy of N-acetylcysteine across a variety of treatment contexts and outcomes. Trial Registration clinicaltrials.gov identifier: NCT 01005810

Gray, Kevin M.; Carpenter, Matthew J.; Baker, Nathaniel L.; DeSantis, Stacia M.; Kryway, Elisabeth; Hartwell, Karen J.; McRae-Clark, Aimee L.; Brady, Kathleen T.

2012-01-01

174

Complete Convergence and Weak Law of Large Numbers for ?-Mixing Sequences of Random Variables  

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In this paper, the complete convergence and weak law of large numbers are established for ?-mixing sequences of random variables. Our results extend and improve the Baum and Katz complete convergence theorem and the classical weak law of large numbers, etc. from independent sequences of random variables to ?-mixing sequences of random va...

Qunying Wu

2012-01-01

175

The distribution of the square sum of Dirichlet random variables and a table with quantiles of Greenwood's statistic  

CERN Multimedia

The exact distribution of the square sum of Dirichlet random variables is given by two different univariate integral representations. Alternatively, three representations by orthogonal series with Jacobi or Legendre polynomials are derived. As a special case the distribution of the square sum of spacings - also called Greenwood's statistic - is obtained. Nine quantiles of this statistic are tabulated with eight digits where the number of squares ranges from 10 to 100.

Royen, Thomas

2010-01-01

176

A ratio-cum-product estimator of population mean in stratified random sampling using two auxiliary variables  

Directory of Open Access Journals (Sweden)

Full Text Available This paper proposes a ratio-cum-product estimator of finite population mean in stratified random sampling using information on population means of two auxiliary variables. The bias and mean squared error expressions are derived under large sample approximations. Proposed estimator has been compared with usual unbiased estimator in stratified sampling, combined ratio estimator and combined product estimator theoretically as well as empirically.

Rajesh Tailor

2012-05-01

177

Letter to the Editor: On the stability and ranking of predictors from random forest variable importance measures  

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A recent study examined the stability of rankings from random forests using two variable importance measures (mean decrease accuracy (MDA) and mean decrease Gini (MDG)) and concluded that rankings based on the MDG were more robust than MDA. However, studies examining data-specific characteristics on ranking stability have been few. Rankings based on the MDG measure showed sensitivity to within-predictor correlation and differences in category frequencies, even when the number of categories wa...

Nicodemus, Kristin K.

2011-01-01

178

A note on the Marchenko-Pastur law for a class of random matrices with dependent entries  

CERN Document Server

We consider a class of real random matrices with dependent entries and show that the limiting empirical spectral distribution is given by the Marchenko-Pastur law. Additionally, we establish a rate of convergence of the expected empirical spectral distribution.

O'Rourke, Sean

2012-01-01

179

Spatial variability and its scale dependency of observed and modeled soil moisture over different climate regions  

Directory of Open Access Journals (Sweden)

Full Text Available Past studies on soil moisture spatial variability have been mainly conducted at catchment scales where soil moisture is often sampled over a short time period; as a result, the observed soil moisture often exhibited smaller dynamic ranges, which prevented the complete revelation of soil moisture spatial variability as a function of mean soil moisture. In this study, spatial statistics (mean, spatial variability and skewness of in situ soil moisture, modeled and satellite-retrieved soil moisture obtained in a warm season (198 days were examined over three large climate regions in the US. The study found that spatial moments of in situ measurements strongly depend on climates, with distinct mean, spatial variability and skewness observed in each climate zone. In addition, an upward convex shape, which was revealed in several smaller scale studies, was observed for the relationship between spatial variability of in situ soil moisture and its spatial mean when statistics from dry, intermediate, and wet climates were combined. This upward convex shape was vaguely or partially observable in modeled and satellite-retrieved soil moisture estimates due to their smaller dynamic ranges. Despite different environmental controls on large-scale soil moisture spatial variability, the correlation between spatial variability and mean soil moisture remained similar to that observed at small scales, which is attributed to the boundedness of soil moisture. From the smaller support (effective area or volume represented by a measurement or estimate to larger ones, soil moisture spatial variability decreased in each climate region. The scale dependency of spatial variability all followed the power law, but data with large supports showed stronger scale dependency than those with smaller supports. The scale dependency of soil moisture variability also varied with climates, which may be linked to the scale dependency of precipitation spatial variability. Influences of environmental controls on soil moisture spatial variability at large scales are discussed. The results of this study should be useful for diagnosing large scale soil moisture estimates and for improving the estimation of land surface processes.

B. Li

2013-03-01

180

Size-dependent mechanical properties of 2D random nanofibre networks  

Science.gov (United States)

The mechanical properties of nanofibre networks (NFNs) are size dependent with respect to different fibre diameters. In this paper, a continuum model is developed to reveal the size-dependent mechanical properties of 2D random NFNs. Since such size-dependent behaviours are attributed to different micromechanical mechanisms, the surface effects and the strain gradient (SG) effects are, respectively, introduced into the mechanical analysis of NFNs. Meanwhile, a modified fibre network model is proposed, in which the axial, bending and shearing deformations are incorporated. The closed-form expressions of effective modulus and Poisson's ratio are obtained for NFNs. Different from the results predicted by conventional fibre network model, the present model predicts the size-dependent mechanical properties of NFNs. It is found that both surface effects and SG effects have significant influences on the effective mechanical properties. Moreover, the present results show that the shearing deformation of fibre segment is also crucial to precisely evaluate the effective mechanical properties of NFNs. This work mainly aims to provide an insight into the micromechanical mechanisms of NFNs. Besides, this work is also expected to provide a more accurate theoretical model for 2D fibre networks.

Lu, Zixing; Zhu, Man; Liu, Qiang

2014-02-01

 
 
 
 
181

Genetic variability of cultivated cowpea in Benin assessed by random amplified polymorphic DNA  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Characterization of genetic diversity among cultivated cowpea [Vigna unguiculata (L.) Walp.] varieties is important to optimize the use of available genetic resources by farmers, local communities, researchers and breeders. Random amplified polymorphic DNA (RAPD) markers were used to evaluate the genetic diversity in 70 cowpea accessions collected throughout Benin. Nine random primers were screened on 24 accessions to assess their ability to reveal polymorphisms in cowpea and four of them wer...

2008-01-01

182

Factors Affecting Blood Pressure Variability: Lessons Learned from Two Systematic Reviews of Randomized Controlled Trials  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Systematic reviews can often reveal much more than the original objective of the work. The objectives of this retrospective analysis were to answer three basic questions about blood pressure variability: 1) Does blood pressure entry criterion have an effect on baseline blood pressure variability? 2) Do thiazide diuretics have a significant effect on blood pressure variability? and 3) Does systolic blood pressure vary to the same degree as diastolic blood pressure? This analysis of blood press...

Musini, Vijaya M.; Wright, James M.

2009-01-01

183

Heart rate variability and cardiac autonomic function in men with chronic alcohol dependence.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Cardiac autonomic function was studied in 23 alcohol dependent men by standard tests of autonomic function and measurement of 24 hour heart rate variability. In all there was peripheral or central nervous system damage or both. Standard tests of autonomic function showed vagal neuropathy in seven. The remainder had normal autonomic function tests. Twenty four hour heart rate variability was measured as the standard deviation of the successive differences between RR intervals from an ambulator...

Malpas, S. C.; Whiteside, E. A.; Maling, T. J.

1991-01-01

184

Universal spin-dependent variable range hopping in wide-band-gap oxide ferromagnetic semiconductors  

International Nuclear Information System (INIS)

This paper proposes a universal spin-dependent variable range hopping theoretical model to describe various experimental transport phenomena observed in wide-band-gap oxide ferromagnetic semiconductors with high transition metal concentration. The contributions of the 'hard gap' energy, Coulomb interaction, correlation energy, and exchange interaction to the electrical transport are considered in the universal variable range hopping theoretical model. By fitting the temperature and magnetic field dependence of the experimental sheet resistance to the theoretical model, the spin polarization ratio of electrical carriers near the Fermi level and interactions between electrical carriers can be obtained

2010-03-01

185

Vertical random variability of the distribution coefficient in the soil and its effect on the migration of fallout radionuclides  

International Nuclear Information System (INIS)

In the field, the distribution coefficient, Kd, for the sorption of a radionuclide by the soil cannot be expected to be constant. Even in a well defined soil horizon, Kd will vary stochastically in horizontal as well as in vertical direction around a mean value. The horizontal random variability of Kd produce a pronounced tailing effect in the concentration depth profile of a fallout radionuclide, much less is known on the corresponding effect of the vertical random variability. To analyze this effect theoretically, the classical convection-dispersion model in combination with the random-walk particle method was applied. The concentration depth profile of a radionuclide was calculated one year after deposition assuming constant values of the pore water velocity, the diffusion/dispersion coefficient, and the distribution coefficient (Kd = 100 cm3 x g-1) and exhibiting a vertical variability for Kd according to a log-normal distribution with a geometric mean of 100 cm3 x g-1 and a coefficient of variation of CV 0.53. The results show that these two concentration depth profiles are only slightly different, the location of the peak is shifted somewhat upwards, and the dispersion of the concentration depth profile is slightly larger. A substantial tailing effect of the concentration depth profile is not perceivable. Especially with respect to the location of the peak, a very good approximation of the concentration depth profile is obtained if the arithmetic mean of the Kd-values (Kd = 113 cm3 x g-1) and a slightly increased dispersion coefficient are used in the analytical solution of the classical convection-dispersion equation with constant Kd. The evaluation of the observed concentration depth profile with the analytical solution of the classical convection-dispersion equation with constant parameters will, within the usual experimental limits, hardly reveal the presence of a log-normal random distribution of Kd in the vertical direction in contrast to the horizontal direction. (author)

2002-10-01

186

Auricular acupuncture for chemically dependent pregnant women: a randomized controlled trial of the NADA protocol  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background The prevalence of maternal drug use during pregnancy in North America has been estimated to be as high as 6-10%. The consequences for the newborn include increased risk for perinatal mortality and ongoing physical, neurobehavioral, and psychosocial problems. Methadone is frequently used to wean women off street drugs but is implicated as a cause of adverse fetal/neonatal outcomes itself. The purpose of our study was to test the ability of maternal acupuncture treatment among mothers who use illicit drugs to reduce the frequency and severity of withdrawal symptoms among their newborns. Methods We randomly assigned chemically dependent pregnant women at BC Women’s Hospital in Vancouver, British Columbia to daily acupuncture treatments versus usual care. By necessity, neither our participants nor acupuncturists were blinded as to treatment allocation. Our primary outcome was days of neonatal morphine treatment for symptoms of neonatal withdrawal. Secondary neonatal outcomes included admission to a neonatal ICU and transfer to foster care. Results We randomized 50 women to acupuncture and 39 to standard care. When analyzed by randomized groups, we did not find benefit of acupuncture; the average length of treatment with morphine for newborns in the acupuncture group was 2.7 (6.3 compared to 2.8 (7.0 in the control group. Among newborns of women who were compliant with the acupuncture regime, we observed a reduction of 2.1 and 1.5 days in length of treatment for neonatal abstinence syndrome compared to the non-compliant and control groups, respectively. These differences were not statistically significant. Conclusions Acupuncture may be a safe and feasible treatment to assist mothers to reduce their dosage of methadone. Our results should encourage ongoing studies to test the ability of acupuncture to mitigate the severity of neonatal abstinence syndrome among their newborns. Clinical Trial Registration http://www.clinicaltrials.gov registry: W05-0041

Janssen Patricia A

2012-12-01

187

Random mutagenesis identifies factors involved in formate-dependent growth of the methanogenic archaeon Methanococcus maripaludis.  

Science.gov (United States)

Methane is a key intermediate in the carbon cycle and biologically produced by methanogenic archaea. Most methanogens are able to conserve energy by reducing CO2 to methane using molecular hydrogen as electron donor (hydrogenotrophic methanogenesis), but several hydrogenotrophic methanogens can also use formate as electron donor for methanogenesis. Formate dehydrogenase (Fdh) oxidizes formate to CO2 and is involved in funneling reducing equivalents into the methanogenic pathway, but details on other factors relevant for formate-dependent physiology of methanogens are not available. To learn more about the factors involved in formate-dependent growth of Methanococcus maripaludis strain JJ, we used a recently developed system for random in vitro mutagenesis, which is based on a modified insect transposable element to create 2,865 chromosomal transposon mutants and screened them for impaired growth on formate. Of 12 M. maripaludis transposon-induced mutants exhibiting this phenotype, the transposon insertion sites in the chromosome were mapped. Among the genes, apparently affecting formate-dependent growth were those encoding archaeal transcription factor S, a regulator of ion transport, and carbon monoxide dehydrogenase/acetyl-CoA synthase. Interestingly, in seven of the mutants, transposons were localized in a 10.2?kb region where Fdh1, one of two Fdh isoforms in the organism, is encoded. Two transcription start sites within the 10.2 kb region could be mapped, and quantification of transcripts revealed that transposon insertion in this region diminished fdhA1 expression due to polar effects. PMID:23801407

Sattler, Christian; Wolf, Sandro; Fersch, Julia; Goetz, Stefan; Rother, Michael

2013-09-01

188

Spatial variability and its scale dependency of observed and modeled soil moisture under different climate conditions  

Directory of Open Access Journals (Sweden)

Full Text Available Past studies on soil moisture spatial variability have been mainly conducted in catchment scales where soil moisture is often sampled over a short time period. Because of limited climate and weather conditions, the observed soil moisture often exhibited smaller dynamic ranges which prevented the complete revelation of soil moisture spatial variability as a function of mean soil moisture. In this study, spatial statistics (mean, spatial variability and skewness of in situ soil moisture measurements (from a continuously monitored network across the US, modeled and satellite retrieved soil moisture obtained in a warm season (198 days were examined at large extent scales (>100 km over three different climate regions. The investigation on in situ measurements revealed that their spatial moments strongly depend on climates, with distinct mean, spatial variability and skewness observed in each climate zone. In addition, an upward convex shape, which was revealed in several smaller scale studies, was observed for the relationship between spatial variability of in situ soil moisture and its spatial mean across dry, intermediate, and wet climates. These climate specific features were vaguely or partially observable in modeled and satellite retrieved soil moisture estimates, which is attributed to the fact that these two data sets do not have climate specific and seasonal sensitive mean soil moisture values, in addition to lack of dynamic ranges. From the point measurements to satellite retrievals, soil moisture spatial variability decreased in each climate region. The three data sources all followed the power law in the scale dependency of spatial variability, with coarser resolution data showing stronger scale dependency than finer ones. The main findings from this study are: (1 the statistical distribution of soil moisture depends on spatial mean soil moisture values and thus need to be derived locally within any given area; (2 the boundedness of soil moisture plays a pivoting role in the dependency of soil moisture spatial variability/skewness on its mean (and thus climate conditions; (3 the scale dependency of soil moisture spatial variability changes with climate conditions.

B. Li

2012-09-01

189

PREDICTING ADHERENCE TO TREATMENT FOR METHAMPHETAMINE DEPENDENCE FROM NEUROPSYCHOLOGICAL AND DRUG USE VARIABLES*  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Although some individuals who abuse methamphetamine have considerable cognitive deficits, no prior studies have examined whether neurocognitive functioning is associated with outcome of treatment for methamphetamine dependence. In an outpatient clinical trial of bupropion combined with cognitive behavioral therapy and contingency management (Shoptaw et al., 2008), 60 methamphetamine-dependent adults completed three tests of reaction time and working memory at baseline. Other variables that we...

Dean, Andy C.; London, Edythe D.; Sugar, Catherine A.; Kitchen, Christina M. R.; Swanson, Aimee-noelle; Heinzerling, Keith G.; Kalechstein, Ari D.; Shoptaw, Steven

2009-01-01

190

Maximal averages along a planar vector field depending on one variable  

CERN Document Server

We prove (essentially) sharp $L^2$ estimates for a restricted maximal operator associated to a planar vector field that depends only on the horizontal variable. The proof combines an understanding of such vector fields from earlier work of the author with a result of Nets Katz on directional maximal operators.

Bateman, Michael

2011-01-01

191

Behavioral Treatment for Marijuana Dependence: Randomized Trial of Contingency Management and Self-Efficacy Enhancement  

Science.gov (United States)

Objective The purpose of the present study was to develop a treatment for marijuana dependence specifically designed to enhance self-efficacy. Method The participants were 215 marijuana-dependent men and women randomized to one of three 9-week outpatient treatments: a condition intended to enhance self-efficacy through successful completion of treatment-related tasks (Mot ivational Enhancement plus Cognitive-Behavioral treatment plus Contingency Management reinforcing completion of treatment homework; MET+CBT+CMHomework); a condition that controlled for all elements except for reinforcement of homework (MET+CBT + Contingency Management reinforcing drug abstinence ; MET+CBT+CMAbstinence); or a Case Management control condition (CaseM). Participants in the two MET+CBT conditions were also asked to complete interactive voice recordings three times per week during treatment to confirm homework completion. Results All patients showed modest improvements over time through 14 months, with few between-treatment effects on outcomes. Latent Class Growth Models, however, indicated that a subsample of patients did extremely well over time. This subsample was more likely to have been treated in the CMAbstinence condition. In turn, this treatment effects appears to have been accounted for by days of continuous abstinence accrued during treatment, and by pre-post increases in self-efficacy. Conclusions The most effective treatments may be those that elicit abstinence while increasing self-efficacy.

Litt, Mark D.; Kadden, Ronald M.; Petry, Nancy M.

2012-01-01

192

Position-dependent effective mass system in a variable potential: displacement operator method  

Science.gov (United States)

Within the framework of the translation operator for a quantum system with position-dependent mass, we examine the quantum state of a position-dependent mass system in a variable potential. By imposing conditions of resolvability, we arrive at a potential with a quartic and a quadratic term. It emerges naturally that the energy eigen states of the system are negative. We have found the quantum mechanical quantities: energy spectrum, eigen functions and uncertainty relation. These quantities depend on the parameters of the potential.

Vubangsi, M.; Tchoffo, M.; Fai, L. C.

2014-02-01

193

Baclofen for maintenance treatment of opioid dependence: A randomized double-blind placebo-controlled clinical trial [ISRCTN32121581  

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Abstract Background Results of preclinical studies suggest that the GABAB receptor agonist baclofen may be useful in treatment of opioid dependence. This study was aimed at assessing the possible efficacy of baclofen for maintenance treatment of opioid dependence. Methods A total of 40 opioid-dependent patients were detoxified and randomly assigned to receive baclofen (60 mg/day) or placebo in a 12-week, double blind, parallel-group trial. Primary out...

Assadi Seyed Mohammad; Radgoodarzi Reza; Ahmadi-Abhari Seyed Ali

2003-01-01

194

The effect of misspecification of random effects distributions in clustered data settings with outcome-dependent sampling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Genetic epidemiologists often gather outcome-dependent samples of family data to measure within-family associations of genetic factors with disease outcomes. Generalized linear mixed models provide effective methods to estimate within-family associations but typically require parametric specification of the random effects distribution. Although misspecification of the random effects distribution often leads to little bias in estimated regression coefficients in standard, prospective clustered...

Neuhaus, John M.; Mcculloch, Charles E.

2011-01-01

195

Ratio Estimators in Simple Random Sampling when Study Variable is an Attribute  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we have suggested a family of estimators for the population mean when study variable itself is qualitative in nature. Expressions for the bias and mean square error (MSE) of the suggested family have been obtained. An empirical study has been carried out to show the superiority of the constructed estimator over others.

Singh, Rajesh; Kumar, Mukesh; Smarandache, Florentin

2010-01-01

196

On construction of random variables with prescribed marginal distributions and correlation coefficients  

CERN Document Server

In this paper we propose a generalized extension of the trivariate reduction method for exact generation of variables with prespecified marginal distributions and the correlation coefficient (positive or negative). We compare the new algorithm to several common approaches, with a particular emphasis on the copula-based ones, and discuss its benefits and limitations.

Dukic, Vanja

2010-01-01

197

On Chung-Teicher type strong law for arrays of vector-valued random variables  

Directory of Open Access Journals (Sweden)

Full Text Available We study the equivalence between the weak and strong laws of large numbers for arrays of row-wise independent random elements with values in a Banach space ℬ. The conditions under which this equivalence holds are of the Chung or Chung-Teicher types. These conditions are expressed in terms of convergence of specific series and o(1 requirements on specific weighted row-wise sums. Moreover, there are not any conditions assumed on the geometry of the underlying Banach space.

Anna Kuczmaszewska

2004-03-01

198

A new mean estimator using auxiliary variables for randomized response models  

Science.gov (United States)

Randomized response models are commonly used in surveys dealing with sensitive questions such as abortion, alcoholism, sexual orientation, drug taking, annual income, tax evasion to ensure interviewee anonymity and reduce nonrespondents rates and biased responses. Starting from the pioneering work of Warner [7], many versions of RRM have been developed that can deal with quantitative responses. In this study, new mean estimator is suggested for RRM including quantitative responses. The mean square error is derived and a simulation study is performed to show the efficiency of the proposed estimator to other existing estimators in RRM.

Ozgul, Nilgun; Cingi, Hulya

2013-10-01

199

Nonparametric changepoint analysis for bernoulli random variables based on neural networks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In many medical, financial, industrial, e.t.c. applications of statistics, the model parameters may undergo changes at unknown moment of time. In this thesis, we consider change point analysis in a regression setting for dichotomous responses, i.e. they can be modeled as Bernoulli or 0-1 variables. Applications are widespread including credit scoring in financial statistics and dose-response relations in biometry. The model parameters are estimated using neural network method. We show that th...

2008-01-01

200

Reduced plasma aldosterone concentrations in randomly selected patients with insulin-dependent diabetes mellitus.  

LENUS (Irish Health Repository)

Abnormalities of the renin-angiotensin system have been reported in patients with diabetes mellitus and with diabetic complications. In this study, plasma concentrations of prorenin, renin, and aldosterone were measured in a stratified random sample of 110 insulin-dependent (Type 1) diabetic patients attending our outpatient clinic. Fifty-four age- and sex-matched control subjects were also examined. Plasma prorenin concentration was higher in patients without complications than in control subjects when upright (geometric mean (95% confidence intervals (CI): 75.9 (55.0-105.6) vs 45.1 (31.6-64.3) mU I-1, p < 0.05). There was no difference in plasma prorenin concentration between patients without and with microalbuminuria and between patients without and with background retinopathy. Plasma renin concentration, both when supine and upright, was similar in control subjects, in patients without complications, and in patients with varying degrees of diabetic microangiopathy. Plasma aldosterone was suppressed in patients without complications in comparison to control subjects (74 (58-95) vs 167 (140-199) ng I-1, p < 0.001) and was also suppressed in patients with microvascular disease. Plasma potassium was significantly higher in patients than in control subjects (mean +\\/- standard deviation: 4.10 +\\/- 0.36 vs 3.89 +\\/- 0.26 mmol I-1; p < 0.001) and plasma sodium was significantly lower (138 +\\/- 4 vs 140 +\\/- 2 mmol I-1; p < 0.001). We conclude that plasma prorenin is not a useful early marker for diabetic microvascular disease. Despite apparently normal plasma renin concentrations, plasma aldosterone is suppressed in insulin-dependent diabetic patients.

Cronin, C C

2012-02-03

 
 
 
 
201

Hysteresis, metastability, and time dependence in d = 2 and d = 3 random-field Ising systems  

International Nuclear Information System (INIS)

The hysteretic properties of random-field Ising model (RFIM) systems were studied. Using neutron scattering, a relatively narrow metastability boundary T/sub F/(H) in the d = 2 (d = d/sub l/) RFIM system Rb2Co/sub 0.85/Mg/sub 0.15/F4 was found to lie well below the rounded specific heat peak ''T/sub c/(H)'' of the (destroyed) phase transition. T/sub F/(H) scales as T/sub N/-T/sub F/(H)proportionalH/sup 2/phi/ with the RF crossover exponent phi = 1.74 +- 0.02. At T/sub F/(H), equilibrium is approached logarithmically with time. In the d = 3 (d>d/sub l/) RFIM system Fe/sub 0.6/Zn/sub 0.4/F2 AF order was found to be stable against changes of T and H below the observed sharp phase transition boundary T/sub c/(H), while the field-cooled domain state was not. Capacitance measurements in Fe/sub 0.68/Zn/sub 0.32/F2 established that equilibrium prevails for T > or = T/sub eq/(H) which is slightly above T/sub c/(H). Pronounced logarithmic time dependence is observed at T < or approx. =T/sub c/(H)

1197-01-00

202

Hysteresis, metastability, and time dependence in d = 2 and d = 3 random-field Ising systems  

Energy Technology Data Exchange (ETDEWEB)

The hysteretic properties of random-field Ising model (RFIM) systems were studied. Using neutron scattering, a relatively narrow metastability boundary T/sub F/(H) in the d = 2 (d = d/sub l/) RFIM system Rb/sub 2/Co/sub 0.85/Mg/sub 0.15/F/sub 4/ was found to lie well below the rounded specific heat peak ''T/sub c/(H)'' of the (destroyed) phase transition. T/sub F/(H) scales as T/sub N/-T/sub F/(H)proportionalH/sup 2/phi/ with the RF crossover exponent phi = 1.74 +- 0.02. At T/sub F/(H), equilibrium is approached logarithmically with time. In the d = 3 (d>d/sub l/) RFIM system Fe/sub 0.6/Zn/sub 0.4/F/sub 2/ AF order was found to be stable against changes of T and H below the observed sharp phase transition boundary T/sub c/(H), while the field-cooled domain state was not. Capacitance measurements in Fe/sub 0.68/Zn/sub 0.32/F/sub 2/ established that equilibrium prevails for T > or = T/sub eq/(H) which is slightly above T/sub c/(H). Pronounced logarithmic time dependence is observed at T < or approx. =T/sub c/(H).

Belanger, D.P.; Rezende, S.M.; King, A.R.; Jaccarino, V.

1985-04-15

203

Efficacy of initiating tobacco dependence treatment in inpatient psychiatry: a randomized controlled trial.  

Science.gov (United States)

Objectives. We evaluated the efficacy of a motivational tobacco cessation treatment combined with nicotine replacement relative to usual care initiated in inpatient psychiatry. Methods. We randomized participants (n?=?224; 79% recruitment rate) recruited from a locked acute psychiatry unit with a 100% smoking ban to intervention or usual care. Prior to hospitalization, participants averaged 19 (SD?=?12) cigarettes per day; only 16% intended to quit smoking in the next 30 days. Results. Verified smoking 7-day point prevalence abstinence was significantly higher for intervention than usual care at month 3 (13.9% vs 3.2%), 6 (14.4% vs 6.5%), 12 (19.4% vs 10.9%), and 18 (20.0% vs 7.7%; odds ratio [OR]?=?3.15; 95% confidence interval [CI]?=?1.22, 8.14; P?=?.018; retention?>?80%). Psychiatric measures did not predict abstinence; measures of motivation and tobacco dependence did. The usual care group had a significantly greater likelihood than the intervention group of psychiatric rehospitalization (adjusted OR?=?1.92; 95% CI?=?1.06, 3.49). Conclusions. The findings support initiation of motivationally tailored tobacco cessation treatment during acute psychiatric hospitalization. Psychiatric severity did not moderate treatment efficacy, and cessation treatment appeared to decrease rehospitalization risk, perhaps by providing broader therapeutic benefit. PMID:23948001

Prochaska, Judith J; Hall, Stephen E; Delucchi, Kevin; Hall, Sharon M

2014-08-01

204

Temperature dependence of resistive switching behaviors in resistive random access memory based on graphene oxide film  

Science.gov (United States)

We reported resistive switching behaviors in the resistive random access memory (RRAM) devices based on the different annealing temperatures of graphene oxide (GO) film as active layers. It was found that the resistive switching characteristics of an indium tin oxide (ITO)/GO/Ag structure have a strong dependence on the annealing temperature of GO film. When the annealing temperature of the GO film was 20 °C, the devices showed typical write-once-read-many-times (WORM) type memory behaviors, which have good memory performance with a higher ON/OFF current ratio (?104), the higher the high resistance state (HRS)/low resistance state (LRS) ratio (?105) and stable retention characteristics (>103 s) under lower programming voltage (?1 V and ?0.5 V). With the increasing annealing temperature of GO film, the resistive switching behavior of RRAM devices gradually weakened and eventually disappeared. This phenomenon could be understood by the different energy level distributions of the charge traps in GO film, and the different charge injection ability from the Ag electrode to GO film, which is caused by the different annealing temperatures of the GO film.

Yi, Mingdong; Cao, Yong; Ling, Haifeng; Du, Zhuzhu; Wang, Laiyuan; Yang, Tao; Fan, Quli; Xie, Linghai; Huang, Wei

2014-05-01

205

Some Data Reduction Methods to Analyze the Dependence with Highly Collinear Variables: A Simulation Study  

Directory of Open Access Journals (Sweden)

Full Text Available The dependence relationship between two sets of variables is a subject of interest in statistical field. A frequent obstacle is that several of the explanatory variables will vary in rather similar ways. As a result, their collective power of explanation is considerably less than the sum of their individual powers. This phenomenon, called multicollinearity, is a common problem in regression analysis. The major problem with multicollinearity is that the ordinary least squares coefficients estimators involved in the linear dependencies have large variances. All additional adverse effects are a consequence of them. In statistical literature several methods have been proposed to counter with multicollinearity problem. By a simulation study and considering different case of collinearity among the regressors, in this paper we have compared, using RV coefficient, five statistical methods, alternative to the ordinary least square regression.

A. D`Ambra

2010-01-01

206

Inclination and orbital-phase-dependent resonance line-profile calculations applied to cataclysmic variable winds  

International Nuclear Information System (INIS)

The observed properties of wind-formed resonance lines in the spectra of nova-like variables and dwarf novae in outburst, are discussed. A method is then presented of calculating inclination-and orbital-phase-dependent resonance line profiles formed in a constant-ionization wind flowing from an accretion disc centre. The particular case of the C IV lambda 1549 line is considered. (author)

1987-02-01

207

Parametric and Semiparametric Estimation in Models with Misclassified Categorical Dependent Variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We consider both a parametric and a semiparametric method to account for classification errors on the dependent variable in an ordered response model. The methods are applied to the analysis of self-reported speaking fluency of male immigrants in Germany. We find some substantial differences in parameter estimates between parametric and semiparametric models, and between predictions of true and reported fluency. We compare the predictions of the three models, and perform a graphical test of t...

Dustmann, C.; Soest, A. H. O.

1999-01-01

208

Remittances, lagged dependent variables and migration stocks as determinants of migration from developing countries  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In regressions for net immigration flows of developing countries we show that (i) savings finance emigration and worker remittances serve to make staying rather than migrating possible until a certain value, beyond which the opposite holds; (ii) lagged dependent migration flows have a negative sign even in the presence of migration stock variables; (iii) migration stocks have S-shaped effects: at sufficiently low values higher migration stocks support emigration; beyond a threshold value they...

2009-01-01

209

Genetic variability analysis among clinical Candida spp. isolates using random amplified polymorphic DNA  

Directory of Open Access Journals (Sweden)

Full Text Available The patterns of genetic variation of samples of Candida spp. isolated from patients infected with human immunodeficiency virus in Vitória, state of Espírito Santo, Brazil, were examined. Thirty-seven strains were isolated from different anatomical sites obtained from different infection episodes of 11 patients infected with the human immunodeficiency virus (HIV. These samples were subjected to randomly amplified polymorphic DNA (RAPD analysis using 9 different primers. Reproducible and complex DNA banding patterns were obtained. The experiments indicated evidence of dynamic process of yeast colonization in HIV-infected patients, and also that certain primers are efficient in the identification of species of the Candida genus. Thus, we conclude that RAPD analysis may be useful in providing genotypic characters for Candida species typing in epidemiological investigations, and also for the rapid identification of pathogenic fungi.

Patrícia M Pinto

2004-03-01

210

Genetic variability analysis among clinical Candida spp. isolates using random amplified polymorphic DNA  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english The patterns of genetic variation of samples of Candida spp. isolated from patients infected with human immunodeficiency virus in Vitória, state of Espírito Santo, Brazil, were examined. Thirty-seven strains were isolated from different anatomical sites obtained from different infection episodes of [...] 11 patients infected with the human immunodeficiency virus (HIV). These samples were subjected to randomly amplified polymorphic DNA (RAPD) analysis using 9 different primers. Reproducible and complex DNA banding patterns were obtained. The experiments indicated evidence of dynamic process of yeast colonization in HIV-infected patients, and also that certain primers are efficient in the identification of species of the Candida genus. Thus, we conclude that RAPD analysis may be useful in providing genotypic characters for Candida species typing in epidemiological investigations, and also for the rapid identification of pathogenic fungi.

Pinto, Patrícia M; Resende, Maria A; Koga-Ito, Cristiane Y; Tendler, Miriam.

211

Random variables in forest policy: A systematic sensitivity analysis using CGE models  

International Nuclear Information System (INIS)

Computable general equilibrium (CGE) models are extensively used to simulate economic impacts of forest policies. Parameter values used in these models often play a central role in their outcome. Since econometric studies and best guesses are the main sources of these parameters, some randomness exists about the 'true' values of these parameters. Failure to incorporate this randomness into these models may limit the degree of confidence in the validity of the results. In this study, we conduct a systematic sensitivity analysis (SSA) to assess the economic impacts of: 1) a 1 % increase in tax on Canadian lumber and wood products exports to the United States (US), and 2) a 1% decrease in technical change in the lumber and wood products and pulp and paper sectors of the US and Canada. We achieve this task by using an aggregated version of global trade model developed by Hertel (1997) and the automated SSA procedure developed by Arndt and Pearson (1996). The estimated means and standard deviations suggest that certain impacts are more likely than others. For example, an increase in export tax is likely to cause a decrease in Canadian income, while an increase in US income is unlikely. On the other hand, a decrease in US welfare is likely, while an increase in Canadian welfare is unlikely, in response to an increase in tax. It is likely that income and welfare both fall in Canada and the US in response to a decrease in the technical change in lumber and wood products and pulp and paper sectors 21 refs, 1 fig, 5 tabs

1999-01-01

212

Spatiotemporal dependency of age-related changes in brain signal variability.  

Science.gov (United States)

Recent theoretical and empirical work has focused on the variability of network dynamics in maturation. Such variability seems to reflect the spontaneous formation and dissolution of different functional networks. We sought to extend these observations into healthy aging. Two different data sets, one EEG (total n = 48, ages 18-72) and one magnetoencephalography (n = 31, ages 20-75) were analyzed for such spatiotemporal dependency using multiscale entropy (MSE) from regional brain sources. In both data sets, the changes in MSE were timescale dependent, with higher entropy at fine scales and lower at more coarse scales with greater age. The signals were parsed further into local entropy, related to information processed within a regional source, and distributed entropy (information shared between two sources, i.e., functional connectivity). Local entropy increased for most regions, whereas the dominant change in distributed entropy was age-related reductions across hemispheres. These data further the understanding of changes in brain signal variability across the lifespan, suggesting an inverted U-shaped curve, but with an important qualifier. Unlike earlier in maturation, where the changes are more widespread, changes in adulthood show strong spatiotemporal dependence. PMID:23395850

McIntosh, A R; Vakorin, V; Kovacevic, N; Wang, H; Diaconescu, A; Protzner, A B

2014-07-01

213

Characterization of randomly amplified polymorphic DNA (RAPD) fragments revealing clonal variability in cercariae of avian schistosome Trichobilharzia szidati (Trematoda: Schistosomatidae)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Recently we applied randomly amplified polymorphic DNA (RAPD) fingerprinting to detect clonal variability among individual cercariae within daughter sporocysts and rediae of 10 digenean trematodes (Platyhelminthes: Trematoda). The most variable RAPD patterns were obtained for Schistosomatidae representative-avian schistosome

Anna Korsunenko; Galina Chrisanfova; Alexander Arifov; Alexey Ryskov; Seraphima Semyenova

2013-01-01

214

A strong uniform convergence rate of a kernel conditional quantile estimator under random left-truncation and dependent data  

CERN Multimedia

In this paper we study some asymptotic properties of the kernel conditional quantile estimator with randomly left-truncated data which exhibit some kind of dependence. We extend the result obtained by Lemdani, Ould-Sa\\"id and Poulin [16] in the iid case. The uniform strong convergence rate of the estimator under strong mixing hypothesis is obtained.

Ould-Saïd, Elias; Necir, Abdelhakim

2008-01-01

215

Multidimensional time-dependent discrete variable representations in multiconfiguration Hartree calculations  

Science.gov (United States)

In the multiconfiguration time-dependent Hartree (MCTDH) approach, the wave function is expanded in time-dependent basis functions, called single-particle functions, to increase the efficiency of the wave-packet propagation. The correlation discrete variable representation (CDVR) approach, which is based on a time-dependent discrete variable representation (DVR), can be employed to evaluate matrix elements of the potential energy. The efficiency of the MCTDH method can be further enhanced by using multidimensional single-particle functions. However, up to now the CDVR approach could not be used in MCTDH calculations employing multidimensional single-particle functions, since this would require a general multidimensional non-direct-product DVR scheme. Recently, Dawes and Carrington presented a practical scheme to implement general non-direct-product multidimensional DVRs [R. Dawes and T. Carrington, Jr., J. Chem. Phys. 121, 726 (2004)]. The present work utilizes their scheme in the MCTDH/CDVR approach. The accuracy is tested using the photodissociation of NOCl as example. The results show that the CDVR scheme based on multidimensional time-dependent DVRs allows for an accurate evaluation of the potential in MCTDH calculations with multidimensional single-particle functions.

van Harrevelt, Rob; Manthe, Uwe

2005-08-01

216

Multidimensional time-dependent discrete variable representations in multiconfiguration Hartree calculations  

International Nuclear Information System (INIS)

In the multiconfiguration time-dependent Hartree (MCTDH) approach, the wave function is expanded in time-dependent basis functions, called single-particle functions, to increase the efficiency of the wave-packet propagation. The correlation discrete variable representation (CDVR) approach, which is based on a time-dependent discrete variable representation (DVR), can be employed to evaluate matrix elements of the potential energy. The efficiency of the MCTDH method can be further enhanced by using multidimensional single-particle functions. However, up to now the CDVR approach could not be used in MCTDH calculations employing multidimensional single-particle functions, since this would require a general multidimensional non-direct-product DVR scheme. Recently, Dawes and Carrington presented a practical scheme to implement general non-direct-product multidimensional DVRs [R. Dawes and T. Carrington, Jr., J. Chem. Phys. 121, 726 (2004)]. The present work utilizes their scheme in the MCTDH/CDVR approach. The accuracy is tested using the photodissociation of NOCl as example. The results show that the CDVR scheme based on multidimensional time-dependent DVRs allows for an accurate evaluation of the potential in MCTDH calculations with multidimensional single-particle functions

2005-08-08

217

Fluctuations in a system depending on several random parameters. Application to reactors (1962)  

International Nuclear Information System (INIS)

We have previously developed a method for studying neutronic fluctuations in nuclear reactors using the analogy between the behaviour of a reactor and that of certain common radioelectric circuits. The fluctuations may then be calculated by introducing into the circuit a suitable noise source. By this method we have been able to consider the overall fluctuations in a particularly simple form and we have provided a physical significance for certain results obtained more laboriously by other methods. The object of the present report is to generalise this method and in particular to extend it to the case of a reactor having a cellular structure and to apply it to fluctuations within a cell. It is thus shown that the fluctuations in a cell are the resultant of two terms: - a rapidly evolving Poissonian noise, not related to the overall fluctuations; - a slowly evolving noise, when the reactor is not too far from criticality, which is related to the overall fluctuations. The first term arises from a rapid 'ordering' of the system, during which time the cells come mutually into equilibrium. The second term is due to the coordinated evolution of all the cells, after the end of the first transitory phase. The conclusions reached show that it would be useful to complete the study with an analysis of non-linear phenomena which can considerably influence the transitory behaviour of the cells during the initial pre-equilibrium phase. This report also Stresses the relationship of the new method to the old methods. It tends also to place pile fluctuation theory in a more general framework, that of the fluctuations of a system depending on several random parameters; from this point of view, the method could easily be transposed and adapted to the study of other physical problems of this type. (authors)

1962-01-01

218

Bayesian methods for instrumental variable analysis with genetic instruments (‘Mendelian randomization’): example with urate transporter SLC2A9 as an instrumental variable for effect of urate levels on metabolic syndrome  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The ‘Mendelian randomization’ approach uses genotype as an instrumental variable to distinguish between causal and non-causal explanations of biomarker–disease associations. Classical methods for instrumental variable analysis are limited to linear or probit models without latent variables or missing data, rely on asymptotic approximations that are not valid for weak instruments and focus on estimation rather than hypothesis testing. We describe a Bayesian approach that overcomes these ...

Mckeigue, Paul M.; Campbell, Harry; Wild, Sarah; Vitart, Veronique; Hayward, Caroline; Rudan, Igor; Wright, Alan F.; Wilson, James F.

2010-01-01

219

Variability of visual responses of superior colliculus neurons depends on stimulus velocity.  

Science.gov (United States)

Visually responding neurons in the superficial, retinorecipient layers of the cat superior colliculus receive input from two primarily parallel information processing channels, Y and W, which is reflected in their velocity response profiles. We quantified the time-dependent variability of responses of these neurons to stimuli moving with different velocities by Fano factor (FF) calculated in discrete time windows. The FF for cells responding to low-velocity stimuli, thus receiving W inputs, increased with the increase in the firing rate. In contrast, the dynamics of activity of the cells responding to fast moving stimuli, processed by Y pathway, correlated negatively with FF whether the response was excitatory or suppressive. These observations were tested against several types of surrogate data. Whereas Poisson description failed to reproduce the variability of all collicular responses, the inclusion of secondary structure to the generating point process recovered most of the observed features of responses to fast moving stimuli. Neither model could reproduce the variability of low-velocity responses, which suggests that, in this case, more complex time dependencies need to be taken into account. Our results indicate that Y and W channels may differ in reliability of responses to visual stimulation. Apart from previously reported morphological and physiological differences of the cells belonging to Y and W channels, this is a new feature distinguishing these two pathways. PMID:20203179

Mochol, Gabriela; Wójcik, Daniel K; Wypych, Marek; Wróbel, Andrzej; Waleszczyk, Wioletta J

2010-03-01

220

Studying the time scale dependence of environmental variables predictability using fractal analysis.  

Science.gov (United States)

Prediction of meteorological and air quality variables motivates a lot of research in the atmospheric sciences and exposure assessment communities. An interesting related issue regards the relative predictive power that can be expected at different time scales, and whether it vanishes altogether at certain ranges. An improved understanding of our predictive powers enables better environmental management and more efficient decision making processes. Fractal analysis is commonly used to characterize the self-affinity of time series. This work introduces the Continuous Wavelet Transform (CWT) fractal analysis method as a tool for assessing environmental time series predictability. The high temporal scale resolution of the CWT enables detailed information about the Hurst parameter, a common temporal fractality measure, and thus about time scale variations in predictability. We analyzed a few years records of half-hourly air pollution and meteorological time series from which the trivial seasonal and daily cycles were removed. We encountered a general trend of decreasing Hurst values from about 1.4 (good autocorrelation and predictability), in the sub-daily time scale to 0.5 (which implies complete randomness) in the monthly to seasonal scales. The air pollutants predictability follows that of the meteorological variables in the short time scales but is better at longer scales. PMID:20465249

Yuval; Broday, David M

2010-06-15

 
 
 
 
221

Phenotypic characterization of Bbs4 null mice reveals age-dependent penetrance and variable expressivity.  

Science.gov (United States)

Bardet-Biedl syndrome (BBS) is a rare oligogenic disorder exhibiting both clinical and genetic heterogeneity. Although the BBS phenotype is variable both between and within families, the syndrome is characterized by the hallmarks of developmental and learning difficulties, post-axial polydactylia, obesity, hypogenitalism, renal abnormalities, retinal dystrophy, and several less frequently observed features. Eleven genes mutated in BBS patients have been identified, and more are expected to exist, since about 20-30% of all families cannot be explained by the known loci. To investigate the etiopathogenesis of BBS, we created a mouse null for one of the murine homologues, Bbs4, to assess the contribution of one gene to the pleiotropic murine Bbs phenotype. Bbs4 null mice, although initially runted compared to their littermates, ultimately become obese in a gender-dependent manner, females earlier and with more severity than males. Blood chemistry tests indicated abnormal lipid profiles, signs of liver dysfunction, and elevated insulin and leptin levels reminiscent of metabolic syndrome. As in patients with BBS, we found age-dependent retinal dystrophy. Behavioral assessment revealed that mutant mice displayed more anxiety-related responses and reduced social dominance. We noted the rare occurrence of birth defects, including neural tube defects and hydrometrocolpos, in the null mice. Evaluations of these null mice have uncovered phenotypic features with age-dependent penetrance and variable expressivity, partially recapitulating the human BBS phenotype. PMID:16794820

Eichers, Erica R; Abd-El-Barr, Muhammad M; Paylor, Richard; Lewis, Richard Alan; Bi, Weimin; Lin, Xiaodi; Meehan, Thomas P; Stockton, David W; Wu, Samuel M; Lindsay, Elizabeth; Justice, Monica J; Beales, Philip L; Katsanis, Nicholas; Lupski, James R

2006-09-01

222

Space-time variability of random cascade model parameters for rainfall disaggregation  

Science.gov (United States)

Rainfall time series with a high temporal resolution are needed in many hydrological and water resources management fields. Observed time series of this kind are very short in most cases, so they cannot be used. Contrary to this, time series with lower temporal resolution (daily measurements) exists for much longer periods. The objective is to derive time series with a long duration and a high resolution by disaggregating time series of the non-recording stations with information of time series of the recording stations. The cascade model can be used for temporal rainfall disaggregation (Olsson, 1998). The parameters of this model can be estimated using time series of nearby recording stations. For the implementation of the model to disaggregate rainfall time series the consistence of the parameters has to be evaluated in space and time. The parameters in time are estimated using different time periods with varying lengths. The consistence in space is analyzed comparing 135 recording stations in the Aller-Leine-Oker-catchment in Lower Saxony/Germany. Only slight changes of the parameters are recognizable in space and time. The estimated probabilities vary in general less than 10 %. The influence of the space-time variability of the cascade model parameters on disaggregated rainfall and derived flood frequencies from rainfall runoff simulations has also to be quantified. The former is analyzed comparing rainfall characteristics like rainfall intensities, average dry spell duration, wet spell duration and wet spell amount. The latter is validated comparing relative values of different flood quantiles from rainfall runoff simulations in one catchment in Lower Saxony. OLSSON, J. (1998): Evaluation of a scaling cascade model for temporal rainfall disaggregation, Hydrology & Earth System Sciences 2 (1), 1998

Müller, H.; Haberlandt, U.

2012-04-01

223

The probability of finding a fixed pattern in random data depends monotonically on the bifix indicator  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We consider the problem of finding a fixed L-ary sequence in a stream of random L-ary data. It is known that the expected search time is a strictly increasing function of the lengths of the bifices of the pattern. In this paper we prove the related statement that the probability of finding the pattern in a finite random word is a strictly decreasing function of the lengths of the bifices of the pattern.

Schreiber, Alex

2012-01-01

224

Variable-temperature time-resolved emission spectra studies of random pyrene urethane methacrylate copolymers with high pyrene incorporation.  

Science.gov (United States)

A series of random co-polyurethane methacrylate comb polymers with pyrene (Py) and 3-pentadecylphenol (PDP) as pendant units were prepared by free radical polymerization. The pyrene labeling was varied from 1 to 100 mol %. The excimer emission of these copolymers were studied as a function of both time and temperature using time-resolved emission spectra (TRES) experiments and variable-temperature steady-state fluorescence measurements. Variable-temperature steady-state as well as decay experiments showed that the contribution from excimers via diffusional encounters increased at the cost of pyrene monomer as the temperature increased until ?50 °C; beyond which nonradiative losses predominated. TRES collected at 25 and 70 °C were compared to study the nature and origin of emitting species as a function of pyrene loading. TRES at 25 °C clearly indicated the presence of ground-state pyrene dimers with emission centered at ?435 nm which soon gave way to emission centered around 465 and 485 nm in the time-gated spectra collected at higher time intervals. In TRES collected at 70 °C, excimer emission centered at 465 and 485 nm was very high even at short time scales. The lowest pyrene loaded polymer PIHPDP-1Py did not exhibit excimer emission in the TRES collected at 25 °C as well as 70 °C. PMID:24001057

Kaushlendra, K; Asha, S K

2013-10-01

225

The use of random amplified polymorphic DNA to evaluate the genetic variability of Ponkan mandarin (Citrus reticulata Blanco accessions  

Directory of Open Access Journals (Sweden)

Full Text Available RAPD analysis of 19 Ponkan mandarin accessions was performed using 25 random primers. Of 112 amplification products selected, only 32 were polymorphic across five accessions. The absence of genetic variability among the other 14 accessions suggested that they were either clonal propagations with different local names, or that they had undetectable genetic variability, such as point mutations which cannot be detected by RAPD.Amplificações RAPD foram desenvolvidas utilizando-se 25 "primers" de seqüência aleatória e 19 acessos de tangerinas pertencentes ao grupo das Ponkan. Dos 112 produtos de amplificação selecionados somente 32 foram polimórficos, sendo este polimorfismo restrito somente a 5 acessos. Nos 14 acessos restantes não pôde ser detectada qualquer variabilidade genética, sugerindo que estes podem ser propagação clonal da tangerina `Ponkan', tendo os mesmos adquirido diferentes nomes regionais ao longo do tempo. Ou, por outro lado, a técnica RAPD utilizada pode não ter detectado qualquer mutação de ponto que tenha ocorrido nestes materiais ao longo do tempo.

Helvécio Della Coletta Filho

2000-03-01

226

The effects of frequency-dependent quasar variability on the celestial reference frame  

Science.gov (United States)

We examine the relationship between source position stability and astrophysical properties of radio-loud quasars making up the International Celestial Reference Frame (ICRF2). Understanding this relationship is important for improving quasar selection and analysis strategies, and therefore reference frame stability. We construct flux density time series, known as light curves, for 95 of the most frequently observed ICRF2 quasars at both the 2.3 and 8.4 GHz geodetic very long baseline interferometry (VLBI) observing bands. Because the appearance of new quasar components corresponds to an increase in quasar flux density, these light curves alert us about potential changes in source structure before they appear in VLBI images. We test how source position stability depends on three astrophysical parameters: (1) flux density variability at X band; (2) time lag between flares in S and X bands; (3) spectral index root-mean-square (rms), defined as the variability in the ratio between S and X band flux densities. We find that the time lag between S and X band light curves provides a good indicator of position stability: sources with time lags 0.06 years are significantly more stable (20 % improvement in weighted rms) than sources with larger time lags. A similar improvement is obtained by observing sources with low 0.12) spectral index variability. On the other hand, there is no strong dependence of source position stability on flux density variability in a single frequency band. These findings can be understood by interpreting the time lag between S and X band light curves as a measure of the size of the source structure. Monitoring of source flux density at multiple frequencies therefore appears to provide a useful probe of quasar structure on scales important to geodesy. The observed astrometric position of the brightest quasar component (the core) is known to depend on observing frequency. We show how multi-frequency flux density monitoring may allow the dependence on frequency of the relative core positions along the jet to be elucidated. Knowledge of the position-frequency relation has important implications for current and future geodetic VLBI programs, as well as the alignment between the radio and optical celestial reference frames.

Shabala, Stanislav S.; Rogers, Jonathan G.; McCallum, Jamie N.; Titov, Oleg A.; Blanchard, Jay; Lovell, James E. J.; Watson, Christopher S.

2014-06-01

227

Solution of the energy-dependent neutron transport equation in plane geometry by separation of variables  

International Nuclear Information System (INIS)

The authors give a new method for solving the energy-dependent transport equation in plane geometry by separating the space, lethargy, and angle variables. The method reduces the solution of the transport equation to the solution of a coupled pair of one-speed and slowing down equations. As these two equations have been studied in detail, their solution procedures are utilized to solve the more complicated energy-dependent equation. The method of this paper is thus basically promising, though it is not clear at the present how it can be implemented for general scattering anisotropy. The fundamental separation constant of the method is a continuous parameter, and the solution is in the form of an integral over this parameter. Suitable discretization of this separation constant reduces the solution to an infinite sum. The authors compare their solution to the exact, though formal, singular eigenfunction-Laplace transform technique and establish a correspondence between the two approaches

2080-01-00

228

A mechanism for the latitudinal dependence of peak-spectrum sea surface height variability  

Science.gov (United States)

studies have shown that the power spectrum of satellite-observed sea surface height (SSH) variability peaks at a certain frequency (or a wave number) band at a given latitude. Lin et al. (2008) attributed this latitudinal dependence to the critical frequency of the first baroclinic mode Rossby waves in the tropical and subtropical oceans. Their study was based on the linear Rossby wave theory and focused on SSH variability in the tropical and subtropical oceans since the altimetry data do not adequately resolve lengths of baroclinic Rossby waves at and near the critical frequency in high latitudes. In this study, we expand their analysis to high-latitude oceanic basins and to include nonlinear eddy effects, by using a linear wave model and a high-resolution model output from the OGCM for the Earth Simulator (OFES). It is found that the linear wave mechanism by and large remains valid in the tropical and subtropical oceans. In higher latitudes as well as in some regions in the western tropical and subtropical oceans, other mechanisms, like nonlinear eddy, play more important role in determining the SSH variability.

Lin, Xiaopei; Yin, Yuqi; Yang, Jiayan

2014-02-01

229

The dependence of damage on internal variables and its incorporation into constitutive equations  

International Nuclear Information System (INIS)

A model is presented for the prediction of the lifetime of metals in the high-temperature range under arbitrary variable uniaxial load. The influence of deformation on damage is discussed. The definition of damage in continuum damage mechanics, which allows indirect measurement of damage via the deformation behaviour, is adopted. To collect some knowledge about the damage evolution, damage is in two ways measured during the strain controlled LCF tests: change of the modulus of elasticity and decrease of the peak stress. Surprisingly, both methods lead to results which are in good agreement. The damage law is then developed by reference to known models and lifetime rules. The damage model is a modification of the creep damage law by Rabotnov. It is extended by a dependence on the inelastic strain rate used instead of the dependence on internal variables describing the internal state. The parameters of the damage model are determined with a view to apply them to AISI 316 L(N) austenitic steel. Some of the parameters are derived from standard creep experiments. To determine further parameters, the damage model is applied to the LCF tests. Both, failure behaviour and damage evolution are described well. (author)

1993-08-15

230

A combinatorial and probabilistic study of initial and end heights of descents in samples of geometrically distributed random variables and in permutations  

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In words, generated by independent geometrically distributed random variables, we study the lth descent, which is, roughly speaking, the lth occurrence of a neighbouring pair ab with a>b. The value a is called the initial height, and b the end height. We study these two random variables (and some similar ones) by combinatorial and probabilistic tools. We find in all instances a generating function ?(v,u), where the coefficient of vjui refers to the jth descent (ascent), and i to the initial ...

Louchard, Guy; Prodinger, Helmut

2007-01-01

231

Randomized Trial of Dual-Focused versus Single-Focused Individual Therapy for Personality Disorders and Substance Dependence  

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We conducted a randomized comparison of Dual Focus Schema Therapy with Individual Drug Counseling as enhancements to residential treatment for 105 substance dependent patients with versus without specific personality disorders. Both therapies were manual-guided and delivered for 6 months by experienced psychotherapists intensively trained and supervised with independent fidelity assessment. Using Cox Proportional Hazards, we found no psychotherapy differences in retention (days in treatment)....

Ball, Samuel A.; Maccarelli, Lisa M.; Lapaglia, Donna M.; Ostrowski, Mark J.

2011-01-01

232

Shape dependency of the extinction and absorption cross sections of dust aerosols modeled as randomly oriented spheroids  

Directory of Open Access Journals (Sweden)

Full Text Available We present computational results on the shape dependency of the extinction and absorption cross sections of dustlike aerosol particles that were modeled as randomly oriented spheroids. Shape dependent variations in the extinction cross sections are largest in the size regime that is governed by the interference structure. Elongated spheroids best fitted measured extinction spectra of re-dispersed Saharan dust samples. For dust particles smaller than 1.5 ?m in diameter and low absorption potential, shape effects on the absorption cross sections are very small.

R. Wagner

2011-09-01

233

Concurrence of Quantum States: Algebraic Dynamical Method Study XXX Models in a Time-Depending Random External Field  

International Nuclear Information System (INIS)

Based on algebraic dynamics and the concept of the concurrence of the entanglement, we investigate the evolutive properties of the two-qubit entanglement that formed by Heisenberg XXX models under a time-depending external held. For this system, the property of the concurrence that is only dependent on the coupling constant J and total values of the external field is proved. Furthermore, we found that the thermal concurrence of the system under a static random external field is a function of the coupling constant J, temperature T, and the magnitude of external held. (general)

2010-06-15

234

Detection of Genetic Variability using Random Amplified Polymorphic DNA Markers in Some Accessions of Moringa oleifera Lam. from Northern Nigeria  

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To investigate genetic variability in Moringa oleifera Lam., 75 accessions from the Sudan and Guinea savanna zones in Nigeria were taxonomically analysed using Random Amplified polymorphic DNA (RAPD) markers. The electrophoresis bands were analysed using NTSYSpc software and the result of their matrices indicated different variability in the accessions. High degrees of polymorphism (74%) among the accessions were observed in terms of genetic relationship and were grouped into five clus...

Abubakar, B. Y.; Wusirika, R.; Mua Zu, S.; Khan, A. U.; Adamu, A. K.

2011-01-01

235

Sex-dependent associations of leptin with metabolic syndrome-related variables: the Stanislas study.  

Science.gov (United States)

Serum leptin has been reported to be associated in a sex-dependent manner with C-reactive protein (CRP), independently of adiposity. We tested the hypothesis that leptin is associated, independently of anthropometry indexes and in a sex-dependent way, with other inflammatory markers and variables related to metabolic syndrome (MS). In 384 healthy middle-aged adults (192 men and 192 women) total fat mass (FM), waist circumference (WC), serum leptin and 15 MS-related parameters (systolic and diastolic blood pressure, triglycerides, cholesterol, high density lipoprotein (HDL)-cholesterol, apo AI and B, fasting glucose, uric acid, CRP, orosomucoid and haptoglobin levels and aspartate aminotransferase (ASAT), alanine aminotransferase (ALAT) and gamma-glutamyl transferase (GGT) activities) were measured. After adjustment for age, alcohol and cigarette consumption, WC, and total FM, leptin concentration was significantly associated with serum triglycerides, total cholesterol, apo B, uric acid and haptoglobin concentrations and liver enzyme activity only in men, and with apo AI, HDL-cholesterol (only borderline) and CRP only in women. Sex interaction terms were significant for total cholesterol, apo B, HDL cholesterol, uric acid, ALAT and GGT, and borderline significant for triglycerides, apo AI and ASAT. In this healthy population, leptin is significantly associated with various MS factors, independently of WC and total FM, depending on gender. Our study provides further evidence of sex-related differences mediated by leptin in inflammatory mechanisms and other MS-related metabolic pathways. PMID:19444226

Samara, Anastasia; Herbeth, Bernard; Aubert, Roberte; Berrahmoune, Hind; Fumeron, Frédéric; Siest, Gérard; Visvikis-Siest, Sophie

2010-01-01

236

A versatile variable field module for field and angular dependent scanning probe microscopy measurements  

CERN Multimedia

We demonstrate a versatile variable field module (VFM) with capability of both field and angular dependent measurements up to 1800 Oe for scanning probe system. The magnetic field strength is changed by adjusting the distance between a rare earth magnet and the probe tip and is monitored in-situ by a built-in Hall sensor. Rotating the magnet allows the field vector to change from the horizontal to vertical direction and makes it possible to do angular dependent measurements. The capability of the VFM system is demonstrated by degaussing a floppy disk media with increasing magnetic field. Angular dependent measurements clearly show the evolution of magnetic domain structures, with a completely reversible magnetic force microscopy phase contrast observed when the magnetic field is rotated by 180{\\deg}. A further demonstration of out-of-plane and in-plane magnetic switching of CoFe2O4 pillars in CoFe2O4-BiFeO3 nanocomposites was presented and discussed.

Liu, Hongxue; Lu, Jiwei; Wolf, Stuart; Hodgson, Jim; Rutgers, Maarten

2013-01-01

237

Central limit theorems for the excursion sets volumes of weakly dependent random fields  

CERN Document Server

The multivariate central limit theorems (CLT) for the volumes of excursion sets of stationary quasi-associated random fields on $\\mathbb{R}^d$ are proved. Special attention is paid to Gaussian and shot noise fields. Formulae for the covariance matrix of the limiting distribution are provided. Statistical versions of the CLT are considered as well. They employ three different estimators of the asymptotic covariance matrix. Some numerical results are also discussed.

Bulinski, Alexander; Timmermann, Florian

2010-01-01

238

A Randomized Clinical Trial of a Therapeutic Workplace for Chronically Unemployed, Homeless, Alcohol-Dependent Adults  

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Aims: To assess the efficacy of the Therapeutic Workplace, a substance abuse intervention that promotes abstinence while simultaneously addressing the issues of poverty and lack of job skills, in promoting abstinence from alcohol among homeless alcoholics. Methods: Participants (n = 124) were randomly assigned to conditions either requiring abstinence from alcohol to engage in paid job skills training (Contingent Paid Training group), offering paid job skills training with no abstinence con...

2011-01-01

239

A Randomized Trial of Two Behavioral Interventions to Improve Outcomes Following Inpatient Detoxification for Alcohol Dependence  

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To determine if the addition of a behavioral intervention during alcohol detoxification would facilitate initiation of subsequent care, we randomized 150 detoxification patients to receive: treatment as usual (TAU), a Motivation Enhancement Therapy (MET) intervention, or a Peer-delivered Twelve Step Facilitation (P-TSF) intervention. The main outcome was the initiation of any type of subsequent care (i.e., professional treatment or self-help) within 30 and 90 days of discharge. Other outcomes...

Blondell, Richard D.; Frydrych, Lynne M.; Jaanima?gi, Urmo; Ashrafioun, Lisham; Homish, Gregory G.; Foschio, Elisa M.; Bashaw, Heather L.

2011-01-01

240

Post traumatic stress symptoms and heart rate variability in Bihar flood survivors following yoga: a randomized controlled study  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background An earlier study showed that a week of yoga practice was useful in stress management after a natural calamity. Due to heavy rain and a rift on the banks of the Kosi river, in the state of Bihar in north India, there were floods with loss of life and property. A week of yoga practice was given to the survivors a month after the event and the effect was assessed. Methods Twenty-two volunteers (group average age ± S.D, 31.5 ± 7.5 years; all of them were males were randomly assigned to two groups, yoga and a non-yoga wait-list control group. The yoga group practiced yoga for an hour daily while the control group continued with their routine activities. Both groups' heart rate variability, breath rate, and four symptoms of emotional distress using visual analog scales, were assessed on the first and eighth day of the program. Results There was a significant decrease in sadness in the yoga group (p Conclusions A week of yoga can reduce feelings of sadness and possibly prevent an increase in anxiety in flood survivors a month after the calamity. Trial Registration Clinical Trials Registry of India: CTRI/2009/091/000285

Joshi Meesha

2010-03-01

 
 
 
 
241

Methodology for the characterization of water quality: Analysis of time-dependent variability  

Science.gov (United States)

The general methodology for characterization of water quality here presented was applied, after elimination of spatial effects, to the analysis of time-dependent variability of physico-chemical parameters measured, on eighteen dates, during the summer months of 1976, at 112 sampling stations on the Saint Lawrence River between Cornwall and Quebec City. Two aspects of water utilization are considered: domestic water-supply and capacity to sustain balanced aquatic life. The methodology, based on use and adaptation of classical multivariate statistical methods (correspondence analysis, hierarchical classification), leads, for a given type of water utilization, to the determination of the most important parameters, of their essential interrelations and shows the relative importance of their variations. Rationalization of network operations is thus obtained through identification of homogeneous behaviour periods as well as of critical dates for the measurement of parameters characterizing a given use.

Lachance, Marius; Bobée, Bernard

1982-11-01

242

A Randomized Trial of Oral Naltrexone for Treating Opioid-Dependent Offenders  

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Offenders with a history of opioid dependence are a particularly difficult group to treat. A large proportion of offenders typically relapse shortly after release from prison, commit drug-related crimes and then are arrested and eventually re-incarcerated. Previous research demonstrated that oral naltrexone was effective in reducing opioid use and preventing recidivism among offenders under federal supervision. The 111 opioid-dependent offenders in this study were under various levels of supe...

2010-01-01

243

Dose dependency and individual variability of the lipopolysaccharide-induced bovine acute phase protein response  

DEFF Research Database (Denmark)

In order to investigate the dose dependency and the individual variability of the lipopolysaccharide (LPS)-induced acute phase protein response in cattle, 8 nonlactating, nonpregnant Danish Holstein cows were challenged 3 times each by intravenous injection of increasing doses (10, 100, and 1000 ng/kg, consecutively) of Escherichia coli LPS with 3-wk intervals. All 3 LPS doses resulted in a rapid increase in serum concentrations of haptoglobin and serum amyloid A (SAA) and a decrease in serum concentrations of albumin in all 8 cows. Serum concentrations of acute phase proteins (APP) remained altered for several days after each LPS injection, and their increase or decrease was significantly related to LPS dose. In addition to dose dependency, the response was also dependent on the individual, as APP concentrations differed significantly among cows. To compare APP production in 2 consecutive challenges, individual APP levels after the challenge with 100 ng LPS/kg were correlated to levels attained after the challenge with 1000 ng LPS/kg. Serum amyloid A concentrations correlated between the 2 challenges, whereas haptoglobin concentrations tended to correlate; no correlation could be demonstrated between SAA and haptoglobin concentrations in either of the challenges, which suggests that the synthesis of haptoglobin and SAA are regulated in different ways. In conclusion, cattle are highly susceptible to LPS, as very low doses of LPS elicited acute phase albumin, SAA, and haptoglobin responses. Concentrations of APP not only reflect the magnitude of LPS exposure but are also influenced by the ability of the individual cow to mount an acute phase response. The ability to produce SAA and haptoglobin may be an innate characteristic of the individual, as responses in consecutive challenges were quantitatively similar.

Jacobsen, S.; Andersen, P.H.

2004-01-01

244

Alcohol-related brief intervention in patients treated for opiate or cocaine dependence: a randomized controlled study  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Despite the importance of heavy drinking and alcohol dependence among patients with opiate and cocaine dependence, few studies have evaluated specific interventions within this group. The aim of the present study was to evaluate the impact of screening with the Alcohol Use Disorders Identification Test (AUDIT and of brief intervention (BI on alcohol use in a sample of patients treated for opioid or cocaine dependence in a specialized outpatient clinic. Methods Adult outpatients treated for opioid or cocaine dependence in Switzerland were screened for excessive alcohol drinking and dependence with the AUDIT. Patients with AUDIT scores that indicated excessive drinking or dependence were randomized into two groups--treatment as usual or treatment as usual together with BI--and assessed at 3 months and 9 months. Results Findings revealed a high rate (44% of problematic alcohol use (excessive drinking and dependence among patients with opiate and cocaine dependence. The number of drinks per week decreased significantly between T0 (inclusion and T3 (month 3. A decrease in average AUDIT scores was observed between T0 and T3 and between T0 and T9 (month 9. No statistically significant difference between treatment groups was observed. Conclusions In a substance abuse specialized setting, screening for alcohol use with the AUDIT, followed by feedback on the score, and use of alcohol BI are both possibly useful strategies to induce changes in problematic alcohol use. Definitive conclusions cannot, however, be drawn from the study because of limitations such as lack of a naturalistic group. An important result of the study is the excellent internal consistency of AUDIT in a population treated for opiate or cocaine dependence.

Khan Riaz

2011-08-01

245

Switching field dependence on heating pulse duration in thermally assisted magnetic random access memories  

Energy Technology Data Exchange (ETDEWEB)

The minimum applied field H{sub SW} required to reverse the magnetic moment of the ferromagnetic/antiferromagnetic storage layer of a thermally assisted magnetic random access memory (TA-MRAM) device during the application of a heating electric pulse is investigated as a function of pulse power P{sub HP} and duration {delta}. For the same power of the heating pulse P{sub HP} (or, equivalently, for the same temperature of the storage layer), H{sub SW} increases with decreasing heating time {delta}. This behavior is consistently interpreted by a thermally activated propagating domain-wall switching model, corroborated by a real-time study of switching. The increase of H{sub SW} with decreasing pulse width introduces a constraint for the minimum power consumption of a TA-MRAM where writing combines heating and magnetic field application.

Papusoi, C. [Spintec, URA 2512 CEA/CNRS, 17 rue des Martyrs, 38054 Grenoble (France)], E-mail: cristian_papusoi@yahoo.com; Conraux, Y.; Prejbeanu, I.L. [Crocus Technology, 5 Robert Schumann, BP 1510, 38025 Grenoble (France); Sousa, R.; Dieny, B. [Spintec, URA 2512 CEA/CNRS, 17 rue des Martyrs, 38054 Grenoble (France)

2009-08-15

246

Switching field dependence on heating pulse duration in thermally assisted magnetic random access memories  

International Nuclear Information System (INIS)

The minimum applied field HSW required to reverse the magnetic moment of the ferromagnetic/antiferromagnetic storage layer of a thermally assisted magnetic random access memory (TA-MRAM) device during the application of a heating electric pulse is investigated as a function of pulse power PHP and duration ?. For the same power of the heating pulse PHP (or, equivalently, for the same temperature of the storage layer), HSW increases with decreasing heating time ?. This behavior is consistently interpreted by a thermally activated propagating domain-wall switching model, corroborated by a real-time study of switching. The increase of HSW with decreasing pulse width introduces a constraint for the minimum power consumption of a TA-MRAM where writing combines heating and magnetic field application.

2009-08-01

247

The Fundamental Manifold of spiral galaxies: ordered versus random motions and the morphology dependence of the Tully-Fisher relation  

CERN Multimedia

(Abridged) We investigate the morphology dependence of the Tully-Fisher relation, and the expansion of the relation into a three-dimensional manifold defined by luminosity, total circular velocity and a third dynamical parameter, to fully characterise spiral galaxies across all morphological types. We use a semi-analytic hierarchical model of galaxy evolution to build the theoretical TF relation. With this tool, we analyse a unique dataset of galaxies for which we cross-match luminosity with total circular velocity and central velocity dispersion. We provide a theoretical framework to calculate such measurable quantities from semi-analytic models. We establish the morphology dependence of the TF relation in both model and data. We analyse the dynamical properties of the model galaxies and determine that the parameter 'sigma/Vc', i.e. the ratio between random and total motions defined by velocity dispersion and circular velocity, accurately characterises the varying slope of the TF relation for different model...

Tonini, Chiara; Mould, Jeremy; Webster, Rachel; Danilovich, Taissa; Ozbilgen, Sinem

2013-01-01

248

Time-dependence in relativistic collisionless shocks: theory of the variable  

Energy Technology Data Exchange (ETDEWEB)

We describe results from time-dependent numerical modeling of the collisionless reverse shock terminating the pulsar wind in the Crab Nebula. We treat the upstream relativistic wind as composed of ions and electron-positron plasma embedded in a toroidal magnetic field, flowing radially outward from the pulsar in a sector around the rotational equator. The relativistic cyclotron instability of the ion gyrational orbit downstream of the leading shock in the electron-positron pairs launches outward propagating magnetosonic waves. Because of the fresh supply of ions crossing the shock, this time-dependent process achieves a limit-cycle, in which the waves are launched with periodicity on the order of the ion Larmor time. Compressions in the magnetic field and pair density associated with these waves, as well as their propagation speed, semi-quantitatively reproduce the behavior of the wisp and ring features described in recent observations obtained using the Hubble Space Telescope and the Chandra X-Ray Observatory. By selecting the parameters of the ion orbits to fit the spatial separation of the wisps, we predict the period of time variability of the wisps that is consistent with the data. When coupled with a mechanism for non-thermal acceleration of the pairs, the compressions in the magnetic field and plasma density associated with the optical wisp structure naturally account for the location of X-ray features in the Crab. We also discuss the origin of the high energy ions and their acceleration in the equatorial current sheet of the pulsar wind.

Spitkovsky, A

2004-02-05

249

Characteristics of heart rate variability in alcohol-dependent subjects and nondependent chronic alcohol users.  

Science.gov (United States)

Heart rate variability (HRV) is an objective and sensitive measure of integrated physiological functioning reflective of heart rhythm responsivity to internal and external demands. Reduced HRV is associated with vulnerability to stress and deterioration of medical and/or psychiatric conditions, while increased HRV is associated with a favorable treatment response and recovery from various medical and/or psychiatric conditions. Our previous review found that acute alcohol consumption caused decreased parasympathetic and increased sympathetic HRV effects in both nonalcoholic and chronic alcohol users. This review investigates the effects of chronic alcohol consumption on HRV in alcohol-dependent subjects and nondependent users. MEDLINE, Scopus, and PubMed were searched for human experimental and clinical trials that measured the effects of chronic alcohol use on HRV. Only publications that included a description of their study designs and clearly stated methodologies for data collections, and outcome measures were reviewed. We have reviewed a total of 24 articles. In nondependent users, low dose (approximating the recommended daily amount of 1 standard drink in women and 2 in men) use is associated with increased HRV parameters compared to those who drink less frequently or abstain altogether. A further increase in consumption is associated with decreased HRV compared to both abstainers and more moderate drinkers. HRV changes during withdrawal generally follow the same negative direction but are more complex and less understood. In dependent subjects, an improvement in HRV was seen following abstinence but remained reduced compared to nonalcoholic controls. This review demonstrates that HRV changes associated with chronic use follow a J-shaped curve. It supports recommendations that limit daily alcohol intake to no more than 2 drinks for men and 1 drink for women. Future studies should investigate HRV as a biomarker of alcoholism development and treatment response as well as the physiological basis for alcohol effects on HRV. PMID:24117482

Karpyak, Victor M; Romanowicz, Magdalena; Schmidt, John E; Lewis, Kriste A; Bostwick, John M

2014-01-01

250

A randomized trial of two behavioral interventions to improve outcomes following inpatient detoxification for alcohol dependence.  

Science.gov (United States)

Participants (n=150), undergoing inpatient alcohol detoxification, were randomized into 3 groups: treatment as usual (TAU), motivation enhancement therapy (MET), or peer-delivered 12-step facilitation (P-TSF). The main outcome was the initiation of any type of subsequent rehabilitation service (i.e., professional treatment or self-help) within 30 and 90 days of discharge. At the 30-day follow-up interview, there was no significant difference among the groups in the rate of initiation of any type of subsequent care (82%, 74%, and 82%, respectively, p=0.617); however, the MET group had significantly more patients initiate subsequent inpatient treatment by the 90-day follow-up interview compared to the P-TSF group (31% and 61%, respectively, p=0.007) and a greater proportion of MET participants completed subsequent inpatient treatment compared to both the TAU and P-TSF groups. There were no differences in drinking-related outcomes. MET during inpatient detoxification may help patients initiate subsequent inpatient rehabilitation treatment. PMID:21491295

Blondell, Richard D; Frydrych, Lynne M; Jaanimagi, Urmo; Ashrafioun, Lisham; Homish, Gregory G; Foschio, Elisa M; Bashaw, Heather L

2011-04-01

251

Satellite derived precipitation and freshwater flux variability and its dependence on the North Atlantic Oscillation  

Science.gov (United States)

The variability of satellite retrieved precipitation and freshwater flux from the `Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite Data' (HOAPS) is assessed with special emphasis on the `North Atlantic Oscillation' (NAO). To cover also land areas, a novel combination of the satellite derived precipitation climatology with the rain gauge based `Full Data Reanalysis Product Version 4', of the `Global Precipitation Climatology Centre' (GPCC) is used. This yields unique high-resolution, quasi-global precipitation fields compiled from two independent data sources. Over the ocean, the response of the freshwater balance and the related parameters to the NAO is investigated for the first time by using a purely satellite based data set. A strong dependence of precipitation patterns to the state of the NAO is found. On synoptic scale this is in accordance with earlier findings by other satellite based and reanalysis products. Furthermore, the consistency of the combined HOAPS-3/GPCC data set allows also detailed regional analyses of precipitation patterns. The response of HOAPS-3 freshwater flux to the NAO is dominated by precipitation at mid and high latitudes, while for the subtropical regions the feedback of the evaporation is stronger.

Andersson, Axel; Bakan, Stephan; Graßl, Hartmut

2010-08-01

252

Dose-Dependent Effects of the Cimicifuga racemosa Extract Ze 450 in the Treatment of Climacteric Complaints: A Randomized, Placebo-Controlled Study.  

Science.gov (United States)

Extracts from Cimicifuga racemosa (CR, synonym Actaea racemosa) have shown efficacy in trials in women with menopausal symptoms. Yet, dose dependency remains unclear. Therefore, 180 female outpatients with climacteric complaints were treated for 12 weeks in a randomized, double-blind, placebo-controlled, 3-armed trial (CR extract Ze 450 in 6.5?mg or 13.0?mg, or placebo). Primary outcome was the difference in menopausal symptoms (vasomotor, psychological, and somatic), assessed by the Kupperman Menopausal Index between baseline and week 12. Secondary efficacy variables were patients' self-assessments of general quality of life (QoL), responder rates, and safety. Compared to placebo, patients receiving Ze 450 showed a significant reduction in the severity of menopausal symptoms in a dose-dependent manner from baseline to endpoint (mean absolute differences 17.0 (95% CI 14.65-19.35) score points, P < 0.0001 for 13.0?mg; mean absolute differences 8.47 (95% CI 5.55-11.39) score points, P = 0.0003 for 6.5?mg). QoL and responder rates corresponded with the main endpoint. Changes in menopausal symptoms and QoL were inversely correlated. Reported adverse events and clinical laboratory testing did not raise safety concerns. The CR extract Ze 450 is an effective and well-tolerated nonhormonal alternative to hormone treatment for symptom relief in menopausal women. PMID:23346194

Schellenberg, Ruediger; Saller, Reinhard; Hess, Lorenzo; Melzer, Jörg; Zimmermann, Christian; Drewe, Juergen; Zahner, Catherine

2012-01-01

253

A Large Cohort Study Concerning Age-Dependent Impacts of Anthropometric Variables on Spirometric Parameters in Nonsmoking Healthy Adults  

Science.gov (United States)

Backgrounds Although height (H) has been considered the principal anthropometric variable governing lung function, the age-dependent differences in its influences on determining spirometric parameters (SPs) have not been conclusively investigated. Moreover, there has been no study centered on age-dependent effects of other anthropometric variables, including body weight (BW) and body fat mass (BFM) on SPs. In addition, the age-dependent influences of these anthropometric variables are anticipated to differ quantitatively between male and female participants. Methods A total of 16,919 nonsmoking healthy Japanese adults (men: 6,116, women: 10,803) were partitioned into six groups stratified by gender and age at intervals of 20-years: young-, middle-, and advanced-age groups of either gender. Using a model in which a SP was described by a logarithmic additive function of age, H, BW, and BFM, we determined the partial regression coefficients of the respective anthropometric variables to predict the reference means of SPs, including FVC, FEV1, FEV1/FVC, PEF, FEF50, and FEF75, in the six groups. Results/Discussion Although the impact of H on FVC and FEV1 was relatively homogeneous irrespective of gender and age, its homogeneity faded for flow parameters, particularly in the female middle- and advanced-age groups, indicating that the age-dependent contribution of H to SPs was enhanced more in women. The impact of BW on SPs differed depending on age, and this effect was also more conspicuous for female participants. H and BW generally exerted positive effects on SPs, whereas BFM had negative effects. Opposite effects of BW and BFM were observed in the female middle-age group in particular. Conclusions The effects of anthropometric variables on spirometric parameters are highly age-dependent, particularly in women, leading to the conclusion that the assumption of age-independent, constant partial regression coefficients of anthropometric variables while predicting the reference mean of a certain spirometric parameter may result in substantial errors.

Omori, Hisamitsu; Onoue, Ayumi; Katoh, Takahiko; Ogata, Yasuhiro; Kawashima, Hidetoshi; Miyao, Naoki; Tsuji, Takao; Aoshiba, Kazutetsu; Nagai, Atsushi; Yamaguchi, Kazuhiro

2014-01-01

254

Calculation of the Effect of Random Superfluid Density on the Temperature Dependence of the Penetration Depth  

Energy Technology Data Exchange (ETDEWEB)

Microscopic variations in composition or structure can lead to nanoscale inhomogeneity in superconducting properties such as the magnetic penetration depth, but measurements of these properties are usually made on longer length scales. We solve a generalized London equation with a non-uniform penetration depth {lambda}(r), obtaining an approximate solution for the disorder-averaged Meissner screening. We find that the effective penetration depth is different from the average penetration depth and is sensitive to the details of the disorder. These results indicate the need for caution when interpreting measurements of the penetration depth and its temperature dependence in systems which may be inhomogeneous.

Lippman, Thomas; Moler, Kathryn A.

2012-07-20

255

Calculation of the effect of random superfluid density on the temperature dependence of the penetration depth  

Science.gov (United States)

Microscopic variations in composition or structure can lead to nanoscale inhomogeneity in superconducting properties such as the magnetic penetration depth, but measurements of these properties are usually made on longer length scales. We solve a generalized London equation with a non-uniform penetration depth ?(r), obtaining an approximate solution for the disorder-averaged Meissner screening. We find that the effective penetration depth is different from the average penetration depth and is sensitive to the details of the disorder. These results indicate the need for caution when interpreting measurements of the penetration depth and its temperature dependence in systems which may be inhomogeneous.

Lippman, Thomas M.; Moler, Kathryn A.

2012-03-01

256

On random orthogonal polynomials  

Directory of Open Access Journals (Sweden)

Full Text Available Let T0?(x,T1?(x,…,Tn?(x be a sequence of normalized Legendre polynomials orthogonal with respect to the interval (?1,1. The asymptotic estimate of the expected number of real zeros of the random polynomial g0T0?(x+g1T1?(x+…+gnTn?(x where gj, j=1,2,…,n are independent identically and normally distributed random variables is known. In this paper, we first present the asymptotic value for the above expected number when coefficients are dependent random variables. Further, for the case of independent coefficients, we define the expected number of zero up-crossings with slope greater than u or zero down-crossings with slope less than ?u. Promoted by the graphical interpretation, we define these crossings as u-sharp. For the above polynomial, we provide the expected number of such crossings.

K. Farahmand

2001-01-01

257

Baclofen for maintenance treatment of opioid dependence: A randomized double-blind placebo-controlled clinical trial [ISRCTN32121581  

Science.gov (United States)

Background Results of preclinical studies suggest that the GABAB receptor agonist baclofen may be useful in treatment of opioid dependence. This study was aimed at assessing the possible efficacy of baclofen for maintenance treatment of opioid dependence. Methods A total of 40 opioid-dependent patients were detoxified and randomly assigned to receive baclofen (60 mg/day) or placebo in a 12-week, double blind, parallel-group trial. Primary outcome measure was retention in treatment. Secondary outcome measures included opioids and alcohol use according to urinalysis and self-report ratings, intensity of opioid craving assessed with a visual analogue scale, opioid withdrawal symptoms as measured by the Short Opiate Withdrawal Scale and depression scores on the Hamilton inventory. Results Treatment retention was significantly higher in the baclofen group. Baclofen also showed a significant superiority over placebo in terms of opiate withdrawal syndrome and depressive symptoms. Non-significant, but generally favorable responses were seen in the baclofen group with other outcome measures including intensity of opioid craving and self-reported opioid and alcohol use. However, no significant difference was seen in the rates of opioid-positive urine tests. Additionally, the drug side effects of the two groups were not significantly different. Conclusion The results support further study of baclofen in the maintenance treatment of opioid dependence.

Assadi, Seyed Mohammad; Radgoodarzi, Reza; Ahmadi-Abhari, Seyed Ali

2003-01-01

258

Baclofen for maintenance treatment of opioid dependence: A randomized double-blind placebo-controlled clinical trial [ISRCTN32121581  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Results of preclinical studies suggest that the GABAB receptor agonist baclofen may be useful in treatment of opioid dependence. This study was aimed at assessing the possible efficacy of baclofen for maintenance treatment of opioid dependence. Methods A total of 40 opioid-dependent patients were detoxified and randomly assigned to receive baclofen (60 mg/day or placebo in a 12-week, double blind, parallel-group trial. Primary outcome measure was retention in treatment. Secondary outcome measures included opioids and alcohol use according to urinalysis and self-report ratings, intensity of opioid craving assessed with a visual analogue scale, opioid withdrawal symptoms as measured by the Short Opiate Withdrawal Scale and depression scores on the Hamilton inventory. Results Treatment retention was significantly higher in the baclofen group. Baclofen also showed a significant superiority over placebo in terms of opiate withdrawal syndrome and depressive symptoms. Non-significant, but generally favorable responses were seen in the baclofen group with other outcome measures including intensity of opioid craving and self-reported opioid and alcohol use. However, no significant difference was seen in the rates of opioid-positive urine tests. Additionally, the drug side effects of the two groups were not significantly different. Conclusion The results support further study of baclofen in the maintenance treatment of opioid dependence.

Ahmadi-Abhari Seyed Ali

2003-11-01

259

A study of probabilistic fatigue crack propagation models in Mg Al Zn alloys under different specimen thickness conditions by using the residual of a random variable  

Energy Technology Data Exchange (ETDEWEB)

The primary aim of this paper was to evaluate several probabilistic fatigue crack propagation models using the residual of a random variable, and to present the model fit for probabilistic fatigue behavior in Mg Al Zn alloys. The proposed probabilistic models are the probabilistic Paris Erdogan model, probabilistic Walker model, probabilistic Forman model, and probabilistic modified Forman models. These models were prepared by applying a random variable to the empirical fatigue crack propagation models with these names. The best models for describing fatigue crack propagation models with these names. The best models for describing fatigue crack propagation models with these names. The best models for describing fatigue crack propagation models with these names. The best models vor describing fatigue crack propagation behavior in Mg Al Zn alloys were generally the probabilistic Paris Erdogan and probabilistic Walker models. The probabilistic Forman model was a good model only for a specimen with a thickness of 9.45mm.

Choi, Seon Soon [Sahmyook Univ., Seoul (Korea, Republic of)

2012-04-15

260

Chronic kidney disease in the type 2 diabetic patients: prevalence and associated variables in a random sample of 2642 patients of a Mediterranean area  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background Kidney disease is associated with an increased total mortality and cardiovascular morbimortality in the general population and in patients with Type 2 diabetes. The aim of this study is to determine the prevalence of kidney disease and different types of renal disease in patients with type 2 diabetes (T2DM). Methods Cross-sectional study in a random sample of 2,642 T2DM patients cared for in primary care during 2007. Studied variables: demogr...

2012-01-01

 
 
 
 
261

Chronic kidney disease in the type 2 diabetic patients: prevalence and associated variables in a random sample of 2642 patients of a Mediterranean area  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Background: Kidney disease is associated with an increased total mortality and cardiovascular morbimortality in the general population and in patients with Type 2 diabetes. The aim of this study is to determine the prevalence of kidney disease and different types of renal disease in patients with type 2 diabetes (T2DM). Methods: Cross-sectional study in a random sample of 2,642 T2DM patients cared for in primary care during 2007. Studied variables: demographic and clinical characteristics, ph...

2012-01-01

262

Contractile Strength during Variable Heart Duration Is Species and Preload Dependent  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate the effect of beat-to-beat variability on cardiac contractility. Cardiac trabeculae were isolated from the right ventricle of rabbits and beagle dogs and stimulated to isometrically contract, alternating between fixed steady state versus variable interbeat intervals. Trabeculae were stimulated at physiologically relevant frequencies for each species (dog 1 and 4?Hz; rabbit 2 and 4?Hz) intercalating fixed periods with 40% variability. A subset of the trabeculae (at 90% of op...

Torres, Carlos A. A.; Janssen, Paul M. L.

2011-01-01

263

Spatial variability and its scale dependency of observed and modeled soil moisture over different climate regions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Past studies on soil moisture spatial variability have been mainly conducted at catchment scales where soil moisture is often sampled over a short time period; as a result, the observed soil moisture often exhibited smaller dynamic ranges, which prevented the complete revelation of soil moisture spatial variability as a function of mean soil moisture. In this study, spatial statistics (mean, spatial variability and skewness) of in situ soil moisture, modeled and satellite-retrieved soil moist...

Li, B.; Rodell, M.

2013-01-01

264

Spatial variability and its scale dependency of observed and modeled soil moisture under different climate conditions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Past studies on soil moisture spatial variability have been mainly conducted in catchment scales where soil moisture is often sampled over a short time period. Because of limited climate and weather conditions, the observed soil moisture often exhibited smaller dynamic ranges which prevented the complete revelation of soil moisture spatial variability as a function of mean soil moisture. In this study, spatial statistics (mean, spatial variability and skewness) of in situ soil moisture...

Li, B.; Rodell, M.

2012-01-01

265

Lactase persistence and bitter taste response: instrumental variables and mendelian randomization in epidemiologic studies of dietary factors and cancer risk  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Consumption of dairy products seems to increase the risk of cancer at several sites, while intake of cruciferous vegetables could have protective effects. However, these dietary intakes are subject to measurement error, and associations with cancer could be due to confounders. Mendelian randomization has been suggested as a way to overcome confounding by exploiting the random allocation of alleles from parents to offspring. In mid-2006, the authors conducted a study of allele frequencies for ...

Matullo, Giuseppe; Vineis, Paolo; Guarrera, Simonetta; Sacerdote, Carlotta

2007-01-01

266

Random-Time, State-Dependent Stochastic Drift for Markov Chains and Application to Stochastic Stabilization Over Erasure Channels  

CERN Multimedia

It is known that state-dependent, multi-step Lyapunov bounds lead to greatly simplified verification theorems for stability, for large classes of Markov chain models --- This is one component of the ``fluid model'' approach to stability of stochastic networks. In this paper we extend the general theory to randomized multi-step Lyapunov theory to obtain criteria for the existence of a finite steady state, as well as finite moments. These results are applied to a remote stabilization problem, in which a controller receives measurements from an erasure channel with limited capacity. Based on the general results in the paper it is shown that stability of the closed loop system is assured provided the capacity is greater than the logarithm of the unstable eigenvalue, plus an additional correction term. Stronger conditions are required for the existence of a finite second moment in steady-state.

Yüksel, Serdar

2010-01-01

267

DEPENDENCE OF THE OPTICAL/ULTRAVIOLET VARIABILITY ON THE EMISSION-LINE PROPERTIES AND EDDINGTON RATIO IN ACTIVE GALACTIC NUCLEI  

International Nuclear Information System (INIS)

The dependence of the long-term optical/UV variability on the spectral and fundamental physical parameters for radio-quiet active galactic nuclei (AGNs) is investigated. The multi-epoch-repeated photometric scanning data in the Stripe-82 region of the Sloan Digital Sky Survey (SDSS) are exploited for two comparative AGN samples (mostly quasars) selected therein: a broad-line Seyfert 1 (BLS1) type sample and a narrow-line Seyfert 1 (NLS1) type AGN sample within redshifts 0.3-0.8. Their spectral parameters are derived from the SDSS spectroscopic data. It is found that on rest-frame timescales of several years the NLS1-type AGNs show systematically smaller variability compared to the BLS1-type AGNs. In fact, the variability amplitude is found to correlate, though only moderately, with the eigenvector 1 parameters, i.e., the smaller the H? linewidth, the weaker the [O III] and the stronger the Fe II emission, the smaller the variability amplitude. Moreover, an interesting inverse correlation is found between the variability and the Eddington ratio, which is perhaps more fundamental. The previously known dependence of the variability on luminosity is not significant, and the dependence on black hole mass-as claimed in recent papers and also present in our data-fades out when controlling for the Eddington ratio in the correlation analysis, though these may be partly due to the limited ranges of luminosity and black hole mass of our samples. Our result strongly supports that an accretion disk is likely to play a major role in producing the optical/UV variability.

2010-06-10

268

Effect of modafinil on impulsivity and relapse in alcohol dependent patients: a randomized, placebo-controlled trial.  

Science.gov (United States)

Poor impulse control plays an important role in the development, course and relapse of substance use disorders. Therefore, improving impulse control may represent a promising approach in the treatment of alcohol dependence. This study aimed to test the effect of modafinil on impulse control and alcohol use in alcohol dependent patients (ADP) in a randomized, double-blind, placebo-controlled trial. Eighty-three abstinent ADP were randomized to 10 weeks modafinil (300 mg/d) or placebo. Alcohol use was quantified using the timeline follow-back method and was assessed until 6 months after treatment discontinuation. Impulsivity was assessed using self-report questionnaires (Barratt Impulsiveness Scale; State Impulsivity questionnaire) and neurocognitive tasks (Stop Signal Task; Delay Discounting Task) administered before, during and after treatment. Modafinil significantly improved self-report measures of state impulsivity, but had no effect on percentage of abstinent days or percentage of heavy drinking days, nor on the behavioral measures of impulsivity. However, subgroup analysis revealed that modafinil prolonged the time to relapse (p=.022) and tended to increase the percentage of abstinent days (p=.066) in ADP with poor response inhibition at baseline, whereas modafinil increased the percentage of heavy drinking days (p=.003) and reduced the percentage of abstinent days (p=.002) in patients with better baseline response inhibition. Overall results do not favor the use of modafinil in order to reduce relapse or relapse severity in ADP, and caution is required in prescribing modafinil to a non-selected sample of ADP. Further research on the effect of modafinil in ADP with poor baseline response inhibition is warranted. PMID:23141152

Joos, Leen; Goudriaan, Anna E; Schmaal, Lianne; Fransen, Erik; van den Brink, Wim; Sabbe, Bernard G C; Dom, Geert

2013-08-01

269

Characterizations of joint distributions, copulas, information, dependence and decoupling, with applications to time series  

CERN Multimedia

In this paper, we obtain general representations for the joint distributions and copulas of arbitrary dependent random variables absolutely continuous with respect to the product of given one-dimensional marginal distributions. The characterizations obtained in the paper represent joint distributions of dependent random variables and their copulas as sums of $U$-statistics in independent random variables. We show that similar results also hold for expectations of arbitrary statistics in dependent random variables. As a corollary of the results, we obtain new representations for multivariate divergence measures as well as complete characterizations of important classes of dependent random variables that give, in particular, methods for constructing new copulas and modeling different dependence structures. The results obtained in the paper provide a device for reducing the analysis of convergence in distribution of a sum of a double array of dependent random variables to the study of weak convergence for a doub...

De la Pena, V H; Sharakhmetov, S; de la Peña, Victor H; Ibragimov, Rustam; Sharakhmetov, Shaturgun

2006-01-01

270

A Comparison of the Prognostic Value of Early PSA Test-Based Variables Following External Beam Radiotherapy, With or Without Preceding Androgen Deprivation: Analysis of Data From the TROG 96.01 Randomized Trial  

International Nuclear Information System (INIS)

Purpose: We sought to compare the prognostic value of early prostate-specific antigen (PSA) test-based variables for the 802 eligible patients treated in the Trans-Tasman Radiation Oncology Group 96.01 randomized trial. Methods and Materials: Patients in this trial had T2b, T2c, T3, and T4 N0 prostate cancer and were randomized to 0, 3, or 6 months of neoadjuvant androgen deprivation therapy (NADT) prior to and during radiation treatment at 66 Gy to the prostate and seminal vesicles. The early PSA test-based variables evaluated were the pretreatment initial PSA (iPSA) value, PSA values at 2 and 4 months into NADT, the PSA nadir (nPSA) value after radiation in all patients, and PSA response signatures in men receiving radiation. Comparisons of endpoints were made using Cox models of local progression-free survival, distant failure-free survival, biochemical failure-free survival, and prostate cancer-specific survival. Results: The nPSA value was a powerful predictor of all endpoints regardless of whether NADT was given before radiation. PSA response signatures also predicted all endpoints in men treated by radiation alone. iPSA and PSA results at 2 and 4 months into NADT predicted biochemical failure-free survival but not any of the clinical endpoints. nPSA values correlated with those of iPSA, Gleason grade, and T stage and were significantly higher in men receiving radiation alone than in those receiving NADT. Conclusions: The postradiation nPSA value is the strongest prognostic indicator of all early PSA-based variables. However, its use as a surrogate endpoint needs to take into account its dependence on pretreatment variables and treatment method.

2011-02-01

271

Angular dependence of multiple-bit upset response in static random access memories under heavy ion irradiation  

International Nuclear Information System (INIS)

Experimental evidence is presented relevant to the angular dependences of multiple-bit upset (MBU) rates and patterns in static random access memories (SRAMs) under heavy ion irradiation. The single event upset (SEU) cross sections under tilted ion strikes are overestimated by 23.9%–84.6%, compared with under normally incident ion with the equivalent linear energy transfer (LET) value of ? 41 MeV/(mg/cm2), which can be partially explained by the fact that the MBU rate for tilted ions of 30° is 8.5%–9.8% higher than for normally incident ions. While at a lower LET of ? 9.5 MeV/(mg/cm2), no clear discrepancy is observed. Moreover, since the ion trajectories at normal and tilted incidences are different, the predominant double-bit upset (DBU) patterns measured are different in both conditions. Those differences depend on the LET values of heavy ions and devices under test. Thus, effective LET method should be used carefully in ground-based testing of single event effects (SEE) sensitivity, especially in MBU-sensitive devices. (condensed matter: structural, mechanical, and thermal properties)

2013-08-01

272

Frequency-dependent hopping conductivity in a static electric field in a random one-dimensional lattice  

International Nuclear Information System (INIS)

The frequency-dependent electrical conductivity is studied in a nearest-neighbor-hopping linear lattice with disordered site energies and barrier heights in the presence of a uniform static electric field, allowing for detailed balance between random rates. Exact expressions are obtained for the conductivity for both high and low frequencies. The results reduce to those obtained by previous authors in the absence of site-energy disorder. However, the latter is found to alter the character of the frequency dependence of the conductivity significantly at low frequencies. In this case the conductivity is expanded as sigma(?) = sigma0+isigma1?-sigma2?2 -isigma3?3+.... We find that sigma1 is nonvanishing only if both site energies and barrier heights are disordered and that sigma2 is positive when the fluctuations in site energies are small compared with the thermal energy but becomes negative in the opposite regime. The ac response is found to vanish [i.e., sigma(?) = 0 for ?not =0] in the absence of disorder in barrier heights

1986-02-15

273

Opioid maintenance therapy suppresses alcohol intake in heroin addicts with alcohol dependence: preliminary results of an open randomized study.  

Science.gov (United States)

An open randomized study lasting 12 months was performed to evaluate the efficacy of methadone or buprenorphine to suppress alcohol use in two hundred and eighteen heroin addicts with alcohol dependence. Daily maintenance doses of methadone were 80, 120, 160, and 200 mg/day, while doses of buprenorphine were 8, 16, 24, and 32 mg/day. As expected, both treatments were able to reduce both heroin use and addiction severity (measured with ASI interview). However, although both medications were able to suppress alcohol use, the highest dose of buprenorphine was better than the highest dose of methadone, in reducing alcohol craving, ethanol intake (measured as daily number of drinks), and the ASI subscale of alcohol use. The mechanism underlying the effects of the opioid maintenance therapy on the reduction of alcohol intake is still unclear. The results of the present study may represent the first clinical evidence of the potential effective use of the highest doses of buprenorphine for the suppression of ethanol intake in heroin addicts with alcohol dependence. PMID:18801404

Nava, Felice; Manzato, Ezio; Leonardi, Claudio; Lucchini, Alfio

2008-12-12

274

Strictly and asymptotically scale invariant probabilistic models of N correlated binary random variables having q-Gaussians as N ? ? limiting distributions  

International Nuclear Information System (INIS)

The celebrated Leibnitz triangle has a remarkable property, namely that each of its elements equals the sum of its south-west and south-east neighbors. In probabilistic terms, this corresponds to a specific form of correlation of N equally probable binary variables which satisfy scale invariance. Indeed, the marginal probabilities of the N-system precisely coincide with the joint probabilities of the (N?1)-system. On the other hand, the non-additive entropy which grounds non-extensive statistical mechanics, is, under appropriate constraints, extremized by the (q-Gaussian) distribution. These distributions also result, as attractors, from a generalized central limit theorem for random variables which have a finite generalized variance, and are correlated in a specific way called q-independence. In order to provide physical enlightenment as regards this concept, we introduce here three types of asymptotically scale invariant probabilistic models with binary random variables, namely (i) a family, characterized by an index ? = 1,2,3,..., unifying the Leibnitz triangle (? = 1) and the case of independent variables (???); (ii) two slightly different discretizations of q-Gaussians; (iii) a special family, characterized by the parameter ?, which generalizes the usual case of independent variables (recovered for ? = 1/2). Models (i) and (iii) are in fact strictly scale invariant. For models (i), we analytically show that the N ? ? probability distribution is a q-Gaussian with q = (??2)/(??1). Models (ii) approach q-Gaussians by construction, and we numerically show that they do so with asymptotic scale invariance. Models (iii), like two other strictly scale invariant models recently discussed by Hilhorst and Schehr, approach instead limiting distributions which are not q-Gaussians. The scenario which emerges is that asymptotic (or even strict) scale invariance is not sufficient but it might be necessary for having strict (or asymptotic) q-independence, which, in turn, mandates q-Gaussian attractors

2008-09-01

275

Methylphenidate for treating tobacco dependence in non-attention deficit hyperactivity disorder smokers: A pilot randomized placebo-controlled trial  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Methylphenidate blocks the re-uptake of dopamine by binding to the dopamine transporter in the presynaptic cell membrane and increases extracellular dopamine levels. Similarities in neuropsychologic effects between nicotine and methylphenidate make it an intriguing potential therapeutic option. Previous research of methylphenidate in smokers has suggested a possible beneficial effect for the relief of nicotine withdrawal symptoms, but showed no efficacy in helping smokers with attention deficit hyperactivity disorder (ADHD to stop smoking. Methods To investigate potential efficacy for relieving nicotine withdrawal symptoms and promoting smoking abstinence, we conducted a randomized, double-blind, placebo-controlled, phase II study of once-a-day osmotic-release oral system methylphenidate (OROS-MPH, Concerta® at a target dose of 54-mg/day for 8 weeks compared with placebo in 80 adult cigarette smokers. Results Of the 80 randomized subjects and median smoking rate was 20 cigarettes per day. At the end of the medication phase, the biochemically confirmed 7-day point prevalence smoking abstinence was 10% (4/40 for the placebo group and 2.5% (1/40 for the OROS-MPH group. Nicotine withdrawal was not found to differ significantly between treatment groups during the first 14 days following the start of medication prior to the target quit date (p = 0.464 or during the first 14 days following the target quit date (p = 0.786. Conclusion We observed no evidence of efficacy of OROS-MPH to aid smokers to stop smoking. Although there are biologically plausible hypotheses that support the use of OROS-MPH for treating tobacco dependence, we found no evidence to support such hypotheses. In addition to no increase in smoking abstinence, we saw no effect of OROS-MPH for tobacco withdrawal symptom relief and no change in smoking rates was observed in the OROS-MPH group compared to the placebo group.

Croghan Ivana T

2011-01-01

276

Experiment and theory of Pb(In1/2Nb1/2)O3. Antiferroelectric, ferroelectric, or relaxor state depending on perovskite B-site randomness  

International Nuclear Information System (INIS)

We review the recent progress in our understanding of the effect of B-site randomness on Pb(In1/2Nb1/2)O3 (PIN) from the experimental and theoretical viewpoints. PIN is one of the ideal systems for investigating the effect of perovskite B-site randomness on relaxor formation, because it can be in the antiferroelectric (AFE), ferroelectric (FE), or relaxor state depending on B-site randomness. Lattice dynamics measured in ordered and disordered PINs indicates the existence of FE instability regardless of the B-site randomness of PIN. AFE is stabilized when the B-site is spatially ordered, overwhelming FE instability. The hidden FE state starts to appear as B-site randomness becomes stronger and suppresses AFE instability. Ultimately, the randomness competes with the development of FE regions and blocks long-range FE ordering, which yields polar nanoregions (PNRs) resulting in relaxor behavior. In order to investigate the interesting behavior of PIN, we constructed a minimal model that includes dipolar interaction and easy-axis anisotropy which depends on B-site randomness. The results from Monte Carlo simulations show that the model well reproduces the phase diagram and dielectric constant of PIN qualitatively. (author)

2010-01-01

277

Experiment and Theory of Pb(In1/2Nb1/2)O3: Antiferroelectric, Ferroelectric, or Relaxor State Depending on Perovskite B-Site Randomness  

Science.gov (United States)

We review the recent progress in our understanding of the effect of B-site randomness on Pb(In1/2Nb1/2)O3 (PIN) from the experimental and theoretical viewpoints. PIN is one of the ideal systems for investigating the effect of perovskite B-site randomness on relaxor formation, because it can be in the antiferroelectric (AFE), ferroelectric (FE), or relaxor state depending on B-site randomness. Lattice dynamics measured in ordered and disordered PINs indicates the existence of FE instability regardless of the B-site randomness of PIN. AFE is stabilized when the B-site is spatially ordered, overwhelming FE instability. The hidden FE state starts to appear as B-site randomness becomes stronger and suppresses AFE instability. Ultimately, the randomness competes with the development of FE regions and blocks long-range FE ordering, which yields polar nanoregions (PNRs) resulting in relaxor behavior. In order to investigate the interesting behavior of PIN, we constructed a minimal model that includes dipolar interaction and easy-axis anisotropy which depends on B-site randomness. The results from Monte Carlo simulations show that the model well reproduces the phase diagram and dielectric constant of PIN qualitatively.

Ohwada, Kenji; Tomita, Yusuke

2010-01-01

278

On history dependence of stress-strain diagrams and creep curves under variable repeated loading  

International Nuclear Information System (INIS)

The ability of structural alloys to 'keep in memory' the loading prehistory becomes of special importance when inelastic variable repeated loading is considered. There are two main approaches to the development of the mathematical description of this phenomenon: the inclusion of hidden state variables in the incremental theory constitutive equations (a) and construction of proper hereditary functionals (b). In this respect the assumption that the 'memory' regarding the previous deformation history is due to structural nonhomogeneity of actual materials proves to be fruitful. (orig.)

1979-08-21

279

Genetic variability in yam cultivars from Guinea-Sudan of Benin assessed by random amplified polymorphic DNA  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Yam (Dioscorea spp.) is an important food and cash crop in the Guinea-Sudan zone of Benin. The genetic diversity of about 70 cultivars of Dioscorea cayenensis/Dioscorea rotundata (Guinea yam) and about 20 cultivars of Dioscorea alata (water yam) was analysed using random amplified polymorphic DNA (RAPD). The amplified bands revealed high polymorphism. These polymorphic DNA fragments were used to construct dendrograms, clustering all accessions into 18 groups: 12 for D. cayenensis/D. rotundata...

2009-01-01

280

A Better Lemon Squeezer? Maximum-Likelihood Regression with Beta-Distributed Dependent Variables  

Science.gov (United States)

Uncorrectable skew and heteroscedasticity are among the "lemons" of psychological data, yet many important variables naturally exhibit these properties. For scales with a lower and upper bound, a suitable candidate for models is the beta distribution, which is very flexible and models skew quite well. The authors present maximum-likelihood…

Smithson, Michael; Verkuilen, Jay

2006-01-01

 
 
 
 
281

Individual variability of 90Sr deposition depending on sample genotype homogeneity  

International Nuclear Information System (INIS)

The study on the range of individual changes in the individual variability of the 90Sr skeleton metabolism in the CBA mice (including sex and age peculiarities) as well as its comparison (by published data) with the range of variability in the outbred animals and small mammals from the natural population living in the epicenter of the Earth-Ural radioactive trail is carried out. The CBA mature mice were subjected intraperitoneally to the 1.0 ml 90Sr solution. The radiometry results showed that soft tissues contained less than 0.4 % from the radionuclide injected quantity, which constitutes 1 % 90Sr contained in the skeleton. Absence of sex differences in the 90Sr deposition and availability of age differences was registered. The variations in the radionuclide accumulation induced do not exceed two times. The analysis of the 90Sr individual deposition variability range in the genetically homogeneous animals in comparison with the outbread nonlinear ones and voles from the natural population indicated the variability of the 90Sr accumulation indices with increase in the samples genotype heterogeneity

2000-01-01

282

Lactase persistence and bitter taste response: instrumental variables and mendelian randomization in epidemiologic studies of dietary factors and cancer risk.  

Science.gov (United States)

Consumption of dairy products seems to increase the risk of cancer at several sites, while intake of cruciferous vegetables could have protective effects. However, these dietary intakes are subject to measurement error, and associations with cancer could be due to confounders. Mendelian randomization has been suggested as a way to overcome confounding by exploiting the random allocation of alleles from parents to offspring. In mid-2006, the authors conducted a study of allele frequencies for the lactase (LCT) and taste receptor, type 2, member 38 (TAS2R38) genes, including 634 volunteers recruited (1992-1998) from the Italian branch of the European Prospective Investigation into Cancer and Nutrition. The authors hypothesized that there would be a lower milk intake among carriers of the LCT CC genotype and a different intake of cruciferous vegetables among carriers of the TAS2R38 variant. Overall, the frequency of the LCT T allele was higher in northern Italy than in southern Italy. Food intake was associated with gene variants. An association was evident for ice cream and LCT variants (p = 0.004); less so for milk intake. In addition, the TAS2R38 variant showed a geographic gradient and an association with cruciferous vegetable intake. These results suggest that the LCT and TAS2R38 variants are good candidates for Mendelian randomization studies of cancer and other health outcomes. PMID:17596267

Sacerdote, Carlotta; Guarrera, Simonetta; Smith, George Davey; Grioni, Sara; Krogh, Vittorio; Masala, Giovanna; Mattiello, Amalia; Palli, Domenico; Panico, Salvatore; Tumino, Rosario; Veglia, Fabrizio; Matullo, Giuseppe; Vineis, Paolo

2007-09-01

283

On the frequency-dependent specific heat and TMDSC: Constitutive modelling based on thermodynamics with internal state variables  

International Nuclear Information System (INIS)

To develop constitutive models to represent the thermomechanically chemically coupled behaviour of curing resins, vulcanizing elastomers or melting and crystallizing polymers the technique of DSC is extremely helpful. In the present study, the method of TMDSC is interpreted and evaluated in the context of thermodynamics with internal state variables. The balance equation of energy and the dissipation principle in the form of the Clausius-Duhem inequality form the theoretical basis of our study. Since the pressure and the temperature are the external variables in DSC, the specific Gibbs free energy is used as thermodynamic potential. It depends on temperature, stress and a set of internal state variables to represent the microstructure of the material on a phenomenological basis. The temperature- and internal variable-induced changes in the Gibbs free energy are approximated by a Taylor series up to second order terms. As a substantial result of this work, closed-form expressions for the dynamic calorimetric response due to harmonic temperature perturbations and the frequency-dependent complex heat capacity are derived. The theory allows a physical interpretation of the complex heat capacity and its underlying phenomena and is in accordance with experimental observations from literature.

2009-06-01

284

Accurate approximate solution to nonlinear oscillators in which the restoring force is inversely proportional to the dependent variable  

International Nuclear Information System (INIS)

A modified generalized, rational harmonic balance method is used to construct approximate frequency-amplitude relations for a conservative nonlinear singular oscillator in which the restoring force is inversely proportional to the dependent variable. The procedure is used to solve the nonlinear differential equation approximately. The approximate frequency obtained using this procedure is more accurate than those obtained using other approximate methods and the discrepancy between the approximate frequency and the exact one is lower than 0.40%

2008-06-01

285

Thermo elastic analysis of functionally graded rotating disks with temperature-dependent material properties: uniform and variable thickness  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A thermo elastic analysis is presented for axisymmetric rotating disks made of functionally graded material (FGM) with variable thickness. Material properties are assumed to be temperature-dependent and graded in the radial direction according to a grading index power law distribution. The temperature field considered is assumed to be uniformly distributed over the disk surface and varied in the radial direction. Semi-analytical solutions for the displacement field are given for solid disk an...

2009-01-01

286

Outer Membrane Targeting of Pseudomonas aeruginosa Proteins Shows Variable Dependence on the Components of Bam and Lol Machineries  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In Gram-negative bacteria, the Lol and Bam machineries direct the targeting of lipidated and nonlipidated proteins, respectively, to the outer membrane (OM). Using Pseudomonas aeruginosa strains with depleted levels of specific Bam and Lol proteins, we demonstrated a variable dependence of different OM proteins on these targeting pathways. Reduction in the level of BamA significantly affected the ability of the ?-barrel membrane protein OprF to localize to the OM, while the targeting of thre...

Hoang, Hanh H.; Nickerson, Nicholas N.; Lee, Vincent T.; Kazimirova, Anastasia; Chami, Mohamed; Pugsley, Anthony P.; Lory, Stephen

2011-01-01

287

Accurate approximate solution to nonlinear oscillators in which the restoring force is inversely proportional to the dependent variable  

Energy Technology Data Exchange (ETDEWEB)

A modified generalized, rational harmonic balance method is used to construct approximate frequency-amplitude relations for a conservative nonlinear singular oscillator in which the restoring force is inversely proportional to the dependent variable. The procedure is used to solve the nonlinear differential equation approximately. The approximate frequency obtained using this procedure is more accurate than those obtained using other approximate methods and the discrepancy between the approximate frequency and the exact one is lower than 0.40%.

Belendez, A; Gimeno, E; Mendez, D I; Alvarez, M L [Departamento de Fisica, IngenierIa de Sistemas y TeorIa de la Senal, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain); Fernandez, E [Departamento de Optica, FarmacologIa y AnatomIa, Universidad de Alicante, Apartado 99, E-03080 Alicante (Spain)], E-mail: a.belendez@ua.es

2008-06-15

288

Nonlinear thermal buckling and postbuckling analyses of imperfect variable thickness temperature-dependent bidirectional functionally graded cylindrical shells  

International Nuclear Information System (INIS)

Influences of the thickness variability and bidirectional material heterogeneity on the thermal buckling of the cylindrical shells have not been investigated so far. In the present paper, nonlinear thermal buckling and postbuckling analyses of imperfect, variable thickness cylindrical shells made of bidirectional functionally graded materials undergoing uniform temperature rises are accomplished for the first time, employing a third-order shear-deformation theory, von Karman-type kinematic nonlinearity, and a nonlinear finite element method. Material properties may vary in both radial and axial directions and can be temperature-dependent. Buckling temperature is detected by a modified Budiansky's criterion. The results reveal that temperature-dependency of the material properties reduces the buckling temperature. Moreover, effects of the volume fraction index on decreasing the buckling temperature are more remarkable for higher radius to thickness ratios. Furthermore, effects of reduction of the thickness in the axial direction may be compensated by an appropriate distribution of the material properties. -- Highlights: • Nonlinear thermal postbuckling of imperfect FGM cylindrical shells is investigated. • Material properties of the shell may vary in both radial and axial directions. • Geometric imperfections and thickness variability are also taken into account. • Material properties are considered to be temperature-dependent. • The nonlinear governing equations are solved by an updating finite element scheme

2013-01-01

289

Construction of an artificially randomized IgNAR phage display library: screening of variable regions that bind to hen egg white lysozyme.  

Science.gov (United States)

To develop a multi-antigen-specific immunoglobulin new antigen receptor (IgNAR) variable (V) region phage display library, CDR3 in the V region of IgNAR from banded houndshark (Triakis scyllium) was artificially randomized, and clones specific for hen egg white lysozyme (HEL) were obtained by the biopanning method. The nucleotide sequence of CDR3 in the V region was randomly rearranged by PCR. Randomized CDR3-containing segments of the V region were ligated into T7 phage vector to construct a phage display library and resulted in a phage titer of 3.7?×?10(7) PFU/ml. Forty clones that contained randomized CDR3 inserts were sequenced and shown to have different nucleotide sequences. The HEL-specific clones were screened by biopanning using HEL-coated ELISA plates. After six rounds of screening, nine clones were identified as HEL-specific, eight of which showed a strong affinity to HEL in ELISA compared to a negative control (i.e., empty phage clone). The deduced amino acid sequences of CDR3 from the HEL-specific phage clones fell into four types (I-IV): type I contains a single cysteine residue and type II-IV contain two cysteine residues. These results indicated that the artificially randomized IgNAR library is useful for the rapid isolation of antigen-specific IgNAR V region without immunization of target antigen and showed that it is possible to isolate an antigen-specific IgNAR V region from this library. PMID:22552958

Ohtani, Maki; Hikima, Jun-ichi; Jung, Tae Sung; Kondo, Hidehiro; Hirono, Ikuo; Aoki, Takashi

2013-02-01

290

DISCRIMINATORY ANALYSIS OF THE YIELD VARIABILITY OF MAIZE HYBRIDS DEPENDING ON THE DOSES AND TIME OF HERBICIDE APPLICATION  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In years 2005-2007, sensitivity assessment of four maize hybrids took place – Gazelle, LG 3225, Lober, and PR 39H32, depending on the time and method of herbicideMustang 306 SE application. Varietal experiment was established using the method of randomized blocks, in three replications, on soil classified as good wheat complex. Weeding was performed mechanically. Hybrids were sprayed with herbicide Mustang 306 SE at the dose of 0.6 dm3•ha-1 at the 3-4- or 6-7-leaf stage, as well as with a...

2010-01-01

291

Patterns of variability in early-life traits of fishes depend on spatial scale of analysis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Estimates of early-life traits of fishes (e.g. pelagic larval duration (PLD) and spawning date) are essential for investigating and assessing patterns of population connectivity. Such estimates are available for a large number of both tropical and temperate fish species, but few studies have assessed their variability in space, especially across multiple scales. The present study, where a Mediterranean fish (i.e. the white seabream Diplodus sargus sargus) was used as a model, shows that spawn...

Di Franco, Antonio; Guidetti, Paolo

2011-01-01

292

Long Period Variables in Globular Clusters and the Galactic Bulge: Their Dependence on Metallicity  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We derive the frequency of occurrence of luminous long period variables (LLPVs) in globular clusters and in the Baade's Window field of the Galactic bulge. LLPVs occur only in clusters with [Fe/H]>/= -1.0. In these clusters their frequency of occurrence relative to the number of giant stars appears to be independent of metallicity. Integrated over all metallicities, Baade's Window appears to be deficient in LLPVs. We estimate [Fe/H] values for Baade's Window LLPVs from their...

Frogel, Jay A.; Whitelock, Patricia A.

1997-01-01

293

Compact radio sources: The dependence of variability and polarization on spectral shape  

International Nuclear Information System (INIS)

VLA observations have been made at 20, 6, and 2 cm of an unbiased sample of 40 flat-spectrum (?>-0.5;Sproportionalv/sup ?/) radio sources selected from the S4 (6 cm strong source) survey. We have explored the polarization properties of these sources and examined their variability over a 6--8 year baseline at 6 cm by comparing our flux density values with the original S4 measurements. Most of the flux density in these sources is from regions unresolved (< or approx. =0.2) on the VLA. We find that the source properties divide fairly clearly when one classifies the sources according to simple spectral shape categories; viz, straight, simple-convex (''humped''), and complex. The complex sources are significantly more variable and reach higher polarizations. The straight sources are relatively quiescent and show signs of substantial Faraday depolarization. The simple-convex sources are also relatively quiescent and show none of the high polarizations seen amonng the complex sources. The complex sources exhibit, on average, about the same degree of polarization at all three wavelengths, but, for a given source, the degree of polarization shows little correlation from one wavelength to another. The VLBI structures may also be related to these spectral shape categories. Possible interpretations of these relations are discussed. We also argue that if the complex, variable sources are relativistically ''beamed'' toward us, then their unbeamed counterparts have not been found, at least in this subset of the S4 survey

1982-04-01

294

Random polarizations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We derive conditions under which random sequences of polarizations (two-point symmetrizations) converge almost surely to the symmetric decreasing rearrangement. The parameters for the polarizations are independent random variables whose distributions need not be uniform. The proof of convergence hinges on an estimate for the expected distance from the limit that also yields a bound on the rate of convergence. In the special case of i.i.d. sequences, we obtain almost sure con...

Burchard, Almut; Fortier, Marc

2011-01-01

295

Multivariate integration of functions depending explicitly on the minimum and the maximum of the variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

By using some basic calculus of multiple integration, we provide an alternative expression of the integral $$ \\int_{]a,b[^n} f(\\mathbf{x},\\min x_i,\\max x_i) \\, d\\mathbf{x}, $$ in which the minimum and the maximum are replaced with two single variables. We demonstrate the usefulness of that expression in the computation of orness and andness average values of certain aggregation functions. By generalizing our result to Riemann-Stieltjes integrals, we also provide a method for the calculation o...

Marichal, Jean-luc

2008-01-01

296

Symplectic integrator for s-dependent static magnetic fields based on mixed-variable generating functions  

International Nuclear Information System (INIS)

We describe a technique for constructing a symplectic transfer map for a charged particle moving through an accelerator component with arbitrary three-dimensional static magnetic field. The transfer map is constructed by symplectic integration; by representing the map at each step of the integration by a mixed-variable generating function, exact symplecticity is ensured. By using an appropriate integration algorithm, there is no necessity to make the paraxial approximation. The technique is illustrated by application (in one degree of freedom) to a quadrupole magnet with strong octupole component and fringe field.

2012-04-01

297

Long Period Variables in Globular Clusters and the Galactic Bulge Their Dependence on Metallicity  

CERN Document Server

We derive the frequency of occurrence of luminous long period variables (LLPVs) in globular clusters and in the Baade's Window field of the Galactic bulge. LLPVs occur only in clusters with [Fe/H]>/= -1.0. In these clusters their frequency of occurrence relative to the number of giant stars appears to be independent of metallicity. Integrated over all metallicities, Baade's Window appears to be deficient in LLPVs. We estimate [Fe/H] values for Baade's Window LLPVs from their period and a log P vs. [Fe/H] relation derived from cluster variables and find that LLPVs with [Fe/H]>/= 0.0 are absent from Baade's Window. We propose that this is because of enhanced mass loss rates in these LLPVs with a consequently abbreviated lifetime compared to lower metallicity LLPVs. A typical lifetime for cluster LLPVs is about 3 x10^5 yrs. Finally, we call attention to the need for a much more complete survey for LLPVs in globular clusters.

Frogel, J A; Frogel, Jay A.; Whitelock, Patricia A.

1997-01-01

298

Short-term heart rate variability--age dependence in healthy subjects.  

Science.gov (United States)

Heart rate variability (HRV) analysis is an established method to characterize the autonomic regulation and is based mostly on 24h Holter recordings. The importance of short-term HRV (less than 30 min) for various applications is growing consistently. Major reasons for this are the suitability for ambulatory care and patient monitoring and the ability to provide an almost immediate test result. So far, there have been only a few studies that provided statistically relevant reference values for short-term HRV. In our study, 5 min short-term HRV indices were determined from 1906 healthy subjects. From these records, linear and nonlinear indices were extracted. To determine general age-related influences, HRV indices were compared from subjects aged 25-49 years with subjects aged 50-74 years. In a second approach, we examined the development of HRV indices by age in terms of age decades (25-34, 35-44, 45-54, 55-64 and 65-74 years). Our results showed significant variations of HRV indices by age in almost all domains. While marked dynamics in terms of parameter change (variability reduction) were observed in the first age decades, in particular the last two age decades showed certain constancy with respect to the HRV indices examined. PMID:22813869

Voss, A; Heitmann, A; Schroeder, R; Peters, A; Perz, S

2012-08-01

299

Vitamin D production depends on ultraviolet-B dose but not on dose rate: a randomized controlled trial  

DEFF Research Database (Denmark)

Ultraviolet-B (UV-B) radiation increases serum vitamin D level expressed as 25-hydroxyvitamin D(3) (25(OH)D), but the dose-response relationship and the importance of dose rate is unclear. Of 172 fair-skinned persons screened for 25(OH)D, 55 with insufficient baseline 25(OH)D=50 nm (mean 31.2 nm) were selected and randomized to one of 11 groups of five participants. Each group was exposed to one of four different UV-B doses: 0.375, 0.75, 1.5 or 3.0 standard erythema dose (SED) for 1, 5, 10 or 20 min. All participants had four UV-B sessions with 2- to 3-day interval with 24% of their skin exposed. Skin pigmentation and 25(OH)D were measured before and after the irradiations. The increase in 25(OH)D after UV-B exposure (adjusted for baseline 25(OH)D) was positively correlated with the UV-B dose (P=0.001; R(2) =0.176) but not to dose rate (1-20 min). 25(OH)D increased in response to four UV-B treatments of 3 SED with 24.8 nm on average and 14.2 nm after four UV-B treatments of just 0.375 SED. In conclusion, the increase in 25(OH)D after UV-B exposure depends on the dose but not on the dose rate (1-20 min). Further, a significant increase in 25(OH)D was achieved with a very low UV-B dose.

Bogh, Morten K B; Schmedes, Anne V

2011-01-01

300

Saddlepoint expansions for sums of Markov dependent variables on a continuous state space  

DEFF Research Database (Denmark)

Based on the conjugate kernel studied in Iscoe et al. (1985) we derive saddlepoint expansions for either the density or distribution function of a sum f(X1)+...+f(Xn), where the Xi's constitute a Markov chain. The chain is assumed to satisfy a strong recurrence condition which makes the results here very similar to the classical results for i.i.d. variables. In particular we establish also conditions under which the expansions hold uniformly over the range of the saddlepoint. Expansions are also derived for sums of the form f(X1, X0)+f(X2, X1)+...+f(Xn, Xn-1) although the uniformity result just mentioned does not generalize. © 1991 Springer-Verlag.

Jensen, J.L.

1991-01-01

 
 
 
 
301

Changing dependence of Zimbabwean rainfall variability on ENSO and the Indian Ocean dipole/zonal mode  

Science.gov (United States)

A novel approach of using variability as a major descriptive parameter for observational time series is adopted to investigate how southeastern African (Zimbabwe) summer rainfall may have been forced by the El Niño southern oscillation (ENSO) and/or the Indian Ocean dipole/zonal mode (IODZM), concurrently with the changing sea surface temperature (SST) background of the Indo-Pacific region. The period is from 1901 to 2007. Wavelet power spectrum and linear statistical analysis, including simple and partial correlation techniques, are utilized to achieve this end. The results reveal epochal changes in teleconnections and other statistical properties linking southeastern African rainfall variability to the Indo-Pacific SSTs. These epochs conspicuously exhibit the period around 1945/1946, 1960/1961, 1972/1973, and 1997/1998 as demarcating distinct systematic climate turning points during the century. The role of the 1976/1977 climate regime shift seems not to be that apparent but instead, 1960/1961 and 1997/1998 appear to be the major turning points, both in the teleconnections and Indo-Pacific SST temporal characteristics. From the early 1960s to 1997, as much as 28% of the rainfall variability was linearly related to the IODZM while the ENSO hardly explained a quarter of this value. During this period, droughts are especially strongly connected to the positive IODZM events but insignificantly linked to El Niño, thus contradicting the conventional knowledge attributing most of regional rainfall suppression to the warm ENSO phase. However, the post 1997 epoch saw the reversal of the two climate modes’ influences. ENSO influence evidently became activated, attaining the previously assumed dominant role which had proved elusive during the earlier epochs. But this increased ENSO control is attributed to only less than 12% of the rainfall variance while IODZM seem to be largely decoupled from the local rainfall influencing processes by hardly explaining a drastically reduced 1% of the rainfall variance. This transformation occurred despite of neither ENSO nor IODZM SST anomalies showing any statistically significant changes. As far as could be established, this epochal behavior may not be forced by the frequency and magnitude of ENSO and IODZM events but most probably by the slow processes inherent in the SST background, especially of the tropical Indian Ocean. Thus, the apparent simultaneous decoupling of the IODZM and coupling of the ENSO to the regional rainfall controlling mechanisms seems to be the result of the unprecedented warming of the intervening tropical western Indian Ocean SSTs in the last decade. Consequently, the knowledge of the states of epochal Indian Ocean SST background variability should be an important regional scientific issue, since these epochal variations may dictate the nature (and successful prediction) of interannual as well as decadal climate fluctuations over southeastern Africa.

Manatsa, D.; Matarira, C. H.

2009-10-01

302

The North Atlantic variability structure, storm tracks, and precipitation depending on the polar vortex strength  

Directory of Open Access Journals (Sweden)

Full Text Available Motivated by the strong evidence that the state of the northern hemisphere vortex in boreal winter influences tropospheric variability, teleconnection patterns over the North Atlantic are defined separately for winter episodes where the zonal wind at 50hPa and 65° N is above or below the critical velocity for vertical propagation of zonal planetary wave 1. We argue that the teleconnection structure in the middle and upper troposphere differs considerably between the two regimes of the polar vortex, while this is not the case at sea level. If the polar vortex is strong, there exists one meridional dipole structure of geopotential height in the upper and middle troposphere, which is situated in the central North Atlantic. If the polar vortex is weak, there exist two such dipoles, one over the western and one over the eastern North Atlantic. Storm tracks (and precipitation related with these are determined by mid and upper tropospheric conditions and we find significant differences of these parameters between the stratospheric regimes. For the strong polar vortex regime, in case of a negative upper tropospheric 'NAO' index we find a blocking height situation over the Northeast Atlantic and the strongest storm track of all. It is reaching far north into the Arctic Ocean and has a secondary maximum over the Denmark Strait. Such storm track is not found in composites based on a classic NAO defined by surface pressure differences between the Icelandic Low and the Azores High. Our results suggest that it is important to include the state of the polar vortex strength in any study of the variability over the North Atlantic.

K. Walter

2005-01-01

303

A time-dependent Poisson random field model for polymorphism within and between two related biological species  

CERN Multimedia

We derive a Poisson random field model for population site polymorphisms differences within and between two species that share a relatively recent common ancestor. The model can be either equilibrium or time inhomogeneous. We first consider a random field of Markov chains that describes the fate of a set of individual mutations. This field is approximated by a Poisson random field from which we can make inferences about the amounts of mutation and selection that have occurred in the history of observed aligned DNA sequences.

Amei, Amei; 10.1214/09-AAP668

2010-01-01

304

Study of temperature-dependent ultrathin oxide growth on Si(111) using variable-angle spectroscopic ellipsometry  

Science.gov (United States)

The monolayer-sensitive variable-angle spectroscopic ellipsometry technique was used to study the temperature-dependent growth mechanisms of an ultrathin oxide layer on top of silicon. The oxidation was done in atomic oxygen produced in a pure oxygen plasma and driven by an RF power source. The results have been compared with the recently proposed model of Murali and Murarka for ultrathin oxide growth on top of silicon. The activation energies of different growth parameters associated with the oxide growth have also been determined.

De, Bhola N.; Woollam, John A.

1990-01-01

305

Numerical solution of the time-dependent Ginzburg-Landau equation for a superconducting mesoscopic disk: Link variable method  

International Nuclear Information System (INIS)

The time dependent GinzburgLandau equations (TDGLE) are used to study the superconducting properties of a disk by taking into account the influence of internal defects. The Link variable algorithm is applied to a circular geometry surrounded by an insulator and immersed in an external magnetic field applied perpendicular to its plane. The TDGLE are used upon taking the magnetic field and the order parameter invariant along z-direction. We show that the magnetic response is substantially modified by the competition between the confinement geometry and the geometric position of the defects leads to vortex configurations which are not compatible with the symmetry of the sample geometry.

2013-02-08

306

Variable domain antibodies specific for viral hemorrhagic septicemia virus (VHSV) selected from a randomized IgNAR phage display library.  

Science.gov (United States)

Phage display libraries are used to screen for nucleotide sequences that encode immunoglobulin variable (V) regions that are specific for a target antigen. We previously constructed an immunoglobulin new antigen receptor (IgNAR) phage display library. Here we used this library to obtain an IgNAR V region that is specific for viral hemorrhagic septicemia virus (VHSV). A phage clone (clone 653) was found to be specific for VHSV by the biopanning method. The V region of clone 653 was used to construct a 6 × His tagged recombinant IgNAR-653 V protein (rIgNAR-653) using the Escherichia coli pET system. The rIgNAR-653 protein bound specifically to VHSV, confirming its activity. PMID:23257206

Ohtani, Maki; Hikima, Jun-ichi; Jung, Tae-Sung; Kondo, Hidehiro; Hirono, Ikuo; Takeyama, Haruko; Aoki, Takashi

2013-02-01

307

Critical points of quadratic renormalizations of random variables and phase transitions of disordered polymer models on diamond lattices.  

Science.gov (United States)

We study the wetting transition and the directed polymer delocalization transition on diamond hierarchical lattices. These two phase transitions with frozen disorder correspond to the critical points of quadratic renormalizations of the partition function. (These exact renormalizations on diamond lattices can also be considered as approximate Migdal-Kadanoff renormalizations for hypercubic lattices.) In terms of the rescaled partition function z=Z/Z(typ) , we find that the critical point corresponds to a fixed point distribution with a power-law tail P(c)(z) ~ Phi(ln z)/z(1+mu) as z-->+infinity [up to some subleading logarithmic correction Phi(ln z)], so that all moments z(n) with n>mu diverge. For the wetting transition, the first moment diverges z=+infinity (case 0random weights determined by the fixed point distribution P(c)(z) are broadly distributed. This induces some changes in the traveling wave solutions with respect to the usual case of more narrow distributions. PMID:18352012

Monthus, Cécile; Garel, Thomas

2008-02-01

308

Generalised extreme value statistics and sum of correlated variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We show that generalised extreme value statistics -the statistics of the k-th largest value among a large set of random variables- can be mapped onto a problem of random sums. This allows us to identify classes of non-identical and (generally) correlated random variables with a sum distributed according to one of the three (k-dependent) asymptotic distributions of extreme value statistics, namely the Gumbel, Frechet and Weibull distributions. These classes, as well as the li...

Bertin, Eric; Clusel, Maxime

2006-01-01

309

Randomized random walk on a random walk  

International Nuclear Information System (INIS)

This paper discusses generalizations of the model introduced by Kehr and Kunter of the random walk of a particle on a one-dimensional chain which in turn has been constructed by a random walk procedure. The superimposed random walk is randomised in time according to the occurrences of a stochastic point process. The probability of finding the particle in a particular position at a certain instant is obtained explicitly in the transform domain. It is found that the asymptotic behaviour for large time of the mean-square displacement of the particle depends critically on the assumed structure of the basic random walk, giving a diffusion-like term for an asymmetric walk or a square root law if the walk is symmetric. Many results are obtained in closed form for the Poisson process case, and these agree with those given previously by Kehr and Kunter. (author)

1983-01-01

310

Energy dependent power spectral states and origin of aperiodic variability in black hole binaries  

CERN Document Server

We found the black hole candidate MAXI J1659-152 showed distinct power spectra, i.e., a power-law noise (PLN) vs. band-limited noise (BLN) plus quasi-periodic oscillations (QPOs), below and above about 2 keV respectively, in the observations with the Swift and the RXTE during the 2010 outburst, indicating a high energy cut-off of the PLN and a low energy cut-off of the BLN and the QPOs around 2 keV. The emergence of the PLN and the fading of the BLN and the QPOs initially took place from below 2 keV when the source entered the hard intermediate state and finally settled in the soft state three weeks later. The evolution was accompanied by the emergence of the disk spectral component and decreases in the amplitudes of variability in the soft X-ray and the hard X-ray bands. Our results indicate that the PLN is associated with the optically thick disk in both hard and intermediate states, and power spectral state is independent of the X-ray energy spectral state in a broadband view. We suggest that in the hard a...

Yu, Wenfei

2013-01-01

311

Basal variability in CREB phosphorylation predicts trait-like differences in amygdala-dependent memory  

Science.gov (United States)

Much of what is known about the neurobiology of learning and memory comes from studies of the average behavior. In contrast, intersubject differences that emerge within groups are difficult to study systematically and are often excluded from scientific discussion. Nevertheless, population-wide variability is a virtually universal feature of both complex traits, such as intelligence, and hardwired responses, such as defensive behaviors. Here, we use outbred rats to investigate if cAMP response element-binding protein (CREB), a transcription factor that has long been known in experimental settings to be crucial for associative plasticity, participates in natural memory phenotypes. Using a combination of behavioral, biochemical, and viral techniques, we show that a subset of rats with trait-like deficits in aversive memory have basally reduced CREB activity in the lateral amygdala but can be induced to perform at average levels by directly or indirectly enhancing pretraining CREB phosphorylation. These data suggest that endogenous CREB activity in the amygdala may set a critical threshold for plasticity during memory formation.

Cowansage, Kiriana K.; Bush, David E. A.; Josselyn, Sheena A.; Klann, Eric; LeDoux, Joseph E.

2013-01-01

312

Time-dependent excitation and ionization modelling of absorption-line variability due to GRB 080310  

CERN Multimedia

We model the time-variable absorption of FeII, FeIII, SiII, CII and CrII detected in UVES spectra of GRB 080310, with the afterglow radiation exciting and ionizing the interstellar medium in the host galaxy at a redshift of z=2.42743. To estimate the rest-frame afterglow brightness as a function of time, we use a combination of the optical VRI photometry obtained by the RAPTOR-T telescope array -- which are presented in this paper -- and Swift's X-Ray Telescope observations. Excitation alone, which has been successfully applied for a handful of other GRBs, fails to describe the observed column-density evolution in the case of GRB 080310. Inclusion of ionization is required to explain the column-density decrease of all observed FeII levels (including the ground state 6D9/2) and increase of the FeIII 7S3 level. The large population of ions in this latter level (up to 10% of all FeIII) can only be explained through ionization of FeII, whereby a large fraction of the ionized FeII ions -- we calculate 31% using th...

Vreeswijk, P M; Raassen, A J J; Smette, A; De Cia, A; Wo?niak, P R; Fox, A J; Vestrand, W T; Jakobsson, P

2012-01-01

313

ALDH5A1 variability in opioid dependent patients could influence response to methadone treatment.  

Science.gov (United States)

Methadone maintenance treatment is the most widely-used therapy in opioid dependence, but some patients relapse or drop out from treatment. We genotyped a genetic variant in the succinic semialdehyde dehydrogenase enzyme gene, ALDH5A1, and found that subjects carrying the T variant allele have a higher risk to be nonresponders to methadone treatment (OR=3.16; 95% CI [1.48-6.73], P=0.0024). This could be due to a reduction in the ALDH5A1 enzyme activity, that would increase endogenous gamma-hydroxbutyric acid (GHB) and gamma-aminobutyric acid (GABA) levels and therefore, inducing symptoms such as sedation and impaired pschomotor performance. These neuropsychological effects related with the reduction in enzyme activity could be responsible for a higher propensity to relapse in these genetically predisposed patients. PMID:24230997

Fonseca, Francina; Gratacòs, Mònica; Escaramís, Geòrgia; De Cid, Rafael; Martín-Santos, Rocío; Farré, Magi; Estivill, Xavier; Torrens, Marta

2014-03-01

314

ENERGY-DEPENDENT POWER SPECTRAL STATES AND ORIGIN OF APERIODIC VARIABILITY IN BLACK HOLE BINARIES  

Energy Technology Data Exchange (ETDEWEB)

We found that the black hole candidate MAXI J1659-152 showed distinct power spectra, i.e., power-law noise (PLN) versus band-limited noise (BLN) plus quasi-periodic oscillations (QPOs) below and above about 2 keV, respectively, in observations with Swift and the Rossi X-ray Timing Explorer during the 2010 outburst, indicating a high energy cutoff of the PLN and a low energy cutoff of the BLN and QPOs around 2 keV. The emergence of the PLN and the fading of the BLN and QPOs initially took place below 2 keV when the source entered the hard intermediate state and settled in the soft state three weeks later. The evolution was accompanied by the emergence of the disk spectral component and decreases in the amplitudes of variability in the soft and hard X-ray bands. Our results indicate that the PLN is associated with an optically thick disk in both hard and intermediate states, and the power spectral state is independent of the X-ray energy spectral state in a broadband view. We suggest that in the hard or intermediate state, the BLN and QPOs emerge from the innermost hot flow subjected to Comptonization, while the PLN originates from the optically thick disk farther out. The energy cutoffs of the PLN and the BLN or QPOs then follow the temperature of the seed photons from the inner edge of the optically thick disk, while the high frequency cutoff of the PLN follows the orbital frequency of the inner edge of the optically thick disk as well.

Yu Wenfei; Zhang Wenda, E-mail: wenfei@shao.ac.cn [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China)

2013-06-20

315

[Scale-dependency of spatial variability of surface soil moisture under different land use types in Heihe Oasis, China].  

Science.gov (United States)

To study the surface soil moisture spatial variability and its scale effect is of significance to understand the real variability of soil moisture and to objectively provide a reference for constructing a logical sampling scheme. By using "re-sampling" method, this paper studied the scale-dependency of the spatial variability of soil surface moisture in the woodland and farmland in the oasis ecological system in the middle reaches of Heihe River. The results showed that the variation degree of the surface soil moisture in the test woodland and farmland increased with increasing soil moisture content, and the coefficient of variation (CV) became closer to the true value when the sampling scale increased. Under both dry and moist conditions, and when the sampling amplitude increased within a definite range, the CV, Moran's I index, nugget, and sill of soil moisture in the woodland and farmland as well as the variation range in the woodland all increased, while the variation range in the farmland under arid condition did not show a stable regular pattern. When the sampling density increased within a definite range, the nugget and variation range increased, but the CV, Moran's I index, and sill showed less change. PMID:24015534

Guo, De-Liang; Fan, Jun; Mi, Mei-Xia

2013-05-01

316

Do drug treatment variables predict cognitive performance in multidrug-treated opioid-dependent patients? A regression analysis study  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Cognitive deficits and multiple psychoactive drug regimens are both common in patients treated for opioid-dependence. Therefore, we examined whether the cognitive performance of patients in opioid-substitution treatment (OST is associated with their drug treatment variables. Methods Opioid-dependent patients (N = 104 who were treated either with buprenorphine or methadone (n = 52 in both groups were given attention, working memory, verbal, and visual memory tests after they had been a minimum of six months in treatment. Group-wise results were analysed by analysis of variance. Predictors of cognitive performance were examined by hierarchical regression analysis. Results Buprenorphine-treated patients performed statistically significantly better in a simple reaction time test than methadone-treated ones. No other significant differences between groups in cognitive performance were found. In each OST drug group, approximately 10% of the attention performance could be predicted by drug treatment variables. Use of benzodiazepine medication predicted about 10% of performance variance in working memory. Treatment with more than one other psychoactive drug (than opioid or BZD and frequent substance abuse during the past month predicted about 20% of verbal memory performance. Conclusions Although this study does not prove a causal relationship between multiple prescription drug use and poor cognitive functioning, the results are relevant for psychosocial recovery, vocational rehabilitation, and psychological treatment of OST patients. Especially for patients with BZD treatment, other treatment options should be actively sought.

Rapeli Pekka

2012-11-01

317

Insulin clearance contributes to the variability of nocturnal insulin requirement in insulin-dependent diabetes mellitus.  

Science.gov (United States)

We have previously described, in insulin-dependent diabetic subjects (IDDM), a small, but significant, increase in the insulin clearance rate (ICR) during 0600-0800 h as compared with 0100-0300 h. To determine whether this increase was also seen at more physiologic levels of insulin replacement, we calculated ICR during euglycemic clamp studies in 13 patients with IDDM with a constant infusion of insulin at 20 mU/min/m2 and during insulin replacement from the Biostator GCIIS without exogenous glucose. During the euglycemic clamp study with constant insulin infusion at 20 mU/min/m2, the ICR was 16% higher at 0600-0800 h than at 0100-0300 h (264 +/- 50 ml/min/m2 versus 228 +/- 51 ml/min/m2; P less than 0.005). During insulin replacement by the Biostator, the mean insulin infusion rate increased by 92 +/- 27% (7.5 +/- 1.1 to 13.5 +/- 1.2 mU/min/m2; P less than 0.001) and ICR increased by 123 +/- 30% (130 +/- 24 to 268 +/- 51 ml/min/m2; P less than 0.01) during the prebreakfast period when compared with 0100-0300 h. There was a highly significant correlation (r = 0.97) between the increment in insulin infusion rate and the increment in ICR. Measurement of insulin concentration in saline solutions, delivered by the Biostator at a same rate and under similar conditions to those in this study, showed that insulin delivery was stable for the 8-h period of this study.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3905459

Dux, S; White, N H; Skor, D A; Santiago, J V

1985-12-01

318

Variability Measures of Positive Random Variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

During the stationary part of neuronal spiking response, the stimulus can be encoded in the firing rate, but also in the statistical structure of the interspike intervals. We propose and discuss two information-based measures of statistical dispersion of the interspike interval distribution, the entropy-based dispersion and Fisher information-based dispersion. The measures are compared with the frequently used concept of standard deviation. It is shown, that standard deviation is not well sui...

Kostal, Lubomir; Lansky, Petr; Pokora, Ondrej

2011-01-01

319

Introduction to Randomness and Statistics  

CERN Document Server

This text provides a practical introduction to randomness and data analysis, in particular in the context of computer simulations. At the beginning, the most basics concepts of probability are given, in particular discrete and continuous random variables. Next, generation of pseudo random numbers is covered, such as uniform generators, discrete random numbers, the inversion method, the rejection method and the Box-Mueller Method. In the third section, estimators, confidence intervals, histograms and resampling using Bootstrap are explained. Furthermore, data plotting using the freely available tools gnuplot and xmgrace is treated. In the fifth section, some foundations of hypothesis testing are given, in particular the chi-squared test, the Kolmogorov-Smirnov test and testing for statistical (in-)dependence. Finally, the maximum-likelihood principle and data fitting are explained. The text is basically self-contained, comes with several example C programs and contains eight practical (mainly programming) exer...

Hartmann, Alexander K

2009-01-01

320

Mathematical modeling of random coupling between polarization modes in single-mode optical fibers: XV. Dependence of integral statistical parameters of polarization modes in single-mode optical fibers with random inhomogeneities on the wavelength of light  

Science.gov (United States)

Spectral dependences of integral statistical elements of the Jones matrix of an extended segment of a single-mode optical fiber (SMOF) with random inhomogeneities, whose length considerably exceeds the correlation length of random inhomogeneities, are found by the method of mathematical modeling. The boundaries of the ranges of optical wavelengths are determined, within the limits of which the parameters under consideration remain quasi-constant. This allows the derivation of analytical expressions for the degree of polarization of nonmonochromatic radiation in an SMOF and for the zero drift in fiber ring interferometers with the help of the approximate method of small perturbations. It is shown that the small-perturbation method leads to adequate results for SMOFs with strong and intermediate linear birefringence.

Malykin, G. B.; Malykin, É. G.; Pozdnyakova, V. I.

2008-03-01

 
 
 
 
321

Cryptography and Algorithmic Randomness  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The secure instantiation of the random oracle is one of the major open problems in modern cryptography. We investigate this problem using concepts and methods of algorithmic randomness. In modern cryptography, the random oracle model is widely used as an imaginary framework in which the security of a cryptographic scheme is discussed. In the random oracle model, the cryptographic hash function used in a cryptographic scheme is formulated as a random variable uniformly distri...

Tadaki, Kohtaro; Doi, Norihisa

2013-01-01

322

Methylphenidate for attention deficit hyperactivity disorder and drug relapse in criminal offenders with substance dependence : a 24-week randomized placebo-controlled trial.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

AIM: To test the efficacy and safety of osmotic release oral system (OROS) methylphenidate (MPH) in doses up to 180?mg/day to treat attention deficit hyperactivity disorder (ADHD) and prevent any drug relapse in individuals with a co-diagnosis of ADHD and amphetamine dependence. DESIGN: Randomized placebo-controlled 24-week double-blind trial with parallel groups design. SETTING: Participants were recruited from medium security prisons in Sweden. The medication started within 2 weeks before...

Konstenius, Maija; Jayaram-lindstro?m, Nitya; Guterstam, Joar; Beck, Olof; Philips, Bjo?rn; Franck, Johan

2014-01-01

323

Dose-Dependent Effects of the Cimicifuga racemosa Extract Ze 450 in the Treatment of Climacteric Complaints: A Randomized, Placebo-Controlled Study  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Extracts from Cimicifuga racemosa (CR, synonym Actaea racemosa) have shown efficacy in trials in women with menopausal symptoms. Yet, dose dependency remains unclear. Therefore, 180 female outpatients with climacteric complaints were treated for 12 weeks in a randomized, double-blind, placebo-controlled, 3-armed trial (CR extract Ze 450 in 6.5?mg or 13.0?mg, or placebo). Primary outcome was the difference in menopausal symptoms (vasomotor, psychological, and somatic), assessed by the Kupp...

2012-01-01

324

Dose-dependent effects of the Cimicifuga racemosa Extract Ze 450 in the treatment of climacteric complaints: A randomized, placebo-controlled study  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Extracts from Cimicifuga racemosa (CR, synonym Actaea racemosa) have shown efficacy in trials in women with menopausal symptoms. Yet, dose dependency remains unclear. Therefore, 180 female outpatients with climacteric complaints were treated for 12 weeks in a randomized, double-blind, placebo-controlled, 3-armed trial (CR extract Ze 450 in 6.5?mg or 13.0?mg, or placebo). Primary outcome was the difference in menopausal symptoms (vasomotor, psychological, and somatic), assessed by the Kupp...

2012-01-01

325

Simulation of temperature history-dependent phenomena of glass-forming materials based on thermodynamics with internal state variables  

International Nuclear Information System (INIS)

In ref. , a profound ansatz for modelling the various phenomena associated with the glass-transition was presented. It extends classical theories, such as the concept of fictive temperature or order parameters, for example, in two ways. Firstly, temperature excitations as well as mechanical loadings are accounted for in a single consistent approach. Secondly, it is not formulated in the ?-p-V space, but rather in the ?-T-E space, taking the tensor character of stress T and strain E into account. Hence, it is a three-dimensional theory where the basic thermodynamic potential, the Gibbs free energy, depends on the stress tensor, the temperature and a set of internal variables. In the current article, expressions for the enthalpy, the entropy, the thermal expansion and the specific heat are derived. The specific heat and the thermal expansion behaviour are looked at for various temperature excitations. It is shown, that the results are in accord with experimental observations in literature.

2011-08-10

326

Observation of a shape-dependent density maximum in random packings and glasses of colloidal silica ellipsoids  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We have measured the random packing density of monodisperse colloidal silica ellipsoids with a well-defined shape, gradually deviating from a sphere shape up to prolates with aspect ratios of about 5, to find for a colloidal system the first experimental observation for the density maximum (at an aspect ratio near 1.6) previously found only in computer simulations of granular packings. Confocal microscopy of ellipsoid packings, prepared by rapidly quenching ellipsoid fluids via ultra-centrifu...

Sacanna, S.; Rossi, L.; Wouterse, A.; Philipse, A. P.

2007-01-01

327

Observation of a shape-dependent density maximum in random packings and glasses of colloidal silica ellipsoids  

International Nuclear Information System (INIS)

We have measured the random packing density of monodisperse colloidal silica ellipsoids with a well-defined shape, gradually deviating from a sphere shape up to prolates with aspect ratios of about 5, to find for a colloidal system the first experimental observation for the density maximum (at an aspect ratio near 1.6) previously found only in computer simulations of granular packings. Confocal microscopy of ellipsoid packings, prepared by rapidly quenching ellipsoid fluids via ultra-centrifugation, demonstrates the absence of orientational order and yields pair correlation functions very much like those for random sphere packings. The density maximum, about 12% above the Bernal random sphere packing density, also manifests itself as a maximum in the hydrodynamic friction that resists the swelling osmotic pressure of the ellipsoid packings. The existence of the density maximum is also predicted to strongly effect the dynamics of colloidal non-sphere glasses: slightly perturbing the sphere shape in a sphere glass will cause it to melt

2007-09-19

328

Observation of a shape-dependent density maximum in random packings and glasses of colloidal silica ellipsoids  

Energy Technology Data Exchange (ETDEWEB)

We have measured the random packing density of monodisperse colloidal silica ellipsoids with a well-defined shape, gradually deviating from a sphere shape up to prolates with aspect ratios of about 5, to find for a colloidal system the first experimental observation for the density maximum (at an aspect ratio near 1.6) previously found only in computer simulations of granular packings. Confocal microscopy of ellipsoid packings, prepared by rapidly quenching ellipsoid fluids via ultra-centrifugation, demonstrates the absence of orientational order and yields pair correlation functions very much like those for random sphere packings. The density maximum, about 12% above the Bernal random sphere packing density, also manifests itself as a maximum in the hydrodynamic friction that resists the swelling osmotic pressure of the ellipsoid packings. The existence of the density maximum is also predicted to strongly effect the dynamics of colloidal non-sphere glasses: slightly perturbing the sphere shape in a sphere glass will cause it to melt.

Sacanna, S; Rossi, L; Wouterse, A; Philipse, A P [Van' t Hoff Laboratory for Physical and Colloid Chemistry, Debye Institute, Utrecht University, Padualaan 8, 3584 CH Utrecht (Netherlands)

2007-09-19

329

Towards Swarm Diversity: Random Sampling in Variable Neighborhoods Procedure Using a Lévy Distribution / Hacia la diversidad de la bandada: procedimiento RSVN usando una distribución de Lévy  

Scientific Electronic Library Online (English)

Full Text Available SciELO Mexico | Language: English Abstract in spanish Particle Swarm Optimization (PSO) es un método de búsqueda no directo para la optimización numérica. Las principales ventajas de esta meta-heurística están relacionadas principalmente con su simplicidad, pocos parámetros y alta tasa de convergencia. En el PSO canónico usando una topología totalmente [...] conectada, una partícula ajusta su posición usando dos atractores: el mejor registro almacenado por el individuo y el mejor punto descubierto por la bandada completa. Este esquema conduce a un alto factor de convergencia, pero también deteriora la diversidad de la población progresivamente. Como resultado la bandada de partículas frecuentemente es atraída por puntos sub-óptimos. Una vez que las partículas han sido atraídas hacia un óptimo local, ellas continúan el proceso de búsqueda dentro de una región muy pequeña del espacio de soluciones, reduciendo las capacidades de exploración del algoritmo. Para tratar esta situación este artículo presenta una variante del procedimiento Random Sampling in Variable Neighborhoods (RSVN) usando una distribución de Lévy. Este algoritmo es capaz de mejorar notablemente la capacidad de búsqueda de los algoritmos PSO en problemas multimodales de optimización. Abstract in english Particle Swarm Optimization (PSO) is a non-direct search method for numerical optimization. The key advantages of this metaheuristic are principally associated to its simplicity, few parameters and high convergence rate. In the canonical PSO using a fully connected topology, a particle adjusts its p [...] osition by using two attractors: the best record stored for the current agent, and the best point discovered for the entire swarm. It leads to a high convergence rate, but also progressively deteriorates the swarm diversity. As a result, the particle swarm frequently gets attracted by sub-optimal points. Once the particles have been attracted to a local optimum, they continue the search process within a small region of the solution space, thus reducing the algorithm exploration. To deal with this issue, this paper presents a variant of the Random Sampling in Variable Neighborhoods (RSVN) procedure using a Lévy distribution, which is able to notably improve the PSO search ability in multimodal problems.

Gonzalo, Nápoles; Isel, Grau; Marilyn, Bello; Rafael, Bello.

330

Time-dependent simulations of emission from FSRQ PKS1510-089: multiwavelength variability of external Compton and SSC models  

CERN Multimedia

[abridged] We present results of modeling the SED and multiwavelength variability of the bright FSRQ PKS1510-089 with our time-dependent multizone Monte Carlo/Fokker-Planck code (Chen et al. 2001). As primary source of seed photons for inverse Compton scattering, we consider radiation from the broad line region (BLR), from the molecular torus, and the local synchrotron radiation (SSC). Different scenarios are assessed by comparing simulated light curves and SEDs with one of the best flares by PKS1510-089, in March 2009. The time-dependence of our code and its correct handling of light travel time effects allow us to fully take into account the effect of the finite size of the active region, and in turn to fully exploit the information carried by time resolved observed SEDs, increasingly available since the launch of Fermi. We confirm that the spectrum adopted for the external radiation has an important impact on the modeling of the SED, in particular for the lower energy end of the Compton component, observed...

Chen, Xuhui; Liang, Edison; Boettcher, Markus

2012-01-01

331

Effect of variability in the 7-day baseline pain diary on the assay sensitivity of neuropathic pain randomized clinical trials: An ACTTION study.  

Science.gov (United States)

The degree of variability in the patient baseline 7-day diary of pain ratings has been hypothesized to have a potential effect on the assay sensitivity of randomized clinical trials of pain therapies. To address this issue, we obtained clinical trial data from the Food and Drug Administration (FDA) through the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION) public-private partnership, and harmonized patient level data from 12 clinical trials (4 gabapentin and 8 pregabalin) in postherpetic neuralgia (PHN) and painful diabetic peripheral neuropathy (DPN). Models were developed using exploratory logistic regression to examine the interaction between available baseline factors and treatment (placebo vs active medication) in predicting patient response to therapy (ie, >30% improvement). Our analysis demonstrated an increased likelihood of response in the placebo-treated group for patients with a higher standard deviation in the baseline 7-day diary without affecting the likelihood of a response in the active medication-treated group, confirming our hypothesis. In addition, there was a small but significant age-by-treatment interaction in the PHN model, and small weight-by-treatment interaction in the DPN model. The patient's sex, baseline pain level, and the study protocol had an effect only on the likelihood of response overall. Our results suggest the possibility that, at least in some disease processes, excluding patients with a highly variable baseline 7-day diary has the potential to improve the assay sensitivity of these analgesic clinical trials, although reductions of external validity must be considered when increasing the homogeneity of the investigated sample. PMID:24831421

Farrar, John T; Troxel, Andrea B; Haynes, Kevin; Gilron, Ian; Kerns, Robert D; Katz, Nathaniel P; Rappaport, Bob A; Rowbotham, Michael C; Tierney, Ann M; Turk, Dennis C; Dworkin, Robert H

2014-08-01

332

Random number generation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The fields of probability and statistics are built over the abstract concepts of probability space and random variable. This has given rise to elegant and powerful mathematical theory, but exact implementation of these concepts on conventional computers seems impossible. In practice, random variables and other random objects are simulated by deterministic algorithms. The purpose of these algorithms is to produce sequences of numbers or objects whose behavior is very hard to distinguish from t...

L Ecuyer, Pierre

2004-01-01

333

How the Landscape of Random Job Shop Scheduling Instances Depends on the Ratio of Jobs to Machines  

CERN Document Server

We characterize the search landscape of random instances of the job shop scheduling problem (JSP). Specifically, we investigate how the expected values of (1) backbone size, (2) distance between near-optimal schedules, and (3) makespan of random schedules vary as a function of the job to machine ratio (N/M). For the limiting cases N/M approaches 0 and N/M approaches infinity we provide analytical results, while for intermediate values of N/M we perform experiments. We prove that as N/M approaches 0, backbone size approaches 100%, while as N/M approaches infinity the backbone vanishes. In the process we show that as N/M approaches 0 (resp. N/M approaches infinity), simple priority rules almost surely generate an optimal schedule, providing theoretical evidence of an "easy-hard-easy" pattern of typical-case instance difficulty in job shop scheduling. We also draw connections between our theoretical results and the "big valley" picture of JSP landscapes.

Smith, S F; 10.1613/jair.2013

2011-01-01

334

The supply voltage scaled dependency of the recovery of single event upset in advanced complementary metal—oxide—semiconductor static random-access memory cells  

International Nuclear Information System (INIS)

Using computer-aided design three-dimensional simulation technology, the supply voltage scaled dependency of the recovery of single event upset and charge collection in static random-access memory cells are investigated. It reveals that the recovery linear energy transfer threshold decreases with the supply voltage reducing, which is quite attractive for dynamic voltage scaling and subthreshold circuit radiation-hardened design. Additionally, the effect of supply voltage on charge collection is also investigated. It is concluded that the supply voltage mainly affects the bipolar gain of the parasitical bipolar junction transistor (BJT) and the existence of the source plays an important role in supply voltage variation. (geophysics, astronomy, and astrophysics)

2013-02-01

335

Intra individual variability in markers of proteinuria for normal subjects and those with cadmium induced renal dysfunction: interpretation of results from untimed, random urine samples.  

Science.gov (United States)

The project aimed to help interpretation of urinary protein measurements, namely -2-microglobulin, retinol-binding protein, albumin and total protein in untimed, random urine samples as indicating significant changes in renal tubular reabsorption and glomerular permeability in an individual. A standard methodology used in clinical laboratory medicine was applied to calculate the intra-individual biological variation for these analytes. This parameter in conjunction with a laboratory's analytical variation allows definition of uncertainty about a single urine protein measurement, significant changes above normal variation in serial measurements within an individual and a defined level of maximum acceptable analytical imprecision. Repeat urine samples were obtained over a period of one week from a group of cadmium-exposed workers, 90% of whom had long-term tubular proteinuria, and a group of five unexposed volunteers with normal renal function. Dilute samples defined as having creatinines less than 3 mmol l-1 were excluded, as were urines with pH less than 5.5 for -2-microglobulin. Samples were analysed twice after randomisation in large batches. There was no evidence of any diurnal variation in the four protein measurements from samples collected between early morning and 16:00 hours. Creatinine or specific gravity correction of urine results for all four proteins only marginally reduced the uncertainty associated with an individual measurement asreflecting the true excretion value. For those subjects with defined tubular proteinuria, variability in retinol-binding protein excretion was less than that for -2- microglobulin. About 30% of the samples had urine pHs of 5.5 or less where -2- microglobulin degradation occurs. Using our laboratory analytical precision the minimum changes between serial creatinine-corrected measurements that are needed to be considered statistically significant (p retinol-binding protein, 177% for -2-microglobulin, 70% for total protein, and 81% for albumin. Unlike published data for cadmium and mercury, the use of creatinine or specific gravity correction of random untimed urine samples for the urinary proteins does not make a large improvement to the interpretation of data by reducing the uncertainty associated with a measurement. There are significant advantages to the use of retinol-binding protein in contrast to -2- microglobulin as an indicator of renal tubular damage. Levels for defined acceptable analytical precision are calculated for laboratories undertaking protein estimations. The data in this report will help in the interpretation of urinary protein measurements without monitoring cadmium workers. PMID:23885829

Howard J Mason Alison J Stevenson Nerys Williams Michael Morgan

1999-01-01

336

Modeling scale-dependent bias on the baryonic acoustic scale with the statistics of peaks of Gaussian random fields  

Science.gov (United States)

Models of galaxy and halo clustering commonly assume that the tracers can be treated as a continuous field locally biased with respect to the underlying mass distribution. In the peak model pioneered by Bardeen et al. [Astrophys. J. 304, 15 (1986)ASJOAB0004-637X10.1086/164143], one considers instead density maxima of the initial, Gaussian mass density field as an approximation to the formation site of virialized objects. In this paper, the peak model is extended in two ways to improve its predictive accuracy. First, we derive the two-point correlation function of initial density peaks up to second order and demonstrate that a peak-background split approach can be applied to obtain the k-independent and k-dependent peak bias factors at all orders. Second, we explore the gravitational evolution of the peak correlation function within the Zel’dovich approximation. We show that the local (Lagrangian) bias approach emerges as a special case of the peak model, in which all bias parameters are scale independent and there is no statistical velocity bias. We apply our formulas to study how the Lagrangian peak biasing, the diffusion due to large scale flows, and the mode coupling due to nonlocal interactions affect the scale dependence of bias from small separations up to the baryon acoustic oscillation (BAO) scale. For 2? density peaks collapsing at z=0.3, our model predicts a ˜5% residual scale-dependent bias around the acoustic scale that arises mostly from first order Lagrangian peak biasing (as opposed to second order gravity mode coupling). We also search for a scale dependence of bias in the large scale autocorrelation of massive halos extracted from a very large N-body simulation provided by the MICE Collaboration. For halos with mass M?1014M?/h, our measurements demonstrate a scale-dependent bias across the BAO feature which is very well reproduced by a prediction based on the peak model.

Desjacques, Vincent; Crocce, Martin; Scoccimarro, Roman; Sheth, Ravi K.

2010-11-01

337

Chronic kidney disease in the type 2 diabetic patients: prevalence and associated variables in a random sample of 2642 patients of a Mediterranean area  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Kidney disease is associated with an increased total mortality and cardiovascular morbimortality in the general population and in patients with Type 2 diabetes. The aim of this study is to determine the prevalence of kidney disease and different types of renal disease in patients with type 2 diabetes (T2DM. Methods Cross-sectional study in a random sample of 2,642 T2DM patients cared for in primary care during 2007. Studied variables: demographic and clinical characteristics, pharmacological treatments and T2DM complications (diabetic foot, retinopathy, coronary heart disease and stroke. Variables of renal function were defined as follows: 1 Microalbuminuria: albumin excretion rate & 30 mg/g or 3.5 mg/mmol, 2 Macroalbuminuria: albumin excretion rate & 300 mg/g or 35 mg/mmol, 3 Kidney disease (KD: glomerular filtration rate according to Modification of Diet in Renal Disease 2 and/or the presence of albuminuria, 4 Renal impairment (RI: glomerular filtration rate 2, 5 Nonalbuminuric RI: glomerular filtration rate 2 without albuminuria and, 5 Diabetic nephropathy (DN: macroalbuminuria or microalbuminuria plus diabetic retinopathy. Results The prevalence of different types of renal disease in patients was: 34.1% KD, 22.9% RI, 19.5% albuminuria and 16.4% diabetic nephropathy (DN. The prevalence of albuminuria without RI (13.5% and nonalbuminuric RI (14.7% was similar. After adjusting per age, BMI, cholesterol, blood pressure and macrovascular disease, RI was significantly associated with the female gender (OR 2.20; CI 95% 1.86–2.59, microvascular disease (OR 2.14; CI 95% 1.8–2.54 and insulin treatment (OR 1.82; CI 95% 1.39–2.38, and inversely associated with HbA1c (OR 0.85 for every 1% increase; CI 95% 0.80–0.91. Albuminuria without RI was inversely associated with the female gender (OR 0.27; CI 95% 0.21–0.35, duration of diabetes (OR 0.94 per year; CI 95% 0.91–0.97 and directly associated with HbA1c (OR 1.19 for every 1% increase; CI 95% 1.09–1.3. Conclusions One-third of the sample population in this study has KD. The presence or absence of albuminuria identifies two subgroups with different characteristics related to gender, the duration of diabetes and metabolic status of the patient. It is important to determine both albuminuria and GFR estimation to diagnose KD.

Coll-de-Tuero Gabriel

2012-08-01

338

Investigations of the space-dependent transfer function for random control rod vibrations in a pressurized water reactor. 3  

International Nuclear Information System (INIS)

The neutron flux noise induced by two control rods positioned mirrorsymmetrically in the reactor core is discussed on the basis of numerical results. Essentially, the reactor transfer function has the same features as in the case of a single eccentric control rod. It shows strong spatial damping which decreases with growing distance from the absorber. Screening of the noise signals by a second absorber is low. The coherence between two detector signals strongly depends on detector positions inside the core. (author)

1985-01-01

339

Nonparametric estimation for stochastic differential equations with random effects  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We consider $N$ independent stochastic processes $(X_j(t), t\\in [0,T])$, $ j=1, \\ldots,N$, defined by a one-dimensional stochastic differential equation with coefficients depending on a random variable $\\phi_j$ and study the nonparametric estimation of the density of the random effect $\\phi_j$ in two kinds of mixed models. A multiplicative random effect and an additive random effect are successively considered. In each case, we build kernel and deconvolution estimators and study their $L^2$-r...

2012-01-01

340

A proof-of-concept randomized controlled study of gabapentin: effects on cannabis use, withdrawal and executive function deficits in cannabis-dependent adults.  

Science.gov (United States)

There are no FDA-approved pharmacotherapies for cannabis dependence. Cannabis is the most widely used illicit drug in the world, and patients seeking treatment for primary cannabis dependence represent 25% of all substance use admissions. We conducted a phase IIa proof-of-concept pilot study to examine the safety and efficacy of a calcium channel/GABA modulating drug, gabapentin, for the treatment of cannabis dependence. A 12-week, randomized, double-blind, placebo-controlled clinical trial was conducted in 50 unpaid treatment-seeking male and female outpatients, aged 18-65 years, diagnosed with current cannabis dependence. Subjects received either gabapentin (1200?mg/day) or matched placebo. Manual-guided, abstinence-oriented individual counseling was provided weekly to all participants. Cannabis use was measured by weekly urine toxicology and by self-report using the Timeline Followback Interview. Cannabis withdrawal symptoms were assessed using the Marijuana Withdrawal Checklist. Executive function was measured using subtests from the Delis-Kaplan Executive Function System. Relative to placebo, gabapentin significantly reduced cannabis use as measured both by urine toxicology (p=0.001) and by the Timeline Followback Interview (p=0.004), and significantly decreased withdrawal symptoms as measured by the Marijuana Withdrawal Checklist (p<0.001). Gabapentin was also associated with significantly greater improvement in overall performance on tests of executive function (p=0.029). This POC pilot study provides preliminary support for the safety and efficacy of gabapentin for treatment of cannabis dependence that merits further study, and provides an alternative conceptual framework for treatment of addiction aimed at restoring homeostasis in brain stress systems that are dysregulated in drug dependence and withdrawal. PMID:22373942

Mason, Barbara J; Crean, Rebecca; Goodell, Vivian; Light, John M; Quello, Susan; Shadan, Farhad; Buffkins, Kimberly; Kyle, Mark; Adusumalli, Murali; Begovic, Adnan; Rao, Santosh

2012-06-01

 
 
 
 
341

Sequential Cross-Validated Bandwidth Selection Under Dependence and Anscombe-Type Extensions to Random Time Horizons  

CERN Document Server

To detect changes in the mean of a time series, one may use previsible detection procedures based on nonparametric kernel prediction smoothers which cover various classic detection statistics as special cases. Bandwidth selection, particularly in a data-adaptive way, is a serious issue and not well studied for detection problems. To ensure data adaptation, we select the bandwidth by cross-validation, but in a sequential way leading to a functional estimation approach. This article provides the asymptotic theory for the method under fairly weak assumptions on the dependence structure of the error terms, which cover, e.g., GARCH($p,q$) processes, by establishing (sequential) functional central limit theorems for the cross-validation objective function and the associated bandwidth selector. It turns out that the proof can be based in a neat way on \\cite{KurtzProtter1996}'s results on the weak convergence of \\ito integrals and a diagonal argument. Our gradual change-point model covers multiple change-points in th...

Steland, Ansgar

2012-01-01

342

Bindweeds or random walks in random environments on multiplexed trees and their asympotics  

CERN Document Server

We report on the asymptotic behaviour of a new model of random walk, we term the bindweed model, evolving in a random environment on an infinite multiplexed tree. The term \\textit{multiplexed} means that the model can be viewed as a nearest neighbours random walk on a tree whose vertices carry an internal degree of freedom from the finite set $\\{1,...,d\\}$, for some integer $d$. The consequence of the internal degree of freedom is an enhancement of the tree graph structure induced by the replacement of ordinary edges by multi-edges, indexed by the set $\\{1,...,d\\}\\times\\{1,...,d\\}$. This indexing conveys the information on the internal degree of freedom of the vertices contiguous to each edge. The term \\textit{random environment} means that the jumping rates for the random walk are a family of edge-indexed random variables, independent of the natural filtration generated by the random variables entering in the definition of the random walk; their joint distribution depends on the index of each component of th...

Menshikov, M V; Menshikov, Mikhail; Petritis, Dimitri; Proxy, Serguei Popov; ccsd-00000952, ccsd

2003-01-01

343

Client satisfaction among participants in a randomized trial comparing oral methadone and injectable diacetylmorphine for long-term opioid-dependency  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Substitution with opioid-agonists (e.g., methadone has shown to be an effective treatment for chronic long-term opioid dependency. Patient satisfaction with treatment has been associated with improved addiction treatment outcomes. However, there is a paucity of studies evaluating patients' satisfaction with Opioid Substitution Treatment (OST. In the present study, participants' satisfaction with OST was evaluated at 3 and 12 months. We sought to test the relationship between satisfaction and patients' characteristics, the treatment modality received and treatment outcomes. Methods Data from a randomized controlled trial, the North American Opiate Medication Initiative (NAOMI, conducted in Vancouver and Montreal (Canada between 2005-2008, was analyzed. The NAOMI study compared the effectiveness of oral methadone vs. injectable diacetylmorphine over 12 months. A small sub-group of patients received injectable hydromorphone on a double blind basis with diacetylmorphine. The Client Satisfaction Questionnaire (CSQ-8 was used to measure satisfaction with treatment. CSQ-8 scores, as well as retention and response to treatment, did not differ between those receiving hydromorphone and diacetylmorphine at 3 or 12 months assessments; therefore, these two groups were analyzed together as the 'injectable' treatment group. Results A total of 232 (92% and 237 (94% participants completed the CSQ-8 at 3 and 12 months, respectively. Participants in both groups were highly satisfied with treatment. Independent of treatment group, participants satisfied with treatment at 3 months were more likely to be retained at 12 months. Multivariate analysis indicated that satisfaction was greater among those randomized to the injection group after controlling for treatment effectiveness. Participants who were retained, responded to treatment, and had fewer psychological symptoms were more satisfied with treatment. Finally, open-ended comments were made by 149 (60.3% participants; concerns about the randomization process and the study ending were most commonly reported by participants receiving the oral and injectable medications, respectively. Conclusions The higher satisfaction among those receiving medically prescribed injectable diacetylmorphine (or hydromorphone supports current evidence regarding the attractiveness of this treatment for long-term, opioid-dependent individuals not benefiting sufficiently from other treatments. In addition, the measurement of treatment satisfaction provides valuable information about participants at risk of relapse and in need of additional services. Trial Registration ClinicalTrials.gov Identifier: NCT00175357

Brissette Suzanne

2011-07-01

344

Asymptotic normality of kernel estimates in a regression model for random fields  

CERN Document Server

We establish the asymptotic normality of the regression estimator in a fixed-design setting when the errors are given by a field of dependent random variables. The result applies to martingale-difference or strongly mixing random fields. On this basis, a statistical test that can be applied to image analysis is also presented.

Machkouri, Mohamed El

2009-01-01

345

Determinants of the Levels of Development Based on the Human Development Index: A Comparison of Regression Models for Limited Dependent Variables  

Directory of Open Access Journals (Sweden)

Full Text Available This paper aims to examine the factors affecting the level of development of countries using various regression models for limited dependent variables including binary logit, probit and Tobit analyses. In this manner, the paper may suggest a road map for high developed countries to achieve very high developed levels. For this purpose, Human Development Indices of 84 countries were involved in the analysis with respect to nine independent variables. The results of the all regression models indicates that determinants including life expectancy at birth, expected years of schooling, labour force participation rate (female-male ratio, and GDP per capita have statistically significant effects on the level of development.

Mirac Eren

2014-01-01

346

Concentration Inequalities in Locally Dependent Spaces  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper studies concentration inequalities for functions of locally dependent random variables. We show that the usual definition of local dependence does not imply concentration for general Hamming Lipschitz functions. We define hypergraph dependence, which is a special case of local dependence, and show that it implies concentration if the maximal neighborhood size is small. We prove concentration in Hamming distance, Talagrand distance, and for self-bounding functions ...

Paulin, Daniel

2012-01-01

347

Copula-based Kernel Dependency Measures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The paper presents a new copula based method for measuring dependence between random variables. Our approach extends the Maximum Mean Discrepancy to the copula of the joint distribution. We prove that this approach has several advantageous properties. Similarly to Shannon mutual information, the proposed dependence measure is invariant to any strictly increasing transformation of the marginal variables. This is important in many applications, for example in feature selection...

Poczos, Barnabas; Ghahramani, Zoubin; Schneider, Jeff

2012-01-01

348

Random Spatial Structure of Geometric Deformations and Bayesian Nonparametrics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Our work is motivated by the geometric study of lower back pain from patient CT images. In this paper, we take a first step towards that goal by introducing a data-driven way of identifying anatomical regions of interest. We propose a probabilistic model of the geometrical variability and describe individual patients as noisy deformations of a random spatial structure (modeled as regions) from a common template. The random regions are generated using the distance dependent Chinese Restaurant ...

Seiler, Christof; Pennec, Xavier; Holmes, Susan

2013-01-01

349

A Markov Random Field Topic Space Model for Document Retrieval  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper proposes a novel statistical approach to intelligent document retrieval. It seeks to offer a more structured and extensible mathematical approach to the term generalization done in the popular Latent Semantic Analysis (LSA) approach to document indexing. A Markov Random Field (MRF) is presented that captures relationships between terms and documents as probabilistic dependence assumptions between random variables. From there, it uses the MRF-Gibbs equivalence to d...

Hand, Scott

2011-01-01

350

Time dependence of the UV resonance lines in the cataclysmic variables SU UMa, RX And and 0623+71  

International Nuclear Information System (INIS)

We present IUE observations of the dwarf novae SU UMa and RX And, and of the nova-like variable 0623 + 71. At the time of observation, SU UMa and RX And were in outburst. All three systems show variability in the wind-formed UV resonance lines of N v ? 1240, Si IV ? 1397 and C IV ? 1549 on timescale of hours. The amplitude of variation is smallest in RX And and largest in 0623 + 71. There is evidence that the variations observed in SU UMa's UV spectrum repeat on the orbital period. Our observations of SU UMa also reveal variability in the continuum flux during the decline from outburst maximum that is much more marked in the UV than at optical wavelengths. (author)

1990-07-15

351

Time dependence of the UV resonance lines in the cataclysmic variables SU UMa, RX And and 0623+71  

Energy Technology Data Exchange (ETDEWEB)

We present IUE observations of the dwarf novae SU UMa and RX And, and of the nova-like variable 0623 + 71. At the time of observation, SU UMa and RX And were in outburst. All three systems show variability in the wind-formed UV resonance lines of N v {lambda} 1240, Si IV {lambda} 1397 and C IV {lambda} 1549 on timescale of hours. The amplitude of variation is smallest in RX And and largest in 0623 + 71. There is evidence that the variations observed in SU UMa's UV spectrum repeat on the orbital period. Our observations of SU UMa also reveal variability in the continuum flux during the decline from outburst maximum that is much more marked in the UV than at optical wavelengths. (author).

Woods, J.A.; Drew, J.E. (Oxford Univ. (UK). Dept. of Astrophysics); Verbunt, Frank (Rijksuniversiteit Utrecht (Netherlands). Astronomical Inst.)

1990-07-15

352

Dimensions of random affine code tree fractals  

CERN Document Server

We calculate the almost sure Hausdorff dimension for a general class of random affine planar code tree fractals. The set of probability measures describing the randomness includes natural measures in random $V$-variable and homogeneous Markov constructions.

Järvenpää, Esa; Käenmäki, Antti; Koivusalo, Henna; Stenflo, Örjan; Suomala, Ville

2012-01-01

353

Static correlation beyond the random phase approximation: Dissociating H2 with the Bethe-Salpeter equation and time-dependent GW  

Science.gov (United States)

We investigate various approximations to the correlation energy of a H2 molecule in the dissociation limit, where the ground state is poorly described by a single Slater determinant. The correlation energies are derived from the density response function and it is shown that response functions derived from Hedin's equations (Random Phase Approximation (RPA), Time-dependent Hartree-Fock (TDHF), Bethe-Salpeter equation (BSE), and Time-Dependent GW) all reproduce the correct dissociation limit. We also show that the BSE improves the correlation energies obtained within RPA and TDHF significantly for intermediate binding distances. A Hubbard model for the dimer allows us to obtain exact analytical results for the various approximations, which is readily compared with the exact diagonalization of the model. Moreover, the model is shown to reproduce all the qualitative results from the ab initio calculations and confirms that BSE greatly improves the RPA and TDHF results despite the fact that the BSE excitation spectrum breaks down in the dissociation limit. In contrast, second order screened exchange gives a poor description of the dissociation limit, which can be attributed to the fact that it cannot be derived from an irreducible response function.

Olsen, Thomas; Thygesen, Kristian S.

2014-04-01

354

Selection of Common Items as an Unrecognized Source of Variability in Test Equating: A Bootstrap Approximation Assuming Random Sampling of Common Items  

Science.gov (United States)

The standard error of equating quantifies the variability in the estimation of an equating function. Because common items for deriving equated scores are treated as fixed, the only source of variability typically considered arises from the estimation of common-item parameters from responses of samples of examinees. Use of alternative, equally…

Michaelides, Michalis P.; Haertel, Edward H.

2014-01-01

355

Predictors of Outcome for Short-Term Medically Supervised Opioid Withdrawal during a Randomized, Multi Center Trial of Buprenorphine-Naloxone and Clonidine in the NIDA Clinical Trials Network Drug and Alcohol Dependence  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Few studies in community settings have evaluated predictors, mediators, and moderators of treatment success for medically supervised opioid withdrawal treatment. This report presents new findings about these factors from a study of 344 opioid dependent men and women prospectively randomized to either buprenorphine-naloxone or clonidine in an open-label 13-day medically-supervised withdrawal study. Subjects were either inpatient or outpatient in community treatment settings; however not random...

2009-01-01

356

Dependence Structure Estimation via Copula  

CERN Document Server

We propose a new framework for dependence structure learning via copula. Copula is a statistical theory on dependence and measurement of association. Graphical models are considered as a type of special case of copula families, named product copula. In this paper, a nonparametric algorithm for copula estimation is presented. Then a Chow-Liu like method based on dependence measure via copula is proposed to estimate maximum spanning product copula with only bivariate dependence relations. The advantage of the framework is that learning with empirical copula focuses only on dependence relations among random variables, without knowing the properties of individual variables. Another advantage is that copula is a universal model of dependence and therefore the framework based on it can be generalized to deal with a wide range of complex dependence relations. Experiments on both simulated data and real application data show the effectiveness of the proposed method.

Ma, Jian

2008-01-01

357

Hidden conditional random fields.  

Science.gov (United States)

We present a discriminative latent variable model for classification problems in structured domains where inputs can be represented by a graph of local observations. A hidden-state Conditional Random Field framework learns a set of latent variables conditioned on local features. Observations need not be independent and may overlap in space and time. PMID:17699927

Quattoni, Ariadna; Wang, Sybor; Morency, Louis-Philippe; Collins, Michael; Darrell, Trevor

2007-10-01

358

Lifshitz tails for a class of Schr\\"odinger operators with random breather-type potential  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We derive bounds on the integrated density of states for a class of Schr\\"odinger operators with a random potential. The potential depends on a sequence of random variables, not necessarily in a linear way. An example of such a random Schr\\"odinger operator is the breather model, as introduced by Combes, Hislop and Mourre. For these models we show that the integrated density of states near the bottom of the spectrum behaves according to the so called Lifshitz asymptotics. Th...

Kirsch, Werner; Veselic, Ivan

2006-01-01

359

Evolution of size-dependent flowering in a variable environment: construction and analysis of a stochastic integral projection model.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Understanding why individuals delay reproduction is a classic problem in evolutionary biology. In plants, the study of reproductive delays is complicated because growth and survival can be size and age dependent, individuals of the same size can grow by different amounts and there is temporal variation in the environment. We extend the recently developed integral projection approach to include size- and age-dependent demography and temporal variation. The technique is then applied to a long-t...

Childs, D. Z.; Rees, M.; Rose, K. E.; Grubb, P. J.; Ellner, S. P.

2004-01-01

360

Thin Film Flow of a Second Grade Fluid over a Stretching/Shrinking Sheet with Variable Temperature-Dependent Viscosity  

International Nuclear Information System (INIS)

Effects of variable viscosity on the flow and heat transfer in a thin film on a horizontal porous stretching sheet are analyzed. The steady boundary layer equations for momentum and thermal energy are simplified by using similarity transformations. The resulted and coupled nonlinear differential equations are solved by Homotopy analysis method. The results are presented graphically to interpret various physical parameters appearing in the problem. (fundamental areas of phenomenology (including applications))

2010-03-01

 
 
 
 
361

Sensitivity of the Erythrocyte Micronucleus Assay: Dependence on Number of Cells Scored and Inter-animal Variability  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Until recently, the in vivo erythrocyte micronucleus assay has been scored using microscopy. Because the frequency of micronucleated cells is typically low, cell counts are subject to substantial binomial counting error. Counting error, along with inter-animal variability, limit the sensitivity of this assay. Recently, flow cytometric methods have been developed for scoring micronucleated erythrocytes and these methods enable many more cells to be evaluated than is possible with microscopic s...

Kissling, Grace E.; Dertinger, Stephen; Hayashi, Makoto; Macgregor, James T.

2007-01-01

362

The Satisfiability Threshold of Random 3-SAT Is at Least 3.52  

CERN Document Server

We prove that a random 3-SAT instance with clause-to-variable density less than 3.52 is satisfiable with high probability. The proof comes through an algorithm which selects (and sets) a variable depending on its degree and that of its complement.

Hajiaghayi, M T; Hajiaghayi, MohammadTaghi; Sorkin, Gregory B.

2003-01-01

363

A Mass-Selective Variable-Temperature Drift Tube Ion Mobility-Mass Spectrometer for Temperature Dependent Ion Mobility Studies  

Science.gov (United States)

A hybrid ion mobility-mass spectrometer (IM-MS) incorporating a variable-temperature (80-400 K) drift tube is presented. The instrument utilizes an electron ionization (EI) source for fundamental small molecule studies. Ions are transferred to the IM-MS analyzer stages through a quadrupole, which can operate in either broad transmission or mass-selective mode. Ion beam modulation for the ion mobility experiment is accomplished by an electronic shutter gate. The variable-temperature ion mobility spectrometer consists of a 30.2 cm uniform field drift tube enclosed within a thermal envelope. Subambient temperatures down to 80 K are achievable through cryogenic cooling with liquid nitrogen, while elevated temperatures can be accessed through resistive heating of the envelope. Mobility separated ions are mass analyzed by an orthogonal time-of-flight (TOF) mass spectrometer. This report describes the technological considerations for operating the instrument at variable temperature, and preliminary results are presented for IM-MS analysis of several small mass ions. Specifically, mobility separations of benzene fragment ions generated by EI are used to illustrate significantly improved (greater than 50%) ion mobility resolution at low temperatures resulting from decreased diffusional broadening. Preliminary results on the separation of long-lived electronic states of Ti+ formed by EI of TiCl4 and hydration reactions of Ti+ with residual water are presented.

May, Jody C.; Russell, David H.

2011-07-01

364

Multivariate Tests for Correlated Data in Completely Randomized Designs.  

Science.gov (United States)

Provides power comparisons for three permutation tests and the Bartlett-Nanda-Pillai trace test (BNP) (M. Bartlett, 1939; D. Nanda, 1950; K. Pillai, 1955) in completely randomized experimental designs with correlated multivariate-dependent variables. The power of the BNP was generally found to be less than that of at least one of the permutation…

Mielke, Paul W., Jr.; Berry, Kenneth J.

1999-01-01

365

Computer-Assisted Dieting: Effects of a Randomized Nutrition Intervention  

Science.gov (United States)

Objectives: To compare the effects of a computer-assisted dieting intervention (CAD) with and without self-management training on dieting among 55 overweight and obese adults. Methods: Random assignment to a single-session nutrition intervention (CAD-only) or a combined CAD plus self-management group intervention (CADG). Dependent variables were…

Schroder, Kerstin E. E.

2011-01-01

366

Relationships among selected physical science misconceptions held by preservice elementary teachers and four variables: Formal reasoning ability, working memory capacity, verbal intelligence, and field dependence/independence  

Science.gov (United States)

The purpose of this study was to determine the relationship of selected cognitive abilities and physical science misconceptions held by preservice elementary teachers. The cognitive abilities under investigation were: formal reasoning ability as measured by the Lawson Classroom Test of Formal Reasoning (Lawson, 1978); working memory capacity as measured by the Figural Intersection Test (Burtis & Pascual-Leone, 1974); verbal intelligence as measured by the Acorn National Academic Aptitude Test: Verbal Intelligence (Kobal, Wrightstone, & Kunze, 1944); and field dependence/independence as measured by the Group Embedded Figures Test (Witkin, Oltman, & Raskin, 1971). The number of physical science misconceptions held by preservice elementary teachers was measured by the Misconceptions in Science Questionnaire (Franklin, 1992). The data utilized in this investigation were obtained from 36 preservice elementary teachers enrolled in two sections of a science methods course at a small regional university in the southeastern United States. Multiple regression techniques were used to analyze the collected data. The following conclusions were reached following an analysis of the data. The variables of formal reasoning ability and verbal intelligence were identified as having significant relationships, both individually and in combination, to the dependent variable of selected physical science misconceptions. Though the correlations were not high enough to yield strong predictors of physical science misconceptions or strong relationships, they were of sufficient magnitude to warrant further investigation. It is recommended that further investigation be conducted replicating this study with a larger sample size. In addition, experimental research should be implemented to explore the relationships suggested in this study between the cognitive variables of formal reasoning ability and verbal intelligence and the dependent variable of selected physical science misconceptions. Further research should also focus on the detection of a broad range of science misconceptions among preservice elementary teachers.

Griffin, Leslie Little

367

Trypanosoma evansi: Genetic variability detected using amplified restriction fragment length polymorphism (AFLP) and random amplified polymorphic DNA (RAPD) analysis of Kenyan isolates  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We compared two methods to generate polymorphic markers to investigate the population genetics of Trypanosoma evansi; random amplified polymorphic DNA (RAPD) and amplified restriction fragment length polymorphism (AFLP) analyses. AFLP accessed many more polymorphisms than RAPD. Cluster analysis of the AFLP data showed that 12 T.evansi isolates were very similar (‘type A’) whereas 2 isolates differed substantially (‘type B’). Type A isolates have been generally regarded as genetically ...

Masiga, D. K.; Ndung’u, K.; Tweedie, A.; Tait, A.; Turner, C.

2006-01-01

368

Cycles in random k-ary maps and the poor performance of random random number generation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Knuth shows that iterations of a random function perform poorly on average as a random number generator. He proposes a generalization in which the next value depends on two or more previous values. This note demonstrates, via an analysis of the cycle length of a random k-ary map, the equally poor performance of a random instance in Knuth's more general model.

Pemantle, Robin

2004-01-01

369

Polarization dependence of (Bi,Pb)-2201 and (Bi,Pb)-2212 low energy excitations by variable polarization ARPES  

International Nuclear Information System (INIS)

The low energy excitations at the M-points of the four quadrants of the first Brillouin zone of superstructure free (Bi,Pb)-2201 and (Bi,Pb)-2212 single crystals have been investigated systematically with respect to their polarization dependence. A new spectrometer with a SCIENTA SES100 and HeI radiation from a duoplasmatron source was used. A polarizer with focusing capability enabled a continuous variation of the polarization vector in the CuO2- plane. Like previously reported the topmost emission consists of two peaks, whose relative intensity varies with the selected polarization and also the M-point under study, showing the M points to be essentially not equivalent. Possible reasons are discussed taking also the results of temperature and photon energy dependent measurements into account.

2012-03-25

370

SiGe Channel Technology: Superior Reliability Toward Ultra-Thin EOT Devices-Part II: Time-Dependent Variability in Nanoscaled Devices and Other Reliability Issues  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The time-dependent variability of nanoscaled Si0.45Ge0.55 pFETs with varying thicknesses of the Si passivation layer is studied. Single charge/discharge events of gate oxide defects are detected by measuring negative bias-temperature instability (NBTI)-like threshold voltage (Vth) shift relaxation transients. The impact of such individually charged defect on device Vth is observed to be exponentially distributed. SiGe channel devices with a reduced thickness of their Si passivation layer show...

Franco, Jacopo; Kaczer, Ben; Toledano-luque, Maria; Roussel, Philippe J.; Kauerauf, Thomas; Mitard, Jerome; Witters, Liesbeth; Grasser, Tibor; Groeseneken, Guido

2013-01-01

371

The LTS{sub N} formulation with continuous dependence in the angular variable; A formulacao LTS{sub N} com dependencia continua na variavel angular  

Energy Technology Data Exchange (ETDEWEB)

The LTS{sub N} formulation, that establishes an analytical solution for the discrete ordinates problems, is used to determinate the average angular fluxes which depend continuously on the angular variable in two dimensional problems. For such, the two dimensional transport equation is integrated, respect to x and y respectively, resulting two one dimensional equations for the average angular fluxes where LTS{sub N} formulation is then applied. Finally, two non-homogeneous first order ordinary differential equations are analytically solved. (author). 6 refs.

Barichello, Liliane B. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Inst. de Matematica; Vilhena, M.T.; Zabadal, Jorge R. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Dept. de Engenharia Nuclear

1995-12-31

372

Evolution of size-dependent flowering in a variable environment: construction and analysis of a stochastic integral projection model.  

Science.gov (United States)

Understanding why individuals delay reproduction is a classic problem in evolutionary biology. In plants, the study of reproductive delays is complicated because growth and survival can be size and age dependent, individuals of the same size can grow by different amounts and there is temporal variation in the environment. We extend the recently developed integral projection approach to include size- and age-dependent demography and temporal variation. The technique is then applied to a long-term individually structured dataset for Carlina vulgaris, a monocarpic thistle. The parameterized model has excellent descriptive properties in terms of both the population size and the distributions of sizes within each age class. In Carlina, the probability of flowering depends on both plant size and age. We use the parameterized model to predict this relationship, using the evolutionarily stable strategy approach. Considering each year separately, we show that both the direction and the magnitude of selection on the flowering strategy vary from year to year. Provided the flowering strategy is constrained, so it cannot be a step function, the model accurately predicts the average size at flowering. Elasticity analysis is used to partition the size- and age-specific contributions to the stochastic growth rate, lambda(s). We use lambda(s) to construct fitness landscapes and show how different forms of stochasticity influence its topography. We prove the existence of a unique stochastic growth rate, lambda(s), which is independent of the initial population vector, and show that Tuljapurkar's perturbation analysis for log(lambda(s)) can be used to calculate elasticities. PMID:15101702

Childs, Dylan Z; Rees, Mark; Rose, Karen E; Grubb, Peter J; Ellner, Stephen P

2004-02-22

373

A factorial randomized controlled trial to evaluate the effect of micronutrients supplementation and regular aerobic exercise on maternal endothelium-dependent vasodilatation and oxidative stress of the newborn  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Many studies have suggested a relationship between metabolic abnormalities and impaired fetal growth with the development of non-transmissible chronic diseases in the adulthood. Moreover, it has been proposed that maternal factors such as endothelial function and oxidative stress are key mechanisms of both fetal metabolic alterations and subsequent development of non-transmissible chronic diseases. The objective of this project is to evaluate the effect of micronutrient supplementation and regular aerobic exercise on endothelium-dependent vasodilation maternal and stress oxidative of the newborn. Methods and design 320 pregnant women attending to usual prenatal care in Cali, Colombia will be included in a factorial randomized controlled trial. Women will be assigned to the following intervention groups: 1. Control group: usual prenatal care (PC and placebo (maltodextrine. 2. Exercise group: PC, placebo and aerobic physical exercise. 3. Micronutrients group: PC and a micronutrients capsule consisting of zinc (30 mg, selenium (70 ?g, vitamin A (400 ?g, alphatocopherol (30 mg, vitamin C (200 mg, and niacin (100 mg. 4. Combined interventions Group: PC, supplementation of micronutrients, and aerobic physical exercise. Anthropometric measures will be taken at the start and at the end of the interventions. Discussion Since in previous studies has been showed that the maternal endothelial function and oxidative stress are related to oxidative stress of the newborn, this study proposes that complementation with micronutrients during pregnancy and/or regular physical exercise can be an early and innovative alternative to strengthen the prevention of chronic diseases in the population. Trial registration NCT00872365.

Girón Sandra

2011-02-01

374

Mendelian randomization in family data  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The phrase "mendelian randomization" has become associated with the use of genetic polymorphisms to uncover causal relationships between phenotypic variables. The statistical methods useful in mendelian randomization are known as instrumental variable techniques. We present an approach to instrumental variable estimation that is useful in family data and is robust to the use of weak instruments. We illustrate our method to measure the causal influence of low-density lipoprotein on hig...

Morris, Nathan J.; Gray-mcguire, Courtney; Stein, Catherine M.

2009-01-01

375

Summer to winter variability in mesospheric calcium ion distribution and its dependence on Sporadic E at Arecibo  

Science.gov (United States)

We present a new investigation of the variability in the metallic calcium ion concentration near the mesopause region, and its relation to the electron concentration during summer and winter seasons at the Arecibo Observatory. During the summer months the ion layer is broader, extending to 87-88 km compared with winter months where it occurs above this altitude around midnight. The concentration maximizes to ˜200 ions cm-3 around 90-95 km close to midnight during the summer. However, for the winter months, the peak occurs during the early morning hours in thin descending layers above 98 km. Summer to winter variation in the calcium ion to electron ratio displays an average value of ˜0.15 and 0.05 during these seasons, respectively. A good correlation between them suggests that Ca+ densities are directly related to the strength of the Sporadic E, which is stronger in the summer. The average abundance of ions is 5.7 × 107 cm-2 and 4.6 × 107 cm-2 during summer and winter months respectively, while that for electrons is 1.2 × 1010 ions cm-2 and 5.8 × 109 ion cm-2 for these seasons. Both Ca+ and Ne display strong descending layers at different altitudes during summer and winter. Calcium ion lifetimes against neutralization are a factor of two lower during the summer than in the winter months around 90 km but similar at altitudes exceeding 95 km.

Raizada, Shikha; Tepley, Craig A.; Williams, Bifford P.; García, Raúl

2012-02-01

376

Estimations of the Central Tendency Measures of the Random-sum Poisson-Weibull Distribution using Saddlepoint Approximation  

Directory of Open Access Journals (Sweden)

Full Text Available The random-sum Poisson-Weibull variable is the sum of a random sample from a Weibull distribution with a sample size that is an independent Poisson random variable. It has a wide range of applications. This random sum is complex and difficult to analyze. Saddlepoint approximations are powerful tools for obtaining accurate expressions for closed-form distribution functions for these complex distributions. The use of saddlepoint approximations almost outperforms other methods with respect to computational costs, though not necessarily with respect to accuracy. This study introduces saddlepoint approximations to the cumulative distribution function for the Poisson-Weibull model, from which we can obtain some important statistical measures of the central tendency of a cumulative distribution. We discuss approximations of a random-sum variable using dependent components, assuming the existence of a moment-generating function. Numerical examples of Poisson-Weibull random sums are presented.

O. Al Mutairi Alya

2014-01-01

377

Variable angle XAFS study of multilayer nanostructure: Determination of selective concentration profile and depth-dependent partial atomic distributions  

International Nuclear Information System (INIS)

We propose a new method for studying multilayer structure using angle resolved extended x-ray absorption fine structure (EXAFS) measurements. The linear integral equation describing a connection between the fluorescence intensity for spectrum of element C, the incident beam energy E, the incident angle ? and the concentration profile p(z,C) has been derived. It is a Fredholm integral equation of the first kind, it belongs to the class of ill-posed problems and for solution it needs special methods. We use the regularization method. For determining the depth-dependent partial interatomic distances we use angle resolved EXAFS data. The effectiveness of the method has been tested during numerical simulation on the model crystalline three-layer with BCC structure: Cr/Fe/Cr.

2009-11-01

378

VARIABILITY OF ANTHOCYANIN CONTENT AND DRY MATTER AMOUNT IN FRUITS OF SOME LONICERA CAERULEA SELECTIONS DEPENDING ON STORAGE CONDITIONS  

Directory of Open Access Journals (Sweden)

Full Text Available Lonicera caerulea var. kamtschatica is a species with multiple uses mainly due to the valuable biologicallyactive substances with high antioxidative potential. The anthocianins occupy an important place in inducing the health-protective benefits of the berries of this species. The aim of our work was to determine the total anthocyanin and drymatter amounts in the fruits collected from Romanian selections of blue honeysuckle, preserved by freezing (three monthsin refrigerator and drying at 60°C (to constant weight. The obtained results showed that the storage conditions havegenerally influenced the anthocyanin content. Thus, in freezing storage conditions, the anthocyanin amount eitherdecreased (C, SL6, SL8, SL15 or increased (SL17, SL57, depending on the biological material, whereas the dryingpreservation declined the anthocyanin level with ~ 80%, also varying with the selections of blue honeysuckle.

Zenovia Olteanu

2013-12-01

379

Variable angle XAFS study of multilayer nanostructure: Determination of selective concentration profile and depth-dependent partial atomic distributions  

Energy Technology Data Exchange (ETDEWEB)

We propose a new method for studying multilayer structure using angle resolved extended x-ray absorption fine structure (EXAFS) measurements. The linear integral equation describing a connection between the fluorescence intensity for spectrum of element C, the incident beam energy E, the incident angle {phi} and the concentration profile p(z,C) has been derived. It is a Fredholm integral equation of the first kind, it belongs to the class of ill-posed problems and for solution it needs special methods. We use the regularization method. For determining the depth-dependent partial interatomic distances we use angle resolved EXAFS data. The effectiveness of the method has been tested during numerical simulation on the model crystalline three-layer with BCC structure: Cr/Fe/Cr.

Babanov, Yuri; Salamatov, Yuri [Institute of Metal Physics Russian Academy of Sciences, 18 S. Kovalevskaya str., 620041 Ekaterinburg (Russian Federation); Mukhamedzhanov, Enver, E-mail: babanov@imp.uran.r [Russian Research Centre ' Kurchatov Institute' , 1 Kurchatov Sq., 123182 Moscow (Russian Federation)

2009-11-15

380

A Random Necklace Model  

CERN Document Server

We consider a Laplace operator on a random graph consisting of infinitely many loops joined symmetrically by intervals of unit length. The arc lengths of the loops are considered to be independent, identically distributed random variables. The integrated density of states of this Laplace operator is shown to have discontinuities provided that the distribution of arc lengths of the loops has a nontrivial pure point part. Some numerical illustrations are also presented.

Kostrykin, V; Kostrykin, Vadim; Schrader, Robert

2004-01-01

 
 
 
 
381

High-Rate Pacing Reduces Variability of Repolarization and Prevents Repolarization-Dependent Arrhythmias in Dogs With Chronic AV Block  

DEFF Research Database (Denmark)

High-rate pacing may have an inhibitory effect on the initiation of Torsade de Pointes arrhythmias (TdP). However, permanent pacing is only indicated in high-risk patients. We performed a proof of concept study into automatic overdrive pacing for prevention of drug-induced TdP, using short-term variability of repolarization (STV) as a feedback parameter of arrhythmic risk. Methods and Results: The minimal signal sampling frequency required for measuring STV was determined through computer simulation. Arrhythmogenic response to dofetilide (25 µg/kg/5minutes) was tested at two different paced heart rates (60â??65 bpm vs 100â??110 bpm) in 7 dogs with chronic atrioventricular block, while recording right and left ventricular (LV) monophasic action potential (MAP) and LV electrogram (EGM). Simulations showed a sampling frequency of 500 Hz is sufficient to capture relevant STV values. High-rate pacing prevented dofetilide-induced TdP seen at the low rate (low: 6/7 vs high: 1/7). At the low rate, STV from LV MAP duration increased before occurrence of spontaneous, ectopic activity and TdP (1.7 ± 0.6â??3.0 ± 1.8 ms, P < 0.05), but at the high-rate STV did not change significantly (0.9 ± 0.2â??1.5 ± 1.4 ms, NS). Regression analysis showed a close relation between STV calculated from LV MAP and from LV EGM (R2= 0.71). Conclusions: High-rate pacing increases repolarization reserve in dogs with chronic atrioventricular block, preventing dofetilide-induced TdP. Changes in repolarization reserve are reflected in values of STV.

Oosterhoff, Peter; Thomsen, Morten Bækgaard

2010-01-01

382

The Harris-Luck criterion for random lattices  

CERN Multimedia

The Harris-Luck criterion judges the relevance of (potentially) spatially correlated, quenched disorder induced by, e.g., random bonds, randomly diluted sites or a quasi-periodicity of the lattice, for altering the critical behavior of a coupled matter system. We investigate the applicability of this type of criterion to the case of spin variables coupled to random lattices. Their aptitude to alter critical behavior depends on the degree of spatial correlations present, which is quantified by a wandering exponent. We consider the cases of Poissonian random graphs resulting from the Voronoi-Delaunay construction and of planar, ``fat'' $\\phi^3$ Feynman diagrams and precisely determine their wandering exponents. The resulting predictions are compared to various exact and numerical results for the Potts model coupled to these quenched ensembles of random graphs.

Janke, W; Janke, Wolfhard; Weigel, Martin

2004-01-01

383

A-Collapsibility of Distribution Dependence and Quantile Regression Coefficients  

CERN Document Server

The Yule-Simpson paradox notes that an association between random variables can be reversed when averaged over a background variable. Cox and Wermuth (2003) introduced the concept of distribution dependence between two random variables X and Y , and developed two dependence conditions, each of which guarantees that reversal cannot occur. Ma, Xie and Geng (2006) studied the collapsibility of distribution dependence over a background variable W, under a rather strong homogeneity condition. Collapsibility ensures the association remains the same for conditional and marginal models, so that Yule-Simpson reversal cannot occur. In this paper, we investigate a more general condition for avoiding e?ect reversal: A-collapsibility. The conditions of Cox and Wermuth imply A-collapsibility, without assuming homogeneity. In fact, we show that, when W is a binary variable, collapsibility is equivalent to A-collapsibility plus homogeneity, and A-collapsibility is equivalent to the conditions of Cox and Wermuth. Recently, Co...

Meerschaert, Mark M

2010-01-01

384

A variable-order time-dependent neutron transport method for nuclear reactor kinetics using analytically-integrated space-time characteristics  

Energy Technology Data Exchange (ETDEWEB)

A new time-dependent neutron transport method based on the method of characteristics (MOC) has been developed. Whereas most spatial kinetics methods treat time dependence through temporal discretization, this new method treats time dependence by defining the characteristics to span space and time. In this implementation regions are defined in space-time where the thickness of the region in time fulfills an analogous role to the time step in discretized methods. The time dependence of the local source is approximated using a truncated Taylor series expansion with high order derivatives approximated using backward differences, permitting the solution of the resulting space-time characteristic equation. To avoid a drastic increase in computational expense and memory requirements due to solving many discrete characteristics in the space-time planes, the temporal variation of the boundary source is similarly approximated. This allows the characteristics in the space-time plane to be represented analytically rather than discretely, resulting in an algorithm comparable in implementation and expense to one that arises from conventional time integration techniques. Furthermore, by defining the boundary flux time derivative in terms of the preceding local source time derivative and boundary flux time derivative, the need to store angularly-dependent data is avoided without approximating the angular dependence of the angular flux time derivative. The accuracy of this method is assessed through implementation in the neutron transport code DeCART. The method is employed with variable-order local source representation to model a TWIGL transient. The results demonstrate that this method is accurate and more efficient than the discretized method. (authors)

Hoffman, A. J.; Lee, J. C. [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Boulevard, Ann Arbor, MI, 48109-2104 (United States)

2013-07-01

385

A variable-order time-dependent neutron transport method for nuclear reactor kinetics using analytically-integrated space-time characteristics  

International Nuclear Information System (INIS)

A new time-dependent neutron transport method based on the method of characteristics (MOC) has been developed. Whereas most spatial kinetics methods treat time dependence through temporal discretization, this new method treats time dependence by defining the characteristics to span space and time. In this implementation regions are defined in space-time where the thickness of the region in time fulfills an analogous role to the time step in discretized methods. The time dependence of the local source is approximated using a truncated Taylor series expansion with high order derivatives approximated using backward differences, permitting the solution of the resulting space-time characteristic equation. To avoid a drastic increase in computational expense and memory requirements due to solving many discrete characteristics in the space-time planes, the temporal variation of the boundary source is similarly approximated. This allows the characteristics in the space-time plane to be represented analytically rather than discretely, resulting in an algorithm comparable in implementation and expense to one that arises from conventional time integration techniques. Furthermore, by defining the boundary flux time derivative in terms of the preceding local source time derivative and boundary flux time derivative, the need to store angularly-dependent data is avoided without approximating the angular dependence of the angular flux time derivative. The accuracy of this method is assessed through implementation in the neutron transport code DeCART. The method is employed with variable-order local source representation to model a TWIGL transient. The results demonstrate that this method is accurate and more efficient than the discretized method. (authors)

2013-05-05

386

Potassium loss from chlorhexidine-treated bacterial pathogens is time- and concentration-dependent and variable between species.  

Science.gov (United States)

The membrane-active antimicrobial agent chlorhexidine is used extensively as an antiseptic during infection prophylaxis and treatment. Whilst known to induce membrane damage that results in loss of internal solutes from bacteria, the present study sought to determine the rate and extent of cytoplasmic potassium loss and whether any species-specific differences exist. Direct measurement of potassium was achieved using flame emission spectrophotometry. Exposure of selected species to minimum inhibitory (MIC) or minimum bactericidal concentration (MBC) resulted in solute loss that was both concentration and time dependent. Within 5-min treatment with MIC levels, losses of 3 % from P. aeruginosa, 9 % from E. coli, and 15 % from S. aureus were recorded, whilst at 5 % w/v chlorhexidine, elevated loss of 20, 28, and 41 % occurred, respectively. Nonlinear potassium release was evident from all species when treated with 5 % chlorhexidine over a 60-min period. After this contact time, potassium loss from E. coli and S. aureus rose to 93 or 90 %, respectively; in contrast, P. aeruginosa retained 62 % intracellular potassium. Results confirm lethal concentrations of chlorhexidine induce rapid and substantial loss of cytoplasmic potassium from common pathogens. However, bacterial responses vary between species and should be borne in mind when considering mechanism of action. PMID:23928905

O'Driscoll, Noelle H; Labovitiadi, Olga; Cushnie, T P Tim; Matthews, Kerr H; Lamb, Andrew J

2014-01-01

387

The spatial random effects and the spatial fixed effects model: The Hausman test in a Cliff and Ord panel model  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper studies the spatial random effects and spatial fixed effects model. The model includes a Cliff and Ord type spatial lag of the dependent variable as well as a spatially lagged one-way error component structure, accounting for both heterogeneity and spatial correlation across units. We discuss instrumental variable estimation under both the fixed and the random effects specification and propose a spatial Hausman test which compares these two models accounting for spatial autocorrela...

Mutl, Jan; Pfaffermayr, Michael

2008-01-01

388

Unit-specific calibration of Actigraph accelerometers in a mechanical setup – Is it worth the effort? The effect on random output variation caused by technical inter-instrument variability in the laboratory and in the field  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Potentially, unit-specific in-vitro calibration of accelerometers could increase field data quality and study power. However, reduced inter-unit variability would only be important if random instrument variability contributes considerably to the total variation in field data. Therefore, the primary aim of this study was to calculate and apply unit-specific calibration factors in multiple accelerometers in order to examine the impact on random output variation caused by inter-instrument variability. Methods Instrument-specific calibration factors were estimated in 25 MTI- and 53 CSA accelerometers in a mechanical setup using four different settings varying in frequencies and/or amplitudes. Calibration effect was analysed by comparing raw and calibrated data after applying unit-specific calibration factors to data obtained during quality checks in a mechanical setup and to data collected during free living conditions. Results Calibration reduced inter-instrument variability considerably in the mechanical setup, both in the MTI instruments (raw SDbetween units = 195 counts*min-1 vs. calibrated SDbetween units = 65 counts*min-1 and in the CSA instruments (raw SDbetween units = 343 counts*min-1 vs. calibrated SDbetween units = 67 counts*min-1. However, the effect of applying the derived calibration to children's and adolescents' free living physical activity data did not alter the coefficient of variation (CV (children: CVraw = 30.2% vs. CVcalibrated = 30.4%, adolescents: CVraw = 36.3% vs. CVcalibrated = 35.7%. High correlations (r = 0.99 & r = 0.98, respectively were observed between raw and calibrated field data, and the proportion of the total variation caused by the MTI- and CSA monitor was estimated to be only 1.1% and 4.2%, respectively. Compared to the CSA instruments, a significantly increased (9.95% mean acceleration response was observed post hoc in the batch of MTI instruments, in which a significantly reduced inter-instrumental reliability was observed over time. Conclusion The application of unit-specific calibration factors to data collected during free living conditions had no apparent effect on inter-instrument variability. In all probability, the effect of technical calibration was primarily attenuated in the field by other more dominant sources of variation. However, routine technical assessments are still very important for determining the acceleration responses in the batch of instruments being used and, if performed after every field use, for preventing decidedly broken instruments from being returned into the field repeatedly.

Andersen Lars B

2008-04-01

389

Unit-specific calibration of Actigraph accelerometers in a mechanical setup - is it worth the effort? The effect on random output variation caused by technical inter-instrument variability in the laboratory and in the field  

DEFF Research Database (Denmark)

BACKGROUND: Potentially, unit-specific in-vitro calibration of accelerometers could increase field data quality and study power. However, reduced inter-unit variability would only be important if random instrument variability contributes considerably to the total variation in field data. Therefore, the primary aim of this study was to calculate and apply unit-specific calibration factors in multiple accelerometers in order to examine the impact on random output variation caused by inter-instrument variability. METHODS: Instrument-specific calibration factors were estimated in 25 MTI- and 53 CSA accelerometers in a mechanical setup using four different settings varying in frequencies and/or amplitudes. Calibration effect was analysed by comparing raw and calibrated data after applying unit-specific calibration factors to data obtained during quality checks in a mechanical setup and to data collected during free living conditions. RESULTS: Calibration reduced inter-instrument variability considerably in the mechanical setup, both in the MTI instruments (raw SDbetween units = 195 counts*min-1 vs. calibrated SDbetween units = 65 counts*min-1) and in the CSA instruments (raw SDbetween units = 343 counts*min-1 vs. calibrated SDbetween units = 67 counts*min-1). However, the effect of applying the derived calibration to children's and adolescents' free living physical activity data did not alter the coefficient of variation (CV) (children: CVraw = 30.2% vs. CVcalibrated = 30.4%, adolescents: CVraw = 36.3% vs. CVcalibrated = 35.7%). High correlations (r = 0.99 & r = 0.98, respectively) were observed between raw and calibrated field data, and the proportion of the total variation caused by the MTI- and CSA monitor was estimated to be only 1.1% and 4.2%, respectively. Compared to the CSA instruments, a significantly increased (9.95%) mean acceleration response was observed post hoc in the batch of MTI instruments, in which a significantly reduced inter-instrumental reliability was observed over time. CONCLUSION: The application of unit-specific calibration factors to data collected during free living conditions had no apparent effect on inter-instrument variability. In all probability, the effect of technical calibration was primarily attenuated in the field by other more dominant sources of variation. However, routine technical assessments are still very important for determining the acceleration responses in the batch of instruments being used and, if performed after every field use, for preventing decidedly broken instruments from being returned into the field repeatedly.

Moeller, Niels C; Korsholm, Lars

2008-01-01

390

Enumerating randoms  

CERN Document Server

We investigate enumerability properties for classes of random reals which permit recursive approximations from below. For four classical notions of randomness (Martin-L\\"of randomness, computable randomness, Schnorr randomness, and Kurtz randomness), as well as for bi-immunity, we detail whether the left-recursive enumerable members can be enumerated, and similarly for the complementary left-r.e. classes. We prove a general equivalence between arithmetic complexity and existence of numberings for classes of left-r.e. reals and give optimal arithmetic hardness results.

Kjos-Hanssen, Bjørn; Teutsch, Jason R

2010-01-01

391

Spartan models of spatial dependence  

Science.gov (United States)

Modelling the variability of spatially distributed data often involves the classical geostatistical framework, which requires calculating two-point variogram functions that characterize the spatial dependence. This is a computationally intensive procedure, especially for large-size samples. In addition, calculation of the variogram from a single sample realization relies on a number of assumptions. We propose an alternative method of modelling spatial dependence, which is based on random fields that we call Spartan, because their probability density function is determined from a small number of parameters. We present some general properties of Spartan random fields, and we further investigate specific models. We also present a specific algorithm for inferring the field parameters from available samples. The algorithm is illustrated with the help of synthetic samples, both with regular (lattice) and irregular (random) spatial distribution. The advantage of the Spartan models is the numerical efficiency of the model inference process, which is considerably faster than the standard variogram calculation.

Hristopulos, D. T.

2003-04-01

392

A Maximal Large Deviation Inequality for Sub-Gaussian Variables  

CERN Document Server

In this short note we prove a maximal concentration lemma for sub-Gaussian random variables stating that for independent Gaussian random variables we have \\[P\\epsilon>) \\le\\exp), \\] where $S_i$ is the sum of $i$ zero mean independent sub-Gaussian random variables and $\\sigma_i$ is the variance of the $i$th random variable.

Di Castro, Dotan; Mannor, Shie

2011-01-01

393

Effects of amlodipine and other classes of antihypertensive drugs on long-term blood pressure variability: evidence from randomized controlled trials.  

Science.gov (United States)

Blood pressure (BP) is monitored and managed to prevent cardiovascular complications of hypertension, but BP variability (BPV) has not been sufficiently studied. This analysis assessed whether patients receiving amlodipine vs other antihypertensive agents had lower BPV after ?12 weeks of treatment. Studies were included if individual subject data were available, had ?1 active comparator, and treatment duration was ?12 weeks. BPV was assessed using standard deviation (SD) and coefficient of variation (CV) of systolic BP across visits from 12 weeks. Individual trial and meta-analyses were performed for SD- and CV-based methodology. Five studies (47,558 BPV-evaluable patients) were included. Patient characteristics were largely consistent across the studies, but BP measurements varied from ?4 months to ?6 years. BPV with amlodipine was significantly (P amlodipine vs all active comparators of -1.23 (0.46; P = .008) mm Hg using SD and -0.86 (0.31; P = .005) using CV. These findings suggest that amlodipine is effective for minimizing BPV. Future studies need to confirm a causal link between BPV and cerebrovascular/cardiovascular outcomes. PMID:24685006

Wang, Ji-Guang; Yan, Ping; Jeffers, Barrett W

2014-05-01

394

Linear and Nonlinear Heart Rate Variability Indexes in Clinical Practice  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Biological organisms have intrinsic control systems that act in response to internal and external stimuli maintaining homeostasis. Human heart rate is not regular and varies in time and such variability, also known as heart rate variability (HRV), is not random. HRV depends upon organism's physiologic and/or pathologic state. Physicians are always interested in predicting patient's risk of developing major and life-threatening complications. Understanding biological signals behavior helps to ...

2012-01-01

395

An inventory model of two-warehouse system with variable demand dependent on instantaneous displayed stock and marketing decisions via hybrid RCGA  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, a single item deterministic inventory model with two separate warehouses called owned warehouse/show-room (OW and rented warehouse (RW is developed. The proposed model of this paper also considers a realistic assumption regarding the storage capacity of the rented warehouse. Demand is a function of selling price, advertisement of an item and displayed inventory level in OW. The stocks of RW are shipped to OW under bulk release pattern where shortages are not allowed. We discuss different scenarios of the proposed model to address relative size of stock dependency parameters and the capacity of owned warehouse. For each scenario, the corresponding problem is formulated as a constrained mixed integer nonlinear programming problem with three integer and two non-integer variables and a real coded genetic algorithm (RCGA is developed to solve the resulted problem. The proposed model of the paper is also examined using some numerical examples and sensitivity analysis is performed.

A. K. Bhunia

2011-04-01

396

Examination of the role of the pituitary-adrenocortical axis, counterregulatory hormones, and insulin clearance in variable nocturnal insulin requirements in insulin-dependent diabetes.  

Science.gov (United States)

In insulin-dependent diabetics, insulin requirements increase significantly after 0600 h, resulting in prebreakfast hyperglycemia with either conventional insulin therapy or constant insulin infusions with insulin infusion devices. In order to clarify the role of the pituitary-adrenocortical axis and further examine the mechanisms of the phenomenon of nocturnal variability in insulin requirements, we studied five IDDs using a closed-loop insulin infusion device (Biostator, GCIIS). The subjects were given saline (SAL) or dexamethasone (DEX) i.v. from 1800 to 0900 h on successive nights. From 2400-0300 to 0600-0900 h, mean insulin infusion rates required to maintain blood glucose values between 109 and 120 mg/dl increased by 0.21 +/- 0.05 mU/kg/min during the SAL infusion, and 0.16 +/- 0.04 mU/kg/min during the DEX infusion, when plasma cortisols were suppressed to less than or equal to 2 micrograms/dl. Mean free insulin concentrations did not increase and remained constant throughout both study nights in spite of the significantly higher 0600-0900-h insulin infusion rates. Growth hormone, glucagon, epinephrine, and norepinephrine concentrations showed normal nocturnal and early morning patterns during both study nights. We conclude that the nocturnal variability in insulin requirements persists despite suppression of the pituitary-adrenocortical axis, and that increased free insulin clearance or degradation may contribute to the "dawn phenomenon" of rising prebreakfast glucose despite constant insulin infusion. PMID:6341122

Skor, D A; White, N H; Thomas, L; Shah, S D; Cryer, P E; Santiago, J V

1983-05-01

397

Random discrete Schr\\"odinger operators from Random Matrix Theory  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate random, discrete Schr\\"odiner operators which arise naturally in the theory of random matrices, and depend parametrically on Dyson's Coulomb gas inverse temperature $\\beta$. They belong to the class of "critical" random Schr\\"odiner operators with random potentials which diminish as $|x|^{-{1/2}}$. We show that as a function of $\\beta$ their eigenstates undergo a transition from extended ($\\beta \\ge 2 $) to power-law localized ($0 < \\beta < 2$).

Breuer, Jonathan; Forrester, Peter J.; Smilansky, Uzy

2005-01-01

398

Modeling dependencies in finance using copulae  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we provide a review of copula theory with applications to finance. We illustrate the idea on the bivariate framework and discuss the simple, elliptical and Archimedean classes of copulae. Since the copulae model the dependency structure between random variables, next we explain the link between the copulae and common dependency measures, such as Kendall's tau and Spearman's rho. In the next section the copulae are generalized to the multivariate case. In this general setup we di...

Ha?rdle, Wolfgang Karl; Okhrin, Ostap; Okhrin, Yarema

2008-01-01

399

Modeling dependencies in finance using copulae  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we provide a review of copula theory with applications to finance. We illustrate the idea on the bivariate framework and discuss the simple, elliptical and Archimedean classes of copulae. Since the cop- ulae model the dependency structure between random variables, next we explain the link between the copulae and common dependency measures, such as Kendall's tau and Spearman's rho. In the next section the copulae are generalized to the multivariate case. In this general setup we ...

Ha?rdle, Wolfgang Karl; Okhrin, Ostap; Okhrin, Yarema

2008-01-01

400

The Stellar Initial Mass Function from Random Sampling in Hierarchical Clouds. II. Statistical Fluctuations and a Mass Dependence for Starbirth Positions and Times  

Science.gov (United States)

Observed variations in the slope of the stellar initial mass function (IMF) are shown to be consistent with a previously introduced model in which the protostellar gas is randomly sampled from clouds with a self-similar hierarchical structure. Root mean square variations in the IMF slope around the Salpeter value are +/-0.4 when only 100 stars are observed, and +/-0.1 when 1000 stars are observed. Similar variations should be present in other stochastic models as well. The hierarchical sampling model reproduces the tendency for massive stars to form closer to the center of a cloud at a time somewhat later than the formation time of the lower mass stars. The systematic variation in birth position results from the tendency for the trunk and larger branches of the hierarchical tree of cloud structure to lie closer to the cloud center, while the variations in birth order result from the relative infrequency of stars with larger masses. The hierarchical cloud sampling model has now reproduced most of the reliably observed features of the cluster IMF. The power-law part of the IMF comes from cloud hierarchical structure that is sampled during various star formation processes with a relative rate proportional to the square root of the local density. These processes include turbulence compression, magnetic diffusion, gravitational collapse, and clump or wavepacket coalescence, all of which have about this rate dependence. The low-mass flattening comes from the inability of gas to form stars below the thermal Jeans mass at typical temperatures and pressures. The thermal Jeans mass is the only relevant scale in the problem. Considerations of heating and cooling processes indicate why the thermal Jeans mass should be nearly constant in normal environments and why this mass might increase in starburst regions. In particular, the relative abundance of high-mass stars should increase where the average density of the interstellar medium is very large; accompanying this increase should be an increase in the average total efficiency of star formation. Alternative models in which the rate of star formation is independent of density and the local efficiency decreases systematically with increasing stellar mass can also reproduce the IMF, but this is an adjustable result and not a fundamental property of hierarchical cloud structure, as is the preferred model. The steep IMF in the extreme field is not explained by the model, but other origins are suggested, including one in which massive stars in low-pressure environments halt star formation in their clouds. In this case, the slope of the extreme field IMF is independent of the slope of each component cluster IMF and is given by (?-1)/? for a cloud mass function slope, -?~-2, and a power-law relation, ML~M?c, between the largest star in a low-pressure cloud, ML, and the cloud mass, Mc. A value of ?~1/4 is required to explain the extreme field IMF as a superposition of individual cluster IMFs; cloud destruction by ionizing has this property. We note that the similarity between cluster IMFs and the average IMF from global studies of galaxies implies that most stars form in clusters and that massive stars do not generally halt star formation in the same cloud.

Elmegreen, Bruce G.

1999-04-01

 
 
 
 
401

Dependence of P-wave dispersion on mean arterial pressure as an independent hemodynamic variable in school children / Dependencia de la dispersión de la onda P en la presión arterial media como variable hemodinámica independiente en niños en edad escolar  

Scientific Electronic Library Online (English)

Full Text Available SciELO Colombia | Language: English Abstract in spanish Resumen Introducción: La relación entre la disfunción diastólica y la dispersión de la onda P (PWD) en el electrocardiograma se ha estudiado durante algún tiempo. En este sentido, la ecocardiografía se está convirtiendo en una herramienta de diagnóstico para mejorar la estratificación de riesgo en l [...] a hipertensión leve. Objetivo: Determinar la dependencia de las PWD en el electrocardiograma de las variables ecocardiográficas en una población pediátrica. Métodos: De un total de 565 niños de tres escuelas primarias, fueron estudiados 515 niños. Fueron excluidos del estudio, aquellos niños cuyos padres se negaron a participar, y los niños con enfermedades congénitas conocidas. Se les realizó electrocardiograma de superficie de 12 derivaciones y se realizaron 4 tomas de presión arterial. Fueron medidas las ondas P del electrocardiograma y calculada su dispersión. Se realizó ecocardiografía para medidas estructurales y Doppler pulsado del flujo mitral. Resultados Se demuestra correlación significativa entre la PWD y la tensión arterial media para prehipertensos e hipertensos r= 0.32, p Abstract in english Abstract Introduction: The relationship between diastolic dysfunction and P-wave dispersion (PWD) in the electrocardiogram has been studied for some time. In this regard, echocardiography is emerging as a diagnostic tool to improve risk stratification for mild hypertension. Objective: To determine t [...] he dependence of PWD on the electrocardiogram and on echocardiographic variables in a pediatric population. Methods: Five hundred and fifteen children from three elementary schools were studiedfrom a total of 565 children. Those whose parents did not want them to take part in the study, as well as those with known congenital diseases, were excluded. Tests including 12-lead surface ECGs and 4 blood pressure (BP) measurements were performed. Maximum and minimum P-values were measured, and the PWD on the electrocardiogram was calculated. Echocardiography for structural measurements and the pulsed Doppler of mitral flow were also performed. Results: A significant correlation in statistical variables was found between PWD and mean BP for pre-hypertensive and hypertensive children, i.e., r= 0.32, p

Elibet, Chávez; Emilio F, González; María del Carmen, Llanes; Merlin, Garí Llanes; Yosvany, Garc.

402

Empirical and sequential empirical copula processes under serial dependence  

CERN Document Server

The empirical copula process plays a central role for statistical inference on copulas. Recently, Segers (2011) investigated the asymptotic behavior of this process under non-restrictive smoothness assumptions for the case of i.i.d. random variables. In the present paper we extend his main result to the case of serial dependent random variables by means of the powerful and elegant functional delta method. Moreover, we utilize the functional delta method in order to obtain conditional consistency of certain bootstrap procedures. Finally, we extend the results to the more general sequential empirical copula process under serial dependence.

Bücher, Axel

2011-01-01

403

Análisis del proceso constructivo y variabilidad de parámetros geotécnicos en la capacidad de carga de micropilotes usando elementos finitos aleatorios Analysis of the construction process and geotechnical parameters variability on the loading capacity of micropiles using random finite elements  

Directory of Open Access Journals (Sweden)

Full Text Available En la práctica normal de ingeniería de cimentaciones se calcula la capacidad de carga de un micropilote sin tener en cuenta que el proceso constructivo puede afectar la geometría del problema. En este trabajo se cuantifica la influencia tanto del proceso constructivo como de la variabilidad inherente de las propiedades del suelo en la capacidad de carga de un micropilote autoperforante e inyectado, a través de simulaciones de la excavación con elementos finitos aleatorios. Se obtiene que al no tener en cuenta el método constructivo del micropilote y la variabilidad de las propiedades del suelo, se sobreestima en un factor entre dos y tres la capacidad de carga por fuste. Por lo tanto, se presenta una explicación racional al factor de seguridad que se debe aplicar para obtener la capacidad de carga de diseño. Finalmente, se presenta un procedimiento para generar cartas de diseño de micropilotes autoperforantes materializado en uno que resalta la importancia de considerar la variabilidad inherente de las propiedades del suelo y el método constructivo.IIn the normal practice of foundation engineering the bearing capacity of micropiles is calculated without taking into account that the construction processes may affect the problem geometry. This work quantifies the influence of both, construction processes and the inherent variability of soil properties in the bearing capacity of a selfbored and gravitationally grouted micropile by means of simulations with random finite element method. When the construction process and the inherent variability are not taken into account, the shaft bearing capacity is overestimated in a factor between two and three. Therefore, a rational explanation of the safety factor is presented in order to calculate the design capacity load. Lastly, a procedure to generating design charts for selfbored and grouted micropiles is presented and its application shows the importance of considerate the inherent variability of the soil properties and the construction process.

Christian Mendoza

2012-01-01

404

A randomized, double-blind, placebo-controlled trial of calcium acetate on serum phosphorus concentrations in patients with advanced non-dialysis-dependent chronic kidney disease  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background Hyperphosphatemia in patients with chronic kidney disease (CKD) contributes to secondary hyperparathyroidism, soft tissue calcification, and increased mortality risk. This trial was conducted to examine the efficacy and safety of calcium acetate in controlling serum phosphorus in pre-dialysis patients with CKD. Methods In this randomized, double-blind, placebo-controlled trial, 110 nondialyzed patients from 34 sites with estimated GFR < 30 mL...

2011-01-01

405

Modeling different dependence structures involving count data with applications to insurance, economics and genetics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This thesis deals with several dependence structures for count responses. These count variables are typically not only overdispersed but also show a large share of zero observations. Based on pair copula constructions a method for sampling from such high-dimensional count random vectors with a specified Pearson correlation will be developed. Temporal dependence structures are investigated based on generalized estimating equations for generalized Poisson variables. In the field of dependent in...

Erhardt, Vinzenz

2010-01-01

406

Learning Dependencies between Case Frame Slots  

CERN Multimedia

We address the problem of automatically acquiring case frame patterns (selectional patterns) from large corpus data. In particular, we propose a method of learning dependencies between case frame slots. We view the problem of learning case frame patterns as that of learning multi-dimensional discrete joint distributions, where random variables represent case slots. We then formalize the dependencies between case slots as the probabilistic dependencies between these random variables. Since the number of parameters in a multi-dimensional joint distribution is exponential, it is infeasible to accurately estimate them in practice. To overcome this difficulty, we settle with approximating the target joint distribution by the product of low order component distributions, based on corpus data. In particular we propose to employ an efficient learning algorithm based on the MDL principle to realize this task. Our experimental results indicate that for certain classes of verbs, the accuracy achieved in a disambiguation...

Li, H; Li, Hang; Abe, Naoki

1996-01-01

407

Metamodelling with independent and dependent inputs  

Science.gov (United States)

In the cases of computationally expensive models the metamodelling technique which maps inputs and outputs is a very useful and practical way of making computations tractable. A number of new techniques which improve the efficiency of the Random Sampling-High dimensional model representation (RS-HDMR) for models with independent and dependent input variables are presented. Two different metamodelling methods for models with dependent input variables are compared. Both techniques are based on a Quasi Monte Carlo variant of RS-HDMR. The first technique makes use of transformation of the dependent input vector into a Gaussian independent random vector and then applies the decomposition of the model using a tensored Hermite polynomial basis. The second approach uses a direct decomposition of the model function into a basis which consists of the marginal distributions of input components and their joint distribution. For both methods the copula formalism is used. Numerical tests prove that the developed methods are robust and efficient.

Zuniga, M. Munoz; Kucherenko, S.; Shah, N.

2013-06-01

408

Limit theorems for associated random fields and related systems  

CERN Document Server

This volume is devoted to the study of asymptotic properties of wide classes of stochastic systems arising in mathematical statistics, percolation theory, statistical physics and reliability theory. Attention is paid not only to positive and negative associations introduced in the pioneering papers by Harris, Lehmann, Esary, Proschan, Walkup, Fortuin, Kasteleyn and Ginibre, but also to new and more general dependence conditions. Naturally, this scope comprises families of independent real-valued random variables. A variety of important results and examples of Markov processes, random measures,

Bulinski, Alexander

2007-01-01

409

CPAP em selo d'água versus CPAP com fluxo variável em recém-nascidos com desconforto respiratório: um ensaio controlado randomizado / Bubble CPAP versus CPAP with variable flow in newborns with respiratory distress: a randomized controlled trial  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: Avaliar a eficácia e segurança da pressão positiva contínua na via aérea (CPAP) utilizando aparelhos de fluxo variável e fluxo contínuo em selo d'água, quanto a falha do CPAP, ocorrência de escape de ar, tempo de uso de CPAP e de oxigênio e tempo de internação em unidade de terapia intensi [...] va e hospitalar em neonatos com desconforto respiratório (DR) moderado e peso de nascimento (PN) > 1.500 g. MÉTODOS: Quarenta recém-nascidos que necessitavam de CPAP foram randomizados em dois grupos: um grupo tratado com fluxo variável (FV) e outro com fluxo contínuo (FC). O estudo foi realizado entre outubro de 2008 e abril de 2010. Foram registrados dados demográficos, falha do CPAP, ocorrência de escape de ar, tempo de uso de CPAP e de oxigênio, entre outros. Os desfechos categóricos foram analisados com o teste do qui-quadrado ou exato de Fisher e as variáveis contínuas com o teste de Mann-Whitney, com significância de p 1.500 g e DR moderado, o CPAP nasal com fluxo contínuo apresentou os mesmos benefícios do CPAP nasal com fluxo variável. Abstract in english OBJECTIVE: To evaluate the efficacy and safety of nasal continuous positive airway pressure (NCPAP) using devices with variable flow or bubble continuous positive airway pressure (CPAP) regarding CPAP failure, presence of air leaks, total CPAP and oxygen time, and length of intensive care unit and h [...] ospital stay in neonates with moderate respiratory distress (RD) and birth weight (BW) > 1,500 g. METHODS: Forty newborns requiring NCPAP were randomized into two study groups: variable flow group (VF) and continuous flow group (CF). The study was conducted between October 2008 and April 2010. Demographic data, CPAP failure, presence of air leaks, and total CPAP and oxygen time were recorded. Categorical outcomes were tested using the chi-square test or the Fisher's exact test. Continuous variables were analyzed using the Mann-Whitney test. The level of significance was set at p 1,500 g and moderate RD, the use of continuous flow NCPAP showed the same benefits as the use of variable flow NCPAP.

Ana Cristina Zanon, Yagui; Luciana Assis Pires Andrade, Vale; Luciana Branco, Haddad; Cristiane, Prado; Felipe de Souza, Rossi; Alice D' Agostini, Deutsch; Celso Moura, Rebello.

410

Portfolio Risk and Dependence Modeling  

Directory of Open Access Journals (Sweden)

Full Text Available This paper has considered portfolio credit risk with a focus on two approaches, the factor model, and copula model. We have reviewed two models with emphasis on the joint default probably. The copula function describes the dependence structure of a multivariate random variable, in this paper, it used as a practical to simulation of generate portfolio with different copula, and we only used Gaussian and t–copula case. We generated portfolio default distributions and studied the sensitivity of commonly used risk measures with respect to the approach in modeling the dependence structure of the portfolio.

Arsalan Azamighaimasi

2012-12-01

411

Can a soda-lime glass be used to demonstrate how patterns of strength dependence are influenced by pre-cementation and resin-cementation variables?  

LENUS (Irish Health Repository)

To determine how the variability in biaxial flexure strength of a soda-lime glass analogue for a PLV and DBC material was influenced by precementation operative variables and following resin-cement coating.

Hooi, Paul

2013-01-01

412

A multi-center, randomized controlled trial of a group psychological intervention for psychosis with comorbid cannabis dependence over the early course of illness.  

LENUS (Irish Health Repository)

Patients who experience the onset of psychotic illness with a comorbid diagnosis of cannabis dependence experience poor clinical outcomes. Few studies have identified interventions that reduce cannabis use and improve clinical outcome in this population.

Madigan, Kevin

2013-01-01

413

Mass parameters in the adiabatic time-dependent Hartree-Fock approximation: I. Theoretical aspects; the case of a single collective variable  

International Nuclear Information System (INIS)

A self-consistent method to evaluate mass parameters is presented in the framework of the adiabatic limit of the time-dependent Hartree-Fock approximation, reduced to a single collective variable. The corresponding collective path is assumed to be given either by solving a constrained Hartree-Fock problem with a given time-even constraining operator Q, or by scaling a static Hartree-Fock equilibrium solution. In the former case, once the path is given, a method for solving the equation of motion (of Hamilton type) is provided, which reduces to a double-constrained Hartree-Fock problem with the time-even constraint Q and with a time-odd constraining operator P. In the case of the scaling path, an analytical solution of the Hamilton equation is discussed and the adiabatic mass for the particular case of isoscalar quadrupole Q_2_0 mode is given. The operator P, which is uniquely determined from the knowledge of Q, has the physical meaning of a momentum operator: it satisfies, together with Q, a weak quantal conjugation relation. Finally, the connection between the two paths is discussed in terms of generalized RPA sum rules

1979-01-01

414

Degree of multicollinearity and variables involved in linear dependence in additive-dominant models / Grau de multicolinearidade e variáveis envolvidas na dependência linear em modelos aditivo-dominantes  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese O objetivo deste trabalho foi avaliar o grau de multicolinearidade e identificar as variáveis envolvidas na dependência linear em modelos aditivo-dominantes. Foram utilizados dados de peso ao nascimento (n=141.567), peso ao ano (n=58.124) e perímetro escrotal (n=20.371) de bovinos de corte compostos [...] Montana Tropical. O diagnóstico de multicolinearidade foi baseado no fator de inflação de variância (VIF) e no exame dos índices de condição e dos autovalores da matriz de correlações entre as variáveis explanatórias. O primeiro modelo estudado (RM) incluiu o efeito fixo de classe de idade da mãe ao parto e as covariáveis associadas aos efeitos aditivos e não aditivos diretos e maternos. O segundo modelo (R) incluiu todos os efeitos do RM, exceto os efeitos aditivos maternos. Detectou-se multicolinearidade em ambos os modelos para todas as características consideradas, com valores de VIF de 1,03 - 70,20, para RM, e de 1,03 - 60,70, para R. As colinearidades aumentaram com o aumento de variáveis no modelo e com a redução no volume de observações, e foram classificadas como fracas, com valores de índice de condição entre 10,00 e 26,77. Em geral, as variáveis associadas aos efeitos aditivos e não aditivos estiveram envolvidas em multicolinearidade, parcialmente em razão da ligação natural entre essas covariáveis como frações dos tipos biológicos na composição racial. Abstract in english The objective of this work was to assess the degree of multicollinearity and to identify the variables involved in linear dependence relations in additive-dominant models. Data of birth weight (n=141,567), yearling weight (n=58,124), and scrotal circumference (n=20,371) of Montana Tropical composite [...] cattle were used. Diagnosis of multicollinearity was based on the variance inflation factor (VIF) and on the evaluation of the condition indexes and eigenvalues from the correlation matrix among explanatory variables. The first model studied (RM) included the fixed effect of dam age class at calving and the covariates associated to the direct and maternal additive and non-additive effects. The second model (R) included all the effects of the RM model except the maternal additive effects. Multicollinearity was detected in both models for all traits considered, with VIF values of 1.03 - 70.20 for RM and 1.03 - 60.70 for R. Collinearity increased with the increase of variables in the model and the decrease in the number of observations, and it was classified as weak, with condition index values between 10.00 and 26.77. In general, the variables associated with additive and non-additive effects were involved in multicollinearity, partially due to the natural connection between these covariables as fractions of the biological types in breed composition.

Juliana, Petrini; Raphael Antonio Prado, Dias; Simone Fernanda Nedel, Pertile; Joanir Pereira, Eler; José Bento Sterman, Ferraz; Gerson Barreto, Mourão.

415

Stochastic relations of random variables and processes  

CERN Multimedia

This paper generalizes the notion of stochastic order to a relation between probability measures over arbitrary measurable spaces. This generalization is motivated by the observation that for the stochastic ordering of two stationary Markov processes, it suffices that the generators of the processes preserve some, not necessarily reflexive or transitive, subrelation of the order relation. The main contributions of the paper are: a functional characterization of stochastic relations, necessary and sufficient conditions for the preservation of stochastic relations, and an algorithm for finding subrelations preserved by probability kernels. The theory is illustrated with applications to hidden Markov processes, population processes, and queueing systems.

Leskelä, Lasse

2008-01-01