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1

Benford's Law and Continuous Dependent Random Variables  

CERN Multimedia

Many systems exhibit a digit bias. For example, the first digit base 10 of the Fibonacci numbers, or of $2^n$, equals 1 not 10% or 11% of the time, as one would expect if all digits were equally likely, but about 30% of the time. This phenomenon, known as Benford's Law, has many applications, ranging from detecting tax fraud for the IRS to analyzing round-off errors in computer science. The central question is determining which data sets follow Benford's law. Inspired by natural processes such as particle decay, our work examines models for the decomposition of conserved quantities. We prove that in many instances the distribution of lengths of the resulting pieces converges to Benford behavior as the number of divisions grow. The main difficulty is that the resulting random variables are dependent, which we handle by a careful analysis of the dependencies and tools from Fourier analysis to obtain quantified convergence rates.

Becker, Thealexa; Miller, Steven J; Ronan, Ryan; Strauch, Frederick W

2011-01-01

2

Complete Convergence for Negatively Dependent Sequences of Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available We study the complete convergence for negatively dependent sequences of random variables. As a result, we extend some complete convergence theorems for independent random variables to the case of negatively dependent random variables without necessarily imposing any extra conditions.

Qunying Wu

2010-01-01

3

Central Limit Theorem for the Sum of a Random Number of Dependent Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, the central limit theorem for certain classes of dependent random variables is explored. The dependency structure, as defined in the class of random variables can be reflected in some physical phenomena. Sufficient conditions for the sum of a random number of dependent random variables tending to normality are provided.

Yilun Shang

2011-01-01

4

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

CERN Multimedia

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

5

An edgeworth expansion for a sum of M-Dependent random variables  

Directory of Open Access Journals (Sweden)

Full Text Available Given a sequence X1,X2,…,Xn of m-dependent random variables with moments of order 3+α (0<α≦1), we give an Edgeworth expansion of the distribution of Sσ−1(S=X1+X2+…+Xn, σ2=ES2) under the assumption that E[exp(it Sσ1)] is small away from the origin. The result is of the best possible order.

Wan Soo Rhee

1985-01-01

6

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

Scientific Electronic Library Online (English)

Full Text Available 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 susceptibility, 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 part (more) ial 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.

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

2003-09-01

7

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 susceptibility, 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.

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

2003-01-01

8

On Complex Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available Normal 0 false false false EN-US X-NONE X-NONE In this paper, it is shown that a complex multivariate random variable is a complex multivariate normal random variable of dimensionality if and only if all nondegenerate complex linear combinations of have a complex univariate normal distribution. The characteristic function of has been derived, and simpler forms of some theorems have been given using this characterization theorem without assuming that the variance-covariance matrix of the vector is Hermitian positive definite. Marginal distributions of have been given. In addition, a complex multivariate t-distribution has been defined and the density derived. A characterization of the complex multivariate t-distribution is given. A few possible uses of this distribution have been suggested.

Anwer Khurshid; Zuhair A. Al-Hemari; Shahid Kamal

2012-01-01

9

Discretized Normal Approximation for Dependent Random Integers  

CERN Document Server

Under the setting of Stein coupling, the distributions of sums of dependent integer-valued random variables are approximated by discretized normal distributions in total variation. The general theorem is illustrated by proving discretized normal approximation results for random integers under local dependence, exchangeable pairs and size biasing.

Fang, Xiao

2011-01-01

10

Complete convergence for randomly indexed sums of random variables  

Energy Technology Data Exchange (ETDEWEB)

The complete convergence of normed sums of independent identically distributed random variables with random indices is studied. Some applications for subsequences and sequences with multidimensional indices are given.

Klesov, O.I. [Kiev Polytechnic Inst. (Ukraine)

1995-08-25

11

Extension of Two-Dimensional Discrete Random Variables Conditional Distribution  

Directory of Open Access Journals (Sweden)

Full Text Available Conditional distribution reflects the dependency link among random variables, but two-dimensional random variables Conditional Distribution has some limitations. In order to rich the content of conditional distribution this paper gives the extension of conditional distribution under discrete random variables and some examples. This article obtains the extension strictly in accordance with the definition of two-dimensional random variables. So it can get conditional distributions after changing the condition and get conditional distributions that are extended into n-dimensional random variables, thereby enriching the contents of the conditional distribution.

Feixue Huang; Cheng Li

2010-01-01

12

On Sums of Conditionally Independent Subexponential Random Variables  

CERN Multimedia

The asymptotic tail-behaviour of sums of independent subexponential random variables is well understood, one of the main characteristics being \\textit{the principle of the single big jump}. We study the case of dependent subexponential random variables, for both deterministic and random sums, using a fresh approach, by considering conditional independence structures on the random variables. We seek sufficient conditions for the results of the theory with independent random variables still to hold. For a subexponential distribution, we introduce the concept of a boundary class of functions, which we hope will be a useful tool in studying many aspects of subexponential random variables. The examples we give in the paper demonstrate a variety of effects owing to the dependence, and are also interesting in their own right.

Foss, Serguei

2008-01-01

13

Independent and dependent variables  

Science.gov (United States)

The National Science Education Standards Science as Inquiry Standard states middle school students should develop general abilities, such as systematic observation, making accurate measurements, and identifying and controlling variables. The Standards acknowledge this can be challenging for students. Resources highlighted here focus on helping learners acquire knowledge of variables in scientific inquiry.

University, Staff A.

2008-03-07

14

Filtered random variables, bialgebras and convolutions  

CERN Multimedia

We introduce the filtered *-bialgebra which is a noncommutative analog of the *-bialgebra of multivariate polynomials with the canonical coproduct and counit. We study the associated filtered convolutions, random walks and random variables. The GNS representations of the limit states lead to filtered fundamental operators which are the CCR fundamental operators on the multiple symmetric Fock space, multiplied by appropriate projections. The importance of filtered random variables and fundamental operators stems from the fact that by addition and strong limits one obtains from them the main types of noncommutative random variables and fundamental operators, respectively, regardless of the type of noncommutative independence.

Lenczewski, R

2001-01-01

15

Random Effect and Latent Variable Model Selection  

CERN Multimedia

Presents various methods for accommodating model uncertainty in random effects and latent variable models. This book focuses on frequentist likelihood ratio and score tests for zero variance components. It also focuses on Bayesian methods for random effects selection in linear mixed effects and generalized linear mixed models

Dunson, David B

2008-01-01

16

Quotient of Laplace and Gumbel random variables  

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Full Text Available The Gumbel and the Laplace distributions are perhaps two of the most applied distributions in engineering. Motivated by engineering issues, the exact distribution of the quotient | X/Y | is derived when X and Y are independent Gumbel and Laplace random variables. Tabulations of the associated percentage points and a computer program for generating them are also given.

2006-01-01

17

Clifford Algebras, Random Graphs, and Quantum Random Variables  

Science.gov (United States)

For fixed n > 0, the space of finite graphs on n vertices is canonically associated with an abelian, nilpotent-generated subalgebra of the Clifford algebra {C}l2n,2n which is canonically isomorphic to the 2n-particle fermion algebra. Using the generators of the subalgebra, an algebraic probability space of "Clifford adjacency matrices" associated with finite graphs is defined. Each Clifford adjacency matrix is a quantum random variable whose mth moment corresponds to the number of m-cycles in the graph G. Each matrix admits a canonical "quantum decomposition" into a sum of three algebraic random variables: a = a? + a? + a?, where a? is classical while a? and a? are quantum. Moreover, within the Clifford algebra context the NP problem of cycle enumeration is reduced to matrix multiplication, requiring no more than n4 Clifford (geo-metric) multiplications within the algebra.

Schott, Ren; Staples, G. Stacey

2008-08-01

18

Concentration for independent random variables with heavy tails  

CERN Multimedia

If a random variable is not exponentially integrable, it is known that no concentration inequality holds for an infinite sequence of independent copies. Under mild conditions, we establish concentration inequalities for finite sequences of $n$ independent copies, with good dependence in $n$.

Barthe, F; Roberto, C; Barthe, Franck; Cattiaux, Patrick; Roberto, Cyril

2005-01-01

19

The Equilibrium Distribution of Counting Random Variables  

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Full Text Available We study the high order equilibrium distributions of a counting random variable. Properties such as moments, the probability generating function, the stop--loss transform and the mean residual lifetime, are derived. Expressions are obtained for higher order equilibrium distribution functions under mixtures and convolutions of a counting distribution. Recursive formulas for higher order equilibrium distribution functions of the (a,b,0) -family of distributions are given.

Shuanming Li

2011-01-01

20

Umbral nature of the Poisson random variables  

CERN Multimedia

Extending the rigorous presentation of the classical umbral calculus given by Rota and Taylor in 1994, the so-called partition polynomials are interpreted with the aim to point out the umbral nature of the Poisson random variables. Among the new umbrae introduced, the main tool is the partition umbra that leads also to a simple expression of the functional composition of the exponential power series. Moreover a new short proof of the Lagrange inversion formula is given.

Nardo, E D

2004-01-01

 
 
 
 
21

Nilpotent adjacency matrices, random graphs and quantum random variables  

International Nuclear Information System (INIS)

While a number of researchers have previously investigated the relationship between graph theory and quantum probability, the current work explores a new perspective. The approach of this paper is to begin with an arbitrary graph having no previously established relationship to quantum probability and to use that graph to construct a quantum probability space in which moments of quantum random variables reveal information about the graph's structure. Given an arbitrary finite graph and arbitrary odd integer m ? 3, fermion annihilation operators are used to construct a family of quantum random variables whose mth moments correspond to the graph's m-cycles. The approach is then generalized to recover a graph's m-cycles for any integer m ? 3 by defining nilpotent adjacency operators in terms of null-square generators of an infinite-dimensional Abelian algebra. It is shown that ordering the vertices of a simple graph induces a canonical decomposition ? = ?+ + ?- on any nilpotent adjacency operator ?. The work concludes with applications to Markov chains and random graphs.

2008-04-18

22

Nilpotent adjacency matrices, random graphs and quantum random variables  

Energy Technology Data Exchange (ETDEWEB)

While a number of researchers have previously investigated the relationship between graph theory and quantum probability, the current work explores a new perspective. The approach of this paper is to begin with an arbitrary graph having no previously established relationship to quantum probability and to use that graph to construct a quantum probability space in which moments of quantum random variables reveal information about the graph's structure. Given an arbitrary finite graph and arbitrary odd integer m {>=} 3, fermion annihilation operators are used to construct a family of quantum random variables whose mth moments correspond to the graph's m-cycles. The approach is then generalized to recover a graph's m-cycles for any integer m {>=} 3 by defining nilpotent adjacency operators in terms of null-square generators of an infinite-dimensional Abelian algebra. It is shown that ordering the vertices of a simple graph induces a canonical decomposition {psi} = {psi}{sup +} + {psi}{sup -} on any nilpotent adjacency operator {psi}. The work concludes with applications to Markov chains and random graphs.

Schott, Rene [IECN and LORIA Universite Henri Poincare-Nancy I, BP 239, 54506 Vandoeuvre-les-Nancy (France); Staples, George Stacey [Department of Mathematics and Statistics, Southern Illinois University Edwardsville, Edwardsville, IL 62026-1653 (United States)], E-mail: schott@loria.fr, E-mail: sstaple@siue.edu

2008-04-18

23

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

24

Random crossings in dependency trees  

CERN Document Server

It has been hypothesized that the remarkably small number of crossings in real syntactic dependency trees is a side-effect of pressure for dependency length minimization. Here we answer a related important research question: what would be the expected number of crossings if the natural order of a sentence was lost? We show that that this number depends only on the number of vertices of the dependency tree (the sentence length) and the second moment of vertex degrees. The expected number of crossings is minimum for a star tree (no crossing is expected) and maximum for a linear tree (the number of crossings is of the order of the square of the sequence length).

Ferrer-i-Cancho, Ramon

2013-01-01

25

Theory of Dependent Hierarchical Normalized Random Measures  

CERN Multimedia

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

26

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; Kasmiran J.M. Ismail; Zurina M. Hanapi

2009-01-01

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

Concentration and Moment Inequalities for Polynomials of Independent Random Variables  

CERN Multimedia

In this work we design a general method for proving moment inequalities for polynomials of independent random variables. Our method works for a wide range of random variables including Gaussian, Boolean, exponential, Poisson and many others. We apply our method to derive general concentration inequalities for polynomials of independent random variables. We show that our method implies concentration inequalities for some previously open problems, e.g. permanent of a random symmetric matrices. We show that our concentration inequality is stronger than the well-known concentration inequality due to Kim and Vu. The main advantage of our method in comparison with the existing ones is a wide range of random variables we can handle and bounds for previously intractable regimes of high degree polynomials and small expectations. On the negative side we show that even for boolean random variables each term in our concentration inequality is tight.

Schudy, Warren

2011-01-01

29

COVAL - A computer code for random variables - How to use  

International Nuclear Information System (INIS)

[en]COVAL CODE computes the probability distribution of a function of random variables given the probability distribution of these variables. The code is divided in two steps. The first step COVAL 1, computes functions in which each variable is contained only once. The second step COVAL 2, computes functions in which variables can be repeated

1978-01-01

30

On the product and ratio of Bessel random variables  

Directory of Open Access Journals (Sweden)

Full Text Available The distributions of products and ratios of random variables are of interest in many areas of the sciences. In this paper, the exact distributions of the product |XY| and the ratio |X/Y| are derived when X and Y are independent Bessel function random variables. An application of the results is provided by tabulating the associated percentage points.

Saralees Nadarajah; Arjun K. Gupta

2005-01-01

31

Promote the Use of Two-dimensional Continuous Random Variables Conditional Distribution  

Directory of Open Access Journals (Sweden)

Full Text Available Conditional distribution reflects the dependency link among random variables, but two-dimensional random variables Conditional Distribution has some limitations. In order to rich the content of conditional distribution this paper gives the extension of conditional distribution and examples in the case of continuous random variables. For the given definition of conditional distribution of three-dimensional continuous random variables, it also gives the proof. This article obtains the extension strictly in accordance with the definition of two-dimensional random variables and it uses the theory of conditional probability to get the proof. So it can get conditional distributions after changing the condition to enrich the contents of the conditional distribution.

Feixue Huang; Cheng Li

2010-01-01

32

On extreme value statistics of correlated random variables  

Science.gov (United States)

The statistics of extreme values of a set on independent and identically distributed random variables is a well established mathematical theory that can be traced back to the late 1920s, with pioneering work by Fisher and Tippett. While efforts have been made to go beyond the uncorrelated case, little is known about the extremes of strongly correlated variables. Notable exceptions are the distribution of extreme eigenvalues of random matrices (Tracy and Widom 1994), the Airy law for one-dimensional random walks (Majumdar and Comtet 2005), and random variables with logarithmic interactions (Fyodorov and Bouchaud 2008). We propose to adapt the equivalence between extremes and sums (Bertin and Clusel 2006) to obtain asymptotic distributions of correlated random variables. We will show how this approach works in the logarithmic case, before extending it to power-law correlations and beyond. We will eventually illustrate these cases with a simple model, a one-dimensional gas of interacting particles.

Clusel, Maxime; Fortin, Jean-Yves

2013-03-01

33

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 Zufallsgren rechneruntersttzt dargestellt und miteinander verknpft werden knnen. Die Verteilungsfunktionen der Zufallsgren werden mit einem Finite-Elemente-Ansatz in einem endlichen Intervall [tmin; tmax] approximiert. Die Addition zweier Zufallsgren wird durch numerische Berechnung des Faltungsintegrals durchgefhrt.

Dr.-Ing. Helge Plehn; Prof. Dr.-Ing. Rainer Bruns

2005-01-01

34

Mathematical Discussions About Data Oriented Modeling of Uniform Random Variable  

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Full Text Available In this study, to show that UDPD is an acceptable and efficient model of uniform random variable, we introduce mathematical and numerical discussions for identification and characterization of it and also we show how to calculate some probabilistic parameters as mean, variance and mathematical expectation by using UDPD. Thus we provide a way to discuss random variables with n digits and make a new theory named numerical probability. This theory is enables us to discuss about random variables with predefined number of digits as required in applied and engineering systems.

Ahmad Habibizad Navin; Mehdi Naghian Fesharaki; Mirkamal Mirnia; Mohammad Teshnehlab

2008-01-01

35

A note on the complete convergence for sequences of pairwise NQD random variables  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract In this paper, complete convergence and strong law of large numbers for sequences of pairwise negatively quadrant dependent (NQD) random variables with non-identically distributed are investigated. The results obtained generalize and extend the relevant result of Wu (Acta. Math. Sinica. 45(3), 617-624, 2002) for sequences of pairwise NQD random variables with identically distributed. 2000 MSC: 60F15.

Huang Haiwu; Wang Dingcheng; Wu Qunying; Zhang Qingxia

2011-01-01

36

Continuum Random Combs and Scale Dependent Spectral Dimension  

CERN Document Server

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

37

A REVIEW OF RANDOMIZED RESPONSES PROCEDURES: THE QUALITATIVE VARIABLE CASE A REVIEW OF RANDOMIZED RESPONSES PROCEDURES: THE QUALITATIVE VARIABLE CASE A REVIEW OF RANDOMIZED RESPONSES PROCEDURES: THE QUALITATIVE VARIABLE CASE A REVIEW OF RANDOMIZED RESPONSES PROCEDURES: THE QUALITATIVE VARIABLE CASE A REVIEW OF RANDOMIZED RESPONSES PROCEDURES: THE QUALITATIVE VARIABLE CASE A REVIEW OF RANDOMIZED RESPONSES PROCEDURES: THE QUALITATIVE VARIABLE CASE  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper a review on the results on randomized responses for qualitative variables is presented. It incorporates recently published papers. It tries to fulfill the lack of a review on the theme and aims completing the oeuvre of Chaudhuri, A . & R. Mukerjee. (1988), (Randomized response: theory and techniques, Marcel Dekker, New York).

Carlos N. Bouza * Carmelo Herrera** and Pasha G. Mitra*** Carlos N. Bouza * Carmelo Herrera** and Pasha G. Mitra***

2010-01-01

38

A theorem for physicists in the theory of random variables  

Science.gov (United States)

A theorem is presented which tells how to calculate the joint probability distribution of m random variables that have been defined as functional transformations of n given random variables (m, n>=1). Although the theorem involves Dirac delta functions and therefore has a rather formal appearance, it turns out to be surprisingly useful. It is used here to develop a number of important results in random variable theory, including: the central limit theorem, the density functions of some common probability distributions (lognormal, chi-square, and Student's-t), the imposition of constraints on random variables, some sampling properties of the normal distribution, and the chi-square goodness-of-fit test. Special attention is given to aspects of these topics that find fruitful application in physics. A broad conclusion seems to be that the theorem presented here provides a systematic way of obtaining many results in random variable theory which, although quite useful in physics, are normally found derived only in moderately advanced mathematics textbooks.

Gillespie, Daniel T.

1983-06-01

39

Cardinality-dependent Variability in Orthogonal Variability Models  

DEFF Research Database (Denmark)

During our work on developing and running a software product line for eco-sustainable greenhouse-production software tools, which currently have three products members we have identified a need for extending the notation of the Orthogonal Variability Model (OVM) to support what we refer to as cardinality range dependencies. The cardinality-rangedependency type enables expressing that the binding of a certain number of variants to a variation point can influence variability in other places in the model. In other words, we acknowledge that variability can be influenced, not necessarily by the specific variants being bound, but by their sheer numbers. This paper contributes with an extension to the meta-model underlying the OVM notation, suggesting a notation for the new type of dependency and shows its applicability. The specific case, which initially required this extension, will work as running example throughout the paper and underline the need for the extension. Finally, the paper evaluates and discusses the general applicability of the proposed notation extension and future perspectives.

Mrsk-Mller, Hans Martin; Jrgensen, Bo Nrregaard

2012-01-01

40

Bayesian nonparametric centered random effects models with variable selection.  

UK PubMed Central (United Kingdom)

In a linear mixed effects model, it is common practice to assume that the random effects follow a parametric distribution such as a normal distribution with mean zero. However, in the case of variable selection, substantial violation of the normality assumption can potentially impact the subset selection and result in poor interpretation and even incorrect results. In nonparametric random effects models, the random effects generally have a nonzero mean, which causes an identifiability problem for the fixed effects that are paired with the random effects. In this article, we focus on a Bayesian method for variable selection. We characterize the subject-specific random effects nonparametrically with a Dirichlet process and resolve the bias simultaneously. In particular, we propose flexible modeling of the conditional distribution of the random effects with changes across the predictor space. The approach is implemented using a stochastic search Gibbs sampler to identify subsets of fixed effects and random effects to be included in the model. Simulations are provided to evaluate and compare the performance of our approach to the existing ones. We then apply the new approach to a real data example, cross-country and interlaboratory rodent uterotrophic bioassay.

Yang M

2013-03-01

 
 
 
 
41

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; Hongwei Ding; Jing Nan; Qianlin Liu

2013-01-01

42

Convergence of weighted sums of independent random variables and an extension to Banach space-valued random variables  

Directory of Open Access Journals (Sweden)

Full Text Available Let {Xk} be independent random variables with EXk=0 for all k and let {ank:n≥1, k≥1} be an array of real numbers. In this paper the almost sure convergence of Sn=∑k=1nankXk, n=1,2,…, to a constant is studied under various conditions on the weights {ank} and on the random variables {Xk} using martingale theory. In addition, the results are extended to weighted sums of random elements in Banach spaces which have Schauder bases. This extension provides a convergence theorem that applies to stochastic processes which may be considered as random elements in function spaces.

W. J. Padgett; R. L. Taylor

1979-01-01

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 s...

Hill, Theodore P.; Schrger, Klaus

44

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

45

ADORAVA - A computer code to sum random variables  

International Nuclear Information System (INIS)

[en]The ADORAVA computer code was carried out aiming to determine the moments of random variable sum distribution when moments are known. The ADORAVA computer code was developed to be applied in probabilistic safety analysis, more specifically for uncertainty propagation in fault trees. The description of ADORAVA algorithm, input, examples and the output of compiled code are presented. (M.C.K.)

1985-01-01

46

On the Linear Combination of Exponential and Gamma Random Variables  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract: The exact distribution of the linear combination α X + β Y is derived when X and Y are exponential and gamma random variables distributed independently of each other. A measure of entropy of the linear combination is investigated. We also provide computer programs for generating tabu...

Saralees Nadarajah; Samuel Kotz

47

Runs of geometrically distributed random variables: a probabilistic analysis  

Science.gov (United States)

Using a Markov chain approach and a polyomino-like description, we study some asymptotic properties of runs of geometrically distributed random variables. We analyze the limiting trajectories, the number of runs and the run length distribution, the hitting time to a length k run and the maximum run length.

Louchard, Guy

2002-05-01

48

Instrumental variable analyses. Exploiting natural randomness to understand causal mechanisms.  

UK PubMed Central (United Kingdom)

Instrumental variable analysis is a technique commonly used in the social sciences to provide evidence that a treatment causes an outcome, as contrasted with evidence that a treatment is merely associated with differences in an outcome. To extract such strong evidence from observational data, instrumental variable analysis exploits situations where some degree of randomness affects how patients are selected for a treatment. An instrumental variable is a characteristic of the world that leads some people to be more likely to get the specific treatment we want to study but does not otherwise change those patients' outcomes. This seminar explains, in nonmathematical language, the logic behind instrumental variable analyses, including several examples. It also provides three key questions that readers of instrumental variable analyses should ask to evaluate the quality of the evidence. (1) Does the instrumental variable lead to meaningful differences in the treatment being tested? (2) Other than through the specific treatment being tested, is there any other way the instrumental variable could influence the outcome? (3) Does anything cause patients to both receive the instrumental variable and receive the outcome?

Iwashyna TJ; Kennedy EH

2013-06-01

49

A Note on Strong Laws of Large Numbers for Dependent Random Sets and Fuzzy Random Sets  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper deals with a sequence of identically distributed random sets or fuzzy random sets with ?(??)-mixing dependence in a separable Banach space. The strong laws of large numbers for these two sequences are derived under Kuratowski-Mosco sense.

Ke-Ang Fu

50

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.; Budsaba, K.

2005-01-01

51

Efficient Reconciliation of Correlated Continuous Random Variables using LDPC Codes  

CERN Document Server

This paper investigates an efficient and practical information reconciliation method in the case where two parties have access to correlated continuous random variables. We show that reconciliation is a special case of channel coding and that existing coded modulation techniques can be adapted for reconciliation. We describe an explicit reconciliation method based on LDPC codes in the case of correlated Gaussian variables. We believe that the proposed method can improve the efficiency of quantum key distribution protocols based on continuous-spectrum quantum states.

Bloch, M; McLaughlin, S W; Bloch, Matthieu; Thangaraj, Andrew; Laughlin, Steven W. Mc

2005-01-01

52

Cram\\'er theorem for Gamma random variables  

CERN Multimedia

In this paper we discuss the following problem: given a random variable $Z=X+Y$ with Gamma law such that $X$ and $Y$ are independent, we want to understand if then $X$ and $Y$ {\\it each} follow a Gamma law. This is related to Cram\\'er's theorem which states that if $X$ and $Y$ are independent then $Z=X+Y$ follows a Gaussian law if and only if $X$ {\\it and} $Y$ follow a Gaussian law. We prove that Cram\\'er's theorem is true in the Gamma context for random variables leaving in a Wiener chaos of fixed order but the result is not true in general. We also give an asymptotic variant of our result.

Bourguin, Solesne

2011-01-01

53

An Exponential Inequality for Negatively Associated Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available An exponential inequality is established for identically distributed negatively associated random variables which have the finite Laplace transforms. The inequality improves the results of Kim and Kim (2007), Nooghabi and Azarnoosh (2009), and Xing et al. (2009). We also obtain the convergence rate O(1)n1/2(log?n)?1/2 for the strong law of large numbers, which improves the corresponding ones of Kim and Kim, Nooghabi and Azarnoosh, and Xing et al.

Soo Hak Sung

2009-01-01

54

On the Linear Combination of Exponential and Gamma Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract: The exact distribution of the linear combination α X + β Y is derived when X and Y are exponential and gamma random variables distributed independently of each other. A measure of entropy of the linear combination is investigated. We also provide computer programs for generating tabulations of the percentage points associated with the linear combination. The work is motivated by examples in automation, control, fuzzy sets, neurocomputing and other areas of computer science.

Saralees Nadarajah; Samuel Kotz

2005-01-01

55

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

56

Average path length in uncorrelated random networks with hidden variables  

CERN Document Server

Analytic solution for the average path length in a large class of uncorrelated random networks with hidden variables is found. We apply the approach to classical random graphs of Erdos and Renyi (ER), evolving networks introduced by Barabasi and Albert (BA) as well as random networks with asymptotic scale-free connectivity distributions characterized by an arbitrary scaling exponent $\\alpha>2$. Our result for $2<\\alpha<3$ shows that structural properties of asymptotic scale-free networks including numerous examples of real-world systems are even more intriguing then ultra-small world behavior noticed in pure scale-free structures and for large system sizes $N\\to\\infty$ there is a saturation effect for the average path length.

Fronczak, A; Holyst, J A; Fronczak, Agata; Fronczak, Piotr; Holyst, Janusz A.

2004-01-01

57

Scaling of Order Dependent Categorical Variables with Correspondence Analysis.  

Science.gov (United States)

Forms of dependence between categorical variables are introduced which induce successively stronger orderings over the categories of the variables. It is proved that if these forms of dependence are present in contingency tables, the orderings are reflect...

B. F. Schriever

1982-01-01

58

Random Time-Dependent Quantum Walks  

CERN Multimedia

We consider the discrete time unitary dynamics given by a quantum walk on the lattice $\\Z^d$ performed by a quantum particle with internal degree of freedom, called coin state, according to the following iterated rule: a unitary update of the coin state takes place, followed by a shift on the lattice, conditioned on the coin state of the particle. We study the large time behavior of the quantum mechanical probability distribution of the position observable in $\\Z^d$ when the sequence of unitary updates is given by an i.i.d. sequence of random matrices. When averaged over the randomness, this distribution is shown to display a drift proportional to the time and its centered counterpart is shown to display a diffusive behavior with a diffusion matrix we compute. A moderate deviation principle is also proven to hold for the averaged distribution and the limit of the suitably rescaled corresponding characteristic function is shown to satisfy a diffusion equation. A generalization to unitary updates distributed ac...

Joye, Alain

2010-01-01

59

Logarithmic Averages of Stable Random Variables are Asymptotically Normal  

UK PubMed Central (United Kingdom)

IntroductionLet X; X 1 ; X 2 ; Delta Delta Delta be independent, identically distributed random variables withEX = 0, EX2= 1. The almost sure central limit theorem (Brosamler (1988), Schatte(1988), Fisher (1989), Lacey and Philipp (1990)) states thatlimn!11log nX1 6 k 6n1kaiS(k)k1=2j=1(2)1=2Z 1Gamma1a(t)eGammat2=2dt a.s. (1:1)where a is the indicator function of any interval and S(k) =P1 6 i

Istv An Berkes; Lajos Horv Ath; Davar Khoshnevisan

60

Oracle Efficient Variable Selection in Random and Fixed Effects Panel Data Models  

DEFF Research Database (Denmark)

This paper generalizes the results for the Bridge estimator of Huang et al. (2008) to linear random and fixed effects panel data models which are allowed to grow in both dimensions. In particular we show that the Bridge estimator is oracle efficient. It can correctly distinguish between relevant and irrelevant variables and the asymptotic distribution of the estimators of the coefficients of the relevant variables is the same as if only these had been included in the model, i.e. as if an oracle had revealed the true model prior to estimation. In the case of more explanatory variables than observations, we prove that the Marginal Bridge estimator can asymptotically correctly distinguish between relevant and irrelevant explanatory variables. We do this without restricting the dependence between covariates and without assuming sub Gaussianity of the error terms thereby generalizing the results of Huang et al. (2008). Furthermore, the number of relevant variables is allowed to be larger than the sample size.

Kock, Anders Bredahl

2010-01-01

 
 
 
 
61

Strong Law of Large Numbers for Weighted Sum of Exchangeable Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, the Marcinkiewicz type theorem is extended to the case of exchangeable random variables. As a generalization,we also obtain two strong laws of large numbers on the weighted sum of exchangeable random variables

Zhaoxia Huang

2009-01-01

62

Homogenization of space-time dependent and degenerate random flows  

CERN Multimedia

We study a diffusion process with random space-time dependent coefficients. Moreover the diffusion matrix is allowed to degenerate. An invariance principle is proved provided that the diffusion coefficient is controlled by a time independent one.

Rhodes, R

2006-01-01

63

Runs of Geometrically Distributed Random Variables: A Probabilistic Analysis  

UK PubMed Central (United Kingdom)

Using a Markov chain approach and a polyomino-like description, we study some asymptoticproperties of runs of geometrically distributed random variables. We analyze the limiting trajectories,the runs number and the run length distribution, the hitting time to a length k run and themaximum run length.1 IntroductionDuring the LATIN 2000 Symposium in Montevideo, our attention was attracted to a talk given byA.Knopfmacher on the run statistics for geometrically distributed random variables (R.V.). Thecorresponding extended abstract by P.J.Grabner, A.Knopfmacher, and H.Prodinger [6] presented aninteresting set of results on the asymptotic properties of runs. Let a GEOM(p) R.V. , with distributionp(i) := pqi 1; q := 1 p . The combinatorics of n GEOM(p) R.V. has attracted recent interest(seemany references in [6]) . We discovered that a Markov chain approach could lead to further asymptoticresults on the runs of equal consecutive values. Runs statistics play a signicant role...

Guy Louchard

64

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 variables without necessarily adding any extra conditions.

Qunying Wu

2012-01-01

65

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

66

A Note on Strong Laws of Large Numbers for Dependent Random Sets and Fuzzy Random Sets  

Directory of Open Access Journals (Sweden)

Full Text Available This paper deals with a sequence of identically distributed random sets or fuzzy random sets with -mixing dependence in a separable Banach space. The strong laws of large numbers for these two sequences are derived under Kuratowski-Mosco sense.

Fu Ke-Ang

2010-01-01

67

A Note on Strong Laws of Large Numbers for Dependent Random Sets and Fuzzy Random Sets  

Directory of Open Access Journals (Sweden)

Full Text Available This paper deals with a sequence of identically distributed random sets or fuzzy random sets with ?(??)-mixing dependence in a separable Banach space. The strong laws of large numbers for these two sequences are derived under Kuratowski-Mosco sense.

Ke-Ang Fu

2010-01-01

68

Variance on the Leaves of a Tree Markov Random Field: Detecting Character Dependencies in Phylogenies  

CERN Document Server

Stochastic models of evolution (Markov random fields on trivalent trees) generally assume that different characters (different runs of the stochastic process) are independent and identically distributed. In this paper we take the first steps towards addressing dependent characters. Specifically we show that, under certain technical assumptions regarding the evolution of individual characters, we can detect any significant, history independent, correlation between any pair of multistate characters. For the special case of the Cavender-Farris-Neyman (CFN) model on two states with symmetric transition matrices, our analysis needs milder assumptions. To perform the analysis, we need to prove a new concentration result for multistate random variables of a Markov random field on arbitrary trivalent trees: we show that the random variable counting the number of leaves in any particular subset of states has variance that is subquadratic in the number of leaves.

Chakrabarty, Deeparnab

2011-01-01

69

Extracting randomness and dependencies via a matrix polarization  

CERN Multimedia

The basic polarization phenomenon for i.i.d. sources is extended to a framework allowing dependencies within and between multiple sources. In particular, it is shown that taking the polar transform of a random matrix with i.i.d. columns of arbitrary (correlated) distribution allows to extract the randomness and dependencies. This result is the used to develop polar coding schemes (having low complexity) for: (1) distributed data compression, i.e., Slepian-Wolf coding (without decomposing the problem into single-user problems), (2) compression of sources with memory, (3) compression of sources on finite fields, extending the polarization phenomenon for alphabets of prime cardinality to powers of primes.

Abbe, Emmanuel

2011-01-01

70

Phase Dependent Spectroscopy of Mira Variable Stars  

CERN Multimedia

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

71

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

72

Some Strong Limit Theorems for Weighted Product Sums of -Mixing Sequences of Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available We study almost sure convergence for -mixing sequences of random variables. Many of the previous results are our special cases. For example, the authors extend and improve the corresponding results of Chen et al. (1996) and Wu and Jiang (2008). We extend the classical Jamison convergence theorem and the Marcinkiewicz strong law of large numbers for independent sequences of random variables to -mixing sequences of random variables without necessarily adding any extra conditions.

Wu Qunying; Jiang Yuanying

2009-01-01

73

A queueing system with a fixed accumulation level, random server capacity and capacity dependent service time  

Directory of Open Access Journals (Sweden)

Full Text Available This paper introduces a bulk queueing system with a single server processing groups of customers of a variable size. If upon completion of service the queueing level is at least r the server takes a batch of size r and processes it a random time arbitrarily distributed. If the queueing level is less than r the server idles until the queue accumulates r customers in total. Then the server capacity is generated by a random number equals the batch size taken for service which lasts an arbitrarily distributed time dependent on the batch size.

Jewgeni H. Dshalalow; Lotfi Tadj

1992-01-01

74

On the Spatial Dependence Structure of Isotropic Pairwise Gaussian-Markov Random Field Models  

CERN Document Server

Markov Random Field (MRF) models are powerful tools for contextual modeling. However, little is known about how the spatial dependence between its elements is encoded in terms of statistical information, more precisely, information-theoretic measures. In this paper, we enlight the connection between Fisher information, Shannon entropy and spatial properties of the random field in the case of Gaussian variables (a Gaussian Markov random field), by defining analytical expressions to compute the local and global versions of these measures using Besag's pseudo-likelihood function (conditional independence assumption). Besides, we use the derived expressions to define an exact expression for the asymptotic variance of the maximum pseudo-likelihood estimator of the spatial dependence parameter, showing that it does not reach the Cramer-R\\'ao lower bound, since information equality fails. The obtained results provide a rich framework for extraction of relevant statistical information in a variety of MRF applications...

Levada, Alexandre L M

2011-01-01

75

Survival probabilities in time-dependent random walks  

Science.gov (United States)

We analyze the dynamics of random walks in which the jumping probabilities are periodic time-dependent functions. In particular, we determine the survival probability of biased walkers who are drifted towards an absorbing boundary. The typical lifetime of the walkers is found to decrease with an increment in the oscillation amplitude of the jumping probabilities. We discuss the applicability of the results in the context of complex adaptive systems.

Nakar, Ehud; Hod, Shahar

2004-07-01

76

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

77

Optimal Constants in the Rosenthal Inequality for Random Variables with Zero Odd Moments.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We obtain estimates for the best constant in the Rosenthal inequality View the MathML source for independent random variables ?1,,?n with l zero first odd moments, lgreater-or-equal, slanted1. The estimates are sharp in the extremal cases l=1 and l=m, that is, in the cases of random variables with ...

Ibragimov, Rustam; Ibragimov, Marat

78

An Inversion Formula for Orlicz Norms and Sequences of Random Variables  

CERN Document Server

Given an Orlicz function $M$, we show which random variables $\\xi_i$, $i=1,...,n$ generate the associated Orlicz norm, i.e., which random variables yield $\\mathbb{E} \\max\\limits_{1\\leq i \\leq n}|x_i\\xi_i| \\sim \

Christensen, Soeren; Riemer, Stiene

2012-01-01

79

Likelihood Ratio and Strong Limit Theorems for the Discrete Random Variable  

Directory of Open Access Journals (Sweden)

Full Text Available 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

80

The Best Lower Bound Depended on Two Fixed Variables for Jensen's Inequality with Ordered Variables  

Directory of Open Access Journals (Sweden)

Full Text Available We give the best lower bound for the weighted Jensen's discrete inequality with ordered variables applied to a convex function , in the case when the lower bound depends on , weights, and two given variables. Furthermore, under the same conditions, we give some sharp lower bounds for the weighted AM-GM inequality and AM-HM inequality.

Cirtoaje Vasile

2010-01-01

 
 
 
 
81

Explaining the Dark Energy, Baryon and Dark Matter Coincidence via Domain-Dependent Random Densities  

CERN Document Server

The dark energy, dark matter and baryon densities in the Universe are observed to be similar, with a factor of no more than 20 between the largest and smallest densities. We show that this coincidence can be understood via superhorizon domains of randomly varying densities when the baryon density at initial collapse of galaxy-forming perturbations is determined by anthropic selection. The baryon and dark matter densities are assumed to be dependent on random variables \\theta_{d} and \\theta_{b} according to \\rho_{dm} ~ \\theta_{d}^{\\alpha} and \\rho_{b} ~ \\theta_{b}^{\\beta}, while the effectively constant dark energy density is dependent upon a random variable \\phi_{Q} according to \\rho_{Q} ~ \\phi_{Q}^{n}. The ratio of the baryon density to the dark energy density at initial collapse, r_{Q}, and the baryon-to-dark matter ratio, r, are then determined purely statistically, with no dependence on the anthropically-preferred baryon density. We compute the probability distribution for r_{Q} and r and show that the ob...

McDonald, John

2013-01-01

82

Explaining the dark energy, baryon and dark matter coincidence via domain-dependent random densities  

Science.gov (United States)

The dark energy, dark matter and baryon densities in the Universe are observed to be similar, with a factor of no more than 20 between the largest and smallest densities. We show that this coincidence can be understood via superhorizon domains of randomly varying densities when the baryon density at initial collapse of galaxy-forming perturbations is determined by anthropic selection. The baryon and dark matter densities are assumed to be dependent on random variables ?d and ?b according to ?dmpropto?d? and ?bpropto?b?, while the effectively constant dark energy density is dependent upon a random variable phiQ according to ?QproptophiQn. The ratio of the baryon density to the dark energy density at initial collapse, rQ, and the baryon-to-dark matter ratio, r, are then determined purely statistically, with no dependence on the anthropically-preferred baryon density. We compute the probability distribution for rQ and r and show that the observed values of rQ and r can be naturally understood within this framework. In particular, for the case ? = 2, ? = 1 and n = 4, which can be physically realized via a combination of axion dark matter, Affleck-Dine baryogenesis and frozen quintessence with a phiQ4 potential, the range of rQ and r which corresponds to the observed Universe is a quite natural, with a probability which is broadly similar to other ranges of rQ and r.

McDonald, John

2013-05-01

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; Muhammad Safian Adeel; Tahir Izhar

2012-01-01

84

Approximation of a random process with variable smoothness  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We consider the rate of piecewise constant approximation to a locally stationary process $X(t),t\\in [0,1]$, having a variable smoothness index $\\alpha(t)$. Assuming that $\\alpha(\\cdot)$ attains its unique minimum at zero and satisfies the regularity condition, we propose a method for construction of...

Hashorva, Enkelejd; Lifshits, Mikhail; Seleznjev, Oleg

85

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

86

Computing the Moments of Order Statistics from Independent Non - Identically Distributed Burr Type XII Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, we derive a recurrence relation for computing all single moments of all order statistics arising from independent but not identically distributed Burr type XII random variables.

A. A. Jamjoom

2006-01-01

87

Random variables as pathwise integrals with respect to fractional Brownian motion  

CERN Document Server

We show that a pathwise stochastic integral with respect to fractional Brownian motion with an adapted integrand $g$ can have any prescribed distribution, moreover, we give both necessary and sufficient conditions when random variables can be represented in this form. We also prove that any random variable is a value of such integral in some improper sense. We discuss some applications of these results, in particular, to fractional Black--Scholes model of financial market.

Mishura, Yuliya; Valkeila, Esko

2011-01-01

88

Estimation of global sensitivity indices for models with dependent variables  

Science.gov (United States)

A novel approach for estimation variance-based sensitivity indices for models with dependent variables is presented. Both the first order and total sensitivity indices are derived as generalizations of Sobol' sensitivity indices. Formulas and Monte Carlo numerical estimates similar to Sobol' formulas are derived. A copula-based approach is proposed for sampling from arbitrary multivariate probability distributions. A good agreement between analytical and numerical values of the first order and total indices for considered test cases is obtained. The behavior of sensitivity indices depends on the relative predominance of interactions and correlations. The method is shown to be efficient and general.

Kucherenko, S.; Tarantola, S.; Annoni, P.

2012-04-01

89

Metamodelling and Global Sensitivity Analysis of Models with Dependent Variables  

Science.gov (United States)

A novel approach for metamodelling and estimation variance based sensitivity indices for models with dependent variables are presented. Both the first order and total sensitivity indices are derived as generalizations of Sobol' sensitivity indices. Formulas and Monte Carlo numerical estimates similar to Sobol' formulas are derived. A Gaussian copula based approach is proposed for sampling from arbitrary multivariate probability distributions. Both methods are shown to be efficient and general.

Kucherenko, Sergei; Munoz Zuniga, Miguel; Tarantola, Stefano; Annoni, Paola

2011-09-01

90

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

91

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

92

Modelling the statistical dependence of rainfall event variables by a trivariate copula function  

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 splitting the problem in two distinct items. Furthermore, goodness-of-fit tests were recently made available and a significant improvement in the function selection reliability has been achieved. Herein a trivariate probability distribution of the rainfall event volume, the wet weather duration and the interevent time is proposed and verified by test statistics with regard to three long time series recorded in different Italian climates. The function was developed by applying a mixing technique to bivariate copulas, which were formerly obtained by analyzing the random variables in pairs. A unique probabilistic model seems to be suitable for representing the dependence structure, despite the sensitivity shown by the dependence parameters 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; B. Bacchi

2011-01-01

93

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish Este artculo presenta el Modelado Con Variables Aleatorias En Simulink Utilizando Simulacin Montecarlo, muchos modelos de sistemas reales contienen elementos que precisan o admiten un modelado estadstico, Sistemas de comunicaciones, Sistemas de conmutacin, Sistemas sensores, Modelado toma forma definiendo, Variables aleatorias que rigen ciertos comportamientos del sistema Procesos estocsticos para modelar variacin de entradas en el tiempo, como lo son las fluc (more) tuaciones en la bolsa de valores e ciertos productos. Se deben definir mtodos para generar muestras de variables aleatorias y muestras de procesos estocsticos. Entre ellos est el mtodo 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 Mtodo ante otros Mtodos 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 governing certain stochastic processes system behavior modelinginputs change over time, as are the fluctiaciones in the stock market andsome products. You must define methods to genera (more) te 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.

Velsquez, Sergio; Velsquez, Ronny

2012-09-01

94

Fatigue and creep at variable temperature. Time dependence forecasting  

International Nuclear Information System (INIS)

Structure materials for nuclear reactors undergo different types of mechanical and thermal stresses for period reaching 300 000 hours. Rapid change of temperature, stress, frequency can occurs in case of accident. Determination of mechanical properties (elongation, creep, fatigue...) of materials for structure dimensioning requires extrapolation of fatigue and creep tests. The comparison of results obtained on steel 316 shows that for creep forecastings agreement is good between the different methods but it is not the case for creep fatigue. For creep in variable conditions, agreement between experiments and calculus is good only in some cases. For fatigue test with samples previously tested for creep, or vice versa, results depend upon the damage evaluation

1984-01-01

95

Distributions of products involving the type II Bessel function random variable  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of the present paper is to study the distributions of product of two independent random variables X and Y which are not everywhere positive. We have taken X to be a type II Bessel function random variate whereas Y belongs to one of normal, Pearson VII or Maxwell-Boltzmann families of distributions. Several special cases have also been obtained.

Mridula Garg; Jaya Agrawal; Saralees Nadarajah

2010-01-01

96

Joint Distribution of Minimum of N Iid Exponential Random Variables and Poisson Marginal  

Directory of Open Access Journals (Sweden)

Full Text Available We introduced a random vector (X,N), where N has Poisson distribution and X are minimum of N independent and identically distributed exponential random variables. We present fundamental properties of this vector such as PDF, CDF and stochastic representations. Our results include explicit formulas for marginal and conditional distributions, moments and moments generating functions. We also derive moments estimators and maximum likelihood estimators of the parameter of this distribution.

Ali Hussein Mahmood Al-Obaidi

2013-01-01

97

The generation of dependent input variables to a performance assessment simulation code  

International Nuclear Information System (INIS)

Mathematical models are being developed in many countries to aid in the assessment of risks associated with the deep geologic disposal of high-level nuclear wastes. The models are designed to simulate one or more steps in the following scenario: waste containment is lost, and the radionuclides are released from the repository, are transported to the biosphere, and become accessible to man. The models typically involve a large number of variables that may be highly dependent. When the models are implemented in computer simulation codes, it becomes necessary to generate input values for these variables. Widely used methods for generating input values, such as simple random sampling (SRS) and Latin hypercube sampling (LHS), do not necessarily produce samples that are consistent with the known dependence structure of the input variables. Moreover, it is procedurally impracticable to generate realizations of correlated input variables from many multivariate probability distributions of interest. Two important cases in which it is feasible to generate multivariate realizations are those in which all input variables are either normally distributed or mutually independent. Neither case is adequate for large-scale performance assessment codes with many input variables. Iman and Conover (1982) have developed a practical method for generating nonzero pairwise rank correlations among the components of an input vector that overcomes some of these difficulties. The method requires samples of specified size from the marginal (univariate) distributions of the input variables. The method further requires a target matrix of desired pairwise correlations among the input variables. The Cholesky decomposition of the target matrix is used to transform the rank matrix of the input sample

1987-01-01

98

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

CERN Multimedia

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

99

On the Distribution of the Minimum or Maximum of a Random Number of i.i.d. Lifetime Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available Statisticians are usually concerned with the proposition of new distributions. In this paper we point out that a unified and concise derivation procedure of the distribution of the minimum or maximum of a random number N of indepen-dent and identically distributed continuous random variables Yi,{i = 1,2,,N} is obtained if one compounds the probability generating function of N with the survival or the distribution func-tion of Yi. Expressions are then derived in closed form for the density, hazard and quantile func-tions of the minimum or maximum. The methodology is illustrated with examples of the distributions proposed by Adamidis and Loukas (1998), Kus (2007), Tahmasbi and Rezaei (2008), Barreto-Souza and Cribari-Neto (2009), Cancho, Louzada, and Barriga (2011) and Louzada, Roman and Cancho (2011).

Francisco Louzada; Estela M. P. Bereta; Maria A. P. Franco

2012-01-01

100

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 probabi...

Andrei Khrennikov

 
 
 
 
101

A note on the distribution of the maximum of a set of Poisson random variables  

CERN Document Server

Given a set of independent Poisson random variables with common mean, we study the distribution of their maximum and obtain an accurate asymptotic formula to locate the most probable value of the maximum. We verify our analytic results with very precise numerical computations.

Briggs, K M; Prellberg, T

2009-01-01

102

Monotone Runs of Uniformly Distributed Integer Random Variables: A Probabilistic Analysis  

UK PubMed Central (United Kingdom)

Using a Markov chain approach and a polyomino-like description, we study some asymptoticproperties of monotone runs of uniformly distributed integer random variables. We analyze thelimiting trajectories, the number of runs and the run length distribution, the hitting time to alength k run and the maximum run length. A preliminary application to DNA analysis is alsogiven.1

Guy Louchard

103

Ascending Runs of Sequences of Geometrically Distributed Random Variables: A Probabilistic Analysis  

UK PubMed Central (United Kingdom)

Using a Markov chain approach and a polyomino-like description, we study some asymptoticproperties of sequences of ascending runs of geometrically distributed random variables. We analyzethe limiting trajectories, the number of runs and the run length distribution, the hitting time to alength k run and the maximum run length.1

Guy Louchard

104

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; B. Bacchi

2011-01-01

105

Tracheostomy in ventilator dependent trauma patients: a prospective, randomized intention-to-treat study.  

UK PubMed Central (United Kingdom)

BACKGROUND: Tracheostomy is a commonly performed procedure in ventilator dependent patients. Many critical care practitioners believe that performing a tracheostomy early in the postinjury period decreases the length of ventilator dependence as well as having other benefits such as better patient tolerance and lower respiratory dead space. We conducted a randomized, prospective, single institution study comparing the length ventilator dependence in critically ill multiple trauma patients who were randomized to two different strategies for performance of a tracheostomy. We hypothesized that earlier tracheostomy would reduce the number of days of mechanical ventilation, frequency of pneumonia and length of intensive care unit (ICU) stay. METHODS: Patients were eligible if they were older than 15 years and either a Glasgow Coma Score (GCS) >4 with a negative brain computed tomography (CT) (no anatomic head injury), or a GCS >9 with a positive head CT (known anatomic head injury). Patients who required tracheostomy for facial/neck injuries were excluded. Patients were randomized to an intention to treat strategy of tracheostomy placement before day 8 or after day 28. RESULTS: The study was halted after the first interim analysis. There were 60 enrolled patients, who had comparable demographics between groups. There was no significant difference between groups in any outcome variable including length of ventilator support, pneumonia rate, or death. CONCLUSION: A strategy of tracheostomy before day 8 postinjury in this group of trauma patients did not reduce the number of days of mechanical ventilation, frequency of pneumonia or ICU length of stay as compared with the group with a tracheostomy strategy involving the procedure at 28 days postinjury or more.

Barquist ES; Amortegui J; Hallal A; Giannotti G; Whinney R; Alzamel H; MacLeod J

2006-01-01

106

Frequency-dependent variability in synchrotron self-Compton models  

Energy Technology Data Exchange (ETDEWEB)

Homogeneous synchrotron self-Compton models are discussed in relation to their variability behaviour in different frequency bands. In compact sources, the energy distribution of the emitting electrons has to be derived self-consistently, as it responds rapidly to changes in the cooling and the injection rates. This gives the unexpected result that large variations in the X-ray flux are possible for small or null variations in the optical and infrared bands, following a change in the magnetic field strength. If this change is produced by compression of the emission region, there is a correlation between the polarization and flux which is dependent on the spectral index of the source. (author).

Ghisellini, G.; George, I.M.; Done, C. (Cambridge Univ. (UK). Inst. of Astronomy)

1989-11-15

107

Frequency-dependent variability in synchrotron self-Compton models  

International Nuclear Information System (INIS)

Homogeneous synchrotron self-Compton models are discussed in relation to their variability behaviour in different frequency bands. In compact sources, the energy distribution of the emitting electrons has to be derived self-consistently, as it responds rapidly to changes in the cooling and the injection rates. This gives the unexpected result that large variations in the X-ray flux are possible for small or null variations in the optical and infrared bands, following a change in the magnetic field strength. If this change is produced by compression of the emission region, there is a correlation between the polarization and flux which is dependent on the spectral index of the source. (author).

1989-01-01

108

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 proposed. The innovation is that we can accurately calculate out the interval of the structural fatigue life and reliability index of a structure according to the probability density function of stress level of random loads and the coefficient of variation of measured loads. By practical calculation example, it is proved that this method is more suitable to practical engineering comparing to traditional methods. It will provide a perfect research approach for reliability analysis of the structure under random loads.

Qiangfeng Wang; Jianjun Li; Shengli Zhang

2013-01-01

109

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

110

Strong Laws of Large Numbers for Arrays of Rowwise ρ∗-Mixing Random Variables  

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Full Text Available Some strong laws of large numbers for arrays of rowwise ρ∗-mixing random variables are obtained. The result obtainted not only generalizes the result of Hu and Taylor (1997) to ρ∗-mixing random variables, but also improves it.

Meng-Hu Zhu

2007-01-01

111

???????????????????? 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.

??; ???; ???

2011-01-01

112

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

Directory of Open Access Journals (Sweden)

Full Text Available 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(0random variables. The sharpness of the results is illustrated by examples.

Le Van Thanh

2006-01-01

113

On general strong laws of large numbers for fields of random variables  

CERN Multimedia

A general method to prove strong laws of large numbers for random fields is given. It is based on the H\\'ajek - R\\'enyi type method presented in Nosz\\'aly and T\\'om\\'acs \\cite{noszaly} and in T\\'om\\'acs and L\\'ibor \\cite{thomas06}. Nosz\\'aly and T\\'om\\'acs \\cite{noszaly} obtained a H\\'ajek-R\\'enyi type maximal inequality for random fields using moments inequalities. Recently, T\\'om\\'acs and L\\'ibor \\cite{thomas06} obtained a H\\'ajek-R\\'enyi type maximal inequality for random sequences based on probabilities, but not for random fields. In this paper we present a H\\'ajek-R\\'enyi type maximal inequality for random fields, using probabilities, which is an extension of the main results of Nosz\\'aly and T\\'om\\'acs \\cite{noszaly} by replacing moments by probabilities and a generalization of the main results of T\\'om\\'acs and L\\'ibor \\cite% {thomas06} for random sequences to random fields. We apply our results to establishing a logarithmically weighted sums without moment assumptions and under general dependence cond...

Hamallah, Cheikhna

2011-01-01

114

Identification and ranking of critical contingencies in dependent variable space  

Energy Technology Data Exchange (ETDEWEB)

Working in dependent-variable space, reliable yet simple computational procedures are presented for the purpose of identifying and ranking line outages which result in the violation of various limits related to power system security. Security limits defined in terms of real-power line flows, generator reactive powers and demand-bus voltage magnitudes are considered in normalised subspaces wherein critical contingencies are identified by a filtering algorithm using the infinite norm as a performance index. Critical contingencies are then ranked using performance indices which are defined in accordance with the subspace of interest. In the case of real-power line flows, ranking is based on a measure related to distance from the center of the corresponding security region whereas, in the case of generator reactive powers and demand-bus voltage magnitudes, ranking is based on measures related to distances from the boundaries of the corresponding regions. Furthermore, an operating point's violation of limits associated with generator reactive powers and demand-bus voltage magnitudes is measured in combined form with due consideration being given to the relationships between these reactive powers and voltage magnitudes.

Wasley, R.G.; Daneshdoost, M.

1983-04-01

115

Lamprey variable lymphocyte receptors mediate complement-dependent cytotoxicity.  

UK PubMed Central (United Kingdom)

An alternative adaptive-immune system is present in the most basal vertebrates--lampreys and hagfish--the only surviving jawless vertebrates. These eel-like fish use leucine-rich repeat-based receptors for Ag recognition instead of the Ig-based receptors used in jawed vertebrates. We report that in Japanese lamprey (Lampetra japonica), variable lymphocyte receptor (VLR)B interacts with C1q and C3 proteins to mediate complement-dependent cytotoxicity for bacteria and tumor cells. The immune-based lysis involves deposition of VLRB and C1q-like protein complex on the surface of target cells, activation of C3, and ultimate disruption of cell wall integrity. The demonstration of functional interaction between VLRB and complement components in lamprey provides evidence for the emergence of cooperative innate and adaptive-immune responses at a pivotal point in vertebrate evolution, before or in parallel with the evolution of Ig-based Abs and the classical complement-activation pathway.

Wu F; Chen L; Liu X; Wang H; Su P; Han Y; Feng B; Qiao X; Zhao J; Ma N; Liu H; Zheng Z; Li Q

2013-02-01

116

On the ratio of Pearson type VII and Bessel random variables  

Directory of Open Access Journals (Sweden)

Full Text Available The exact distribution of the ratio |X/Y| is derived when X and Y are, respectively, Pearson type VII and Bessel function random variables distributed independently of each other. The work is motivated by previously published approximate relationships between these two distributions. An application of the result is provided by computing “correction factors” for some of these approximations.

Saralees Nadarajah; Samuel Kotz

2005-01-01

117

Optimization of Reorder Point Strategy of Assembly Manufacturer with Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available For assembly system, randomness and variableness make it impossible to control the inventory accuratelyspecially. Because the negative effect of them have ripple effects. So we investigate reorder point optimizationstrategy of assembly manufacturing system with random demand and random lead time. We seek themanufacturers order strategy for the minimum integration of the supply chain inventory cost. And we use scalebenefits parameters of suppliers in this system to reflect actual influence of the lots scale. Numerical example oftwo components assembly system is given to illustrate the effectiveness of the reorder point strategy. From thenumerical simulation, it is can be seen backorder rate and order scale effect will impact the total supply chaincost dramatically.

Shuangyan Li; Dezhi Zhang; Fangping Jin

2013-01-01

118

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

119

Universality classes of transport in time-dependent random potentials.  

UK PubMed Central (United Kingdom)

The growth of the average kinetic energy of classical particles is studied for potentials that are random both in space and time. Such potentials are relevant for recent experiments in optics and in atom optics. It is found that for small velocities uniform acceleration takes place, and at a later stage fluctuations of the potential are encountered, resulting in a regime of anomalous diffusion. This regime was studied in the framework of the Fokker-Planck approximation. The diffusion coefficient in velocity was expressed in terms of the average power spectral density, which is the Fourier transform of the potential correlation function. This enabled to establish a scaling form for the Fokker-Planck equation and to compute the large and small velocity limits of the diffusion coefficient. A classification of the random potentials into universality classes, characterized by the form of the diffusion coefficient in the limit of large and small velocity, was performed. It was shown that one-dimensional systems exhibit a large variety of universality classes, contrary to systems in higher dimensions, where only one universality class is possible. The relation to Chirikov resonances, which are central in the theory of chaos, was demonstrated. The general theory was applied and numerically tested for specific physically relevant examples.

Krivolapov Y; Fishman S

2012-09-01

120

Joint variable selection for fixed and random effects in linear mixed-effects models.  

Science.gov (United States)

It is of great practical interest to simultaneously identify the important predictors that correspond to both the fixed and random effects components in a linear mixed-effects (LME) model. Typical approaches perform selection separately on each of the fixed and random effect components. However, changing the structure of one set of effects can lead to different choices of variables for the other set of effects. We propose simultaneous selection of the fixed and random factors in an LME model using a modified Cholesky decomposition. Our method is based on a penalized joint log likelihood with an adaptive penalty for the selection and estimation of both the fixed and random effects. It performs model selection by allowing fixed effects or standard deviations of random effects to be exactly zero. A constrained expectation-maximization algorithm is then used to obtain the final estimates. It is further shown that the proposed penalized estimator enjoys the Oracle property, in that, asymptotically it performs as well as if the true model was known beforehand. We demonstrate the performance of our method based on a simulation study and a real data example. PMID:20163404

Bondell, Howard D; Krishna, Arun; Ghosh, Sujit K

2010-12-01

 
 
 
 
121

Joint variable selection for fixed and random effects in linear mixed-effects models.  

UK PubMed Central (United Kingdom)

It is of great practical interest to simultaneously identify the important predictors that correspond to both the fixed and random effects components in a linear mixed-effects (LME) model. Typical approaches perform selection separately on each of the fixed and random effect components. However, changing the structure of one set of effects can lead to different choices of variables for the other set of effects. We propose simultaneous selection of the fixed and random factors in an LME model using a modified Cholesky decomposition. Our method is based on a penalized joint log likelihood with an adaptive penalty for the selection and estimation of both the fixed and random effects. It performs model selection by allowing fixed effects or standard deviations of random effects to be exactly zero. A constrained expectation-maximization algorithm is then used to obtain the final estimates. It is further shown that the proposed penalized estimator enjoys the Oracle property, in that, asymptotically it performs as well as if the true model was known beforehand. We demonstrate the performance of our method based on a simulation study and a real data example.

Bondell HD; Krishna A; Ghosh SK

2010-12-01

122

Cluster-size dependent randomization traffic flow model  

Science.gov (United States)

In order to exhibit the meta-stable states, several slow-to-start rules have been investigated as modification to Nagel-Schreckenberg (NS) model. These models can reproduce some realistic phenomena which are absent in the original NS model. But in these models, the size of cluster is still not considered as a useful parameter. In real traffic, the slow-to-start motion of a standing vehicle often depends on the degree of congestion which can be measured by the clusters' size. According to this idea, we propose a cluster-size dependent slow-to-start model based on the speed-dependent slow-to-start rule (VDR) model. It gives expected results through simulations. Comparing with the VDR model, our new model has a better traffic efficiency and shows richer complex characters.

Gao, Kun; Wang, Bing-Hong; Fu, Chuan-Ji; Lu, Yu-Feng

2007-11-01

123

Effect of modafinil on cognitive functions in alcohol dependent patients: A randomized, placebo-controlled trial.  

UK PubMed Central (United Kingdom)

Cognitive deficits are highly prevalent in alcohol-dependent (AD) patients and may have a detrimental impact on treatment response and treatment outcome. Enhancing cognitive functions may improve treatment success. Modafinil is a promising compound in this respect. Therefore, a randomized double-blind placebo-controlled trial was conducted with modafinil (300 mg/d) or placebo in 83 AD patients for 10 weeks. Various cognitive functions (digit span task, Tower of London task, Stroop task) were measured at baseline, during and after treatment. Compared to placebo, modafinil improved verbal short-term memory (number of forward digit spans) (p=0.030), but modafinil exerted a negative effect on the working memory score of the digit span task (p=0.003). However, subgroup analyses revealed that modafinil did improve both working memory and verbal short-term memory in AD patients with a poor working memory ability at baseline (25% worst performers), whereas no significant treatment effect of modafinil was found on these two dependent variables in patients with good working memory skills at baseline (25% best performers). No effect of modafinil was found on measures of planning (Tower of London task) and selective attention (Stroop task). Further research is needed to better understand the relationship between cognitive remediation and treatment outcome in order to design targeted treatments.

Joos L; Goudriaan AE; Schmaal L; van den Brink W; Sabbe BG; Dom G

2013-09-01

124

Effect of modafinil on cognitive functions in alcohol dependent patients: A randomized, placebo-controlled trial.  

Science.gov (United States)

Cognitive deficits are highly prevalent in alcohol-dependent (AD) patients and may have a detrimental impact on treatment response and treatment outcome. Enhancing cognitive functions may improve treatment success. Modafinil is a promising compound in this respect. Therefore, a randomized double-blind placebo-controlled trial was conducted with modafinil (300 mg/d) or placebo in 83 AD patients for 10 weeks. Various cognitive functions (digit span task, Tower of London task, Stroop task) were measured at baseline, during and after treatment. Compared to placebo, modafinil improved verbal short-term memory (number of forward digit spans) (p=0.030), but modafinil exerted a negative effect on the working memory score of the digit span task (p=0.003). However, subgroup analyses revealed that modafinil did improve both working memory and verbal short-term memory in AD patients with a poor working memory ability at baseline (25% worst performers), whereas no significant treatment effect of modafinil was found on these two dependent variables in patients with good working memory skills at baseline (25% best performers). No effect of modafinil was found on measures of planning (Tower of London task) and selective attention (Stroop task). Further research is needed to better understand the relationship between cognitive remediation and treatment outcome in order to design targeted treatments. PMID:24045883

Joos, Leen; Goudriaan, Anna E; Schmaal, Lianne; van den Brink, Wim; Sabbe, Bernard Gc; Dom, Geert

2013-09-17

125

Effect of modafinil on cognitive functions in alcohol dependent patients: A randomized, placebo-controlled trial.  

UK PubMed Central (United Kingdom)

Cognitive deficits are highly prevalent in alcohol-dependent (AD) patients and may have a detrimental impact on treatment response and treatment outcome. Enhancing cognitive functions may improve treatment success. Modafinil is a promising compound in this respect. Therefore, a randomized double-blind placebo-controlled trial was conducted with modafinil (300 mg/d) or placebo in 83 AD patients for 10 weeks. Various cognitive functions (digit span task, Tower of London task, Stroop task) were measured at baseline, during and after treatment. Compared to placebo, modafinil improved verbal short-term memory (number of forward digit spans) (p=0.030), but modafinil exerted a negative effect on the working memory score of the digit span task (p=0.003). However, subgroup analyses revealed that modafinil did improve both working memory and verbal short-term memory in AD patients with a poor working memory ability at baseline (25% worst performers), whereas no significant treatment effect of modafinil was found on these two dependent variables in patients with good working memory skills at baseline (25% best performers). No effect of modafinil was found on measures of planning (Tower of London task) and selective attention (Stroop task). Further research is needed to better understand the relationship between cognitive remediation and treatment outcome in order to design targeted treatments.

Joos L; Goudriaan AE; Schmaal L; van den Brink W; Sabbe BG; Dom G

2013-11-01

126

On homogenization of space-time dependent and degenerate random flows  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study a diffusion process with random space-time dependent coefficients. Moreover the diffusion matrix is allowed to degenerate. An invariance principle is proved provided that the diffusion coefficient is controlled by a time independent one.

Rhodes, Rmi

127

Estimating equations with information loss on at least one dependent variable  

Digital Repository Infrastructure Vision for European Research (DRIVER)

variables reduces to separate estimation of each equation. This is no longer the case if information has been lost on at least one dependent variable; for example, if all that is recorded is whether some value is...

Conniffe, Denis

128

Records and sequences of records from random variables with a linear trend  

Science.gov (United States)

We consider records and sequences of records drawn from discrete time series of the form Xn = Yn + cn, where the Yn are independent and identically distributed random variables and c is a constant drift. For very small and very large drift velocities, we investigate the asymptotic behavior of the probability pn(c) of a record occurring in the nth step and the probability PN(c) that all N entries are records, i.e. that X_1 \\lt X_2 \\lt \\cdots \\lt X_N . Our work is motivated by the analysis of temperature time series in climatology, and by the study of mutational pathways in evolutionary biology.

Franke, Jasper; Wergen, Gregor; Krug, Joachim

2010-10-01

129

On the LP-convergence for multidimensional arrays of random variables  

Directory of Open Access Journals (Sweden)

Full Text Available For a d-dimensional array of random variables {Xn,n∈ℤ+d} such that {|Xn|p,n∈ℤ+d} is uniformly integrable for some 0

Le Van Thanh

2005-01-01

130

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

131

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

CERN Multimedia

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

132

Determination of variable dependence information through abstract interpretation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Traditional schemes for abstract interpretation-based global analysis of logic programs generally focus on obtaining procedure argument mode and type information. Variable sharing information is often given only the attention needed to preserve the correctness of the analysis. However, such sharing ...

Muthukumar, Kalyan; Hermenegildo Salinas, Manuel Vicente

133

Heart rate variability during sleep in detoxified alcohol-dependent males: A comparison with healthy controls.  

UK PubMed Central (United Kingdom)

CONTEXT: Alcohol dependence can lead to autonomic neuropathy resulting in increased cardiac morbidity and mortality. This has previously been evaluated using heart-rate variability. AIMS: We compared sleep heart-rate variability of alcohol-dependent patients with that of healthy controls in this study. SETTINGS AND DESIGN: This study was conducted at NIMHANS, Bangalore. A case control study design was adopted. MATERIALS AND METHODS: Sleep heart-rate variability of 20 male alcohol-dependent inpatients was recorded on the 5(th) day after detoxification. Sleep heart-rate variability was also recorded in 18 age- and gender-matched healthy controls. STATISTICAL ANALYSIS: The groups were compared using t-test for continuous variables and Chi-squared test for discrete variables. RESULTS: Both time and frequency domain measures were significantly lower in the patients as compared to the controls, indicating decreased HRV in alcohol-dependent individuals. CONCLUSIONS: Decreased HRV in alcohol dependence indicates potential autonomic neuropathy.

Ganesha S; Thirthalli J; Muralidharan K; Benegal V; Gangadhar BN

2013-04-01

134

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

Directory of Open Access Journals (Sweden)

Full Text Available 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(0random variables. The sharpness of the results is illustrated by examples.

Le Van Thanh

2006-01-01

135

Quantum chaotic scattering in time-dependent external fields: random matrix approach  

CERN Multimedia

We review the random matrix description of electron transport through open quantum dots, subject to time-dependent perturbations. All characteristics of the current linear in the bias can be expressed in terms of the scattering matrix, calculated for a time-dependent Hamiltonian. Assuming that the Hamiltonian belongs to a Gaussian ensemble of random matrices, we investigate various statistical properties of the direct current in the ensemble. Particularly, even at zero bias the time-dependent perturbation induces current, called photovoltaic current. We discuss dependence of the photovoltaic current and its noise on the frequency and the strength of the perturbation. We also describe the effect of time-dependent perturbation on the weak localization correction to the conductance and on conductance fluctuations.

Vavilov, M G

2005-01-01

136

Heart rate variability exhibits complication-dependent changes postsurgery.  

UK PubMed Central (United Kingdom)

"Surgical stress response" is tissue damage postsurgery, leading to a systemic response (inflammation, sympathetic upregulation, and release of vasoactive chemicals), which is typically measured by C-reactive protein (CRP). We assessed arterial stiffness and heart rate variability (HRV)-additional parameters reflecting autonomic and vascular functions-in this response and their potential associations with postoperative complications. In 47 participants undergoing abdominal surgery, CRP, arterial stiffness, and HRV were measured pre- and postoperatively (days 1 and 2). C-reactive protein was significantly higher postoperatively in participants experiencing complications but not preoperatively. Compared to participants without complications, those with complications had increased HRV and pnn50 (time domain) and tendency toward increasing low-frequency/high-frequency ratio (frequency domain) on postoperative day 2. Therefore, time and frequency domain HRV parameters show perioperative changes in relation to complication development. These findings suggest the applicability of this noninvasive technology to a variety of abdominal operations. Larger studies need to confirm these findings.

Scheffler P; Muccio S; Egiziano G; Doonan RJ; Yu A; Carli F; Daskalopoulou SS

2013-11-01

137

Records and sequences of records from random variables with a linear trend  

CERN Multimedia

We consider records and sequences of records drawn from discrete time series of the form $X_{n}=Y_{n}+cn$, where the $Y_{n}$ are independent and identically distributed random variables and $c$ is a constant drift. For very small and very large drift velocities, we investigate the asymptotic behavior of the probability $p_n(c)$ of a record occurring in the $n$th step and the probability $P_N(c)$ that all $N$ entries are records, i.e. that $X_1 < X_2 < ... < X_N$. Our work is motivated by the analysis of temperature time series in climatology, and by the study of mutational pathways in evolutionary biology.

Franke, Jasper; Krug, Joachim

2010-01-01

138

Dynamical properties of a randomly diluted neural network with variable activity  

CERN Multimedia

The subject of study is a neural network with binary neurons, randomly diluted synapses and variable pattern activity. We look at the system with parallel updating using a probabilistic approach to solve the one step dynamics with one condensed pattern. We derive restrictions on the storage capacity and the mutual information content occuring during the retrieval process. Special focus is on the constraints on the threshold for optimal performance. We also look at the effect of noisy updating, giving a dynamical version of the critical temperature, the corresponding threshold and an approximation for the time evolution for small temperatures. The description is applicable to the whole retrieval process in the limit of strong dilution. The analysis is carried out as exactly as possible and over the full parameter ranges, generalizing some former results.

Grosskinsky, S

1999-01-01

139

Polymers on disordered hierarchical lattices: A nonlinear combination of random variables  

International Nuclear Information System (INIS)

The problem of directed polymers on disordered hierarchical and hypercubic lattices is considered. For the hierarchical lattices the problem can be reduced to the study of the stable laws for combining random variables in a nonlinear way. The authors present the results of numerical simulations of two hierarchical lattices, finding evidence of a phase transition in one case. For a limiting case they extend the perturbation theory developed by Derrida and Griffiths to nonzero temperature and to higher order and use this approach to calculate thermal and geometrical properties (overlaps) of the model. In this limit they obtain an interpolation formula, allowing one to obtain the noninteger moments of the partition function from the integer moments. They obtain bounds for the transition temperature for hierarchical and hypercubic lattices, and some similarities between the problem on the two different types of lattice are discussed.

1989-01-01

140

Polymers on disordered hierarchical lattices: A nonlinear combination of random variables  

Energy Technology Data Exchange (ETDEWEB)

The problem of directed polymers on disordered hierarchical and hypercubic lattices is considered. For the hierarchical lattices the problem can be reduced to the study of the stable laws for combining random variables in a nonlinear way. The authors present the results of numerical simulations of two hierarchical lattices, finding evidence of a phase transition in one case. For a limiting case they extend the perturbation theory developed by Derrida and Griffiths to nonzero temperature and to higher order and use this approach to calculate thermal and geometrical properties (overlaps) of the model. In this limit they obtain an interpolation formula, allowing one to obtain the noninteger moments of the partition function from the integer moments. They obtain bounds for the transition temperature for hierarchical and hypercubic lattices, and some similarities between the problem on the two different types of lattice are discussed.

Cook, J. (Commissariat a l' Energie Atomique, Gif-sur-Yvette (France) Univ. of Edinburgh (England)); Derrida, B. (Commissariat a l' Energie Atomique, Gif-sur-Yvette (France))

1989-10-01

 
 
 
 
141

On exchangeable random variables and the statistics of large graphs and hypergraphs  

CERN Multimedia

De Finetti's classical result identifying the law of an exchangeable family of random variables as a mixture of i.i.d. laws was extended to structure theorems for more complex notions of exchangeability by Aldous, Hoover and Kallenberg. On the other hand, such exchangeable laws were first related to questions from combinatorics in an independent analysis by Fremlin and Talagrand, and again more recently in work of Tao, where they appear as a natural proxy for the `leading order statistics' of colourings of large graphs or hypergraphs. Moreover, this relation appears implicitly in the study of various more bespoke formalisms for handling `limit objects' of sequences of dense graphs or hypergraphs in a number of recent works. However, the connection between these works and the earlier probabilistic structural results seems to have gone largely unappreciated. In this survey we recall the basic results of the theory of exchangeable laws, and then explain the probabilistic versions of various interesting questions...

Austin, Tim D

2008-01-01

142

Hot-spot model for accretion disc variability as random process  

CERN Multimedia

Theory of random processes provides an attractive mathematical tool to describe the fluctuating signal from accreting sources, such as active galactic nuclei and Galactic black holes observed in X-rays. These objects exhibit featureless variability on different timescales, probably originating from an accretion disc. We study the basic features of the power spectra in terms of a general framework, which permits semi-analytical determination of the power spectral density (PSD) of the resulting light curve. We consider the expected signal generated by an ensemble of spots randomly created on the accretion disc surface. Spot generation is governed by Poisson or by Hawkes processes. We include general relativity effects shaping the signal on its propagation to a distant observer. We analyse the PSD of a spotted disc light curve and show the accuracy of our semi-analytical approach by comparing the obtained PSD with the results of Monte Carlo simulations. The asymptotic slopes of PSD are 0 at low frequencies and t...

Pechacek, T; Czerny, B

2008-01-01

143

Data analysis with ordinal and interval dependent variables: examples from a study of real estate salespeople  

Directory of Open Access Journals (Sweden)

Full Text Available This paper re-examines the problems of estimating the parameters of an underlying linear model using survey response data in which the dependent variables are in discrete categories of ascending order (ordinal, as distinct from numerical) or, where they are observed to fall into certain groups on a continuous scale (interval), where the actual values remain unobserved. An ordered probit model is discussed as an appropriate framework for statistical analysis for ordinal dependent variables. Next, a maximum likelihood estimator (MLE) derived from grouped data regression for interval dependent variable is discussed. Using LIMDEP, a packaged statistical program, survey data from an earlier manuscript are analyzed and the findings presented.

G. Martin Izzo; Barry E. Langford

2008-01-01

144

Use of wrapper algorithms coupled with a random forests classifier for variable selection in large-scale genomic association studies.  

UK PubMed Central (United Kingdom)

Modern large-scale genetic association studies generate increasingly high-dimensional datasets. Therefore, some variable selection procedure should be performed before the application of traditional data analysis methods, for reasons of both computational efficiency and problems related to overfitting. We describe here a "wrapper" strategy (SIZEFIT) for variable selection that uses a Random Forests classifier, coupled with various local search/optimization algorithms. We apply it to a large dataset consisting of 2,425 African-American and non-Hispanic white individuals genotyped for 4,869 single-nucleotide polymorphisms (SNPs) in a coronary heart disease (CHD) case-cohort association study (Atherosclerosis Risk in Communities), using incident CHD and plasma low-density lipoprotein (LDL) cholesterol levels as the dependent variables. We show that most SNPs can be safely removed from the dataset without compromising the predictive (classification) accuracy, with only a small number of SNPs (sometimes less than 100) containing any predictive signal. A statistical (SUMSTAT) approach is also applied to the dataset for comparison purposes. We describe a novel method for refining the subset of signal-containing SNPs (FIXFIT), based on an Extremal Optimization algorithm. Finally, we compare the top SNP rankings obtained by different methods and devise practical guidelines for researchers trying to generate a compact subset of predictive SNPs from genome-wide association datasets. Interestingly, there is a significant amount of overlap between seemingly very heterogeneous rankings. We conclude by constructing compact optimal predictive SNP subsets for CHD (less than 150 SNPs) and LDL (less than 300 SNPs) phenotypes, and by comparing various rankings for two well-known positive control SNPs for LDL in the apolipoprotein E gene.

Rodin AS; Litvinenko A; Klos K; Morrison AC; Woodage T; Coresh J; Boerwinkle E

2009-12-01

145

On the statistical dependence for the components of random elasticity tensors exhibiting material symmetry properties  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This work is concerned with the characterization of the statistical dependence between the components of random elasticity tensors that exhibit some given material symmetries. Such an issue has historically been addressed with no particular reliance on probabilistic reasoning, ending up in almost al...

Guilleminot, J.; Soize, C.

146

On homogenization of space-time dependent and degenerate random flows II  

CERN Multimedia

We study the long time behavior (homogenization) of a diffusion in random medium with time and space dependent coefficients. The diffusion coefficient may degenerate. In Stochastic Process. Appl. (2007) (to appear), an invariance principle is proved for the critical rescaling of the diffusion. Here, we generalize this approach to diffusions whose space-time scaling differs from the critical one.

Rhodes, Rmi

2008-01-01

147

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 ?- 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; C. Stefanovic; N. Sekulovic; Z. Popovic; M. Stefanovic

2012-01-01

148

Tail Asymptotic of Sum and Product of Random Variables with Applications in the Theory of Extremes of Conditionally Gaussian Processes  

CERN Document Server

We consider two independent random variables with the given tail asymptotic (e.g. power or exponential). We find tail asymptotic for their sum and product. This is done by some cumbersome but purely technical computations and requires the use of the Laplace method for asymptotic of integrals. We also recall the results for asymptotic of a self-similar locally stationary centered Gaussian process plus a deterministic drift; and we find the asymptotic for the same probability after multiplying the drift by a random variable, which is independent of this process. Keywords: tail asymptotic, Laplace method, self-similar processes, Gaussian processes, locally stationary processes.

Sarantsev, Andrey

2011-01-01

149

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

CERN Multimedia

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, Galle; Prieur, Clmentine

2011-01-01

150

Scale-dependent measurement and analysis of ground surface temperature variability in alpine terrain  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Measurements of environmental variables are often used to validate and calibrate physically-based models. Depending on their application, the models are used at different scales, ranging from few meters to tens of kilometers. Environmental variables can vary strongly within the grid cells of these m...

Gubler, S; Fiddes, J; Keller, M; Gruber, S

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.

Dug Hun Hong; Seok Yoon Hwang

1999-01-01

152

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

CERN Multimedia

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 as a dependency-graph functional and the limit is evaluated through a special law of large numbers for stabilizing graph functionals. The exponent is analyzed for different values of the variance ratio and correlation. It is found that a more correlated GMRF has a higher exponent at low values of the variance ratio whereas the situation is reversed at high values of the variance ratio.

Anandkumar, Animashree; Swami, Ananthram

2007-01-01

153

Time-Dependent Random Walks and the Theory of Complex Adaptive Systems  

Science.gov (United States)

Motivated by novel results in the theory of complex adaptive systems, we analyze the dynamics of random walks in which the jumping probabilities are time dependent. We determine the survival probability in the presence of an absorbing boundary. For an unbiased walk, the survival probability is maximized in the case of large temporal oscillations in the jumping probabilities. On the other hand, a random walker who is drifted towards the absorbing boundary performs best with a constant jumping probability. We use the results to reveal the underlying dynamics responsible for the phenomenon of self-segregation and clustering observed in the evolutionary minority game.

Hod, Shahar

2003-03-01

154

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

155

A Classification Study of Respiratory Syncytial Virus (RSV) Inhibitors by Variable Selection with Random Forest  

Directory of Open Access Journals (Sweden)

Full Text Available Experimental pEC50s for 216 selective respiratory syncytial virus (RSV) inhibitors are used to develop classification models as a potential screening tool for a large library of target compounds. Variable selection algorithm coupled with random forests (VS-RF) is used to extract the physicochemical features most relevant to the RSV inhibition. Based on the selected small set of descriptors, four other widely used approaches, i.e., support vector machine (SVM), Gaussian process (GP), linear discriminant analysis (LDA) and k nearest neighbors (kNN) routines are also employed and compared with the VS-RF method in terms of several of rigorous evaluation criteria. The obtained results indicate that the VS-RF model is a powerful tool for classification of RSV inhibitors, producing the highest overall accuracy of 94.34% for the external prediction set, which significantly outperforms the other four methods with the average accuracy of 80.66%. The proposed model with excellent prediction capacity from internal to external quality should be important for screening and optimization of potential RSV inhibitors prior to chemical synthesis in drug development.

Ming Hao; Yan Li; Yonghua Wang; Shuwei Zhang

2011-01-01

156

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

2008-01-01

157

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

2005-01-01

158

On Chung-Teicher Type Strong Law of Large Numbers for ρ∗-Mixing Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper the classical strong laws of large number of Kolmogorov, Chung, and Teicher for independent random variables were generalized on the case of ρ∗-mixing sequence. The main result was applied to obtain a Marcinkiewicz SLLN.

Anna Kuczmaszewska

2008-01-01

159

Limit theorems for subcritical Branching Process in Random Environment depending on the initial number of particles  

CERN Multimedia

Asymptotic behaviors for subcritical Branching Processes in Random Environment (BPRE) starting with several particles depend on whether the BPRE is strongly subcritical (SS), intermediate subcritical (IS) or weakly subcritical (WS) (see \\cite{bpree}). Descendances of particles for BPRE are not independent. In the (SS+IS) case, the asymptotic probability of survival is proportional to the initial number of particles. And conditionally on the survival of the population, only one initial particle survives a.s. These two properties do not hold in the (WS) case and different asymptotics are established, which require to prove new results on random walk with negative drift. We provide an interpretation of these results by characterizing the sequence of environments selected when we condition by the survival of particles. This also raises the problem of the dependence of the Yaglom quasistationary distributions on the initial number of particles and the asymptotic behavior of the Q-process associated with a subcriti...

Bansaye, Vincent

2008-01-01

160

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.

YUYU SURYASARI POERBA; DIYAH MARTANTI

2008-01-01

 
 
 
 
161

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

UK PubMed Central (United Kingdom)

OBJECTIVE: Preclinical findings suggest that the over-the-counter supplement N-acetylcysteine (NAC), via glutamate modulation in the nucleus accumbens, holds promise as a pharmacotherapy for substance dependence. The authors investigated NAC as a novel cannabis cessation treatment in adolescents, a vulnerable group for whom existing treatments have shown limited efficacy. METHOD: In an 8-week double-blind randomized placebo-controlled trial, treatment-seeking cannabis-dependent adolescents (ages 15-21 years; N=116) received NAC (1200 mg) or placebo twice daily as well as a contingency management intervention and brief (<10 minutes) weekly cessation counseling. The primary efficacy measure was the odds of negative weekly urine cannabinoid test results during treatment among participants receiving NAC compared with those receiving placebo, in an intent-to-treat analysis. The primary tolerability measure was frequency of adverse events, compared by treatment group. RESULTS: Participants receiving NAC had more than twice the odds, compared with those receiving placebo, of having negative urine cannabinoid test results during treatment (odds ratio=2.4, 95% CI=1.1-5.2). Exploratory secondary abstinence outcomes favored NAC but were not statistically significant. NAC was well tolerated, with minimal adverse events. CONCLUSIONS: This is the first randomized controlled trial of pharmacotherapy for cannabis dependence in any age group to yield a positive primary cessation outcome in an intent-to-treat analysis. Findings support NAC as a pharmacotherapy to complement psychosocial treatment for cannabis dependence in adolescents.

Gray KM; Carpenter MJ; Baker NL; DeSantis SM; Kryway E; Hartwell KJ; McRae-Clark AL; Brady KT

2012-08-01

162

Interspacing dependence of spin-dependent variable range hopping for cold-pressed Fe3O4 nanoparticles  

Science.gov (United States)

The influence of the contact between monodisperse Fe3O4 nanoparticles (NPs) on the spin-dependent transport mechanism has been investigated by only changing the cold-press pressures from 20.0 MPa to 5.0 GPa. For the sample cold-pressed under 20.0 MPa, the temperature dependence of resistivity ?-T curve is best fitted by the log ? ~ T-1/2 relation, suggesting the Efros's variable range hopping (VRH) mechanism, while the ?-T curves of the samples cold-pressed under 1.0 GPa to 5.0 GPa can be best fit with the relation of log ? ~ T-1/4, revealing the Mott's VRH mechanism. The different mechanisms are related to the interspacing dependence of charging energy and exchange energy between NPs. Monte Carlo simulations indicated that the charging energy plays a dominant role in the former mechanism, while the spin-dependent exchange energy is dominated in the latter one.

Song, Ning-Ning; Yang, Hai-Tao; Li, Fei-Ye; Li, Zi-An; Han, Wei; Ren, Xiao; Luo, Yi; Wang, Xian-Cheng; Jin, Chang-Qing; Zhang, Xiang-Qun; Cheng, Zhao-Hua

2013-05-01

163

Punishment-induced behavioral and neurophysiological variability reveals dopamine-dependent selection of kinematic movement parameters.  

UK PubMed Central (United Kingdom)

Action selection describes the high-level process that selects between competing movements. In animals, behavioral variability is critical for the motor exploration required to select the action that optimizes reward and minimizes cost/punishment and is guided by dopamine (DA). The aim of this study was to test in humans whether low-level movement parameters are affected by punishment and reward in ways similar to high-level action selection. Moreover, we addressed the proposed dependence of behavioral and neurophysiological variability on DA and whether this may underpin the exploration of kinematic parameters. Participants performed an out-and-back index finger movement and were instructed that monetary reward and punishment were based on its maximal acceleration (MA). In fact, the feedback was not contingent on the participant's behavior but predetermined. Blocks highly biased toward punishment were associated with increased MA variability relative to blocks either with reward or without feedback. This increase in behavioral variability was positively correlated with neurophysiological variability, as measured by changes in corticospinal excitability with transcranial magnetic stimulation over the primary motor cortex. Following the administration of a DA antagonist, the variability associated with punishment diminished and the correlation between behavioral and neurophysiological variability no longer existed. Similar changes in variability were not observed when participants executed a predetermined MA, nor did DA influence resting neurophysiological variability. Thus, under conditions of punishment, DA-dependent processes influence the selection of low-level movement parameters. We propose that the enhanced behavioral variability reflects the exploration of kinematic parameters for less punishing, or conversely more rewarding, outcomes.

Galea JM; Ruge D; Buijink A; Bestmann S; Rothwell JC

2013-02-01

164

Pilot randomized trial of bupropion for adolescent methamphetamine abuse/dependence.  

UK PubMed Central (United Kingdom)

PURPOSE: To perform a pilot clinical trial of bupropion for methamphetamine abuse/dependence among adolescents. METHODS: Nineteen adolescents with methamphetamine abuse (n= 2) or dependence (n= 17) were randomly assigned to bupropion SR 150 mg twice daily or placebo for 8 weeks with outpatient substance abuse counseling. RESULTS: Bupropion was well-tolerated except for one female in the bupropion group who was hospitalized for suicidal ideation during a methamphetamine relapse. Adolescents receiving bupropion and females provided significantly fewer methamphetamine-free urine tests compared to participants receiving placebo (p= .043) and males (p= .005) respectively. CONCLUSIONS: Results do not support the feasibility of additional trials of bupropion for adolescent methamphetamine abuse/dependence. Future studies should investigate the influence of gender on adolescent methamphetamine abuse and treatment outcomes.

Heinzerling KG; Gadzhyan J; van Oudheusden H; Rodriguez F; McCracken J; Shoptaw S

2013-04-01

165

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

166

Numerical Simulation of Blinking Quantum dot Based on Temperature Dependence 3-Dimensional Levy Random Walk  

Directory of Open Access Journals (Sweden)

Full Text Available Blinking statistics of quantum dot has attracted much attraction in recent years. Various experiments were conducted and various theories have been given to explain this phenomenon. However, the problem is not yet resolved. The weak temperature dependence of the power law parameters have complicated the phenomena. We have simulated the blinking statistics of quantum dot based on the random walk model. We have shown that three-dimensional biased Levy random walk of electrons, the bias being the Columbic interaction between electrons and ionized atoms can explain the observed experimental results. We have simulated the blinking properties of quantum dots in a broad temperature range (10-300 K). The distributions exhibit power law behavior for a wide range of temperature, but the power law parameter increases marginally with temperature. The trend of change is independent of the size of the quantum dots as confirmed from the simulation.

Anita Sharma; M.N. Bapat

2011-01-01

167

Classical and Quantum Action-Phase Variables for Time-Dependent Oscillators  

CERN Multimedia

For a time-dependent classical quadratic oscillator we introduce pairs of real and complex invariants that are linear in position and momentum. Each pair of invariants realize explicitly a canonical transformation from the phase space to the invariant space, in which the action-phase variables are defined. We find the action operator for the time-dependent oscillator via the classical-quantum correspondence. Candidate phase operators conjugate to the action operator are discussed, but no satisfactory ones are found.

Kim, S P; Kim, Sang Pyo; Page, Don N.

2001-01-01

168

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

UK PubMed Central (United Kingdom)

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.

Zhou Y; Ghim YS; Fard A; Davies A

2013-08-01

169

Double-blind, randomized placebo-controlled clinical trial of benfotiamine for severe alcohol dependence.  

UK PubMed Central (United Kingdom)

Alcohol dependence is associated with severe nutritional and vitamin deficiency. Vitamin B1 (thiamine) deficiency erodes neurological pathways that may influence the ability to drink in moderation. The present study examines tolerability of supplementation using the high-potency thiamine analog, benfotiamine (BF), and BF's effects on alcohol consumption in severely affected, self-identified, alcohol dependent subjects. A randomized, double-blind, placebo-controlled trial was conducted on 120 non-treatment seeking, actively drinking, alcohol dependent men and women volunteers (mean age=47 years) from the Kansas City area who met DSM-IV-TR criteria for current alcohol dependence. Subjects were randomized to receive 600mg benfotiamine or placebo (PL) once daily by mouth for 24 weeks with 6 follow-up assessments scheduled at 4 week intervals. Side effects and daily alcohol consumption were recorded. Seventy (58%) subjects completed 24 weeks of study (N=21 women; N=49 men) with overall completion rates of 55% (N=33) for PL and 63% (N=37) for BF groups. No significant adverse events were noted and alcohol consumption decreased significantly for both treatment groups. Alcohol consumption decreased from baseline levels for 9 of 10 BF treated women after 1 month of treatment compared with 2 of 11 on PL. Reductions in total alcohol consumption over 6 months were significantly greater for BF treated women (BF: N=10, -611380 standard drinks; PL: N=11, -159562 standard drinks, p-value=0.02). BF supplementation of actively drinking alcohol dependent men and women was well-tolerated and may discourage alcohol consumption among women. The results do support expanded studies of BF treatment in alcoholism.

Manzardo AM; He J; Poje A; Penick EC; Campbell J; Butler MG

2013-08-01

170

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

171

Cryptography based on chaotic random maps with position dependent weighting probabilities  

Energy Technology Data Exchange (ETDEWEB)

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.

Behnia, S. [Department of Physics, IAU, Urmia (Iran, Islamic Republic of)], E-mail: s.behnia@iaurmia.ac.ir; Akhshani, A. [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Ahadpour, S. [Department of Physics, Mohaghegh Ardabili University, Ardabil (Iran, Islamic Republic of); Akhavan, A. [School of Computer Science, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Mahmodi, H. [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia)

2009-04-15

172

Cryptography based on chaotic random maps with position dependent weighting probabilities  

International Nuclear Information System (INIS)

[en]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

173

Incorporating Variability Dependency Graphs Into Multi-Paradigm Design With Feature Modeling  

UK PubMed Central (United Kingdom)

Multi-paradigm design enables to map the structures of an application (problem) domain to the appropriate structures (paradigms) supported by a solution domain (programming language). Both application and solution domain, partitioned into subdomains, can be represented as feature models, which is better than the table representation used in the original multiparadigm design. Feature modeling is not capable of expressing all the important dependencies between the subdomains. Therefore the application of variability dependency graphs, used in the original multiparadigm design, in addition to feature modeling is proposed here. Since diagrams similar to variability dependency graphs are used in generative programming, as well as feature modeling, multi-paradigm design and generative programming are briefly compared.

Valentino Vrani

174

Assessing Heart Rate Variability Using A 12 lead ECG In Patients With Alcohol Dependence Syndrome  

Directory of Open Access Journals (Sweden)

Full Text Available Heavy or hazardous drinking is associated with an increased risk of cardiac morbidity and mortality and this has been attributed to abnormalities in cardiac autonomic regulation. Current study aimed to assess the role of simple indices derived from 12 lead ECG in subjects with chronic alcohol dependence. Data suggested that alcohol group had significantly lower 12 lead ECG derived RR variability compared to age and gender matched controls. Study further supports the implication of 12 lead derived RR variability indices in various clinical settings.

S. Sucharita; Raynette Clark; Priya Sreedaran; K. Srinivasan

2009-01-01

175

Nutrition education intervention for dependent patients: protocol of a randomized controlled trial  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Malnutrition in dependent patients has a high prevalence and can influence the prognosis associated with diverse pathologic processes, decrease quality of life, and increase morbidity-mortality and hospital admissions. The aim of the study is to assess the effect of an educational intervention for caregivers on the nutritional status of dependent patients at risk of malnutrition. Methods/Design Intervention study with control group, randomly allocated, of 200 patients of the Home Care Program carried out in 8 Primary Care Centers (Spain). These patients are dependent and at risk of malnutrition, older than 65, and have caregivers. The socioeconomic and educational characteristics of the patient and the caregiver are recorded. On a schedule of 0612 months, patients are evaluated as follows: Mini Nutritional Assessment (MNA), food intake, dentures, degree of dependency (Barthel test), cognitive state (Pfeiffer test), mood status (Yesavage test), and anthropometric and serum parameters of nutritional status: albumin, prealbumin, transferrin, haemoglobin, lymphocyte count, iron, and ferritin. Prior to the intervention, the educational procedure and the design of educational material are standardized among nurses. The nurses conduct an initial session for caregivers and then monitor the education impact at home every month (4 visits) up to 6 months. The North American Nursing Diagnosis Association (NANDA) methodology will be used. The investigators will study the effect of the intervention with caregivers on the patients nutritional status using the MNA test, diet, anthropometry, and biochemical parameters. Bivariate normal test statistics and multivariate models will be created to adjust the effect of the intervention. The SPSS/PC program will be used for statistical analysis. Discussion The nutritional status of dependent patients has been little studied. This study allows us to know nutritional risk from different points of view: diet, anthropometry and biochemistry in dependent patients at nutritional risk and to assess the effect of a nutritional education intervention. The design with random allocation, inclusion of all patients, validated methods, caregivers education and standardization between nurses allows us to obtain valuable information about nutritional status and prevention. Trial Registration number Clinical Trial Registration-URL: http://www.clinicaltrials.gov. Unique identifier: NCT01360775

Arija Victoria; Martn Nria; Canela Teresa; Anguera Carme; Castelao Ana I; Garca-Barco Montserrat; Garca-Campo Antoni; Gonzlez-Bravo Ana I; Lucena Carme; Martnez Teresa; Fernndez-Barrs Silvia; Pedret Roser; Badia Waleska; Basora Josep

2012-01-01

176

Aripiprazole for the treatment of methamphetamine dependence: a randomized, double-blind, placebo-controlled trial.  

UK PubMed Central (United Kingdom)

AIMS: To test aripiprazole for efficacy in decreasing use in methamphetamine-dependent adults, compared to placebo. DESIGN: Participants were randomized to receive 12 weeks of aripiprazole or placebo, with a 3-month follow-up and a platform of weekly 30-minute substance abuse counseling. SETTING: The trial was conducted from January 2009 to March 2012 at the San Francisco Department of Public Health. PARTICIPANTS: Ninety actively using, methamphetamine-dependent, sexually active adults were recruited from community venues. MEASUREMENTS: The primary outcome was regression estimated reductions in weekly methamphetamine-positive urines. Secondary outcomes were study medication adherence [by self-report and medication event monitoring systems (MEMS)], sexual risk behavior and abstinence from methamphetamine. FINDINGS: Participant mean age was 38.7 years, 87.8% were male, 50.0% white, 18.9% African American, and 16.7% Latino. Eighty-three per cent of follow-up visits and final visits were completed. By intent-to-treat, participants assigned to aripiprazole had similar reductions in methamphetamine-positive urines as participants assigned to placebo [risk ratio (RR) 0.88, 95% confidence interval (CI): 0.66-1.19, P = 0.41]. Urine positivity declined from 73% (33 of 45 participants) to 45% (18 of 40) in the placebo arm and from 77% (34 of 44) to 44% (20 of 35) in the aripiprazole arm. Adherence by MEMS and self-report was 42 and 74%, respectively, with no significant difference between arms (MEMS P = 0.31; self-report P = 0.17). Most sexual risk behaviors declined similarly among participants in both arms (all P > 0.05). There were no serious adverse events related to study drug, although participants randomized to aripiprazole reported more akathisia, fatigue and drowsiness (P < 0.05). CONCLUSION: Compared with placebo, aripiprazole did not reduce methamphetamine use significantly among actively using, dependent adults.

Coffin PO; Santos GM; Das M; Santos DM; Huffaker S; Matheson T; Gasper J; Vittinghoff E; Colfax GN

2013-04-01

177

Chronic care management for dependence on alcohol and other drugs: the AHEAD randomized trial.  

UK PubMed Central (United Kingdom)

IMPORTANCE: People with substance dependence have health consequences, high health care utilization, and frequent comorbidity but often receive poor-quality care. Chronic care management (CCM) has been proposed as an approach to improve care and outcomes. OBJECTIVE: To determine whether CCM for alcohol and other drug dependence improves substance use outcomes compared with usual primary care. DESIGN, SETTING, AND PARTICIPANTS: The AHEAD study, a randomized trial conducted among 563 people with alcohol and other drug dependence at a Boston, Massachusetts, hospital-based primary care practice. Participants were recruited from September 2006 to September 2008 from a freestanding residential detoxification unit and referrals from an urban teaching hospital and advertisements; 95% completed 12-month follow-up. INTERVENTIONS: Participants were randomized to receive CCM (n=282) or no CCM (n=281). Chronic care management included longitudinal care coordinated with a primary care clinician; motivational enhancement therapy; relapse prevention counseling; and on-site medical, addiction, and psychiatric treatment, social work assistance, and referrals (including mutual help). The no CCM (control) group received a primary care appointment and a list of treatment resources including a telephone number to arrange counseling. MAIN OUTCOMES AND MEASURES: The primary outcome was self-reported abstinence from opioids, stimulants, or heavy drinking. Biomarkers were secondary outcomes. RESULTS: There was no significant difference in abstinence from opioids, stimulants, or heavy drinking between the CCM (44%) and control (42%) groups (adjusted odds ratio, 0.84; 95% CI, 0.65-1.10; P=.21). No significant differences were found for secondary outcomes of addiction severity, health-related quality of life, or drug problems. No subgroup effects were found except among those with alcohol dependence, in whom CCM was associated with fewer alcohol problems (mean score, 10 vs 13; incidence rate ratio, 0.85; 95% CI, 0.72-1.00; P=.048). CONCLUSIONS AND RELEVANCE: Among persons with alcohol and other drug dependence, CCM compared with a primary care appointment but no CCM did not increase self-reported abstinence over 12 months. Whether more intensive or longer-duration CCM is effective requires further investigation. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00278447.

Saitz R; Cheng DM; Winter M; Kim TW; Meli SM; Allensworth-Davies D; Lloyd-Travaglini CA; Samet JH

2013-09-01

178

A randomized trial of concurrent versus delayed smoking intervention for patients in alcohol dependence treatment.  

UK PubMed Central (United Kingdom)

OBJECTIVE: Fear of jeopardizing drinking outcomes has resulted in a reluctance to treat tobacco dependence concurrently with alcohol dependence, in spite of the high prevalence of smoking among patients with alcohol dependence. The objective of this study was to compare the effects of smoking treatment and intensive treatment for alcohol dependence, delivered concurrently, with delayed smoking treatment on smoking and alcohol use. METHOD: For the study, 1,943 patients in intensive treatment for alcohol dependence or abuse were screened for participation. Of these, 499 smokers were enrolled and randomized to concurrent (during alcohol treatment) or delayed (6 months later) smoking intervention. The smoking intervention included individual behavioral counseling and nicotine replacement. The main smoking outcome measure was 7-day point prevalent tobacco abstinence, and the main drinking outcome was 6-month prolonged abstinence from alcohol; both measured 18 months after study enrollment. RESULTS: Participants in the concurrent group were more likely to participate in smoking treatment than those in the delayed group (78.5% vs 64.5%, p = .005), but there was no significant difference in cessation rates at 18 months (12.4% vs 13.7%). Prolonged, 6-month abstinence from alcohol was worse in the concurrent group than in the delayed group at 6, 12 and 18 months (41% vs 56%, p =.001; 33% vs 42%,p = .06; 41% vs 48%, p = .14, respectively), and 30-day prolonged alcohol abstinence was also worse in the concurrent treatment group (51% vs 64%, p = .004; 46% vs 53%, p = .11; 48% vs 60%, p = .01, respectively). CONCLUSIONS: These data show that patients in alcohol treatment are interested in smoking cessation, participate in treatment and demonstrate success; but there was no benefit of concurrent treatment. Drinking outcomes were worse with concurrent tobacco treatment. These findings suggest that smoking cessation intervention should be provided to patients after intensive alcohol treatment; however, the data require confirmation because they are not consistent with the existing literature.

Joseph AM; Willenbring ML; Nugent SM; Nelson DB

2004-11-01

179

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 Womens 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; Demorest Louise C; Kelly Anne; Thiessen Paul; Abrahams Ron

2012-01-01

180

Contribution to the application of the random vibration theory to the seismic analysis of structures via state variables  

International Nuclear Information System (INIS)

Several problems related to the application of the theory of random by means of state variables are studied. The well-known equations that define the propagation of the mean and the variance for linear and non-linear systems are first presented. The Monte Carlo method is next resorted to in order to determine the applicability of the hypothesis of a normally distributed output in case of linear systems subjected to non-Gaussian excitations. Finally, attention is focused on the properties of linear filters and modulation functions proposed to simulate seismic excitations as non stationary random processes. Acceleration spectra obtained by multiplying rms spectra by a constant factor are compared with design spectra suggested by several authors for various soil conditions. In every case, filter properties are given. (Author).

1979-01-01

 
 
 
 
181

Method of nuclear reactor control using a variable temperature load dependent set point  

International Nuclear Information System (INIS)

A method and apparatus for controlling a nuclear reactor in response to a variable average reactor coolant temperature set point is disclosed. The set point is dependent upon percent of full power load demand. A manually-actuated ''droop mode'' of control is provided whereby the reactor coolant temperature is allowed to drop below the set point temperature a predetermined amount wherein the control is switched from reactor control rods exclusively to feedwater flow

1982-01-01

182

Method of nuclear reactor control using a variable temperature load dependent set point  

Energy Technology Data Exchange (ETDEWEB)

A method and apparatus for controlling a nuclear reactor in response to a variable average reactor coolant temperature set point is disclosed. The set point is dependent upon percent of full power load demand. A manually-actuated ''droop mode'' of control is provided whereby the reactor coolant temperature is allowed to drop below the set point temperature a predetermined amount wherein the control is switched from reactor control rods exclusively to feedwater flow.

Kelly, J.J.; Rambo, G.E.

1982-04-27

183

Advancing density waves and phase transitions in a velocity dependent randomization traffic cellular automaton  

CERN Document Server

Within the class of stochastic cellular automata models of traffic flows, we look at the velocity dependent randomization variant (VDR-TCA) whose parameters take on a specific set of extreme values. These initial conditions lead us to the discovery of the emergence of four distinct phases. Studying the transitions between these phases, allows us to establish a rigorous classification based on their tempo-spatial behavioral characteristics. As a result from the system's complex dynamics, its flow-density relation exhibits a non-concave region in which forward propagating density waves are encountered. All four phases furthermore share the common property that moving vehicles can never increase their speed once the system has settled into an equilibrium.

Maerivoet, S; Maerivoet, Sven; Moor, Bart De

2004-01-01

184

A modified NaSch model with density-dependent randomization for traffic flow  

Science.gov (United States)

Based on the Nagel-Schreckenberg (NaSch) model of traffic flow, a modified cellular automaton (CA) traffic model with the density-dependent randomization (abbreviated as the DDR model) is proposed to simulate traffic flow. The fundamental diagram obtained by simulation shows the ability of this modified NaSch model to capture the essential features of traffic flow, e.g., synchronized flow, metastable state, hysteresis and phase separation at higher densities. Comparisons are made between this DDR model and the NaSch model, also between this DDR model and the VDR model. And the underlying mechanism is analyzed. All these results indicate that the presented model is reasonable and more realistic.

Zhu, H. B.; Ge, H. X.; Dong, L. Y.; Dai, S. Q.

2007-05-01

185

Spatiotemporal Dependency of Age-Related Changes in Brain Signal Variability.  

UK PubMed Central (United Kingdom)

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.

McIntosh AR; Vakorin V; Kovacevic N; Wang H; Diaconescu A; Protzner AB

2013-02-01

186

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

2013-02-01

187

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

CERN Multimedia

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

188

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

CERN Document Server

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; Smarandache, Florentin

2010-01-01

189

Variable selection for discriminant analysis with Markov random field priors for the analysis of microarray data  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Motivation: Discriminant analysis is an effective tool for the classification of experimental units into groups. Here, we consider the typical problem of classifying subjects according to phenotypes via gene expression data and propose a method that incorporates variable selection into the inferenti...

Stingo, Francesco C.; Vannucci, Marina

190

Existence and Uniqueness Conditions for the Maximum Likelihood Solution In Regression Models For Correlated Bernoulli Random Variables  

Directory of Open Access Journals (Sweden)

Full Text Available We give sufficient and necessary conditions for the existence of the maximum likelihood estimate in a class of multivariate regression models for correlated Bernoulli random variables. The models use the concept of threshold crossing technique of an underlying multivariate latent variable with univariate components formulated as a linear regression model. However, in place of their Gaussian assumptions, any specified distribution with a strictly increasing cumulative distribution function is allowed for error terms. A well known member of this class of models is the multivariate probit model. We show that our results are a generalization of the concepts of separation and overlap of Albert and Anderson for the study of the existence of maximum likelihood estimate in generalized linear models. Implications of our findings are illustrated through some hypothetical examples.

David Todem; KyungMann Kim

2007-01-01

191

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

2004-01-01

192

On angular momentum and parity dependence of nuclear level densities in a simple random sampling approach  

Energy Technology Data Exchange (ETDEWEB)

Based on simple random sampling (SRS), we propose a Monte Carlo method for the faster computation of the smoothed part of the density of nuclear states. To test the applicability of the SRS approach we study in this framework the excitation energy (E), angular momentum (J) and parity dependence of nuclear level densities for an independent particle system. As an illustrative example, we consider a pf-shell nucleus, {sup 48}Cr. It is found that the values of a few lower order moments for the state density I(E) calculated using SRS and combinatorial (or direct counting) methods are almost the same and a locally smoothed part of the state density can be constructed using these moments in a univariate Edgeworth expansion. We calculate the energy dependent spin-cutoff factor and parity asymmetry and find that for both cases the SRS approach works quite well. We use the SRS moments to construct different forms of the bivariate distribution for I(E,M) (M is the z-component of J) namely (a) a bivariate Edgeworth expansion, (b) a product of the univariate Edgeworth expansion (I(E)) and a Gaussian form for conditional M distribution I(M vertical stroke E) and (c) a product of the univariate Edgeworth expansions for both I(E) and I(M vertical stroke E) and compare the resulting fixed-J level density I{sub l}(E,J) with the corresponding combinatorial results. (orig.).

Majumdar, D. [Institute of Physics, Bhubaneswar (India); Agrawal, B.K. [Institute of Physics, Bhubaneswar (India); Kataria, S.K. [Bhabha Atomic Research Centre, Bombay (India). Nuclear Physics Div.

1996-01-29

193

Demographic variability and density-dependent dynamics of a free-ranging rhesus macaque population.  

Science.gov (United States)

Density-dependence is hypothesized as the major mechanism of population regulation. However, the lack of long-term demographic data has hampered the use of density-dependent models in nonhuman primates. In this study, we make use of the long-term demographic data from Cayo Santiago's rhesus macaques to parameterize and analyze both a density-independent and a density-dependent population matrix model, and compare their projections with the observed population changes. We also employ a retrospective analysis to determine how variance in vital rates, and covariance among them, contributed to the observed variation in long-term fitness across different levels of population density. The population exhibited negative density-dependence in fertility and the model incorporating this relationship accounted for 98% of the observed population dynamics. Variation in survival and fertility of sexually active individuals contributed the most to the variation in long-term fitness, while vital rates displaying high temporal variability exhibited lower sensitivities. Our findings are novel in describing density-dependent dynamics in a provisioned primate population, and in suggesting that selection is acting to lower the variance in the population growth rate by minimizing the variation in adult survival at high density. Because density-dependent mechanisms may become stronger in wild primate populations due to increasing habitat loss and food scarcity, our study demonstrates that it is important to incorporate variation in population size, as well as demographic variability into population viability analyses for a better understanding of the mechanisms regulating the growth of primate populations. Am. J. Primatol. 75:1152-1164, 2013. 2013 Wiley Periodicals, Inc. PMID:23847126

Hernndez-Pacheco, Raisa; Rawlins, Richard G; Kessler, Matthew J; Williams, Lawrence E; Ruiz-Maldonado, Tagrid M; Gonzlez-Martnez, Janis; Ruiz-Lambides, Angelina V; Sabat, Alberto M

2013-07-11

194

Variables involved in the cue modulation of the startle reflex in alcohol-dependent patients.  

UK PubMed Central (United Kingdom)

Cue modulation of the startle reflex is a paradigm that has been used to understand the emotional mechanisms involved in alcohol dependence. Attenuation of the startle reflex has been demonstrated when alcohol-dependent subjects are exposed to alcohol-related stimuli. However, the role of clinical variables on the magnitude of this response is unknown. The objective of this study was to determine the relationship between a number of clinical variables-severity of alcoholism, family history of alcoholism (FHA+), personality traits related to the sensitivity to reward-and the startle reflex response when subjects with alcohol dependence were viewing alcohol-related cues. After detoxification, 98 participants completed self-report instruments and had eye blink electromyograms measured to acoustic startle probes [100-millisecond burst of white noise at 95 dB(A)] while viewing alcohol-related pictures, and standardised appetitive, aversive and neutral control scenes. Ninety-eight healthy controls were also assessed with the same instruments. There were significant differences on alcohol-startle magnitude between patients and controls. Comparisons by gender showed that women perceived alcohol cues and appetitive cues more appetitive than men. Male and female patients showed more appetitive responses to alcohol cues when compared with their respective controls. Our patients showed an appetitive effect of alcohol cues that was positively related to severity of alcohol dependence, sensitivity to reward and a FHA+. The data confirmed that the pattern of the modulation of the acoustic startle reflex reveals appetitive effects of the alcohol cues and extended it to a variety of clinical variables.

Rubio G; Borrell J; Jimnez M; Jurado R; Grsser SM; Heinz A

2013-01-01

195

Variables involved in the cue modulation of the startle reflex in alcohol-dependent patients.  

Science.gov (United States)

Cue modulation of the startle reflex is a paradigm that has been used to understand the emotional mechanisms involved in alcohol dependence. Attenuation of the startle reflex has been demonstrated when alcohol-dependent subjects are exposed to alcohol-related stimuli. However, the role of clinical variables on the magnitude of this response is unknown. The objective of this study was to determine the relationship between a number of clinical variables-severity of alcoholism, family history of alcoholism (FHA+), personality traits related to the sensitivity to reward-and the startle reflex response when subjects with alcohol dependence were viewing alcohol-related cues. After detoxification, 98 participants completed self-report instruments and had eye blink electromyograms measured to acoustic startle probes [100-millisecond burst of white noise at 95 dB(A)] while viewing alcohol-related pictures, and standardised appetitive, aversive and neutral control scenes. Ninety-eight healthy controls were also assessed with the same instruments. There were significant differences on alcohol-startle magnitude between patients and controls. Comparisons by gender showed that women perceived alcohol cues and appetitive cues more appetitive than men. Male and female patients showed more appetitive responses to alcohol cues when compared with their respective controls. Our patients showed an appetitive effect of alcohol cues that was positively related to severity of alcohol dependence, sensitivity to reward and a FHA+. The data confirmed that the pattern of the modulation of the acoustic startle reflex reveals appetitive effects of the alcohol cues and extended it to a variety of clinical variables. PMID:21967507

Rubio, Gabriel; Borrell, Jos; Jimnez, Mnica; Jurado, Rosa; Grsser, Sabine M; Heinz, Andreas

2011-10-04

196

On the weak law of large numbers for normed weighted sums of I.I.D. random variables  

Directory of Open Access Journals (Sweden)

Full Text Available For weighted sums ∑j=1najYj of independent and identically distributed random variables {Yn,n≥1}, a general weak law of large numbers of the form (∑j=1najYj−νn)/bn→P0 is established where {νn,n≥1} and {bn,n≥1} are statable constants. The hypotheses involve both the behavior of the tail of the distribution of |Y1| and the growth behaviors of the constants {an,n≥1} and {bn,n≥1}. Moreover, a weak law is proved for weighted sums ∑j=1najYj indexed by random variables {Tn,n≥1}. An example is presented wherein the weak law holds but the strong law fails thereby generalizing a classical example.

Andr Adler; Andrew Rosalsky

1991-01-01

197

[Reincarceration of drug-dependent prisoners released into a therapeutic community, according to pretreatment variables].  

Science.gov (United States)

The main aim of this paper is to identify the criminal and penitentiary pretreatment variables associated with re-entry into prison in a population of drug-dependent inmates who had been released from different prisons in Castilla and Leon (Spain) to finish their prison sentence in a Therapeutic Community. The study population was 120 male inmates. The documentary sources consulted for collecting information were the prison record, the classification and treatment protocol and the social record. These official records were consulted in the Burgos Penitentiary, responsible for custody of the documents. Applying a descriptive statistical analysis with contingency tables, the pre-treatment variables that showed the strongest association with re-entry into prison were family prison history, total sentence exceeding five years, imprisonments prior to the sentence in question, change to a higher security level, revocation of parole, breach of the terms of a sentence, completion of sentence in prison and, especially, age at first entry into prison between 16 and 21 years. It was confirmed through logistic regression analysis that the variable age at which participants entered prison for the first time is critical, given the impact that prison can have at an early age. These results provide a profile of the drug-dependent inmate at greatest risk of making poor use of measures alternative to prison. PMID:23241720

Ramos Barbero, Victoria; Carcedo Gonzlez, Rodrigo J

2012-01-01

198

[Reincarceration of drug-dependent prisoners released into a therapeutic community, according to pretreatment variables].  

UK PubMed Central (United Kingdom)

The main aim of this paper is to identify the criminal and penitentiary pretreatment variables associated with re-entry into prison in a population of drug-dependent inmates who had been released from different prisons in Castilla and Leon (Spain) to finish their prison sentence in a Therapeutic Community. The study population was 120 male inmates. The documentary sources consulted for collecting information were the prison record, the classification and treatment protocol and the social record. These official records were consulted in the Burgos Penitentiary, responsible for custody of the documents. Applying a descriptive statistical analysis with contingency tables, the pre-treatment variables that showed the strongest association with re-entry into prison were family prison history, total sentence exceeding five years, imprisonments prior to the sentence in question, change to a higher security level, revocation of parole, breach of the terms of a sentence, completion of sentence in prison and, especially, age at first entry into prison between 16 and 21 years. It was confirmed through logistic regression analysis that the variable age at which participants entered prison for the first time is critical, given the impact that prison can have at an early age. These results provide a profile of the drug-dependent inmate at greatest risk of making poor use of measures alternative to prison.

Ramos Barbero V; Carcedo Gonzlez RJ

2012-01-01

199

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 Vitria, state of Esprito 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.

Patrcia M Pinto; Maria A Resende; Cristiane Y Koga-Ito; Miriam Tendler

2004-01-01

200

Variable selection for spatial random field predictors under a Bayesian mixed hierarchical spatial model.  

UK PubMed Central (United Kingdom)

A health outcome can be observed at a spatial location and we wish to relate this to a set of environmental measurements made on a sampling grid. The environmental measurements are covariates in the model but due to the interpolation associated with the grid there is an error inherent in the covariate value used at the outcome location. Since there may be multiple measurements made on different covariates there could be considerable uncertainty in the covariate values to be used. In this paper we examine a Bayesian approach to the interpolation problem and also a Bayesian solution to the variable selection issue. We present a series of simulations which outline the problem of recovering the true relationships, and also provide an empirical example.

Kim JI; Lawson AB; McDermott S; Aelion CM

2009-10-01

 
 
 
 
201

EDSS variability before randomization may limit treatment discovery in primary progressive MS.  

UK PubMed Central (United Kingdom)

BACKGROUND: Baseline Expanded Disability Status Scale (EDSS) is usually based on a single measurement. Here we evaluated whether using a baseline EDSS derived from two pre-treatment measurements improves the detection of progression events and the ability to demonstrate a therapeutic effect in delaying MS disability progression. METHODS: Real data from OLYMPUS, a phase II/III randomized, placebo-controlled trial of rituximab in patients with primary progressive multiple sclerosis (PPMS), as well as simulated data were analyzed. Several definitions of baseline EDSS were used to capture sustained disability progression (SDP) events. Variations in the EDSS were estimated by linear mixed-effect models. RESULTS: Selecting the higher of two baseline EDSS scores lowered the number of SDP events in both treatment groups, so decreasing sensitivity, and reduced the number of false SDP events, so increasing specificity. Conversely, selecting the lower of two baseline scores increased sensitivity but decreased specificity. Increased power (~7% based on the simulation study) was observed when the average of screening and Week 0 EDSS scores was used for baseline. CONCLUSION: Baseline EDSS derived from two pre-treatment EDSS measurements may enhance the ability of detecting a therapeutic effect in slowing disability progression in PPMS. This strategy could be implemented in future clinical trials of patients with MS.

Zhang J; Waubant E; Cutter G; Wolinsky JS; Glanzman R

2013-05-01

202

Infliximab plus azathioprine for steroid-dependent Crohn's disease patients: a randomized placebo-controlled trial.  

UK PubMed Central (United Kingdom)

BACKGROUND & AIMS: The aim of this study was to evaluate the usefulness of short-term infliximab combined with azathioprine (AZA) or 6-mercaptopurine (6-MP) in steroid-dependent Crohn's disease patients. METHODS: Patients with active disease despite prednisone given for more than 6 months were eligible and were stratified as follows: the failure stratum consisted of patients receiving AZA/6-MP at a stable dose for more than 6 months, and the naive stratum consisted of patients not treated previously with AZA/6-MP. Patients were randomized to infliximab 5 mg/kg or placebo at weeks 0, 2, and 6. All patients were treated with AZA/6-MP maintained at a stable dose throughout the 52 weeks of the study. The primary end point was remission off steroids at week 24. RESULTS: Among the 113 enrolled patients (55 in the failure stratum), 57 were assigned to infliximab. At week 24, the success rate (intent-to-treat analysis) was higher in the infliximab group than in the placebo group (57% vs 29%; P = .003); at weeks 12 and 52, the corresponding rates were 75% vs 38% (P < .001) and 40% vs 22% (P = .04), respectively. In each stratum, the success rate was significantly higher in the infliximab group at weeks 12 and 24, and a trend was found at week 52. In the failure stratum, only 27% of the patients in the infliximab group were still in remission off steroids, compared with 52% in the naive stratum. Steroid resistance was less common and the cumulative dose of prednisone was lower in the infliximab group. CONCLUSIONS: Infliximab plus AZA/6-MP is more effective than AZA/6-MP alone in steroid-dependent Crohn's disease patients.

Lmann M; Mary JY; Duclos B; Veyrac M; Dupas JL; Delchier JC; Laharie D; Moreau J; Cadiot G; Picon L; Bourreille A; Sobahni I; Colombel JF

2006-04-01

203

A voltage dependency analysis of the fixed kVp approach in variable part thickness radiography  

International Nuclear Information System (INIS)

[en]The dependency upon tube voltage of any accurate 'fixed kVp' approach to variable part thickness radiography is investigated by employing a theoretical model involving variation of the effective linear attenuation coefficient with tube voltage, for both ideal narrow and broad beam attenuation. Predicted increase rate ranges for tube charge (mAs) per unit thickness (centimetre) increment are presented as a function of tube voltage (kV) for several filtration cases. The increase rates range from 80 per cent per centimetre to approximately zero across the considered ranges of filtration, tube voltage, and beam area. The increase rates are seen to be heavily dependent upon the beam area/attenuation conditions at the image receptor and generally disagree significantly from the commonly used 25 per cent value of the standard approach. Copyright (2002) Australian Institute of Radiography

2002-01-01

204

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

International Nuclear Information System (INIS)

[en]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

1197-01-00

205

Efficacy of Initiating Tobacco Dependence Treatment in Inpatient Psychiatry: A Randomized Controlled Trial.  

UK PubMed Central (United Kingdom)

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. (Am J Public Health. Published online ahead of print August 15, 2013: e1-e9. doi:10.2105/AJPH.2013.301403).

Prochaska JJ; Hall SE; Delucchi K; Hall SM

2013-08-01

206

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

Science.gov (United States)

The effects of spatial confinements and smooth cutoffs of the waiting time distribution in continuous-time random walks 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 nonequilibrium ensemble. For both ensembles, it is shown that the time-averaged mean square displacement (TAMSD) exhibits a crossover from normal to anomalous diffusion due to the spatial confinement and this crossover does not vanish even in the long measurement time limit. Moreover, for the nonequilibrium ensemble, we show that the probability density function of the diffusion constant of TAMSD follows the transient Mittag-Leffler distribution, and that scatter in the TAMSD shows a clear transition from weak ergodicity breaking (an irreproducible regime) to ordinary ergodic behavior (a reproducible regime) as the measurement time increases. This convergence to ordinary ergodicity requires a long measurement time compared to common distributions such as the exponential distribution; in other words, the weak ergodicity breaking persists for a long time. In addition, it is shown that, aside from the TAMSD, a class of observables also exhibits this slow convergence to ergodicity. We also point out that, even though the system with the equilibrium initial ensemble shows no aging, its behavior is quite similar to that for the nonequilibrium ensemble.

Miyaguchi, Tomoshige; Akimoto, Takuma

2013-03-01

207

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)

1993-01-01

208

Does naltrexone treatment lead to depression? Findings from a randomized controlled trial in subjects with opioid dependence  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Objective: Dysphoria and depression have been cited as side effects of the opioid antagonist naltrexone. We aimed to assess whether depressive symptoms are a clinically relevant side effect in a population receiving naltrexone as a treatment for opioid dependence. Methods: We carried out a randomize...

Dean, Angela J.; Saunders, John B.; Jones, Rod T.; Young, Ross M.; Connor, Jason P.; Lawford, Bruce R.

209

Variable Temperature Time-Resolved Emission Spectra (TRES) Studies of Random Pyrene Urethane Methacrylate Copolymers with High Pyrene Incorporation.  

UK PubMed Central (United Kingdom)

A series of random copolyurethane methacrylate comb polymers with pyrene (Py) and 3-pentadecyl phenol (PDP) as pendant units were prepared by free radical polymerization. The pyrene labelling 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 temperature increased until ~ 50?C; beyond which non-radiative losses predominated. The TRES collected at 25?C 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 ~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 the TRES collected at 70?C, excimer emission centered at 455 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.

Kaushlendra K; Asha SK

2013-09-01

210

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

UK PubMed Central (United Kingdom)

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.

Samara A; Herbeth B; Aubert R; Berrahmoune H; Fumeron F; Siest G; Visvikis-Siest S

2010-01-01

211

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, Frdric; Siest, Grard; Visvikis-Siest, Sophie

2009-05-14

212

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

CERN Document Server

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

213

Lower limits for distributions of randomly stopped sums  

CERN Document Server

We study lower limits for the ratio $\\frac{\\bar{F^{*\\tau}}(x)}{\\bar F(x)}$ of tail distributions where $ F^{*\\tau}$ is a distribution of a sum of a random size $\\tau$ of i.i.d. random variables having a common distribution $F$, and a random variable $\\tau$ does not depend on summands.

Denisov, Denis; Korshunov, Dmitry

2007-01-01

214

Investigation of stochastic reactor noise models--A one-variable space-time-dependent model  

Energy Technology Data Exchange (ETDEWEB)

Using the Markovian description of stochastic processes, the fluctuations in pressurized water reactor cores (for example, temperature and bubble population fluctuations) are modeled. The model includes one-dimensional space and time dependence. Fluctuations are described with the help of a single stochastic variable N(z,t). Generally this approach is not satisfactory in practical problems, but in this way spatial effects can be investigated by a simple model. For this case, connections between moments of N(z,t) are derived. These moments are calculated both for transient and steady-state processes. Introducing spectral density functions in frequency and wave-number domains, a condition is given for the validity of the point model approach.

Mesko, L.; Kozma, R.

1984-09-01

215

Complexity of two-variable Dependence Logic and IF-Logic  

CERN Multimedia

We study the two-variable fragments D^2 and IF^2 of dependence logic and independence-friendly logic. We consider the satisfiability and finite satisfiability problems of these logics and show that for D^2, both problems are NEXPTIME-complete, whereas for IF^2, the problems are undecidable. We also show that D^2 is strictly less expressive than IF^2 and that already in D^2, equicardinality of two unary predicates and infinity can be expressed (the latter in the presence of a constant symbol). This is an extended version of a publication in the proceedings of the 26th Annual IEEE Symposium on Logic in Computer Science (LICS 2011).

Kontinen, Juha; Lohmann, Peter; Virtema, Jonni

2011-01-01

216

Influence of dimethylpolysiloxane addition to edible oils: dependence on the main variables of the frying process  

Directory of Open Access Journals (Sweden)

Full Text Available Experiments were carried out in the absence of food to define the influence of significant variables of the frying process, i.e. oil unsaturation, temperature, surface-to-oil volume ratio, type of heating and dimethylpolysiloxane (DMPS) addition. Special emphasis was placed on clarifying the action of the addition of low concentrations of DMPS to frying oils. From statistical evaluation based on the content of polar compounds, the strong influence of the variables surface-to-oil volume ratio, DMPS addition and oil unsaturation was deduced. However, changes due to 10C difference in temperature were not significant. Analysis of two-way interactions demonstrated that interactions between type of heating/DMPS addition, type of heating/oil unsaturation, surface-to-oil volume ratio/DMPS addition and surface-to-oiI volume ratio/oil unsaturation were significant, thus indicating the complexity of the frying process. Finally, it was found that increase in specific groups of compounds formed through oxidative polymerization as well as loss of natural antioxidants depended mainly on the total content of polar compounds and, at a second level, on the oil unsaturation.

Jorge, N.; Mrquez-Ruiz, G.; Martn-Polvillo, M.; Ruiz-Mendez, M. V.; Dobarganes, M. C.

1996-01-01

217

Characterizing non-linear dependencies among pairs of clinical variables and imaging data.  

Science.gov (United States)

Advances in computer-aided diagnosis (CAD) systems have shown the benefits of using computer-based techniques to obtain quantitative image measurements of the extent of a particular disease. Such measurements provide more accurate information that can be used to better study the associations between anatomical changes and clinical findings. Unfortunately, even with the use of quantitative image features, the correlations between anatomical changes and clinical findings are often not apparent and definite conclusions are difficult to reach. This paper uses nonparametric exploration techniques to demonstrate that even when the associations between two-variables seems weak, advanced properties of the associations can be studied and used to better understand the relationships between individual measurements. This paper uses quantitative imaging findings and clinical measurements of 85 patients with pulmonary fibrosis to demonstrate the advantages of non-linear dependency analysis. Results show that even when the correlation coefficients between imaging and clinical findings seem small, statistical measurements such as the maximum asymmetry score (MAS) and maximum edge value (MEV) can be used to better understand the hidden associations between the variables. PMID:23366482

Caban, Jesus J; Bagci, Ulas; Mehari, Alem; Alam, Shoaib; Fontana, Joseph R; Kato, Gregory J; Mollura, Daniel J

2012-01-01

218

Cast microstructure of Inconel 713C and its dependence on solidification variables  

International Nuclear Information System (INIS)

The dependence of cast microstructure of Inconel 713C on solidification variables was investigated over a wide range of local cooling rates, epsilon, and thermal gradients in the liquid at the solid-liquid interface, G. The shape of MC carbide particles was found to depend greatly on: 1) the G/R ratio at the solid-liquid interface, where R is growth rate, through the effect of this ratio on the solid phase, ?/sub g/, growth morphology. Under planar front growth conditions the carbide particles were octahedral, under cellular growth conditions they were plate-like, elongated along the cellular growth direction, and under dendritic growth conditions they were irregularly shaped; 2) the local cooling rate, epsilon, when ? was dendritic, with a transition from octahedral to dendritic with increasing epsilon. The size of MC carbide particles was found to be controlled by coarsening and to become finer with increasing epsilon. In this alloy the composition of the MC carbide was established as (Nb0.63Ti0.31M00.06)C and was practically independent of local cooling rate. Other observations were that the precipitation of ?, d the formation of nonequilibrium eutectics, such as MC-?, ?-?' or MC-?-?' were suppressed at splat-cooling rates. Also, microsegregation of all alloying elements with the exception of aluminum was normal, with concentration increasing from the dendrite center-line to the dendrite arm boundary. Aluminum behaved in the opposite manner. Within the cooling rate range used herein, this variable had only a slight effect on microsegregation.

1975-01-01

219

Time-dependent reliability of corrosion-affected RC beams. Part 3: Effect of corrosion initiation time and its variability on time-dependent failure probability  

International Nuclear Information System (INIS)

This paper forms the third part of a study which addresses time-dependent reliability analyses of reinforced concrete (RC) beams affected by reinforcement corrosion. Parts 1 and 2 of the reliability study are presented in companion papers. Part 1 of the reliability study presents evaluation of probabilistic descriptions for time-dependent strengths of a typical simply supported corrosion-affected RC beam. These probabilistic descriptions, i.e., mean and coefficient of variation (c.o.v.) for the time-dependent strengths are presented for two limit states: (a) flexural failure; and (b) shear failure. Part 2 of the reliability study presents evaluation of time-dependent failure probability for the considered RC beam by utilizing the information on probabilistic descriptions for time-dependent strengths available in Part 1. Evaluation of time-dependent failure probability considering the variability in time-dependent strengths and/or time-dependent degradation functions is also presented. This paper investigates the effects of time to corrosion initiation and its variability on failure probability of the same RC beam presented in companion papers. By considering variability in the identified variables that could affect the expected time of first corrosion, simple estimations are presented for mean time to corrosion initiation and variability associated with time to corrosion initiation. Evaluation of time-dependent failure probability for the beam is presented by considering estimated probabilistic descriptions, i.e., mean and c.o.v. for time to corrosion initiation. Parametric analyses show that failure probability for the beam is sensitive to the mode of strength degradation and time to corrosion initiation.

2011-01-01

220

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 Trichobilharzia szidati. In this work, 50 polymorphic DNA fragments of approximately 300-1500 bp from RAPD patterns of individual T. szidati cercariae were cloned and sequenced. As a result genomic DNA sequences (total length of approximately 41,000 bp) revealing clonal variability in T. szidati cercariae were obtained and analyzed. The analysis indicated that these sequences contained tandem, inverted and dispersed repeats as well as regions homological to retroelements of two human parasites, Schistosoma mansoni and S. japonicum. Tandem and inverted repeats constituted 8.9% and 22.1% respectively, while the percentage of dispersed repeats was 21.0%. The average content of these components was 41.7% with the average AT content being 59.0%. About 40% of sequences included regions ranging in length from 96 to 1005 bp which displayed amino acid homology with open reading frame pol products of S. mansoni and S. japonicum retroelements: non-long terminal repeat retrotransposons (nLTRs, 76%), long terminal repeat retrotransposons (LTRs, 14%), and Penelope-like elements (PLEs, 10%). Most of these regions (86.4%) contained frameshifts, gaps, and stop-codons. The largest portion of them was homological to nLTRs of the RTE clade (67%). The number of sequences homologous to the members of CR1 lineage was 7 times smaller (9%). Homology with LTRs of Gypsy/Ty3 and BEL clades was revealed in 5% and 9% of cases respectively. We assume that the repetitive elements including retroelement-like sequences described in the current study may serve as the source of clonal variability detected previously in T. szidati and other digenean trematodes. Such genome regions rapidly accumulate mutations and thus may play an important functional role in the life history of the species.

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

2013-01-01

 
 
 
 
221

Parkinsonian rigidity shows variable properties depending on the elbow joint angle.  

UK PubMed Central (United Kingdom)

Parkinsonian rigidity has been thought to be constant through a full range of joint angle. The aim of this study was to perform a detailed investigation of joint angle dependency of rigidity. We first measured muscle tone at the elbow joint in 20 healthy subjects and demonstrated that an angle of approximately 60 of flexion marks the division of two different angle-torque characteristics. Then, we measured muscle tone at the elbow joint in 24 Parkinson's Disease (PD) patients and calculated elastic coefficients in flexion and extension in the ranges of 10-60 (distal) and 60-110 (proximal). Rigidity as represented by the elastic coefficient in the distal phase of elbow joint extension was best correlated with the UPDRS rigidity score (r = 0.77). A significant difference between the UPDRS rigidity score 0 group and 1 group was observed in the elastic coefficient in the distal phase of extension (P < 0.0001), whereas no significant difference was observed in the proximal phase of extension and in each phase of flexion. Parkinsonian rigidity shows variable properties depending on the elbow joint angle, and it is clearly detected at the distal phase of elbow extension.

Endo T; Hamasaki T; Okuno R; Yokoe M; Fujimura H; Akazawa K; Sakoda S

2013-01-01

222

Sensitivity and reliability analysis on shear behavior of a discontinuity in uncertain underground structure considering multi-random variables  

International Nuclear Information System (INIS)

In this study, a sensitivity analysis on shear failure of a discontinuity adjacent to a circular opening has been performed based on a series system reliability analysis. To realize the failure surface of the system, Mohr-Coulomb yield criteria and other empirical models suggested by Jaeger, Ladanyi and Archambault, and Barton and Bandis have been adopted. Discontinuity direction, initial stress, pore water pressure and various physical properties obtainable from site investigation and Lab. test in discontinuous rock mass before the design stage are selected as multi-random variables, all of which could be simulated in terms of normal distribution, log-normal distribution, or beta distribution. In order to obtain generalized reliability index and failure probability, FORM(First-order reliability method) and PNET method have been adopted with modified HL-RF method as for an optimization scheme. A computer program has been developed and verified by comparing the analysis results by Monte Carlo simulation. The effect on probability of failure of cavern size, distance between a cavern and a discontinuity, and correlation coefficients have been reviewed through reliability analysis. The most sensitive parameter on system failure has been obtained through sensitivity study.

1998-01-01

223

Sensitivity and reliability analysis on shear behavior of a discontinuity in uncertain underground structure considering multi-random variables  

Energy Technology Data Exchange (ETDEWEB)

In this study, a sensitivity analysis on shear failure of a discontinuity adjacent to a circular opening has been performed based on a series system reliability analysis. To realize the failure surface of the system, Mohr-Coulomb yield criteria and other empirical models suggested by Jaeger, Ladanyi and Archambault, and Barton and Bandis have been adopted. Discontinuity direction, initial stress, pore water pressure and various physical properties obtainable from site investigation and Lab. test in discontinuous rock mass before the design stage are selected as multi-random variables, all of which could be simulated in terms of normal distribution, log-normal distribution, or beta distribution. In order to obtain generalized reliability index and failure probability, FORM(First-order reliability method) and PNET method have been adopted with modified HL-RF method as for an optimization scheme. A computer program has been developed and verified by comparing the analysis results by Monte Carlo simulation. The effect on probability of failure of cavern size, distance between a cavern and a discontinuity, and correlation coefficients have been reviewed through reliability analysis. The most sensitive parameter on system failure has been obtained through sensitivity study.

Choi, K. S.; Hwang, S. I. [KNETEC, Taejon (Korea, Republic of)

1998-10-01

224

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

Telles Shirley; Singh Nilkamal; Joshi Meesha; Balkrishna Acharya

2010-01-01

225

Dependence of the average to-node distance on the node degree for random graphs and growing networks  

Science.gov (United States)

In a connected graph, nodes can be characterised locally (with their degree k) or globally (e.g. with their average length path ? to other nodes). Here we investigate how ? depends on k. The numerical algorithm based on the construction of the distance matrix is applied to random graphs and the growing networks: the scale-free ones and the exponential ones. The results are relevant for search strategies in different networks.

Malarz, K.; Ku?akowski, K.

2004-10-01

226

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

International Nuclear Information System (INIS)

[en]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

227

Computation of the temperature dependence of the heat capacity of complex molecular systems using random color noise  

CERN Document Server

We propose a new method for computing the temperature dependence of the heat capacity in complex molecular systems. The proposed scheme is based on the use of the Langevin equation with low frequency color noise. We obtain the temperature dependence of the correlation time of random noises, which enables to model the partial thermalization of high-frequency vibrations, which is a pure quantum effect. By applying the method to carbon nanotubes, we show that the consideration of the color noise in the Langevin equation allows to reproduce the temperature evolution of the specific heat with good accuracy.

Buyukdagli, Sahin; Hu, Bambi

2008-01-01

228

Copulas: an Approach How to Model the Dependence Structure of Random Vectors  

Directory of Open Access Journals (Sweden)

Full Text Available Copulas enabling to characterize the joint distributions of random vectors bymeans of the corresponding one-dimensional marginal distributions are presented anddiscussed. Some properties of copulas and several construction methods, especially when apartial knowledge is available, are included. Possible applications are indicated.

Radko Mesiar; Magda Komornkov

2009-01-01

229

Random matrix theory and universal statistics for disordered quantum conductors with spin-dependent hopping  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Transfer matrix spectra, which are directly related to the conductance g of a many channel elastic scatterer, are studied in presence of random spin-orbit interactions. A first method, inspired by Imry's theory of universal conductance fluctuations, leads us to describe these spectra by a distributi...

Zanon, N.; Pichard, J.-L.

230

The Dependence of Cloud Particle Size on Non-Aerosol-Loading Related Variables  

Energy Technology Data Exchange (ETDEWEB)

An enhanced concentration of aerosol may increase the number of cloud drops by providing more cloud condensation nuclei (CCN), which in turn results in a higher cloud albedo at a constant cloud liquid water path. This process is often referred to as the aerosol indirect effect (AIE). Many in situ and remote sensing observations support this hypothesis (Ramanathan et al. 2001). However, satellite observed relations between aerosol concentration and cloud drop size are not always in agreement with the AIE. Based on global analysis of cloud effective radius (r{sub e}) and aerosol number concentration (N{sub a}) derived from satellite data, Sekiguchi et al. (2003) found that the correlations between the two variables can be either negative, or positive, or none, depending on the location of the clouds. They discovered that significantly negative r{sub e} - N{sub a} correlation can only be identified along coastal regions of the continents where abundant continental aerosols inflow from land, whereas Feingold et al. (2001) found that the response of r{sub e} to aerosol loading is the greatest in the region where aerosol optical depth ({tau}{sub a}) is the smallest. The reason for the discrepancy is likely due to the variations in cloud macroscopic properties such as geometrical thickness (Brenguier et al. 2003). Since r{sub e} is modified not only by aerosol but also by cloud geometrical thickness (H), the correlation between re and {tau}{sub a} actually reflects both the aerosol indirect effect and dependence of H. Therefore, discussing AIE based on the r{sub e}-{tau}{sub a} correlation without taking into account variations in cloud geometrical thickness may be misleading. This paper is motivated to extract aerosols' effect from overall effects using the independent measurements of cloud geometrical thickness, {tau}{sub a} and r{sub e}.

Shao, H.; Liu, G.

2005-03-18

231

[Relationship between psychopathological comorbidity and outcomes variables in-treatment cocaine dependent subject in therapeutic community].  

Science.gov (United States)

Over the last years, the therapeutic community treatment with people who have cocaine problems and psychopathological comorbidity has been increasing and it is important to know more about the success of these treatments. The aim of this paper is to study the psychopathological profile of cocaine-dependent patients and its association with outcome variables. It is interviewed by the Psychiatric Research Interview for Substance and Mental Disorders (PRISM-IV) and the Conners' Adult ADHD Diagnostic Interview for DSM-IV (CAADID) a total sample of 218 patients who sought treatment at any of the six public therapeutics community of Andalusia (Spain). The results show that the retention rate after three months of 68.3% (149), 43.5% that leaves the resource with a therapeutic discharge and 52.8% with clinically significant changes. Besides, the 57.8% have psychopathological comorbidity. Finally, there is a higher treatment success (measured by days of stay, type of discharge and therapeutic community outcome clinical impression) among people without psychopathological comorbidity. These data show the need to adapt the therapeutic communities to treat people with comorbid psychopathology and, thus, improve therapeutic success. PMID:23748941

Vergara-Moragues, Esperanza; Gonzlez-Saiz, Francisco; Lozano-Rojas, Oscar; Fernndez Caldern, Fermn; Verdejo Garca, Antonio; Betanzos Espinosa, Patricia; Bilbao Acedos, Izaskun; Prez Garca, Miguel

2013-01-01

232

[Relationship between psychopathological comorbidity and outcomes variables in-treatment cocaine dependent subject in therapeutic community].  

UK PubMed Central (United Kingdom)

Over the last years, the therapeutic community treatment with people who have cocaine problems and psychopathological comorbidity has been increasing and it is important to know more about the success of these treatments. The aim of this paper is to study the psychopathological profile of cocaine-dependent patients and its association with outcome variables. It is interviewed by the Psychiatric Research Interview for Substance and Mental Disorders (PRISM-IV) and the Conners' Adult ADHD Diagnostic Interview for DSM-IV (CAADID) a total sample of 218 patients who sought treatment at any of the six public therapeutics community of Andalusia (Spain). The results show that the retention rate after three months of 68.3% (149), 43.5% that leaves the resource with a therapeutic discharge and 52.8% with clinically significant changes. Besides, the 57.8% have psychopathological comorbidity. Finally, there is a higher treatment success (measured by days of stay, type of discharge and therapeutic community outcome clinical impression) among people without psychopathological comorbidity. These data show the need to adapt the therapeutic communities to treat people with comorbid psychopathology and, thus, improve therapeutic success.

Vergara-Moragues E; Gonzlez-Saiz F; Lozano-Rojas O; Fernndez Caldern F; Verdejo Garca A; Betanzos Espinosa P; Bilbao Acedos I; Prez Garca M

2013-01-01

233

Remarks on random evolutions in Hamiltonian representation  

CERN Multimedia

telegrapher's equations and some random walks of Poisson type are shown to fit into the framework of the Hamiltonian formalism after an appropriate time-dependent rescaling of the basic variables has been made.

Kupershmidt, Boris A

2009-01-01

234

Sequence fluctuation-dependent adsorption endash depletion transition for random heteropolymers  

International Nuclear Information System (INIS)

[en]We develop a model for the adsorption of random heteropolymers onto solid surfaces from solutions that have a finite concentration of polymer. Previous studies that properly average over the quenched sequence distribution have been concerned with isolated chains near surfaces. Our self-consistent-field theory predicts a transition from situations where the surface segment density is enhanced compared with bulk solution concentration to one wherein the surface segment density is depleted. For a specific chemical identity of the random heteropolymer segments and the surface, this adsorption endash depletion transition occurs above a threshold value of the strength of the sequence fluctuations. This intriguing finding can be tested directly via neutron scattering experiments (in the reflection mode), and offers opportunities for manipulating interfacial properties. The variation of the excess surface density of segments with polymer concentration in solution near the adsorption endash depletion transition is also elucidated. copyright 1996 American Institute of Physics

1996-01-01

235

[Injectable extended-release naltrexone for opioid dependence: a double-blind, placebo-controlled, multicentre randomized trial].  

UK PubMed Central (United Kingdom)

We aimed to assess the efficacy and safety of an injectable, once monthly extended-release formulation of the opioid antagonist naltrexone (XR-NTX) for treatment of patients with opioid dependence after detoxification. Two hundreds and fifty patients with opioid dependence were enrolled into the double-blind, placebo-controlled, randomized, 24-week trial. Patients aged 18 years or over who had inpatient detoxification and 7 days or more off all opioids were enrolled at 13 clinical sites in Russia. We randomly assigned patients (1:1) to either 380 mg XR-NTX (n=124) or placebo (n=126). Participants also received 12 biweekly counseling sessions. The primary endpoint was the response profile for confirmed abstinence during weeks 5-24 assessed by urine drug tests and self report of non-use. Secondary endpoints were self-reported opioid- free days, opioid craving scores, number of days of retention, and relapse to physiological opioid dependence. In conclusion: XR-NTX represents a new treatment option. XR-NTX in conjunction with psychosocial treatment was more effective for treatment of opioid dependence compare to psychosocial support and placebo.

Krupitski? EM; Nunes EV; Ling W; Illeperuma A; Gastfriend DR; Blokhina EA; Silverman BL

2012-01-01

236

Testing for Cross-Sectional Dependence in a RandomEffects Model  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper extends and generalizes the works of [1,2] to allow for cross-sectional dependence in the context of a two-way error components model and consequently develops LM test. The cross-sectional dependence follows the first order spatial autoregressive error (SAE) process and is imposed on the ...

Afees Salisu; Sam Olofin; Eugene Kouassi

237

Alaskan soil carbon stocks: spatial variability and dependence on environmental factors  

Directory of Open Access Journals (Sweden)

Full Text Available The direction and magnitude of soil organic carbon (SOC) changes in response to climate change depend on the spatial and vertical distributions of SOC. We estimated spatially-resolved SOC stocks from surface to C horizon, distinguishing active-layer and permafrost-layer stocks, based on geospatial analysis of 472 soil profiles and spatially referenced environmental variables for Alaska. Total Alaska state-wide SOC stock was estimated to be 77 Pg, with 61% in the active-layer, 27% in permafrost, and 12% in non-permafrost soils. Prediction accuracy was highest for the active-layer as demonstrated by highest ratio of performance to deviation (1.5). Large spatial variability was predicted, with whole-profile, active-layer, and permafrost-layer stocks ranging from 1296 kg C m?2, 2166 kg m?2, and 0232 kg m?2, respectively. Temperature and soil wetness were found to be primary controllers of whole-profile, active-layer, and permafrost-layer SOC stocks. Secondary controllers, in order of importance, were: land cover type, topographic attributes, and bedrock geology. The observed importance of soil wetness rather than precipitation on SOC stocks implies that the poor representation of high-latitude soil wetness in Earth System Models may lead to large uncertainty in predicted SOC stocks under future climate change scenarios. Under strict caveats described in the text and assuming temperature changes from the A1B Intergovernmental Panel on Climate Change emissions scenario, our geospatial model indicates that the equilibrium average 2100 Alaska active-layer depth could deepen by 11 cm, resulting in a thawing of 13 Pg C currently in permafrost. The equilibrium SOC loss associated with this warming would be highest under continuous permafrost (31%), followed by discontinuous (28%), isolated (24.3%), and sporadic (23.6%) permafrost areas. Our high resolution mapping of soil carbon stock reveals the potential vulnerability of high-latitude soil carbon and can be used as a basis for future studies of anthropogenic and climatic perturbations.

U. Mishra; W. J. Riley

2012-01-01

238

Alaskan soil carbon stocks: spatial variability and dependence on environmental factors  

Directory of Open Access Journals (Sweden)

Full Text Available The direction and magnitude of soil organic carbon (SOC) changes in response to climate change depend on the spatial and vertical distributions of SOC. We estimated spatially resolved SOC stocks from surface to C horizon, distinguishing active-layer and permafrost-layer stocks, based on geospatial analysis of 472 soil profiles and spatially referenced environmental variables for Alaska. Total Alaska state-wide SOC stock was estimated to be 77 Pg, with 61% in the active-layer, 27% in permafrost, and 12% in non-permafrost soils. Prediction accuracy was highest for the active-layer as demonstrated by highest ratio of performance to deviation (1.5). Large spatial variability was predicted, with whole-profile, active-layer, and permafrost-layer stocks ranging from 1296 kg C m?2, 2166 kg m?2, and 0232 kg m?2, respectively. Temperature and soil wetness were found to be primary controllers of whole-profile, active-layer, and permafrost-layer SOC stocks. Secondary controllers, in order of importance, were found to be land cover type, topographic attributes, and bedrock geology. The observed importance of soil wetness rather than precipitation on SOC stocks implies that the poor representation of high-latitude soil wetness in Earth system models may lead to large uncertainty in predicted SOC stocks under future climate change scenarios. Under strict caveats described in the text and assuming temperature changes from the A1B Intergovernmental Panel on Climate Change emissions scenario, our geospatial model indicates that the equilibrium average 2100 Alaska active-layer depth could deepen by 11 cm, resulting in a thawing of 13 Pg C currently in permafrost. The equilibrium SOC loss associated with this warming would be highest under continuous permafrost (31%), followed by discontinuous (28%), isolated (24.3%), and sporadic (23.6%) permafrost areas. Our high-resolution mapping of soil carbon stock reveals the potential vulnerability of high-latitude soil carbon and can be used as a basis for future studies of anthropogenic and climatic perturbations.

U. Mishra; W. J. Riley

2012-01-01

239

A New Epsilon-Local Dependence Measure and Dependence Maps  

Directory of Open Access Journals (Sweden)

Full Text Available In the present work, we introduce a new local dependence function characterizing dependence structure between two random variables in an ?-neighborhood of a particular point from the domain of underlying bivariate distribution and investigate its properties. As an example the local dependence function for Farlie-Gumbel-Morgenstern distribution is provided. Also, we construct dependence maps for some pairs of random variables. We use the estimator of local dependence function to construct the dependence map. Permutation test algorithm is applied for P=500 to obtain more accurate result in dependence map and also several examples are provided.

Burcu H. Ucer; Ismihan Bayramoglu

2007-01-01

240

Random distribution pattern and non-adaptivity of genome size in a highly variable population of Festuca pallens.  

UK PubMed Central (United Kingdom)

BACKGROUND AND AIMS: The spatial and statistical distribution of genome sizes and the adaptivity of genome size to some types of habitat, vegetation or microclimatic conditions were investigated in a tetraploid population of Festuca pallens. The population was previously documented to vary highly in genome size and is assumed as a model for the study of the initial stages of genome size differentiation. METHODS: Using DAPI flow cytometry, samples were measured repeatedly with diploid Festuca pallens as the internal standard. Altogether 172 plants from 57 plots (2.25 m(2)), distributed in contrasting habitats over the whole locality in South Moravia, Czech Republic, were sampled. The differences in DNA content were confirmed by the double peaks of simultaneously measured samples. KEY RESULTS: At maximum, a 1.115-fold difference in genome size was observed. The statistical distribution of genome sizes was found to be continuous and best fits the extreme (Gumbel) distribution with rare occurrences of extremely large genomes (positive-skewed), as it is similar for the log-normal distribution of the whole Angiosperms. Even plants from the same plot frequently varied considerably in genome size and the spatial distribution of genome sizes was generally random and unautocorrelated (P > 0.05). The observed spatial pattern and the overall lack of correlations of genome size with recognized vegetation types or microclimatic conditions indicate the absence of ecological adaptivity of genome size in the studied population. CONCLUSIONS: These experimental data on intraspecific genome size variability in Festuca pallens argue for the absence of natural selection and the selective non-significance of genome size in the initial stages of genome size differentiation, and corroborate the current hypothetical model of genome size evolution in Angiosperms (Bennetzen et al., 2005, Annals of Botany 95: 127-132).

Smarda P; Bures P; Horov L

2007-07-01

 
 
 
 
241

Integrated exposure-based therapy for co-occurring posttraumatic stress disorder and substance dependence: a randomized controlled trial.  

UK PubMed Central (United Kingdom)

CONTEXT: There is concern that exposure therapy, an evidence-based cognitive-behavioral treatment for posttraumatic stress disorder (PTSD), may be inappropriate because of risk of relapse for patients with co-occurring substance dependence. OBJECTIVE: To determine whether an integrated treatment for PTSD and substance dependence, Concurrent Treatment of PTSD and Substance Use Disorders Using Prolonged Exposure (COPE), can achieve greater reductions in PTSD and substance dependence symptom severity compared with usual treatment for substance dependence. DESIGN, SETTING, AND PARTICIPANTS: Randomized controlled trial enrolling 103 participants who met DSM-IV-TR criteria for both PTSD and substance dependence. Participants were recruited from 2007-2009 in Sydney, Australia; outcomes were assessed at 9 months postbaseline, with interim measures collected at 6 weeks and 3 months postbaseline. INTERVENTIONS: Participants were randomized to receive COPE plus usual treatment (n = 55) or usual treatment alone (control) (n = 48). COPE consists of 13 individual 90-minute sessions (ie, 19.5 hours) with a clinical psychologist. MAIN OUTCOME MEASURES: Change in PTSD symptom severity as measured by the Clinician-Administered PTSD Scale (CAPS; scale range, 0-240) and change in severity of substance dependence as measured by the number of dependence criteria met according to the Composite International Diagnostic Interview version 3.0 (CIDI; range, 0-7), from baseline to 9-month follow-up. A change of 15 points on the CAPS scale and 1 dependence criterion on the CIDI were considered clinically significant. RESULTS: From baseline to 9-month follow-up, significant reductions in PTSD symptom severity were found for both the treatment group (mean difference, -38.24 [95% CI, -47.93 to -28.54]) and the control group (mean difference, -22.14 [95% CI, -30.33 to -13.95]); however, the treatment group demonstrated a significantly greater reduction in PTSD symptom severity (mean difference, -16.09 [95% CI, -29.00 to -3.19]). No significant between-group difference was found in relation to improvement in severity of substance dependence (0.43 vs 0.52; incidence rate ratio, 0.85 [95% CI, 0.60 to 1.21), nor were there any significant between-group differences in relation to changes in substance use, depression, or anxiety. CONCLUSION: Among patients with PTSD and substance dependence, the combined use of COPE plus usual treatment, compared with usual treatment alone, resulted in improvement in PTSD symptom severity without an increase in severity of substance dependence. TRIAL REGISTRATION: isrctn.org Identifier: ISRCTN12908171.

Mills KL; Teesson M; Back SE; Brady KT; Baker AL; Hopwood S; Sannibale C; Barrett EL; Merz S; Rosenfeld J; Ewer PL

2012-08-01

242

Wigner theorems for random matrices with dependent entries: Ensembles associated to symmetric spaces and sample covariance matrices  

CERN Multimedia

It is a classical result of Wigner that for an hermitian matrix with independent entries on and above the diagonal, the mean empirical eigenvalue distribution converges weakly to the semicircle law as matrix size tends to infinity. In this paper, we prove analogs of Wigner's theorem for random matrices taken from all infinitesimal versions of classical symmetric spaces. This is a class of models which contains those studied by Wigner and Dyson, along with seven others arising in condensed matter physics. Like Wigner's, our results are universal in that they only depend on certain assumptions about the moments of the matrix entries, but not on the specifics of their distributions. What is more, we allow for a certain amount of dependence among the matrix entries, in the spirit of a recent generalization of Wigner's theorem, due to Schenker and Schulz-Baldes. As a byproduct, we obtain a universality result for sample covariance matrices with dependent entries.

Hofmann-Credner, Katrin

2007-01-01

243

Testing for Cross-Sectional Dependence in a RandomEffects Model  

Directory of Open Access Journals (Sweden)

Full Text Available This paper extends and generalizes the works of [1,2] to allow for cross-sectional dependence in the context of a two-way error components model and consequently develops LM test. The cross-sectional dependence follows the first order spatial autoregressive error (SAE) process and is imposed on the remainder disturbances. It is important to note that this paper does not consider alternative forms of spatial lag dependence other than SAE. It also does not allow for endogeneity of the regressors and requires the normality assumption to derive the LM test.

Afees Salisu; Sam Olofin; Eugene Kouassi

2012-01-01

244

Being selective at the plate: Processing dependence between perceptual variables relates to hitting goals and performance.  

UK PubMed Central (United Kingdom)

Performance of a skill that involves acting on a goal object (e.g., a ball to be hit) can influence one's judgment of the size and speed of that object. The present study examined how these action-specific effects are affected when the goal of the actor is varied and they are free to choose between alternative actions. In Experiment 1, expert baseball players were asked to perform three different directional hitting tasks in a batting simulation and make interleaved perceptual judgments about three ball parameters (speed, plate crossing location, and size). Perceived ball size was largest (and perceived speed was slowest) when the ball crossing location was optimal for the particular hitting task the batter was performing (e.g., an "outside" pitch for opposite-field hitting). The magnitude of processing dependency between variables (speed vs. location and size vs. location) was positively correlated with batting performance. In Experiment 2, the action-specific effects observed in Experiment 1 were mimicked by systematically changing the ball diameter in the simulation as a function of plate crossing location. The number of swing initiations was greater when ball size was larger, and batters were more successful in the hitting task for which the larger pitches were optimal (e.g., greater number of pull hits than opposite-field hits when "inside" pitches were larger). These findings suggest attentional accentuation of goal-relevant targets underlies action-related changes in perception and are consistent with an action selection role for these effects. (PsycINFO Database Record (c) 2013 APA, all rights reserved).

Gray R

2013-08-01

245

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.

Feldman Nelson; Chatton Anne; Khan Riaz; Khazaal Yasser; Zullino Daniele

2011-01-01

246

Quantum mechanics with a time-dependent random unitary Hamiltonian: A perturbative study of the nonlinear Keldysh sigma-model  

CERN Multimedia

We analyze the perturbative series of the Keldysh-type sigma-model proposed recently for describing the quantum mechanics with time-dependent Hamiltonians from the unitary Wigner-Dyson random-matrix ensemble. We observe that vertices of orders higher than four cancel, which allows us to reduce the calculation of the energy-diffusion constant to that in a \\phi^4-type model. We further verify that the perturbative four-loop correction to the energy-diffusion constant in the high-velocity limit cancel, in agreement with the conjecture of one of the authors.

Ivanov, D A

2006-01-01

247

Stochastic Finite Element Technique for Stochastic One-Dimension Time-Dependent Differential Equations with Random Coefficients  

Directory of Open Access Journals (Sweden)

Full Text Available The stochastic finite element method (SFEM) is employed for solving stochastic one-dimension time-dependent differential equations with random coefficients. SFEM is used to have a fixed form of linear algebraic equations for polynomial chaos coefficients of the solution process. Four fixed forms are obtained in the cases of stochastic heat equation with stochastic heat capacity or heat conductivity coefficients and stochastic wave equation with stochastic mass density or elastic modulus coefficients. The relation between the exact deterministic solution and the mean of solution process is numerically studied.

M. M. Saleh; I. L. El-Kalla; M. M. Ehab

2007-01-01

248

Fixed-interval versus OCT-guided variable dosing of intravitreal bevacizumab in the management of neovascular age-related macular degeneration: a 12-month randomized prospective study.  

UK PubMed Central (United Kingdom)

PURPOSE: To compare the efficacy of as-needed or variable dosing of intravitreal bevacizumab to continuous fixed-interval dosing in the management of neovascular age-related macular degeneration (AMD). DESIGN: Prospective, open-label, randomized clinical study. METHODS: One hundred twenty eyes of 120 patients with treatment-nave subfoveal neovascular AMD participated in this study at the American University of Beirut and Hotel Dieu de France Retina Clinics. Eyes were randomized (1:1) to fixed-interval dosing (every 4 to 6 weeks) or variable dosing with intravitreal bevacizumab (1.25 mg/0.05 mL). Best-corrected visual acuity (BCVA) and central retinal thickness (CRT) using optical coherence tomography (OCT) were measured at baseline and at each follow-up visit. Presence or recurrence of fluid on OCT was the main indicator for retreatment in variable dosing. Main outcome measure was improvement in BCVA and CRT at 12 months. RESULTS: Compared to baseline, variable dosing had a mean improvement in BCVA of 11.0 letters after 12 months vs 9.2 letters for fixed-interval dosing (P = .81). Similarly, CRT decreased after 12 months by 80.7 ?m for variable dosing vs 100.5 ?m for fixed-interval dosing (P = .37). The average number of injections over 12 months was higher for fixed-interval dosing than variable dosing (9.5 vs 3.8 injections, P < .001). CONCLUSIONS: Fixed-interval and variable dosing regimens of intravitreal bevacizumab improved visual acuity and anatomic outcomes after 12 months in eyes with neovascular AMD. However, variable dosing had a reduced treatment burden. Larger trials are needed to confirm these results.

El-Mollayess GM; Mahfoud Z; Schakal AR; Salti HI; Jaafar D; Bashshur ZF

2012-03-01

249

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.  

UK PubMed Central (United Kingdom)

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 limitations, using the JAGS program to compute the log-likelihood ratio (lod score) between causal and non-causal explanations of a biomarker-disease association. To demonstrate the approach, we examined the relationship of plasma urate levels to metabolic syndrome in the ORCADES study of a Scottish population isolate, using genotype at six single-nucleotide polymorphisms in the urate transporter gene SLC2A9 as an instrumental variable. In models that allow for intra-individual variability in urate levels, the lod score favouring a non-causal over a causal explanation was 2.34. In models that do not allow for intra-individual variability, the weight of evidence against a causal explanation was weaker (lod score 1.38). We demonstrate the ability to test one of the key assumptions of instrumental variable analysis--that the effects of the instrument on outcome are mediated only through the intermediate variable--by constructing a test for residual effects of genotype on outcome, similar to the tests of 'overidentifying restrictions' developed for classical instrumental variable analysis. The Bayesian approach described here is flexible enough to deal with any instrumental variable problem, and does not rely on asymptotic approximations that may not be valid for weak instruments. The approach can easily be extended to combine information from different study designs. Statistical power calculations show that instrumental variable analysis with genetic instruments will typically require combining information from moderately large cohort and cross-sectional studies of biomarkers with information from very large genetic case-control studies.

McKeigue PM; Campbell H; Wild S; Vitart V; Hayward C; Rudan I; Wright AF; Wilson JF

2010-06-01

250

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.  

Science.gov (United States)

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 limitations, using the JAGS program to compute the log-likelihood ratio (lod score) between causal and non-causal explanations of a biomarker-disease association. To demonstrate the approach, we examined the relationship of plasma urate levels to metabolic syndrome in the ORCADES study of a Scottish population isolate, using genotype at six single-nucleotide polymorphisms in the urate transporter gene SLC2A9 as an instrumental variable. In models that allow for intra-individual variability in urate levels, the lod score favouring a non-causal over a causal explanation was 2.34. In models that do not allow for intra-individual variability, the weight of evidence against a causal explanation was weaker (lod score 1.38). We demonstrate the ability to test one of the key assumptions of instrumental variable analysis--that the effects of the instrument on outcome are mediated only through the intermediate variable--by constructing a test for residual effects of genotype on outcome, similar to the tests of 'overidentifying restrictions' developed for classical instrumental variable analysis. The Bayesian approach described here is flexible enough to deal with any instrumental variable problem, and does not rely on asymptotic approximations that may not be valid for weak instruments. The approach can easily be extended to combine information from different study designs. Statistical power calculations show that instrumental variable analysis with genetic instruments will typically require combining information from moderately large cohort and cross-sectional studies of biomarkers with information from very large genetic case-control studies. PMID:20348110

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

2010-03-25

251

Effect of an office worksite-based yoga program on heart rate variability: outcomes of a randomized controlled trial.  

UK PubMed Central (United Kingdom)

BACKGROUND: Chronic work-related stress is an independent risk factor for cardiometabolic diseases and associated mortality, particularly when compounded by a sedentary work environment. The purpose of this study was to determine if an office worksite-based hatha yoga program could improve physiological stress, evaluated via heart rate variability (HRV), and associated health-related outcomes in a cohort of office workers. METHODS: Thirty-seven adults employed in university-based office positions were randomized upon the completion of baseline testing to an experimental or control group. The experimental group completed a 10-week yoga program prescribed three sessions per week during lunch hour (50 min per session). An experienced instructor led the sessions, which emphasized asanas (postures) and vinyasa (exercises). The primary outcome was the high frequency (HF) power component of HRV. Secondary outcomes included additional HRV parameters, musculoskeletal fitness (i.e. push-up, side-bridge, and sit & reach tests) and psychological indices (i.e. state and trait anxiety, quality of life and job satisfaction). RESULTS: All measures of HRV failed to change in the experimental group versus the control group, except that the experimental group significantly increased LF:HF (p = 0.04) and reduced pNN50 (p = 0.04) versus control, contrary to our hypotheses. Flexibility, evaluated via sit & reach test increased in the experimental group versus the control group (p < 0.001). No other adaptations were noted. Post hoc analysis comparing participants who completed ?70% of yoga sessions (n = 11) to control (n = 19) yielded the same findings, except that the high adherers also reduced state anxiety (p = 0.02) and RMSSD (p = 0.05), and tended to improve the push-up test (p = 0.07) versus control. CONCLUSIONS: A 10-week hatha yoga intervention delivered at the office worksite during lunch hour did not improve HF power or other HRV parameters. However, improvements in flexibility, state anxiety and musculoskeletal fitness were noted with high adherence. Future investigations should incorporate strategies to promote adherence, involve more frequent and longer durations of yoga training, and enrol cohorts who suffer from higher levels of work-related stress. TRIAL REGISTRATION: ACTRN12611000536965.

Cheema BS; Houridis A; Busch L; Raschke-Cheema V; Melville GW; Marshall PW; Chang D; Machliss B; Lonsdale C; Bowman J; Colagiuri B

2013-01-01

252

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  

International Nuclear Information System (INIS)

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

2012-01-01

253

Mindfulness training modifies cognitive, affective, and physiological mechanisms implicated in alcohol dependence: results of a randomized controlled pilot trial.  

UK PubMed Central (United Kingdom)

Mindfulness training may disrupt the risk chain of stress-precipitated alcohol relapse. In 2008, 53 alcohol-dependent adults (mean age = 40.3) recruited from a therapeutic community located in the urban southeastern U.S. were randomized to mindfulness training or a support group. Most participants were male (79.2%), African American (60.4%), and earned less than $20,000 annually (52.8%). Self-report measures, psychophysiological cue-reactivity, and alcohol attentional bias were analyzed via repeated measures ANOVA. Thirty-seven participants completed the interventions. Mindfulness training significantly reduced stress and thought suppression, increased physiological recovery from alcohol cues, and modulated alcohol attentional bias. Hence, mindfulness training appears to target key mechanisms implicated in alcohol dependence, and therefore may hold promise as an alternative treatment for stress-precipitated relapse among vulnerable members of society.

Garland EL; Gaylord SA; Boettiger CA; Howard MO

2010-06-01

254

SPATIAL DEPENDENCE OF RANDOM SETS AND ITS APPLICATION TO DISPERSION OF BARK BEETLE INFESTATION IN A NATURAL FOREST  

Directory of Open Access Journals (Sweden)

Full Text Available A large spatio-temporal data set monitoring the annual progress of bark beetle infestation in the Bavarian Forest National Park (Germany) is statistically analysed by means of complex image analysis algorithms. The infestation data were obtained by color-infrared (CIR) aerial image interpretation and cover 10 subsequent years (20012010). Newly emerged infestation patches are hypothesized as spatially correlated to locations of previous years infestation. Both areas, source patches and subsequently emerged patches, are considered as two disjoint random sets. Their spatio-temporal dependence is analysed by two methods: the classical approach based on the measurement of cross-covariance functions, and a second one based on nearest neighbor distances. The resulting characteristics can be interpreted as pre-disposition probabilities of bark beetle infestation depending on distance to sources. Both methods show a strong short-range preference, which decreases with increasing distances.

Markus Kautz; Jochen Dll; Joachim Ohser

2011-01-01

255

Lesions of an avian basal ganglia circuit prevent context-dependent changes to song variability.  

UK PubMed Central (United Kingdom)

Trial-by-trial variability is important in feedback-based motor learning. Variation in motor output enables evaluation mechanisms to differentially reinforce patterns of motor activity that produce desired behaviors. Here, we studied neural substrates of variability in the performance of adult birdsong, a complex, learned motor skill used for courtship. Song performance is more variable when male birds sing alone (undirected) than when they sing to females (directed). We test the role of the anterior forebrain pathway (AFP), an avian basal ganglia-forebrain circuit, in this socially driven modulation of song variability. We show that lesions of the lateral magnocellular nucleus of the anterior nidopallium (LMAN), the output nucleus of the AFP, cause a reduction in the moment-by-moment variability in syllable structure during undirected song to the level present during directed song. This elimination of song modulation is immediate and long-lasting. We further show that the degree of syllable variability and its modulation are both attenuated in older birds, in concert with decreased variability of LMAN activity in these birds. In contrast to the requirement of LMAN for social modulation of syllable structure, we find that LMAN is not required for modulation of other features of song, such as the number of introductory elements and motif repetitions and the ordering of syllables or for other motor and motivational aspects of courtship. Our findings suggest that a key function of avian basal ganglia circuitry is to regulate vocal performance and plasticity by specifically modulating moment-by-moment variability in the structure of individual song elements.

Kao MH; Brainard MS

2006-09-01

256

Rate of adjudication of radiological progression in rheumatoid arthritis randomized controlled trials depending on preset limits of agreement: a pooled analysis from 15 randomized trials.  

UK PubMed Central (United Kingdom)

OBJECTIVE: The aim of this study is to provide data on the adjudication rate for a predetermined threshold of difference in change score between two readers in randomized controlled trials (RCTs). METHODS: Fifteen datasets from RCTs in RA were scored by 13 experienced readers as pairs according to the modified Sharp-van der Heijde method. The theoretical adjudication rates for thresholds of between 3 and 20 units were calculated. We investigated the influence of the number of time points within the same session, the length of the interval and disease duration on the adjudication rates. RESULTS: A total of 21,295 time points from 7643 patients from 15 databases were included in the analysis. The adjudication rate was inversely related to the threshold. Higher adjudication rates were observed with a higher number of time points, longer time intervals and in early versus established RA. The adjudication rates ranged from 0% to 22% depending on the scenario. CONCLUSION: With trained and experienced readers, the adjudication rate in RA RCTs is low even with very conservative adjudication thresholds.

Navarro-Compn V; Landew R; Ahmad HA; Miller CG; Xu D; Wolterbeek R; van der Heijde D

2013-08-01

257

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, Jrg; Zimmermann, Christian; Drewe, Juergen; Zahner, Catherine

2012-12-23

258

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

UK PubMed Central (United Kingdom)

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.

Schellenberg R; Saller R; Hess L; Melzer J; Zimmermann C; Drewe J; Zahner C

2012-01-01

259

Lessons learned from a randomized trial of fixed and escalating contingency management schedules in opioid-dependent pregnant women.  

UK PubMed Central (United Kingdom)

BACKGROUND: Contingency management (CM) has shown promise for treating substance use disorders in pregnant women. METHODS: A randomized clinical trial compared the relative efficacy of three conditions on the measures of opioid and cocaine abstinence and days retained in treatment. A total of 133 pregnant patients attending treatment for substance use disorders were randomized either to an escalating reinforcement condition, a fixed reinforcement condition, or an attendance control condition. Conditions were compared on drug abstinence rates and days retained in treatment. RESULTS: As expected, the pooled escalating + fixed conditions received a greater total amount of voucher money than the control condition mean [M = 392.40 (SE = 40.47) vs. 219.74 (SE = 39.78)], respectively; p < .001. However, the escalating and fixed conditions did not differ on the outcome variables of drug abstinence and treatment retention. CONCLUSIONS: The CM conditions examined in the current study did not emerge as superior to the control condition. The lack of significant differences among study conditions may be attributed, in part, to study sample size. Additionally, methodological issues related to the CM intervention may also have compromised outcomes, including delay in reinforcement following the target behavior and limited contact with the reinforcer. SCIENTIFIC SIGNIFICANCE: This study highlights the importance of key CM implementation features, including immediate reinforcement, and adequate access to the reinforcer. It may also be that the reset feature for missing samples in CM interventions is an essential contingency for promoting behavior change.

Tuten M; Svikis DS; Keyser-Marcus L; O'Grady KE; Jones HE

2012-07-01

260

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

 
 
 
 
261

Can We Depend on Investigators to Identify and Register Randomized Controlled Trials?  

Science.gov (United States)

Purpose To reduce publication bias, systematic reviewers are advised to search conference abstracts to identify randomized controlled trials (RCTs) conducted in humans and not published in full. We assessed the information provided by authors to aid identification of RCTs for reviews. Methods We handsearched the Association for Research in Vision and Ophthalmology (ARVO) meeting abstracts for 2004 to 2009 to identify reports of RCTs. We compared our classification with that of authors (requested by ARVO 20042006), and authors report of trial registration (required by ARVO 20072009). Results Authors identified their study as a clinical trial for 169/191 (88%; 95% CI, 8493) RCTs we identified for 2004, 174/212 (82%; 95% CI, 7787) for 2005 and 162/215 (75%; 95% CI, 7081) for 2006. Authors provided registration information for 107/172 (62%; 95% CI, 5569) RCTs for 2007, 103/153 (67%; 95% CI, 6075) for 2008, and 126/171 (74%; 95% CI, 6780) for 2009. Most RCT authors providing a trial register name specified ClinicalTrials.gov (276/312; 88%; 95% CI, 8592) and provided a valid ClinicalTrials.gov registration number (261/276; 95%; 95% CI, 9297). Based on information provided by authors, trial registration information would be accessible for 48% (83/172) (95% CI, 4156) of all ARVO abstracts describing RCTs in 2007, 63% (96/153) (95% CI, 5570) in 2008, and 70% in 2009 (118/171) (95% CI, 6276). Conclusions Authors of abstracts describing RCTs frequently did not classify them as clinical trials nor comply with reporting trial registration information, as required by the conference organizers. Systematic reviewers cannot rely on authors to identify relevant unpublished trials or report trial registration, if present.

Scherer, Roberta W.; Sieving, Pamela C.; Ervin, Ann-Margret; Dickersin, Kay

2012-01-01

262

Stimulus-dependent variability and noise correlations in cortical MT neurons.  

UK PubMed Central (United Kingdom)

Population codes assume that neural systems represent sensory inputs through the firing rates of populations of differently tuned neurons. However, trial-by-trial variability and noise correlations are known to affect the information capacity of neural codes. Although recent studies have shown that stimulus presentation reduces both variability and rate correlations with respect to their spontaneous level, possibly improving the encoding accuracy, whether these second order statistics are tuned is unknown. If so, second-order statistics could themselves carry information, rather than being invariably detrimental. Here we show that rate variability and noise correlation vary systematically with stimulus direction in directionally selective middle temporal (MT) neurons, leading to characteristic tuning curves. We show that such tuning emerges in a stochastic recurrent network, for a set of connectivity parameters that overlaps with a single-state scenario and multistability. Information theoretic analysis shows that second-order statistics carry information that can improve the accuracy of the population code.

Ponce-Alvarez A; Thiele A; Albright TD; Stoner GR; Deco G

2013-08-01

263

Physically-based internal variable model for rate-dependent plasticity  

International Nuclear Information System (INIS)

A unified model is developed for creep and plasticity in metals, using internal state variables to reflect the current microstructure. The inelastic flow rule is taken to be a power function incorporating a kinematic and an isotropic internal variable, where the microstructural origins of these properties are dislocation pileups and dislocation obstacle interaction, respectively. The model is generalized for three-dimensional deformation and evolutionary functions are developed for the internal variables to account for strain hardening and thermal recovery. An experimental test and data reduction procedure is presented which allows all the material constants to be determined for materials which exhibit secondary creep. The procedure is applied to pure aluminum. This generalized model provides a physical basis for predicting mechanical response along arbitrary deformation paths.

1978-06-29

264

Age Dependent Variability in Gene Expression in Fischer 344 Rat Retina.  

Science.gov (United States)

Recent evidence suggests older adults may be a sensitive population with regard to environmental exposure to toxic compounds. One source of this sensitivity could be an enhanced variability in response. Studies on phenotypic differences have suggested that variation in response d...

265

Tuning Randomization  

UK PubMed Central (United Kingdom)

s able to prove unsatisability.More recently, the introduction of randomization in the backtrack step hasalso been proposed. Here, the conict clause is used for randomly deciding whichdecision assignment variable is to be toggled. This contrasts with the usualnon-chronological backtracking approach, in which the most recent decision assignmentvariable is selected as the backtrack point.Nonetheless, the use of randomization entails, by denition, an unpredictablebehavior. Consequently, tuning the use of randomization is not only a key aspect,but can also be a dicult and challenging task. The analysis of experimental resultsobtained for dierent congurations of randomized algorithms can certainlybring some key insights on this topic [1].References

Propositional Satis

266

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%.

2008-01-01

267

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

268

Framework for assessing key variable dependencies in loose-abrasive grinding and polishing  

Energy Technology Data Exchange (ETDEWEB)

This memo describes a framework for identifying all key variables that determine the figuring performance of loose-abrasive lapping and polishing machines. This framework is intended as a tool for prioritizing R&D issues, assessing the completeness of process models and experimental data, and for providing a mechanism to identify any assumptions in analytical models or experimental procedures. Future plans for preparing analytical models or performing experiments can refer to this framework in establishing the context of the work.

Taylor, J.S.; Aikens, D.M.; Brown, N.J.

1995-12-01

269

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

UK PubMed Central (United Kingdom)

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 (300mg/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.

Joos L; Goudriaan AE; Schmaal L; Fransen E; van den Brink W; Sabbe BG; Dom G

2013-08-01

270

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 (300mg/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

2012-11-08

271

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

CERN Document Server

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 Pea, Victor H; Ibragimov, Rustam; Sharakhmetov, Shaturgun

2006-01-01

272

Gains from modelling dependence of rainfall variables into a stochastic model: application of the copula approach at several sites  

Science.gov (United States)

Since the last decade, copulas have become more and more widespread in the construction of hydrological models. Unlike the multivariate statistics which are traditionally used, this tool enables scientists to model different dependence structures without drawbacks. The authors propose to apply copulas to improve the performance of an existing model. The hourly rainfall stochastic model SHYPRE is based on the simulation of descriptive variables. It generates long series of hourly rainfall and enables the estimation of distribution quantiles for different climates. The paper focuses on the relationship between two variables describing the rainfall signal. First, Kendall's tau is estimated on each of the 217 rain gauge stations in France, then the False Discovery Rate procedure is used to define stations for which the dependence is significant. Among three usual archimedean copulas, a unique 2-copula is chosen to model this dependence for any station. Modelling dependence leads to an obvious improvement in the reproduction of the standard and extreme statistics of maximum rainfall, especially for the sub-daily rainfall. An accuracy test for the extreme values shows the good asymptotic behaviour of the new rainfall generator version and the impacts of the copula choice on extreme quantile estimation.

Cantet, P.; Arnaud, P.

2012-10-01

273

A randomized, double-blind, placebo-controlled trial of citicoline for bipolar and unipolar depression and methamphetamine dependence.  

UK PubMed Central (United Kingdom)

BACKGROUND: Methamphetamine use disorders are common and severe problems. Persons with mood disorders, particularly bipolar disorder, have high rates of substance use disorders. We previously reported promising findings on drug use, memory and study retention in patients with a history of mania and cocaine dependence given the nutritional supplement citicoline. In the current proof-of-concept study, we examined citicoline in bipolar or unipolar depression and methamphetamine dependence. METHODS: Sixty adults with bipolar depression or major depressive disorder and methamphetamine dependence were randomized to citicoline (2000mg/day) or placebo for 12 weeks. Mood was assessed using Inventory of Depressive Symptomatology-Clinician Version (IDS-C), and cognition with the Hopkins Auditory Verbal Learning Test (HVLT). Drug use was assessed by urine drug screens. RESULTS: An ANCOVA of the intent-to-treat sample showed that those receiving citicoline (n=28) had a statistically significantly greater improvement in IDS-C scores than those receiving placebo (n=20). Survival in the study was significantly longer and completion rates significantly greater with citicoline than placebo. No significant differences were observed in memory or methamphetamine use. Citicoline was well tolerated. LIMITATIONS: Sample heterogeneity and small sample size were limitations. CONCLUSIONS: To our knowledge this is the first placebo-controlled trial in a dual diagnosis sample with methamphetamine use disorders. Findings suggest that citicoline may have antidepressant properties in this population. Greater treatment retention with citicoline is also noteworthy in a patient population with substance dependence. Larger trials targeting depressive symptoms and treatment retention seem warranted.

Brown ES; Gabrielson B

2012-12-01

274

A randomized, controlled, pilot trial of methylphenidate and cognitive-behavioral group therapy for cocaine dependence in heroin prescription.  

UK PubMed Central (United Kingdom)

Cocaine dependence has proved difficult to treat, whether it occurs alone or in combination with opiate dependence. No intervention has been demonstrated to be uniquely effective. Patients might benefit most from combined pharmacotherapeutic and psychotherapeutic interventions. The present study sought to evaluate the feasibility, tolerability, and efficacy of methylphenidate (MP) and cognitive-behavioral group therapy (CBGT) for cocaine dependence in diacetylmorphine-maintained patients. Sixty-two cocaine-dependent diacetylmorphine-maintained patients participated in a dual-site, double-blind, placebo-controlled pilot trial with 4 treatment conditions. The participants were randomly assigned to receive MP or a placebo each combined with either CBGT or treatment as usual for 12 weeks. Methylphenidate 30 mg and a placebo in identical capsules were administered onsite twice daily under supervision in a fixed-dose regimen without titration. Manual-guided CBGT consisted of 12 weekly sessions. Participation in the CBGT sessions was voluntary. Primary outcome measures were retention in pharmacologic treatment, cocaine-free urine samples, self-reported cocaine use, and adverse effects. Urine screens were performed thrice weekly. Seventy-one percent of the participants completed the study protocol. Methylphenidate was well tolerated with similar retention rates compared with the placebo. No serious adverse effects occurred. No difference in cocaine-free urine screens was found across the 4 treatment groups. Self-reported cocaine use was reduced in all 4 study groups. Methylphenidate and CBGT did not provide an advantage over a placebo or treatment as usual in reducing cocaine use. There were no signs of additive benefits of MP and CBGT. Because of the small sample size, the results are preliminary.

Drsteler-MacFarland KM; Farronato NS; Strasser J; Boss J; Kuntze MF; Petitjean SA; Brki C; Wiesbeck GA

2013-02-01

275

Magnetic localization and field-dependent variable-range hopping in disordered CuCr2S4  

Science.gov (United States)

A study has been made of the magnetic and transport properties of CuCr2S4 powder compacts consisting of nanosized crystallites synthesized by mechanical alloying of the constituent elements at ambient temperature. It is found that the material is a typical spin glass with a spin freezing temperature of about 30 K, and that the temperature dependence of resistivity (?) is well described by ln(?/?0)=(T0/T)1/4 in both the high-temperature (>100 K) and low-temperature (<50 K) ranges with different values of T0. The magnetoresistance, defined as \\{?(0)-?(50 kOe)\\}/?(0), increases monotonically with decreasing temperature and reaches 0.3 at 5 K. It is shown that the temperature and field dependence of resistivity is consistently described in terms of spin-dependent variable-range hopping of the Cr t2g electrons localized by magnetic disorder.

Muroi, M.; Street, R.; McCormick, P. G.

2001-02-01

276

Method of nuclear reactor control using a variable temperature load dependent set point  

International Nuclear Information System (INIS)

This invention provides a method and apparatus for nuclear reactor control using a variable reactor coolant temperature set point which is a function of power load demand. The set point has a constant temperature at the mid range of power load and a decreasing temperature at the higher range. A manual control is provided which is based exclusively on feedwater flow and allows power changes of up to 5 percent full power a minute with less boron concentration change than would otherwise be required

1979-10-02

277

Anomalous statistics of random relaxations in random environments.  

UK PubMed Central (United Kingdom)

We comprehensively analyze the emergence of anomalous statistics in the context of the random relaxation (RARE) model [Eliazar and Metzler, J. Chem. Phys. 137, 234106 (2012)], a recently introduced versatile model of random relaxations in random environments. The RARE model considers excitations scattered randomly across a metric space around a reaction center. The excitations react randomly with the center, the reaction rates depending on the excitations' distances from this center. Relaxation occurs upon the first reaction between an excitation and the center. Addressing both the relaxation time and the relaxation range, we explore when these random variables display anomalous statistics, namely, heavy tails at zero and at infinity that manifest, respectively, exceptionally high occurrence probabilities of very small and very large outliers. A cohesive set of closed-form analytic results is established, determining precisely when such anomalous statistics emerge.

Eliazar I; Metzler R

2013-02-01

278

Re-examining the ontogeny of the context preexposure facilitation effect in the rat through multiple dependent variables.  

Science.gov (United States)

The capability to acquire context conditioning does not emerge until weaning, at least when the defining features of the context lack explicit and salient olfactory cues. Contextual learning deficits in preweanling rats have been associated with functional immaturity of the dorsal hippocampus. According to recent studies, the so-called context preexposure facilitation effect (CPFE) - a hippocampus-dependent effect - is not observed until postnatal day 23 (PD23). In these studies the footshock intensity employed was higher (1.5 mA) than in adult studies, and context conditioning was inferred from a single behavioral measure (percentage of freezing). The present study examined the CPFE on PD17 and PD23 by analyzing multiple dependent variables, including fecal boli and an ethogram covering the complete behavioral repertoire of the rat. A non-shocked control group was included in the design and two footshock intensities were employed (0.5 and 1.5 mA). Results showed clear evidence of contextual fear conditioning in preweanling and weanling rats, as well as evidence of conditioned fear in non-preexposed rats from both age groups. In some cases, some dependent variables, such as grooming or vertical exploration, were more sensitive than freezing for detecting evidence of memory. Strong fear responses were detected in weanling (but not preweanling) rats, when rats were evaluated in a different context from the one employed at conditioning. These results indicate that preweanling rats are capable of acquiring contextual conditioning, even in a context lacking explicit odor cues, and highlight the importance of multiple dependent variables for analyzing the ontogeny of memory. PMID:22561035

Pisano, M V; Ferreras, S; Krapacher, F A; Paglini, G; Arias, C

2012-04-27

279

Effect of 200?G/day of vitamin K1 on the variability of anticoagulation control in patients on warfarin: a randomized controlled trial.  

UK PubMed Central (United Kingdom)

BACKGROUND: Controversy exists whether low-dose vitamin K supplementation can improve anticoagulation control in patients with unstable anticoagulation under warfarin. In a single- centre randomized, double-blind, placebo-controlled study, we evaluated the effectiveness of 200 ?g/day of vitamin K1 in patients with unstable control under warfarin. METHODS: Effectiveness of Vitamin K1 supplementation was primarily assessed by the percentage (%) of Time-in-Therapeutic-Range (TTR) and secondarily by the standard deviation (SD) of the patient's INR values; the proportion of out-of-range INRs; and the number of dose changes on warfarin. Their change scores were obtained by subtracting the mean value in the 6 months pre-randomization from the mean value in the 6 months post-randomization. Multivariable linear-regressions identified factors associated with anticoagulation instability. RESULTS: Fifty out of 54 patients were analyzed (intervention: n=26; placebo: n=24). Most indications (87%) for anticoagulation were venous thromboembolism (VTE). The intervention was associated with a greater reduction in the change scores for the SD of INRs between the pre and post-randomization periods compared with placebo. The mean change score was -0.2590.307 with the intervention and -0.0460.345 with placebo (p=0.026). There was no effect on the change scores of the (%) TTR (p=0.98), the number of INRs out-of-range (p=0.58) and the number of dose changes (p=0.604). Factors independently associated with increased variability in the SD of INRs were increased alcoholic drinks/week (p=0.017), dosing errors (p=0.0009) and missed INR appointments (p=0.035). CONCLUSION: Vitamin K1 supplementation reduces the SD of INRs as an indicator of the variability in anticoagulation control in patients treated with warfarin for VTE.

Majeed H; Rodger M; Forgie M; Carrier M; Taljaard M; Scarvelis D; Gonsalves C; Rodriguez RA; Wells PS

2013-09-01

280

A randomized, placebo-controlled trial of aripiprazole for the treatment of methamphetamine dependence and associated psychosis.  

UK PubMed Central (United Kingdom)

OBJECTIVES: The objectives of this study were to determine the efficacy and safety of aripiprazole for treatment of psychosis, retention and abstinence in patients with methamphetamine dependence. METHODS: This was a double-blind study where 37 methamphetamine dependent patients with history of psychosis were randomly assigned to receive aripiprazole (5-10 mg daily, N = 19) or placebo (N = 18) for 8 weeks. Follow-up evaluation was scheduled on day 7, 14, 28, 42 day 56 after enrolment. RESULTS: Participants on aripiprazole were retained significantly longer in treatment (48.7 days, SD =4.0) compared to placebo (37.1 days, SD =5.0). The Kaplan-Meier survival analysis showed that participants on aripiprazole were less likely to drop out of the study than the placebo group (P =0.02, ?(2) =5.3). Psychotic symptoms significantly decreased among those on aripiprazole as compared to placebo (P < 0.05). However, no statistically significance was found between the two groups in maintaining abstinence (generalised estimation equation (GEE) analysis, P = 0.41). No serious adverse events were reported in either group. CONCLUSION: Aripiprazole was no more effective than placebo in maintaining abstinence from methamphetamine use. However, it facilitated treatment retention and reduced the severity of psychotic symptoms. Aripiprazole was found to be generally safe and well tolerated.

Sulaiman AH; Gill JS; Said MA; Zainal NZ; Hussein HM; Guan NC

2013-06-01

 
 
 
 
281

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

2007-06-27

282

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

UK PubMed Central (United Kingdom)

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.

Sacerdote C; Guarrera S; Smith GD; Grioni S; Krogh V; Masala G; Mattiello A; Palli D; Panico S; Tumino R; Veglia F; Matullo G; Vineis P

2007-09-01

283

Beyond step-down analysis: a new test for decomposing the importance of dependent variables in MANOVA.  

UK PubMed Central (United Kingdom)

Multivariate analysis of variance (MANOVA) is often categorized as a tool for experimental psychologists. However, it also continues to be a popular statistical procedure used by organizational scientists. Unfortunately, when the dependent variables (DV) are correlated with one another, interpreting the significant omnibus test in MANOVA becomes difficult. The present article proposes a novel way of interpreting a significant MANOVA that draws from work dedicated to understanding the relative importance of correlated predictors in multiple regression. Relative importance analyses are specifically designed to overcome the limitations caused by correlated variables and permit researchers to appropriately partition shared variance. We derive and extend relative weight analysis to MANOVA designs and demonstrate how these weights may be used to draw inferences concerning the relative contribution of each DV to the overall multivariate effect. Through our example, we illustrate how researchers must consider the correlations among the DVs when interpreting a significant multivariate effect, and our procedure provides an effective mechanism for doing just that.

Tonidandel S; LeBreton JM

2013-05-01

284

Fast-axis orientation dependence on driving voltage for a Stokes polarimeter based on concrete liquid-crystal variable retarders.  

UK PubMed Central (United Kingdom)

Nowadays liquid-crystal variable retarders (LCVRs) are widely used in optical systems because of their capacity to provide a controlled variable optical retardance by means of an applied voltage, without the need of any moving mechanical part. Nevertheless, the main disadvantages of these components, reported by users in several papers, are the necessity of using a temperature control system for precise measurements, the degradation under UV irradiation, and the lack of spatial retardance homogeneity. In this paper, we report that the orientation of the LCVR fast axis may also be dependent on applied voltage. The consideration of this phenomenon improves the performances of an imaging polarimeter. In this work, we present the problem, introduce the method of calibration that was used for the experiment, and discuss the results.

Terrier P; Charbois JM; Devlaminck V

2010-08-01

285

Pilot randomized trial of hydrocortisone in ventilator-dependent extremely preterm infants: effects on regional brain volumes.  

UK PubMed Central (United Kingdom)

OBJECTIVE: To test the hypothesis that high-risk ventilator-dependent extremely low birth weight (birth weight ?1000 g) infants treated with 7 days of hydrocortisone will have larger total brain tissue volumes than placebo treated infants. STUDY DESIGN: A predetermined sample size of 64 extremely low birth weight infants, between 10-21 days old and ventilator-dependent with a respiratory index score ?2, were randomized to systemic hydrocortisone (17 mg/kg cumulative dose) or saline placebo. Primary outcome was total brain tissue volume. Volumetric magnetic resonance imaging was performed at 38 weeks postmenstrual age; brain tissue regions were segmented and quantified automatically with a high degree of accuracy and 9 structures were segmented manually. All analyses of regional brain volumes were adjusted by postmenstrual age at magnetic resonance imaging scan. RESULTS: The study groups were similar at baseline and 8 infants died in each arm. Unadjusted total brain tissue volume (mean SD) in the hydrocortisone (N = 23) and placebo treated infants (N = 21) was 272 40.3 cm(3) and 277.8 59.1 cm(3), respectively (adjusted mean difference: 6.35 cm(3) (95% CI: (-20.8, 32.5); P = .64). Three of the 31 hydrocortisone treated infants and 5 of the 33 placebo treated infants survived without severe bronchopulmonary dysplasia (relative risk 0.62, 95% CI: 0.13, 2.66; P = .49). No significant differences were noted in prespecified secondary outcomes of regional structural volumes or days on respiratory support. No adverse effects of hydrocortisone were observed. CONCLUSIONS: Low dose hydrocortisone in high-risk ventilator-dependent infants after a week of age had no discernible effect on regional brain volumes or pulmonary outcomes prior to neonatal intensive care unit discharge.

Parikh NA; Kennedy KA; Lasky RE; McDavid GE; Tyson JE

2013-04-01

286

Short-term effects of fish-oil supplementation on heart rate variability in humans: a meta-analysis of randomized controlled trials.  

UK PubMed Central (United Kingdom)

BACKGROUND: The effects of fish oil on heart rate variability in humans remain unclear. OBJECTIVE: A meta-analysis of randomized controlled trials was performed to investigate the influence of fish oil on heart rate variability. DESIGN: Human intervention studies were identified by systematic search of PubMed, Embase, The Cochrane Library, and references of related reviews and studies. A random-effects model was applied to estimate the pooled results. RESULTS: Fifteen studies were included. Results of the meta-analysis showed that the SD of normal-to-normal interval [standardized mean difference (SMD) = 0.10, P = 0.35] and square of successive differences (SMD = 0.05, P = 0.35), 2 of the time-domain parameters of heart rate variability, were not significantly influenced by fish-oil supplementation. For the frequency-domain parameters, the high-frequency power (HF), a surrogate of vagal function, was significantly increased by fish-oil supplementation (SMD = 0.30, P = 0.005), the low-frequency power (LF) was not significantly affected (SMD = 0.03, P = 0.79), and the ratio of LF to HF (LF/HF) showed a trend of reduction (SMD = -0.22, P = 0.08). The trend for a treatment effect on LF/HF became significant at P = 0.01 when the 2 studies with a dose <1000 mg/d were omitted. Subgroup analyses according to predefined study characteristics showed no significant results. CONCLUSION: Short-term fish-oil supplementation may favorably influence the frequency domain of heart rate variability, as indicated by an enhanced vagal tone, which may be an important mechanism underlying the antiarrhythmic and other clinical effects of fish oil.

Xin W; Wei W; Li XY

2013-05-01

287

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.

Hurt Richard D; Ebbert Jon O; Croghan Ivana T; Schroeder Darrell R; Sood Amit; Hays J Taylor

2011-01-01

288

A randomized, placebo-controlled laboratory study of the effects of D-cycloserine on craving in cocaine-dependent individuals.  

UK PubMed Central (United Kingdom)

RATIONALE: D-Cycloserine (DCS), a partial glutamate N-methyl-D-aspartate (NMDA) receptor agonist, enhances extinction of conditioned fear responding; preliminary data suggest that it may facilitate extinction of drug cue reactivity. OBJECTIVE: This study investigates DCS effects on cocaine cue craving and drug use in cocaine-dependent subjects. METHODS: Thirty-two subjects were randomly assigned to receive (1) DCS only, (2) DCS before sessions 1 and 3, placebo (PBO) before session 2, or (3) PBO only 15-min before each of 3 1-h cocaine cue exposure sessions conducted 1 day apart. Craving ratings were obtained before, during, and after sessions. Drug use and cue-induced craving were assessed 1 week after the last cue session. RESULTS: Repeated presentation of cocaine cues resulted in decreased craving both within and between sessions. DCS did not facilitate extinction learning and may have enhanced craving. The group that received three doses of DCS had significantly higher craving than the PBO group at the baseline ratings taken before sessions 2 and 3, as well as significantly higher cue-induced craving at follow-up. The group that received two doses of DCS did not differ from the PBO group. There were no group differences in postextinction cocaine use. CONCLUSIONS: The reduction of cocaine cue reactivity in the PBO group suggests that the study procedures were sufficient to produce extinction. Under these conditions, DCS did not facilitate extinction and may have enhanced craving. Further studies of glutamatergic agents and extinction in cocaine dependence should include consideration of procedural variables that could have a major impact on study outcomes.

Price KL; Baker NL; McRae-Clark AL; Saladin ME; Desantis SM; Santa Ana EJ; Brady KT

2013-04-01

289

Time-dependent excitation and ionization modelling of absorption-line variability due to GRB080310  

DEFF Research Database (Denmark)

We model the time-variable absorption of Feii, Feiii, Siii, Cii and Crii detected in Ultraviolet and Visual Echelle Spectrograph (UVES) spectra of gamma-ray burst (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 is presented in this paper, and Swift's X-Ray Telescope (XRT) 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 GRB080310. Inclusion of ionization is required to explain the column density decrease of all observed Feii levels (including the ground state D) and increase of the Feiii S level. The large population of ions in this latter level (up to 10% of all Feiii) can only be explained through ionization of Feii, as a large fraction of the ionized Feii ions (we calculate 31% using the Flexible Atomic and Cowan codes) initially populate the S level of Feiii rather than the ground state. This channel for producing a significant Feiii S level population may be relevant for other objects in which absorption lines from this level, the UV34 triplet, are observed, such as broad absorption line (BAL) quasars and Carinae. This provides conclusive evidence for time-variable ionization in the circumburst medium, which to date has not been convincingly detected. However, the best-fit distance of the neutral absorbing cloud to the GRB is 200-400 pc, i.e. similar to GRB-absorber distance estimates for GRBs without any evidence for ionization. We find that the presence of time-varying ionization in GRB080310 is likely due to a combination of the super-solar iron abundance ([Fe/H] = +0.2) and the low Hi column density (log N(Hi) = 18.7) in the host of GRB080310. Finally, the modelling provides indications for the presence of an additional cloud at 10 50 pc from the GRB with log N(Hi) ~ 19 20 before the burst, which became fully ionized by the radiation released during the first few tens of minutes after the GRB. 2012 ESO.

Vreeswijk, P.M.; De Cia, A.

2013-01-01

290

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

UK PubMed Central (United Kingdom)

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 KK; Bush DE; Josselyn SA; Klann E; Ledoux JE

2013-09-01

291

Dependence of photoelectric behavior of TiO/sub 2/ electrodes on processing variables  

Energy Technology Data Exchange (ETDEWEB)

The photoelectrochemical conversion behavior of TiO/sub 2/ ceramic electrodes has been investigated as a function of electrode processing variables such as Al/sub 2/O/sub 3/ dopant, surface roughness, and grain size. The photocurrent increased with Al/sub 2/O/sub 3/ dopant up to 0.1 and 0.05 wt. % in the specimens reduced at 700 and 800 /sup 0/C, respectively, and then decreased. However, the photoresponse appeared around 415 nm, which very closely corresponded to the energy band gap of TiO/sub 2/(approx.3.0 eV), regardless of reduction temperature and the amount of Al/sub 2/O/sub 3/. These results suggest a bulk excitation process involving dopant and a defect-related state in the gap of the TiO/sub 2/ semiconductor. The photocurrent increased with increasing surface roughness and grain size in the undoped TiO/sub 2/ ceramic electrode behavior due to adsorption and/or reflection of light and the grain-boundary effect.

Yoon, K.H.; Park, K.B.

1988-08-15

292

Bias correction of OLSE in the regression model with lagged dependent variables  

UK PubMed Central (United Kingdom)

It is well known that the ordinary least-squares estimates (OLSE) of autoregressive models are biasedin small sample. In this paper, an attempt is made to obtain the unbiased estimates in the senseof median or mean. Using Monte Carlo simulation techniques, we extend the median-unbiased estimatorproposed by Andrews (1993, Econometrica 61 (1), 139--165) to the higher-order autoregressiveprocesses, the nonnormal error term and inclusion of any exogenous variables. Also, we introduce themean-unbiased estimator, which is compared with OLSE and the medium-unbiased estimator. Somesimulation studies are performed to examine whether the proposed estimation procedure works wellor not, where AR(p) for p =1; 2; 3 models are examined. We obtain the results that it is possible torecover the true parameter values from OLSE and that the proposed procedure gives us the less-biasedestimators than OLSE. Finally, using actually obtained data, an empirical example of the median- andmean-unbiased estimators are shown. c

Hisashi Tanizaki

293

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

294

Positive random variables with a discrete probability mass at the origin: Parameter estimation for left-censored samples with application to air quality monitoring data  

Energy Technology Data Exchange (ETDEWEB)

The concentration of a contaminant measured in a particular medium might be distributed as a positive random variable when it is present, but it may not always be present. If there is a level below which the concentration cannot be distinguished from zero by the analytical apparatus, a sample from such a population will be censored on the left. The presence of both zeros and positive values in the censored portion of such samples complicates the problem of estimating the parameters of the underlying positive random variable and the probability of a zero observation. Using the method of maximum likelihood, it is shown that the solution to this estimation problem reduces largely to that of estimating the parameters of the distribution truncated at the point of censorship. The maximum likelihood estimate of the proportion of zero values follows directly. The derivation of the maximum likelihood estimates for a lognormal population with zeros is given in detail, and the asymptotic properties of the estimates are examined. The estimation method was used to fit several different distributions to a set of severely censored /sup 85/Kr monitoring data from six locations at the Savannah River Plant chemical separations facilities.

Gogolak, C.V.

1986-11-01

295

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

296

[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

297

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

UK PubMed Central (United Kingdom)

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.

Guo DL; Fan J; Mi MX

2013-05-01

298

Effects of docosahexaenoic acid supplementation during pregnancy on fetal heart rate and variability: a randomized clinical trial.  

UK PubMed Central (United Kingdom)

DHA (22:6n-3) supplementation during infancy has been associated with lower heart rate (HR) and improved neurobehavioral outcomes. We hypothesized that maternal DHA supplementation would improve fetal cardiac autonomic control and newborn neurobehavior. Pregnant women were randomized to 600 mg/day of DHA or placebo oil capsules at 14.4 (+/-4) weeks gestation. Fetal HR and HRV were calculated from magnetocardiograms (MCGs) at 24, 32 and 36 weeks gestational age (GA). Newborn neurobehavior was assessed using the Neonatal Behavioral Assessment Scale (NBAS). Post-partum maternal and infant red blood cell (RBC) DHA was significantly higher in the supplemented group as were metrics of fetal HRV and newborn neurobehavior in the autonomic and motor clusters. Higher HRV is associated with more responsive and flexible autonomic nervous system (ANS). Coupled with findings of improved autonomic and motor behavior, these data suggest that maternal DHA supplementation during pregnancy may impart an adaptive advantage to the fetus.

Gustafson KM; Carlson SE; Colombo J; Yeh HW; Shaddy DJ; Li S; Kerling EH

2013-05-01

299

Effects of docosahexaenoic acid supplementation during pregnancy on fetal heart rate and variability: a randomized clinical trial.  

Science.gov (United States)

DHA (22:6n-3) supplementation during infancy has been associated with lower heart rate (HR) and improved neurobehavioral outcomes. We hypothesized that maternal DHA supplementation would improve fetal cardiac autonomic control and newborn neurobehavior. Pregnant women were randomized to 600 mg/day of DHA or placebo oil capsules at 14.4 (+/-4) weeks gestation. Fetal HR and HRV were calculated from magnetocardiograms (MCGs) at 24, 32 and 36 weeks gestational age (GA). Newborn neurobehavior was assessed using the Neonatal Behavioral Assessment Scale (NBAS). Post-partum maternal and infant red blood cell (RBC) DHA was significantly higher in the supplemented group as were metrics of fetal HRV and newborn neurobehavior in the autonomic and motor clusters. Higher HRV is associated with more responsive and flexible autonomic nervous system (ANS). Coupled with findings of improved autonomic and motor behavior, these data suggest that maternal DHA supplementation during pregnancy may impart an adaptive advantage to the fetus. PMID:23433688

Gustafson, K M; Carlson, S E; Colombo, J; Yeh, H-W; Shaddy, D J; Li, S; Kerling, E H

2013-02-20

300

Reticulocyte dynamic and hemoglobin variability in hemodialysis patients treated with Darbepoetin alfa and C.E.R.A.: a randomized controlled trial.  

UK PubMed Central (United Kingdom)

BACKGROUND: In a simulation based on a pharmacokinetic model we demonstrated that increasing the erythropoiesis stimulating agents (ESAs) half-life or shortening their administration interval decreases hemoglobin variability. The benefit of reducing the administration interval was however lessened by the variability induced by more frequent dosage adjustments. The purpose of this study was to analyze the reticulocyte and hemoglobin kinetics and variability under different ESAs and administration intervals in a collective of chronic hemodialysis patients. METHODS: The study was designed as an open-label, randomized, four-period cross-over investigation, including 30 patients under chronic hemodialysis at the regional hospital of Locarno (Switzerland) in February 2010 and lasting 2 years. Four subcutaneous treatment strategies (C.E.R.A. every 4 weeks Q4W and every 2 weeks Q2W, Darbepoetin alfa Q4W and Q2W) were compared with each other. The mean square successive difference of hemoglobin, reticulocyte count and ESAs dose was used to quantify variability. We distinguished a short- and a long-term variability based respectively on the weekly and monthly successive difference. RESULTS: No difference was found in the mean values of biological parameters (hemoglobin, reticulocytes, and ferritin) between the 4 strategies. ESAs type did not affect hemoglobin and reticulocyte variability, but C.E.R.A induced a more sustained reticulocytes response over time and increased the risk of hemoglobin overshooting (OR 2.7, p = 0.01). Shortening the administration interval lessened the amplitude of reticulocyte count fluctuations but resulted in more frequent ESAs dose adjustments and in amplified reticulocyte and hemoglobin variability. Q2W administration interval was however more favorable in terms of ESAs dose, allowing a 38% C.E.R.A. dose reduction, and no increase of Darbepoetin alfa. CONCLUSIONS: The reticulocyte dynamic was a more sensitive marker of time instability of the hemoglobin response under ESAs therapy. The ESAs administration interval had a greater impact on hemoglobin variability than the ESAs type. The more protracted reticulocyte response induced by C.E.R.A. could explain both, the observed higher risk of overshoot and the significant increase in efficacy when shortening its administration interval.Trial registrationClinicalTrials.gov NCT01666301.

Forni V; Bianchi G; Ogna A; Salvad I; Vuistiner P; Burnier M; Gabutti L

2013-07-01

 
 
 
 
301

The relations of go and stop wave to car accidents in a cellular automaton with velocity-dependent randomization  

Science.gov (United States)

In this paper we numerically study the probability P of the occurrence of traffic accidents in the Nagel Schreckenberg (NS) model with velocity-dependent randomization (VDR). Numerical results show that there is a critical density over which car accidents occur, but below which no car accidents happen. Different from the accident probability in the NS model, the accident probability in the VDR model monotonously decreases with increase of car density above the critical density. The value of the accident probability is only determined by the stochastic noise and the number of cars on road. In the stochastic VDR model with the speed limit v=1, no critical density exists and car accidents happen in the whole density region. The braking probabilities of standing cars and moving cars have different influences on the accident probability. A mean-field theory reveals that the accident probability is proportional to the mean density of go and stop wave per time step. Theoretical analyses give excellent agreement with numerical results in the VDR model.

Yang, Xian-Qing; Zhang, Wei; Qiu, Kang; Xu, Wen-Tao; Tang, Gang; Ren, Lin

2007-10-01

302

Time dependent simulations of multiwavelength variability of the blazar Mrk 421 with a Monte Carlo multi-zone code  

CERN Document Server

(abridged) We present a new time-dependent multi-zone radiative transfer code and its application to study the SSC emission of Mrk 421. The code couples Fokker-Planck and Monte Carlo methods, in a 2D geometry. For the first time all the light travel time effects (LCTE) are fully considered, along with a proper treatment of Compton cooling, which depends on them. We study a set of simple scenarios where the variability is produced by injection of relativistic electrons as a `shock front' crosses the emission region. We consider emission from two components, with the second one either being pre-existing and co-spatial and participating in the evolution of the active region, or spatially separated and independent, only diluting the observed variability. Temporal and spectral results of the simulation are compared to the multiwavelength observations of Mrk 421 in March 2001. We find parameters that can adequately fit the observed SEDs and multiwavelength light curves and correlations. There remain however a few o...

Chen, Xuhui; Liang, Edison; Boettcher, Markus

2011-01-01

303

On the variability of the McGurk effect: audiovisual integration depends on prestimulus brain states.  

UK PubMed Central (United Kingdom)

The McGurk effect demonstrates the influence of visual cues on auditory perception. Mismatching information from both sensory modalities can fuse to a novel percept that matches neither the auditory nor the visual stimulus. This illusion is reported in 60-80% of trials. We were interested in the impact of ongoing brain oscillations-indexed by fluctuating local excitability and interareal synchronization-on upcoming perception of identical stimuli. The perception of the McGurk effect is preceded by high beta activity in parietal, frontal, and temporal areas. Beta activity is pronounced in the left superior temporal gyrus (lSTG), which is considered as a site of multimodal integration. This area is functionally (de)coupled to distributed frontal and temporal regions in illusion trials. The disposition to fuse multisensory information is enhanced as the lSTG is more strongly coupled to frontoparietal regions. Illusory perception is accompanied by a decrease in poststimulus theta-band activity in the cuneus, precuneus, and left superior frontal gyrus. Event-related activity in the left middle temporal gyrus is pronounced during illusory perception. Thus, the McGurk effect depends on fluctuating brain states suggesting that functional connectedness of left STS at a prestimulus stage is crucial for an audiovisual percept.

Keil J; Mller N; Ihssen N; Weisz N

2012-01-01

304

On the variability of the McGurk effect: audiovisual integration depends on prestimulus brain states.  

Science.gov (United States)

The McGurk effect demonstrates the influence of visual cues on auditory perception. Mismatching information from both sensory modalities can fuse to a novel percept that matches neither the auditory nor the visual stimulus. This illusion is reported in 60-80% of trials. We were interested in the impact of ongoing brain oscillations-indexed by fluctuating local excitability and interareal synchronization-on upcoming perception of identical stimuli. The perception of the McGurk effect is preceded by high beta activity in parietal, frontal, and temporal areas. Beta activity is pronounced in the left superior temporal gyrus (lSTG), which is considered as a site of multimodal integration. This area is functionally (de)coupled to distributed frontal and temporal regions in illusion trials. The disposition to fuse multisensory information is enhanced as the lSTG is more strongly coupled to frontoparietal regions. Illusory perception is accompanied by a decrease in poststimulus theta-band activity in the cuneus, precuneus, and left superior frontal gyrus. Event-related activity in the left middle temporal gyrus is pronounced during illusory perception. Thus, the McGurk effect depends on fluctuating brain states suggesting that functional connectedness of left STS at a prestimulus stage is crucial for an audiovisual percept. PMID:21625011

Keil, Julian; Mller, Nadia; Ihssen, Niklas; Weisz, Nathan

2011-05-30

305

Random variation and systematic error caused by various preanalytical variables, estimated by linear mixed-effects models.  

UK PubMed Central (United Kingdom)

BACKGROUND: We wanted to determine whether specific, preanalytical sample handling increases preanalytical variation and bias test results compared with optimal handling. METHODS: Blood was collected into 4 serum-separation tubes from each arm of 60 outpatients. In 30 of the patients, half of the tubes were transported in the pneumatic tube system, while the other half were manually delivered. In the remaining patients, the blood samples were collected using 21-gauge straight needles (green needles) and 23-gauge butterfly needles. Half of the tubes were mixed by inverting 5-6 times, and the other half by one inversion. Linear mixed-effects models were used as statistical method. RESULTS: Transporting samples in the pneumatic tube system caused a significant bias to the results for LD (4.5 U/L, p<0.001) and magnesium (0.0021 mmol/L, p=0.003). For CK and glucose, the preanalytical variation was significantly higher for samples transported in the pneumatic tube system vs manual delivery. Using butterfly needles resulted in lower values (p<0.05) for calcium (-0.0072 mmol/L), CK (-0.75 U/L) and LD (-1.6 U/L) compared with 21-gauge needles. The preanalytical variation for ALP was significantly higher with butterfly needles. CONCLUSIONS: The specific sample handling had significant but small random and systematic effects on results for some analytes.

Sylte MS; Wentzel-Larsen T; Bolann BJ

2013-01-01

306

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-contro...

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

307

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-contro...

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

308

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

309

Tacrolimus versus cyclophosphamide in steroid-dependent or steroid-resistant focal segmental glomerulosclerosis: a randomized controlled trial.  

UK PubMed Central (United Kingdom)

BACKGROUND: The efficacy and safety of tacrolimus (TAC) and cyclophosphamide (CTX) were prospectively examined in steroid-dependent or steroid-resistant primary focal segmental glomerulosclerosis (FSGS). METHODS: Patients with biopsy-proven FSGS were enrolled and randomly divided into two groups: CTX and TAC. Patients treated with CTX (0.5-0.75 g/m(2)month, i.v.) received prednisone at 0.8 mg/kgday, while patients treated with TAC (0.1 mg/kgday) received prednisone at 0.5 mg/kgday. The plasma concentration of TAC was monitored and maintained at 5-10 ng/ml. After a 6-month treatment the patients were evaluated. Patients with complete remission (CR) and partial remission (PR) continued the treatment for 12 months with the dose tapered, whereas the patients with no response were excluded from the study and underwent an alternative treatment. RESULTS: A total of 33 patients were recruited and 27 completed the 12-month follow-up. The TAC-treated patients (n = 15) showed a quick remission. The initial remission time averaged 1.23 0.21 versus 2.21 0.77 months in the CTX group (n = 18), but no significant difference was achieved (p > 0.05). At 6 months, the two groups showed a similar outcome. Ten patients from each group showed remission (7 CR and 3 PR). At 12 months, the CTX group had 9 CR and 3 PR while the TAC group had 6 CR and 5 PR. Remission rates in TAC tended to be higher than that in CTX, but there was no difference. CTX patients had a high prevalence of infections (50.0 vs. 13.3% in TAC, p < 0.05). In contrast, TAC-treated patients showed a high incidence of hyperglycemia (26.7 vs. 0.0% in CTX, p < 0.05). CONCLUSION: These results suggest that CTX and TAC had a similar efficacy in steroid-dependent and steroid-resistant FSGS as manifested by reduced proteinuria, improved serum albumin level and renal function.

Ren H; Shen P; Li X; Pan X; Zhang W; Chen N

2013-01-01

310

Instances of the product of independent beta random variables and of the Meijer G and Fox H functions with finite representations  

Science.gov (United States)

The authors show how we may, through the use of some extended product expressions for the Gamma function and some detailed work on the characteristic functions of the negative logarithm of the product of particular independent Beta random variables, whose second parameters are rational, obtain in a single shot (i) simple expressions for both the probability density and cumulative distribution functions of this product, as well as, concomitantly (ii) very simple and easy to compute alternative finite form expressions for instances of the Meijer G and Fox H functions. These alternative expressions are based on the expressions for the probability density and cumulative distribution functions of the Generalized Integer Gamma distribution and they are not used or recognized by the available software.

Coelho, Carlos A.; Arnold, Barry C.

2012-09-01

311

A Monte Carlo Study of EC-estimation in Panel Data Models with Limited Dependent Variables and Heterogeneity  

UK PubMed Central (United Kingdom)

The EC (Estimation-Classification) estimator, and its companion EC-algorithm, were introducedin El-Gamal and Grether (1995), and their properties further analyzed in El-Gamal and Grether(1996). The purpose of EC estimation is to uncover heterogeneity in panel data models in a mannerwhich is more parsimonious and computationally less costly than some of the standard methods (e.g.fixed effects). The latter concern is particularly evident in limited dependent variable models whereno simple method of estimating fixed effects is available (e.g. probits). One of the applicationsof El-Gamal and Grether (1996) employed the EC algorithm to estimate multiple probits in apopulation of 257 individuals, each being observed for 14 to 19 periods, providing very satisfactoryresults. Since the asymptotic theory behind EC estimation relies on "Large T " approximation(i.e. we require T " 1, then n " 1 in proving consistency of the estimator), we provided adiagnostic statistic (called the Averag...

Mahmoud A. El-gamal; David M. Grether

312

Prospective randomized comparison between omega-3 fatty acid supplements plus simvastatin versus simvastatin alone in Korean patients with mixed dyslipidemia: lipoprotein profiles and heart rate variability.  

UK PubMed Central (United Kingdom)

BACKGROUND: This study was designed to evaluate the effects of omega-3 fatty acids supplements and simvastatin on lipoproteins and heart rate variability (HRV), a surrogate parameter of cardiac autonomic function, in patients with mixed dyslipidemia. METHODS: This study was a prospective, randomized, open-label study. Among the 171 patients screened, 62 who met the inclusion criteria after 6 weeks on a strict diet therapy were randomized into two treatment groups. The inclusion criteria were mixed dyslipidemia with a high triglyceride level (200-499 mg per 100 ml) and a total cholesterol level >200 mg per 100 ml. After a run-in period of 6 weeks, the patients were randomized into two groups and given a combination treatment with 4 g of omega-3 fatty acids (four 1 g Omacor (eicosapentaenoic acid, 465 mg; docosahexaenoic acid, 375 mg; other omega-3 fatty acids, 60 mg; others 100 mg, Gun-il Pharmacy, Seoul, Korea)) and 20 mg of simvastatin daily or a monotherapy of 20 mg simvastatin for 6 weeks. In the combination therapy group, seven patients dropped out, and in the simvastatin alone therapy group, five patients dropped out during the study period. RESULTS: After 6 weeks of drug treatment, triglyceride levels decreased by 41.0% in the combination treatment group and 13.9% in the simvastatin monotherapy group (from 309.2 95 mg per 100 ml to 177.7 66 versus 294.6 78 mg per 100 ml to 238.3 84 mg per 100 ml, respectively, P = 0.0007). No significant changes in the HRV parameters were observed in either group. CONCLUSION: The combination of omega-3 fatty acids plus simvastatin, which achieved a significantly greater reduction of triglycerides without adverse reactions, should be considered as an optimal treatment option for patients with mixed dyslipidemia.

Kim SH; Kim MK; Lee HY; Kang HJ; Kim YJ; Kim HS

2011-01-01

313

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

314

Outer membrane targeting of Pseudomonas aeruginosa proteins shows variable dependence on the components of Bam and Lol machineries.  

UK PubMed Central (United Kingdom)

UNLABELLED: 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 three secretins that are functionally related OM proteins was less affected (PilQ and PscC) or not at all affected (XcpQ). Depletion of LolB affected all lipoproteins examined and had a variable effect on the nonlipidated proteins. While the levels of OprF, PilQ, and PscC were significantly reduced by LolB depletion, XcpQ was unaffected and was correctly localized to the OM. These results suggest that certain ?-barrel proteins such as OprF primarily utilize the complete Bam machinery. The Lol machinery participates in the OM targeting of secretins to variable degrees, likely through its involvement in the assembly of lipidated Bam components. XcpQ, but not PilQ or PscC, was shown to assemble spontaneously into liposomes as multimers. This work raises the possibility that there is a gradient of utilization of Bam and Lol insertion and targeting machineries. Structural features of individual proteins, including their ?-barrel content, may determine the propensity of these proteins for folding (or misfolding) during periplasmic transit and OM insertion, thereby influencing the extent of utilization of the Bam targeting machinery, respectively. IMPORTANCE: Targeting of lipidated and nonlipidated proteins to the outer membrane (OM) compartment in Gram-negative bacteria involves the transfer across the periplasm utilizing the Lol and Bam machineries, respectively. We show that depletion of Bam and Lol components in Pseudomonas aeruginosa does not lead to a general OM protein translocation defect, but the severity (and therefore, Lol and Bam dependence), varies with individual proteins. XcpQ, the secretin component of the type II secretion apparatus, is translocated into the OM without the assistance of Bam or Lol machineries. The hypothesis that XcpQ, after secretion across the cytoplasmic membrane, does not utilize the OM targeting machineries was supported by demonstrating that in vitro-synthesized XcpQ (but not the other P. aeruginosa secretins) can spontaneously incorporate into lipid vesicles. Therefore, the requirement for ancillary factors appears to be, in certain instances, dictated by the intrinsic properties of individual OM proteins, conceivably reflecting their propensities to misfold during periplasmic transit.

Hoang HH; Nickerson NN; Lee VT; Kazimirova A; Chami M; Pugsley AP; Lory S

2011-01-01

315

Time-dependent prediction and evaluation of variable importance using superlearning in high-dimensional clinical data.  

UK PubMed Central (United Kingdom)

BACKGROUND: Prediction of outcome after injury is fraught with uncertainty and statistically beset by misspecified models. Single-time point regression only gives prediction and inference at one time, of dubious value for continuous prediction of ongoing bleeding. New statistical machine learning techniques such as SuperLearner (SL) exist to make superior prediction at iterative time points while evaluating the changing relative importance of each measured variable on an outcome. This then can provide continuously changing prediction of outcome and evaluation of which clinical variables likely drive a particular outcome. METHODS: PROMMTT data were evaluated using both naive (standard stepwise logistic regression) and SL techniques to develop a time-dependent prediction of future mortality within discrete time intervals. We avoided both underfitting and overfitting using cross validation to select an optimal combination of predictors among candidate predictors/machine learning algorithms. SL was also used to produce interval-specific robust measures of variable importance measures (VIM resulting in an ordered list of variables, by time point) that have the strongest impact on future mortality. RESULTS: Nine hundred eighty patients had complete clinical and outcome data and were included in the analysis. The prediction of ongoing transfusion with SL was superior to the naive approach for all time intervals (correlations of cross-validated predictions with the outcome were 0.819, 0.789, 0.792 for time intervals 30-90, 90-180, 180-360, >360 minutes). The estimated VIM of mortality also changed significantly at each time point. CONCLUSION: The SL technique for prediction of outcome from a complex dynamic multivariate data set is superior at each time interval to standard models. In addition, the SL VIM at each time point provides insight into the time-specific drivers of future outcome, patient trajectory, and targets for clinical intervention. Thus, this automated approach mimics clinical practice, changing form and content through time to optimize the accuracy of the prognosis based on the evolving trajectory of the patient.

Hubbard A; Munoz ID; Decker A; Holcomb JB; Schreiber MA; Bulger EM; Brasel KJ; Fox EE; del Junco DJ; Wade CE; Rahbar MH; Cotton BA; Phelan HA; Myers JG; Alarcon LH; Muskat P; Cohen MJ

2013-07-01

316

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

CERN Document Server

[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

317

Analysis of Variability in the Amaranthus Bioassay for Cytokinins: Effects of Water Stress on Benzyladenine- and Fusicoccin-dependent Responses.  

UK PubMed Central (United Kingdom)

The use of only the upper part of the hypocotyl and the cotyledons in the Amaranthus tricolor bioassay for cytokinins, instead of the whole seedling, was found to reduce the endogenous response and give a higher benzyladenine-dependent response. There is no marked difference in the uptake or metabolism of benzyladenine in whole seedlings compared with that in excised cotyledons.Analysis of variability in the bioassay showed that water availability to the cut seedlings and to whole seedlings is a major factor in the amounts of betacyanin accumulated during the subsequent induction period. The increase in the amount of betacyanin accumulated in response to benzyladenine, following conditions of water stress, is not correlated with differences in benzyladenine uptake. Endogenous production and fusicoccin stimulation is also increased following water loss by cut seedlings. Possible explanations for this stress induction may be found in responses of active transport to changes in turgor pressure.Although pretreatment of the roots of seedlings with mannitol stimulated subsequent induction by excised cotyledons, the presence of mannitol during the induction period inhibited the accumulation of betacyanin. This inhibition is not due to any effect on benzyladenine uptake. The susceptibility of amino acid uptake and polysome profiles to water stress suggests that the inhibition of betacyanin synthesis, a process dependent on protein synthesis, may be due to inhibition either of precursor (tyrosine) uptake or of the synthesis or activity of some enzyme in the pathway.

Elliott DC

1979-02-01

318

Analysis of Variability in the Amaranthus Bioassay for Cytokinins: Effects of Water Stress on Benzyladenine- and Fusicoccin-dependent Responses.  

Science.gov (United States)

The use of only the upper part of the hypocotyl and the cotyledons in the Amaranthus tricolor bioassay for cytokinins, instead of the whole seedling, was found to reduce the endogenous response and give a higher benzyladenine-dependent response. There is no marked difference in the uptake or metabolism of benzyladenine in whole seedlings compared with that in excised cotyledons.Analysis of variability in the bioassay showed that water availability to the cut seedlings and to whole seedlings is a major factor in the amounts of betacyanin accumulated during the subsequent induction period. The increase in the amount of betacyanin accumulated in response to benzyladenine, following conditions of water stress, is not correlated with differences in benzyladenine uptake. Endogenous production and fusicoccin stimulation is also increased following water loss by cut seedlings. Possible explanations for this stress induction may be found in responses of active transport to changes in turgor pressure.Although pretreatment of the roots of seedlings with mannitol stimulated subsequent induction by excised cotyledons, the presence of mannitol during the induction period inhibited the accumulation of betacyanin. This inhibition is not due to any effect on benzyladenine uptake. The susceptibility of amino acid uptake and polysome profiles to water stress suggests that the inhibition of betacyanin synthesis, a process dependent on protein synthesis, may be due to inhibition either of precursor (tyrosine) uptake or of the synthesis or activity of some enzyme in the pathway. PMID:16660710

Elliott, D C

1979-02-01

319

Influence of Some Formulation Variables on the Optimization of pH-dependent, Colon-targeted, Sustained-release Mesalamine Microspheres  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim of this work was to understand the influence of different formulation variables on the optimization of pH-dependent, colon-targeted, sustained-release mesalamine microspheres prepared by O/O emulsion solvent evaporation method, employing pH-dependent Eudragit S and hydrophobic pH-independent...

El-Bary, Ahmed Abd; Aboelwafa, Ahmed A.; Al Sharabi, Ibrahim M.

320

Comparison of heart rate variability response in children undergoing elective endotracheal intubation with and without neuromuscular blockade: a randomized controlled trial.  

UK PubMed Central (United Kingdom)

BACKGROUND: The routine use of neuromuscular blocking drugs (NMBD) for endotracheal intubation in children is the subject of much controversy. The analysis of heart rate variability (HRV) can reveal information about the functional state of the autonomic nervous system (ANS). AIM: The purpose of this study was to determine if HRV elucidates differences in the sympathovagal balance of children undergoing elective endo-tracheal intubation with and without neuromuscular blockade (NMB). METHODS: In this prospective study, 38 children (2-6years) scheduled for adenotonsillectomy were randomized into two groups to receive fentanyl 2?gkg(-1) and propofol 4mgkg(-1) , with either mivacurium 0.25mgkg(-1) (NMB group) or saline solution (NoNMB group) for anesthesia induction. The same experienced, blinded anesthesiologist performed endotracheal intubation. Heart rate variability, RR intervals, ECG as well as an electroencephalogram were recorded with HRV and BIS XP monitors, respectively. Heart rate variability was analyzed in the frequency domain. RESULTS: There was no significant difference in HRV changes immediately after mivacurium administration compared with an administration of saline. The groups were comparable for the bispectral index value (NMB 35 [33-41] vs NoNMB 34 [32-42]) during endotracheal intubation. Changes in both the low-frequency power and the low-/high-frequency ratio immediately after endotracheal intubation compared with the unstimulated state before laryngoscopy were significantly higher without NMB (P=0.015 and P=0.006, respectively), whereas there was no significant difference with respect to the high-frequency power. CONCLUSIONS: The stress response during endotracheal intubation in pediatric patients represented by the frequency domain analysis of HRV was found to be higher without NMB. When mivacurium was added to a propofol-fent-anyl induction regimen, the ANS alterations during endotracheal intubation decreased significantly.

Janda M; Bajorat J; Kudlik C; Pohl B; Schubert A; Nldge-Schomburg G; Hofmockel R

2013-08-01

 
 
 
 
321

Reader- and instrument-dependent variability in the electrocardiographic assessment of arrhythmogenic right ventricular dysplasia/cardiomyopathy.  

UK PubMed Central (United Kingdom)

INTRODUCTION: Despite the use of standardized definitions, widely varying prevalence estimates of electrocardiographic (ECG) features related to arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) have been reported in different cohorts. This study was aimed at examining the variability in the ECG interpretation resulting from the same reader, different readers, and using different ECG-resolutions. METHODS AND RESULTS: Blinded to other clinical data, 2 readers examined quantitative and qualitative ECG features of 20 (10 ARVD/C) randomly selected individuals. ECGs were recorded at standard-speed (SS) and double-speed-double-amplitude (DS) settings. The SS ECGs were scanned, magnified 4, and evaluated using electronic calipers (EL). One reader repeated all measurements. For both readers, the intraclass correlation coefficient (ICC) for the measurement of QRS duration was good between conventional and electronic evaluation [DS vs EL: Reader 1--0.64 (0.52-0.73); Reader 2--0.67 (0.55-0.76)][SS vs EL: Reader 1--0.60 (0.47-0.70); Reader 2--0.60 (0.47-0.70)]. Using the same resolution, the intrareader ICC was good for SS [0.70 (0.59-0.78)], DS [0.85 (0.80-0.90)], and EL [0.70 (0.69-0.83)] resolutions, but deteriorated for interreader comparisons [0.50 (0.36-0.62), 0.75 (0.66-0.82), and 0.75 (0.66-0.82), respectively]. For qualitative parameters, the intra- and interreader agreement was inconsistent for all but 2 parameters. Both readers were in perfect agreement while interpreting right precordial T-wave inversion [?= 1] and right bundle branch block morphology (RBBB) [?= 0.83 (0.5-1.0)] even when using SS resolution. CONCLUSIONS: Right precordial t-wave inversion and RBBB are the only ECG parameters that can be detected consistently even using the conventionally used ECG-resolution. The substantial variability in evaluation of other parameters is not improved even with the use of higher resolutions.

Jain R; Tandri H; Daly A; Tichnell C; James C; Abraham T; Judge DP; Calkins H; Dalal D

2011-05-01

322

Cycle structure of random permutations with cycle weights  

CERN Document Server

We investigate the typical cycle lengths, the total number of cycles, and the number of finite cycles in random permutations whose probability involves cycle weights. Typical cycle lengths and total number of cycles depend strongly on the parameters, while the distributions of finite cycles are usually independent Poisson random variables.

Ercolani, Nicholas M

2011-01-01

323

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

324

The A-repeat links ASF/SF2-dependent Xist RNA processing with random choice during X inactivation.  

Science.gov (United States)

One X chromosome, selected at random, is silenced in each female mammalian cell. Xist encodes a noncoding RNA that influences the probability that the cis-linked X chromosome will be silenced. We found that the A-repeat, a highly conserved element within Xist, is required for the accumulation of spliced Xist RNA. In addition, the A-repeat is necessary for X-inactivation to occur randomly. In combination, our data suggest that normal Xist RNA processing is important in the regulation of random X-inactivation. We propose that modulation of Xist RNA processing may be part of the stochastic process that determines which X chromosome will be inactivated. PMID:20657585

Royce-Tolland, Morgan E; Andersen, Angela A; Koyfman, Hannah R; Talbot, Dale J; Wutz, Anton; Tonks, Ian D; Kay, Graham F; Panning, Barbara

2010-07-25

325

Menopausal hot flushes do not associate with changes in heart rate variability in controlled testing: a randomized trial on hormone therapy.  

UK PubMed Central (United Kingdom)

OBJECTIVE: To compare in controlled cardiovascular autonomic function tests the effects of hormone therapy (HT) on heart rate variability (HRV) responses in postmenopausal women with and without pretreatment hot flushes. DESIGN: A randomized placebo-controlled trial. SETTING: Finland, Helsinki University Central Hospital. POPULATION: A total of 150 recently postmenopausal and healthy women with prospectively evaluated hot flushes. METHODS: Women (72 with and 78 without hot flushes) were randomized to receive estradiol alone or in combination with medroxyprogesterone acetate or placebo for 6 months. Time and frequency domain measures of HRV were assessed at baseline and after HT with short-term recordings during paced quiet and deep breathing and with active orthostatic tests, both under carefully controlled laboratory conditions to avoid confounding factors present in long-term ambulatory HRV measurements. MAIN OUTCOME MEASURES: Responses of time and frequency domain measures of HRV to HT. RESULTS: At baseline HRV was similar in women with and without hot flushes. Pretreatment hot flushes did not associate with changes in time domain parameters of HRV during controlled quiet or deep breathing or active orthostatic tests after different types of HT. However, HT reduced HRV in very low frequency power in women with pretreatment hot flushes (from 371 40 to 258 28 ms(2) , p = 0.018). HT did not have an effect on other frequency domain measures during quiet breathing or active orthostatic tests. CONCLUSIONS: Hormone therapy did not significantly modify the HRV responses in women with or without hot flushes under controlled short-term measurements of the cardiovascular autonomic nervous system.

Hautamki H; Mikkola TS; Sovijrvi AR; Piiril P; Haapalahti P

2013-08-01

326

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, . G.; Pozdnyakova, V. I.

2008-03-01

327

Comparison of the effect of two sugar-substituted chewing gums on different caries- and gingivitis-related variables: a double-blind, randomized, controlled clinical trial.  

Science.gov (United States)

OBJECTIVE: The aim of this study was to compare the effect of two sugar-substituted chewing gums besides toothbrushing on different clinical, microbiological, and biochemical caries- and gingivitis-related variables. MATERIALS AND METHODS: The study was designed as a double-blind, randomized, controlled trial with three parallel arms. A total of 130 dental students, who volunteered after signing an informed consent, were randomly allocated to receive one of the following interventions: hexitol-sweetened gum containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), pentitol-sweetened gum containing no CPP-ACP, and control group with no gum. Subjects within the experimental groups chewed two gum pellets for 20min three times a day after meals. The daily consumption level of both polyols was 6.0g. Clinical examinations and salivary samplings were conducted at baseline and after 30days of gum use. Pre- and post-intervention stimulated whole saliva samples were quantified for calcium/phosphate ionic concentration, total facultative bacterial load, Streptococcus mutans/Lactobacillus spp. counts, and Gram-negative percentage. RESULTS: A statistically significant reduction in visible plaque score was displayed in the hexitol/CPP-ACP gum group after the intervention when compared with baseline, but the order of the effect was in the same order as the differences between the groups at baseline. A similar tendency was seen in both the pentitol/non-CPP-ACP gum and control groups regarding total salivary facultative bacterial load and S. mutans count, but median values of these parameters were more significantly reduced in the pentitol/non-CPP-ACP gum group in comparison with those of the control group. Alterations of salivary Lactobacillus spp. were demonstrated only in the pentitol/non-CPP-ACP gum group. CONCLUSION: Although these findings might indicate that a 30-day protocol of daily chewing of pentitol-sweetened gum containing no CPP-ACP might have some a reducing effect on the salivary levels of facultative bacteria, S. mutans and Lactobacillus spp., there was only a marginal, if any, benefit from the chewing gums under study on some microbiological caries- and gingivitis-related variables. CLINICAL RELEVANCE: Taking into account that for transferring results into clinically relevant conclusions the findings need to be strong and consistent, adhering to single significant differences appears not appropriate. Hence, the clinical significance of chewing gums as an adjunctive tool for daily oral care remained questionable. PMID:23604701

Martnez-Pabn, Mara C; Duque-Agudelo, Lucas; Daz-Gil, Juan D; Isaza-Guzmn, Diana M; Tobn-Arroyave, Sergio I

2013-04-19

328

Comparison of the effect of two sugar-substituted chewing gums on different caries- and gingivitis-related variables: a double-blind, randomized, controlled clinical trial.  

UK PubMed Central (United Kingdom)

OBJECTIVE: The aim of this study was to compare the effect of two sugar-substituted chewing gums besides toothbrushing on different clinical, microbiological, and biochemical caries- and gingivitis-related variables. MATERIALS AND METHODS: The study was designed as a double-blind, randomized, controlled trial with three parallel arms. A total of 130 dental students, who volunteered after signing an informed consent, were randomly allocated to receive one of the following interventions: hexitol-sweetened gum containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), pentitol-sweetened gum containing no CPP-ACP, and control group with no gum. Subjects within the experimental groups chewed two gum pellets for 20min three times a day after meals. The daily consumption level of both polyols was 6.0g. Clinical examinations and salivary samplings were conducted at baseline and after 30days of gum use. Pre- and post-intervention stimulated whole saliva samples were quantified for calcium/phosphate ionic concentration, total facultative bacterial load, Streptococcus mutans/Lactobacillus spp. counts, and Gram-negative percentage. RESULTS: A statistically significant reduction in visible plaque score was displayed in the hexitol/CPP-ACP gum group after the intervention when compared with baseline, but the order of the effect was in the same order as the differences between the groups at baseline. A similar tendency was seen in both the pentitol/non-CPP-ACP gum and control groups regarding total salivary facultative bacterial load and S. mutans count, but median values of these parameters were more significantly reduced in the pentitol/non-CPP-ACP gum group in comparison with those of the control group. Alterations of salivary Lactobacillus spp. were demonstrated only in the pentitol/non-CPP-ACP gum group. CONCLUSION: Although these findings might indicate that a 30-day protocol of daily chewing of pentitol-sweetened gum containing no CPP-ACP might have some a reducing effect on the salivary levels of facultative bacteria, S. mutans and Lactobacillus spp., there was only a marginal, if any, benefit from the chewing gums under study on some microbiological caries- and gingivitis-related variables. CLINICAL RELEVANCE: Taking into account that for transferring results into clinically relevant conclusions the findings need to be strong and consistent, adhering to single significant differences appears not appropriate. Hence, the clinical significance of chewing gums as an adjunctive tool for daily oral care remained questionable.

Martnez-Pabn MC; Duque-Agudelo L; Daz-Gil JD; Isaza-Guzmn DM; Tobn-Arroyave SI

2013-04-01

329

Treatment effect estimates varied depending on the definition of the provider prescribing preference-based instrumental variables.  

UK PubMed Central (United Kingdom)

OBJECTIVE: The instrumental variable (IV) method can remove bias because of unobserved confounding, but it is unclear to what extent the choice of the IV may affect the results. We compared the estimates obtained with different provider-based IVs in a real-life observational comparative drug effectiveness study. STUDY DESIGN AND SETTING: We assessed the effectiveness of rhythm vs. rate control treatment in reducing 5-years mortality in a population-based cohort of patients with atrial fibrillation. We compared the IV treatment effect estimates obtained from two-stage least square regression models using nine alternative provider-based IVs defined at either hospital or physician level. RESULTS: All nine IVs reduced the covariate imbalance between the treatment groups. Yet, there were large variations in both the point estimates and the width of the confidence intervals obtained with alternative IVs. Relative to the physician-based IVs, the hospital-based IVs were stronger, had smaller variance, and produced less extreme point estimates. CONCLUSIONS: The IV estimates of treatment effect may vary considerably depending on the IV definition. Choosing the strongest IV could reduce the variance of the IV estimates.

Ionescu-Ittu R; Abrahamowicz M; Pilote L

2012-02-01

330

Radiocaesium contamination of meadow vegetation--time-dependent variability and influence of soil characteristics at grassland sites in Austria  

International Nuclear Information System (INIS)

[en]Long-term trends of 137Cs and 40K concentrations in meadow grass and soil-plant transfer data at eight different sites in Upper Austria are presented. Geometric means of 137Cs TF-data and Tagg values vary between 0.03-1.06 and 0.0005-0.0184 depending on site, respectively. 40K results are less variable with TF values covering a range of 0.31-2.01. Only at one site was a significant decrease of 137Cs concentration (decay-corrected) in meadow vegetation observed during the observation period 1992-1999. Seasonal trends of 40K and 137Cs were investigated at one site in 1996. Both elements show decreasing concentrations in plants from beginning of May-July, followed by a peak in September. Although this pattern was not very pronounced, there are some hints that it may explain deviations of long-term trends in 137Cs levels in grass caused by unusual weather conditions as indicated by phenological climate data (beginning of sweet cherry and black elder blossoming). Finally, TF values were correlated with soil characteristics, revealing a negative correlation of radiocaesium soil-plant transfer with soil pH, exchangeable and extractable fractions of Mg, Ca and Na as well as a positive correlation with exchangeable Al

2002-01-01

331

Random Variables and Correlational Overkill  

Science.gov (United States)

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

Kunce, Joseph T.; And Others

1975-01-01

332

Algebraic polynomials with random coefficients  

Directory of Open Access Journals (Sweden)

Full Text Available This paper provides an asymptotic value for the mathematical expected number of points of inflections of a random polynomial of the form a0(?)+a1(?)(n1)1/2x+a2(?)(n2)1/2x2+an(?)(nn)1/2xn when n is large. The coefficients {aj(w)}j=0n, w?? are assumed to be a sequence of independent normally distributed random variables with means zero and variance one, each defined on a fixed probability space (A,?,Pr). A special case of dependent coefficients is also studied.

K. Farahmand

2002-01-01

333

Prophylactic glycopyrrolate prevents bradycardia after spinal anesthesia for Cesarean section: a randomized, double-blinded, placebo-controlled prospective trial with heart rate variability correlation.  

UK PubMed Central (United Kingdom)

STUDY OBJECTIVE: To determine if prophylactic glycopyrrolate prevents bradycardia after spinal anesthesia. DESIGN: Prospective, randomized, double-blinded, placebo-controlled study. SETTING: Large university-affiliated community hospital. PATIENTS: 81 consecutive term parturients (not in active labor) who were scheduled for elective Cesarean section. INTERVENTIONS: Parturients received 1.0 to 1.5 L of intravenous Ringer's lactate and either glycopyrrolate 0.4 mg or an equal volume of saline, with caregivers blinded to the immediate sequelae of study drug. Each patient received intrathecal bupivacaine (12 to 14 mg) with morphine sulfate (0.1 to 0.2 mg). MEASUREMENTS: Continuous heart rate (HR) and blood pressure monitoring occurred for 20 minutes, with the minimum HR recorded for each 5-minute epoch. Heart rates < 60 beats per minute defined bradycardia. Heart rate variability (HRV) analysis occurred offline. MAIN RESULTS: None of 34 patients administered glycopyrrolate and 6 of 35 (17%) patients receiving saline experienced bradycardia (P = 0.02476). Time domain, frequency domain, and nonlinear and embedded spectrum entropy analyses all reflected the decrease in HRV accompanying administration of glycopyrrolate. CONCLUSION: Bradycardia after spinal anesthesia occurs commonly. Prophylactic glycopyrrolate may prevent the bradycardia, but not necessarily the hypotension.

Chamchad D; Horrow JC; Nakhamchik L; Sauter J; Roberts N; Aronzon B; Gerson A; Medved M

2011-08-01

334

Methylphenidate for ADHD and Drug Relapse in Criminal Offenders with Substance Dependence: A 24-week Randomized Placebo-controlled Trial.  

UK PubMed Central (United Kingdom)

CONCLUSIONS: Methylphenidate treatment reduces attention deficit hyperactivity disorder (ADHD) symptoms and the risk for relapse to substance use in criminal offenders with ADHD and substance dependence.

Konstenius M; Jayaram-Lindstrm N; Guterstam J; Beck O; Philips B; Franck J

2013-10-01

335

An efficient algorithm to generate random uncorrelated Euclidean distances: the random link model  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english A disordered medium is often constructed by N random points independently and identically distributed in a d-dimensional hyperspace. Characteristics related to the statistics of this system are known as the random point problem. As d , the distances between two points become independent random variables, leading to its mean field description: the random link model. While the numerical treatment of large random point problems poses no major di (more) fficulty, due to Euclidean restrictions the same is not true for large random link systems. Exploring the deterministic nature of the pseudo-random number generators, we present techniques which allow to consider models with memory consumption of O(N), instead of O(N) obtained by a naive implementation, but with the same time dependence O(N).

Terariol, Csar Augusto Sangaletti; Martinez, Alexandre Souto

2006-03-01

336

An efficient algorithm to generate random uncorrelated Euclidean distances: the random link model  

Directory of Open Access Journals (Sweden)

Full Text Available A disordered medium is often constructed by N random points independently and identically distributed in a d-dimensional hyperspace. Characteristics related to the statistics of this system are known as the random point problem. As d , the distances between two points become independent random variables, leading to its mean field description: the random link model. While the numerical treatment of large random point problems poses no major difficulty, due to Euclidean restrictions the same is not true for large random link systems. Exploring the deterministic nature of the pseudo-random number generators, we present techniques which allow to consider models with memory consumption of O(N), instead of O(N) obtained by a naive implementation, but with the same time dependence O(N).

Terariol Csar Augusto Sangaletti; Martinez Alexandre Souto

2006-01-01

337

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 A...

Feldman Nelson; Chatton Anne; Khan Riaz; Khazaal Yasser; Zullino Daniele

338

Angle-dependence of the frequency correlation in random photonic media: the diffusive regime and its breakdown near localization  

CERN Multimedia

The frequency correlations of light in complex photonic media are of interest as a tool for characterizing the dynamical aspects of light diffusion. We demonstrate here that the frequency correlation shows a pronounced angle dependence both in transmission and in reflection geometries. Using a broadband white light supercontinuum, this angle dependence is characterized and explained theoretically by a combination of propagation effects outside the medium and coherent backscattering. We report a strong dependence of the coherent backscattering contribution on the scattering strength which cannot be explained by the diffusion theory. Our results indicate that coherent backscattering of the frequency correlation forms a sensitive probe for the breakdown of the diffusive regime near localization.

Muskens, Otto L; Lagendijk, Ad

2011-01-01

339

Dynamics of a quantum phase transition in the random Ising model: Logarithmic dependence of defect density on transition rate  

CERN Document Server

A quantum phase transition from paramagnetic to ferromagnetic phase is driven by a time-dependent external magnetic field. For any rate of the transition the quantum evolution is non-adiabatic and excites finite density of defects in the ferromagnetic state. The density of excitations has only weak logarithmic dependence on the transition rate. These results can be explained following general principles of the Kibble-Zurek mechanism of defect formation, but the logarithmic dependence in place of the usual power law scaling is a novel characteristic of a disordered system.

Dziarmaga, J

2006-01-01

340

Function monitoring method for agricultural machine using evaluation of detected vibration signal via variable filtering dependent on mean rotation rate of working parts  

UK PubMed Central (United Kingdom)

The function monitoring method uses at least one sensor for detecting vibrations ((SCH)) and a number of sensors for detecting the rotation rates (n1-N) of the individual working parts of the agricultural machine, which are filtered for providing a mean rotation rate, the vibration signal evaluated via variable filtering in dependence on the mean rotation rate.

KAPPICH JOACHIM; STANKEWITZ BRITTA

 
 
 
 
341

Quality of life after sipuleucel-T therapy: results from a randomized, double-blind study in patients with androgen-dependent prostate cancer.  

UK PubMed Central (United Kingdom)

OBJECTIVE: To collect and analyze quality-of-life (QOL) data from PROvenge Treatment and Early Cancer Treatment trial (PROTECT, NCT00779402), a phase III, randomized controlled trial of sipuleucel-T in patients with asymptomatic androgen-dependent prostate cancer. METHODS: Patients experiencing prostate-specific antigen relapse after radical prostatectomy entered a 3- to 4-month run-in phase of androgen-deprivation therapy (ADT), followed by 2:1 randomization to sipuleucel-T or control. QOL was assessed throughout the run-in and 26-week post-randomization phases using the Brief Fatigue Inventory (BFI), Linear Analog Self-Assessment (LASA) scale, Global Rating of Change (GRoC) scale, and an elicited symptoms list. RESULTS: One hundred seventy-six patients were randomized into 2 groups, the sipuleucel-T group (n = 117) or the control group (n = 59). The sample provided 80% power to detect a difference in fatigue interference score between treatment arms of 0.9 points. QOL declined predictably during ADT. At week 26, 26.2% of sipuleucel-T-treated patients and 21.6% of control-treated patients (P = .68) reported fatigue in the previous week, and the mean score for fatigue interference in the past 24 hours was 0.9 for both arms (P = .88). Results were comparable for usual fatigue (P = .91) and worst fatigue (P >.99). Mean LASA scores decreased in both groups (P = .26). The proportion of patients reporting better overall QOL on GRoC was similar (P = .62). CONCLUSION: There is no clinically significant negative impact on QOL after sipuleucel-T treatment compared with control after a period of ADT in patients with asymptomatic androgen-dependent prostate cancer.

Beer TM; Schellhammer PF; Corman JM; Glod LM; Hall SJ; Whitmore JB; Frohlich MW; Penson DF

2013-08-01

342

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% 1.862.59), microvascular disease (OR 2.14; CI 95% 1.82.54) and insulin treatment (OR 1.82; CI 95% 1.392.38), and inversely associated with HbA1c (OR 0.85 for every 1% increase; CI 95% 0.800.91). Albuminuria without RI was inversely associated with the female gender (OR 0.27; CI 95% 0.210.35), duration of diabetes (OR 0.94 per year; CI 95% 0.910.97) and directly associated with HbA1c (OR 1.19 for every 1% increase; CI 95% 1.091.3). 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; Mata-Cases Manel; Rodriguez-Poncelas Antonio; Pepi Josep MA; Roura Pilar; Benito Belen; Franch-Nadal Josep; Saez Marc

2012-01-01

343

History dependence of peak effect in $CeRu_{2}$ and $V_{3}Si$ an analogy with the random field Ising systems  

CERN Multimedia

We present results of transport measurements showing distinct path dependence of the electrical resistance in the superconducting vortex state of single crystal samples of CeRu$_2$ and V$_3$Si. Resistance measured in the vortex state of both the systems prepared by field cooling (FC), indicates a relatively higher degree of disorder than when it is prepared by isothermal variation of field. Small oscillations of magnetic field modify the resistance in the FC state, highlighting the metastable nature of that state. An analogy is drawn with the FC state of the random-field Ising systems.

Chaudhary, S; Singh, K J; Roy, S B; Chaddah, P; Chaudhary, Sujeet; Singh, Kanwal Jeet

2000-01-01

344

Quantum mechanics with a time-dependent random unitary Hamiltonian: A perturbative study of the non-linear Keldysh sigma-model  

International Nuclear Information System (INIS)

We analyze the perturbative series of the Keldysh-type sigma-model proposed recently for describing the quantum mechanics with time-dependent Hamiltonians from the unitary Wigner-Dyson random-matrix ensemble. We observe that vertices of orders higher than four cancel, which allows us to reduce the calculation of the energy-diffusion constant to that in a special kind of the matrix ?4 model. We further verify that the perturbative four-loop correction to the energy-diffusion constant in the high-velocity limit cancels, in agreement with the conjecture of one of the authors

2006-03-13

345

The relationship between hepatitis B surface antigen and antibody and continued drug use in narcotic dependency: a randomized controlled study.  

Science.gov (United States)

Hepatitis B surface antigen (HBsAg) and antibody (antiHBs) were determined in 556 narcotic addicts entering a randomized prospective study of alcoholism in patients on methadone maintenance. Only 37% of patients were either negative for HBsAg or without detectable titers of antiHBs. No difference in reactivity existed between alcoholic as compared to nonalcoholic patients and the use of street heroin as compared to use of methadone upon entry to the study. At least a one year follow-up was obtained in 229 (41%) patients with 25 of 88 (28%) patients initially without titers to antiHBs developing detectable titers. No relationship existed between development of antiHBs titers and elevation of liver function tests or the subsequent use of parenteral heroin. These findings suggest that the development of titers to antiHBs in persons on methadone maintenance should not be used as an indication of parenteral drug use. PMID:7166137

Stimmel, B; Korts, D; Jackson, G

346

The relationship between hepatitis B surface antigen and antibody and continued drug use in narcotic dependency: a randomized controlled study.  

UK PubMed Central (United Kingdom)

Hepatitis B surface antigen (HBsAg) and antibody (antiHBs) were determined in 556 narcotic addicts entering a randomized prospective study of alcoholism in patients on methadone maintenance. Only 37% of patients were either negative for HBsAg or without detectable titers of antiHBs. No difference in reactivity existed between alcoholic as compared to nonalcoholic patients and the use of street heroin as compared to use of methadone upon entry to the study. At least a one year follow-up was obtained in 229 (41%) patients with 25 of 88 (28%) patients initially without titers to antiHBs developing detectable titers. No relationship existed between development of antiHBs titers and elevation of liver function tests or the subsequent use of parenteral heroin. These findings suggest that the development of titers to antiHBs in persons on methadone maintenance should not be used as an indication of parenteral drug use.

Stimmel B; Korts D; Jackson G

1982-10-01

347

A randomized trial adapting contingency management targets based on initial abstinence status of cocaine-dependent patients  

Science.gov (United States)

Objective Contingency management (CM) reduces drug use, but questions remain regarding optimal targets and magnitudes of reinforcement for specific patient subgroups. We evaluated the efficacy of CM reinforcing attendance in patients who initiated treatment with cocaine-negative samples, and of higher magnitude abstinence-based CM in patients who began treatment cocaine positive. Methods Initially cocaine-negative patients (n=333) were randomized to: standard care (SC), SC+CM reinforcing submission of negative samples with $250 in prizes ($250Abs), or SC+CM reinforcing attendance ($250Att). Initially cocaine-positive patients (n=109) were randomized to: SC, $250Abs, or higher magnitude CM ($560Abs). Results For initially cocaine-negative patients, $250Abs and $250Att were equally efficacious to SC in enhancing longest duration of abstinence during treatment (LDA); $250Att patients submitted lower proportions of negative samples when missing samples were considered missing, but these patients also attended more study sessions, provided more samples, and submitted a higher proportion of negative samples than SC patients when expected samples were analyzed, ps<.05. In initially cocaine-positive patients, both CM conditions increased proportions of negative samples relative to SC when missing samples were excluded from analyses, but only $560Abs was efficacious in increasing LDA and proportion of negative samples when expected samples were analyzed, ps<.05. Follow-ups revealed no differences in drug use among groups, but LDA was consistently associated with abstinence during follow-up, p<.05. Conclusions High magnitude abstinence-based reinforcement improved all abstinence outcomes in patients who began treatment while using cocaine. For patients initiating treatment abstinent, both attendance- and abstinence-based CM resulted in improvements on some measures.

Petry, Nancy M.; Barry, Danielle; Alessi, Sheila M.; Rounsaville, Bruce J.; Carroll, Kathleen M.

2013-01-01

348

Gender-dependent effects of metformin on vaspin and adiponectin in type 2 diabetes patients: a randomized clinical trial.  

Science.gov (United States)

The aim of the study was to assess the effects of metformin on serum concentrations of vaspin and adiponectin in diabetes. Randomized clinical trial of 99 newly diagnosed, medication-nave, type 2 diabetes patients (NCT01521624) was carried out. Patients were randomly assigned to either metformin 1 000 mg daily plus advice for exercise and lifestyle modification (n=50) or modification alone (n=49). A third group of 50 normoglycemic subjects were also enrolled to compare adipokine concentrations between healthy and diabetes subjects. Serum concentrations of adipokines were measured at baseline and after 12 weeks using ELISA method. Healthy subjects had significantly higher adiponectin levels, but lower concentrations of serum vaspin (p<0.001 in all cases). Vaspin and adiponectin concentrations were 23% and 26% higher in women compared with men. Vaspin dropped significantly after 3-month metformin therapy only in women (1.36 vs. 0.98, p=0.003 in women and 1.31 vs. 1.20, p=0.335 in men). Metformin therapy did not change adiponectin concentration in neither women nor men of the case group (12.66 vs. 12.44 p=0.699 in women and 10.13 vs. 10.94 p=0.253 in men). Comparing case and control groups, metformin decreased vaspin levels more significantly than lifestyle modification in the final multivariate model after controlling for potential confounders only in women (p=0.002) but not men (p=0.896). Conversely, adiponectin levels increased more significantly in the control group, again only in women (p=0.012 and 0.579 for women and men, respectively). Our findings suggest that metformin therapy reduces vaspin concentration in a gender-specific manner. Metformin exerts little benefit in increasing adiponectin levels in diabetes patients. PMID:23225237

Esteghamati, A; Mousavizadeh, M; Noshad, S; Zandieh, A; Zarei, H; Nakhjavani, M

2012-12-07

349

Statistical Analysis of U.S. Navy Major Aircraft Accident Rates, Pilot and Aircraft Time-Dependent Variables.  

Science.gov (United States)

Aircraft accident rates by month were analyzed for randomness, cyclic pattern or increasing/decreasing trends for all attack, fighter and propeller type aircrafts. The technique of Runs test was employed to the runs above and below the median. The analysi...

A. Rashid

1977-01-01

350

An efficient algorithm to generate large random uncorrelated Euclidean distances: the random link model  

CERN Document Server

A disordered medium is often constructed by $N$ points independently and identically distributed in a $d$-dimensional hyperspace. Characteristics related to the statistics of this system is known as the random point problem. As $d \\to \\infty$, the distances between two points become independent random variables, leading to its mean field description: the random link model. While the numerical treatment of large random point problems pose no major difficulty, the same is not true for large random link systems due to Euclidean restrictions. Exploring the deterministic nature of the congruential pseudo-random number generators, we present techniques which allow the consideration of models with memory consumption of order O(N), instead of $O(N^2)$ in a naive implementation but with the same time dependence $O(N^2)$.

Tercariol, C A S; Tercariol, Cesar Augusto Sangaletti; Martinez, Alexandre Souto

2005-01-01

351

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

International Nuclear Information System (INIS)

[en]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

352

Nonlinear Schroedinger equations under random nonlinearity management  

International Nuclear Information System (INIS)

[en]We consider effects of random time modulation of the nonlinearity coefficient on the dynamics of one- and two-dimensional (1D and 2D) solitary waves in the nonlinear Schroedinger equation (NLSE). In particular, the cases of a single Gaussian random variable, and a temporally correlated Gaussian process are considered. In the 1D case, we demonstrate the robustness of solitons against the random nonlinearity management. In the 2D case, the share (percentage) of realizations that lead to collapse of a localized pulse is computed, in order to quantify the effect of the randomness in preventing the collapse. Dependences of this share on the mean value, standard deviation, and correlation length of the random process are obtained, and, whenever possible, compared to analytical predictions

2009-03-30

353

Nonlinear Schrdinger equations under random nonlinearity management  

Science.gov (United States)

We consider effects of random time modulation of the nonlinearity coefficient on the dynamics of one- and two-dimensional (1D and 2D) solitary waves in the nonlinear Schrdinger equation (NLSE). In particular, the cases of a single Gaussian random variable, and a temporally correlated Gaussian process are considered. In the 1D case, we demonstrate the robustness of solitons against the random nonlinearity management. In the 2D case, the share (percentage) of realizations that lead to collapse of a localized pulse is computed, in order to quantify the effect of the randomness in preventing the collapse. Dependences of this share on the mean value, standard deviation, and correlation length of the random process are obtained, and, whenever possible, compared to analytical predictions.

Chen, Qian-Yong; Kevrekidis, P. G.; Malomed, Boris A.

2009-03-01

354

Nonlinear Schroedinger equations under random nonlinearity management  

Energy Technology Data Exchange (ETDEWEB)

We consider effects of random time modulation of the nonlinearity coefficient on the dynamics of one- and two-dimensional (1D and 2D) solitary waves in the nonlinear Schroedinger equation (NLSE). In particular, the cases of a single Gaussian random variable, and a temporally correlated Gaussian process are considered. In the 1D case, we demonstrate the robustness of solitons against the random nonlinearity management. In the 2D case, the share (percentage) of realizations that lead to collapse of a localized pulse is computed, in order to quantify the effect of the randomness in preventing the collapse. Dependences of this share on the mean value, standard deviation, and correlation length of the random process are obtained, and, whenever possible, compared to analytical predictions.

Chen Qianyong; Kevrekidis, P.G. [Department of Mathematics and Statistics, University of Massachusetts, Amherst, MA 01003-4515 (United States); Malomed, Boris A. [Department of Physical Electronics, School of Electrical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978 (Israel)], E-mail: malomed@eng.tau.ac.il

2009-03-30

355

Naltrexone (50 mg) plus psychotherapy in alcohol-dependent patients: a meta-analysis of randomized controlled trials.  

UK PubMed Central (United Kingdom)

BACKGROUND: Alcoholism is a chronic and potentially fatal disease. One of the therapeutic options is pharmacotherapy with the opioid antagonist naltrexone in combination with psychotherapy. OBJECTIVES: The objective of this review was to compare the clinical effectiveness of naltrexone (50 mg/day) versus that of a placebo in alcohol-dependent patients receiving psychotherapy. METHODS: The clinical effectiveness of the treatment was assessed in accordance with the principles of systematic review, as outlined in the Cochrane Collaboration guidelines (Cochrane Reviewer's Handbook) and the guidelines of the Polish Agency for Health Technology Assessment (AHTAPol). RESULTS: Statistical significances in favor of the treatment modality were found in both the percentage of patients maintaining total abstinence and the percentage of relapsed patients. CONCLUSION: The analysis herein demonstrates that for short (12-16 weeks) period of treatment, a combination of naltrexone administration and psychotherapy results in high clinical efficacy with a safety profile comparable to that of the placebo in the treatment of alcohol-dependent patients. The side effects of naltrexone treatment are usually mild and transient.

Jarosz J; Miernik K; W?chal M; Walczak J; Krumpl G

2013-05-01

356

Alteration of substrate specificity: the variable N-terminal domain of tobacco Ca(2+)-dependent protein kinase is important for substrate recognition.  

UK PubMed Central (United Kingdom)

Protein kinases are major signaling molecules that are involved in a variety of cellular processes. However, the molecular mechanisms whereby protein kinases discriminate specific substrates are still largely unknown. Ca(2+)-dependent protein kinases (CDPKs) play central roles in Ca(2+) signaling in plants. Previously, we found that a tobacco (Nicotiana tabacum) CDPK1 negatively regulated the transcription factor REPRESSION OF SHOOT GROWTH (RSG), which is involved in gibberellin feedback regulation. Here, we found that the variable N-terminal domain of CDPK1 is necessary for the recognition of RSG. A mutation (R10A) in the variable N-terminal domain of CDPK1 reduced both RSG binding and RSG phosphorylation while leaving kinase activity intact. Furthermore, the R10A mutation suppressed the in vivo function of CDPK1. The substitution of the variable N-terminal domain of an Arabidopsis thaliana CDPK, At CPK9, with that of Nt CDPK1 conferred RSG kinase activities. This chimeric CDPK behaved according to the identity of the variable N-terminal domain in transgenic plants. Our results open the possibility of engineering the substrate specificity of CDPK by manipulation of the variable N-terminal domain, enabling a rational rewiring of cellular signaling pathways.

Ito T; Nakata M; Fukazawa J; Ishida S; Takahashi Y

2010-05-01

357

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

358

Vertical Atmospheric Structure in a Variable Brown Dwarf: Pressure-dependent Phase Shifts in Simultaneous HST-Spitzer Light Curves  

CERN Document Server

Heterogeneous clouds or temperature perturbations in rotating brown dwarfs produce variability in the observed flux. We report time-resolved simultaneous observations of the variable T6.5 brown dwarf 2MASSJ22282889-431026 over the wavelength ranges 1.1-1.7 microns and broadband 4.5 microns. Spectroscopic observations were taken with Wide Field Camera 3 onboard the Hubble Space Telescope and photometry with the Spitzer Space Telescope. The object shows sinusoidal infrared variability with a period of 1.4 hours at most wavelengths with peak-to-peak amplitudes between 1.45% and 5.3% of the mean flux. While the light curve shapes are similar at all wavelengths, their phases differ from wavelength to wavelength with a maximum difference of more than half of a rotational period. We compare the spectra with atmospheric models of different cloud prescriptions, from which we determine the pressure levels probed at different wavelengths. We find that the phase lag increases with decreasing pressure level, or higher alt...

Buenzli, Esther; Morley, Caroline V; Flateau, Davin; Showman, Adam P; Burrows, Adam; Marley, Mark S; Lewis, Nikole K; Reid, I Neill

2012-01-01

359

Strong approximation of density estimators from weakly dependent observations by density estimators from independent observations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We derive an approximation of a density estimator based on weakly dependent random vectors by a density estimator built from independent random vectors. We construct, on a sufficiently rich probability space, such a pairing of the random variables of both experiments that the set of observations (X-...

Neumann, MH

360

Impact of personalized in-home nursing care plans on dependence in ADLs/IADLs and on family burden among adults diagnosed with Schizophrenia: a randomized controlled study.  

UK PubMed Central (United Kingdom)

PURPOSE: The study aims to assess the impact of personalized in-home nursing care plans on the degree of dependence among adult patients with schizophrenia, and on family burden. DESIGN AND METHODS: This is a randomized controlled study with 94 participants: The experimental group received a personalized in-home nursing care plan. The comparison group got a standard care at its mental health center. FINDINGS: The pretest-posttest multivariate analysis of covariance revealed statistically significant group differences (p = .003). The help received the positive activity and the degree of independence in the experimental group improved mainly due to intervention. PRACTICE IMPLICATIONS: A personalized in-home nursing care plan improves the degree of independence of people diagnosed with schizophrenia living in the community and reduces the burden perceived by the family.

Roldn-Merino J; Garca IC; Ramos-Pichardo JD; Foix-Sanjuan A; Quilez-Jover J; Montserrat-Martinez M

2013-07-01

 
 
 
 
361

A randomized, double-blind, placebo-controlled clinical trial of acamprosate in alcohol-dependent individuals with bipolar disorder: a preliminary report.  

UK PubMed Central (United Kingdom)

BACKGROUND: Alcohol use disorders commonly co-occur with bipolar disorder and are associated with a more severe course of bipolar illness, yet treatment research in this important clinical population is scarce. The current study assessed the effects of acamprosate on alcohol use and mood symptoms in subjects with co-occurring bipolar disorder and active alcohol dependence. METHODS: Thirty-three adults meeting criteria for bipolar I or bipolar II disorder and current alcohol dependence were randomized to receive add-on acamprosate (1998 mg/day) or placebo while concurrently maintained on mood stabilizing medications. Participants were assessed weekly for frequency and quantity of alcohol consumption and general clinical severity for eight weeks. Depressive symptoms, manic symptoms, and alcohol craving were assessed biweekly. Biomarkers of alcohol use were assessed at study baseline and endpoint. RESULTS: Of the 33 subjects randomized, 23 (69.7%) completed all active phase visits. Over the trial as a whole, no statistically significant treatment differences were detected in drinking outcomes. Post-hoc analysis revealed lower Clinical Global Impression scores of substance use severity in acamprosate-treated participants in weeks 7-8 of the trial. No significant differences in depressive symptoms, manic symptoms, or adverse events were observed between groups. CONCLUSIONS: Acamprosate was well-tolerated, with no worsening of depressive or manic symptoms, and appeared to confer some clinical benefit in study completers in the last two weeks of the trial. Larger studies of longer duration are required to fully explore the utility of acamprosate in this population.

Tolliver BK; Desantis SM; Brown DG; Prisciandaro JJ; Brady KT

2012-02-01

362

Dependence Structure Estimation via Copula  

CERN Multimedia

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

363

Normal canine prostate gland: repeatability, reproducibility, observer-dependent variability of ultrasonographic measurements of the prostate in healthy intact beagles.  

UK PubMed Central (United Kingdom)

Most prostatic diseases in dogs are associated with prostatomegaly, and transabdominal ultrasonography has become the imaging modality of choice for evaluation of the prostate gland in the dog. The aim of the present study was to assess the reproducibility, the repeatability and interobserver variations of sonographic measurements of prostate and to determine which measurement had the lowest variability. Length and height of prostate gland were measured on longitudinal views, width of the prostate gland and height of left and right lobes of the gland on transversal views. The within-day and between-day variabilities of the prostatic parameters were determined by performing 1350 (270 length, 270 height, 270 width, 270 height of right lobe and 270 height of left lobe) examinations on ten healthy intact beagle dogs on six different days, in a two-week period (three days for the five dogs, three different days for the five others). Three observers with different levels of experience in ultrasonography performed the examinations. The lowest within-day and between-day standard deviation and coefficient of variation values were observed for the width of the prostate. The width of the gland measured on transverse frozen images seems to be the most reliable measurement for evaluating size of prostate glands in healthy dogs, although the shape, position, outline, and echogenicity of the prostate should also be assessed.

Leroy C; Conchou F; Layssol-Lamour C; Deviers A; Sautet J; Concordet D; Mogicato G

2013-10-01

364

Normal canine prostate gland: repeatability, reproducibility, observer-dependent variability of ultrasonographic measurements of the prostate in healthy intact beagles.  

Science.gov (United States)

Most prostatic diseases in dogs are associated with prostatomegaly, and transabdominal ultrasonography has become the imaging modality of choice for evaluation of the prostate gland in the dog. The aim of the present study was to assess the reproducibility, the repeatability and interobserver variations of sonographic measurements of prostate and to determine which measurement had the lowest variability. Length and height of prostate gland were measured on longitudinal views, width of the prostate gland and height of left and right lobes of the gland on transversal views. The within-day and between-day variabilities of the prostatic parameters were determined by performing 1350 (270 length, 270 height, 270 width, 270 height of right lobe and 270 height of left lobe) examinations on ten healthy intact beagle dogs on six different days, in a two-week period (three days for the five dogs, three different days for the five others). Three observers with different levels of experience in ultrasonography performed the examinations. The lowest within-day and between-day standard deviation and coefficient of variation values were observed for the width of the prostate. The width of the gland measured on transverse frozen images seems to be the most reliable measurement for evaluating size of prostate glands in healthy dogs, although the shape, position, outline, and echogenicity of the prostate should also be assessed. PMID:23293870

Leroy, C; Conchou, F; Layssol-Lamour, C; Deviers, A; Sautet, J; Concordet, D; Mogicato, G

2013-01-07

365

The impact of clinical and demographic variables on cognitive performance in methamphetamine-dependent individuals in rural South Carolina.  

UK PubMed Central (United Kingdom)

Inconsistencies in reports on methamphetamine (METH) associated cognitive dysfunction may be attributed, at least in part, to the diversity of study sample features (eg, clinical and demographic characteristics). The current study assessed cognitive function in a METH-dependent population from rural South Carolina, and the impact of demographic and clinical characteristics on performance. Seventy-one male (28.2%) and female (71.8%) METH-dependent subjects were administered a battery of neurocognitive tests including the Test of Memory Malingering (TOMM), Shipley Institute of Living Scale, Paced Auditory Serial Addition Test (PASAT), Symbol Digit Modalities Test (SDMT), Grooved Pegboard Test, California Verbal Learning Test (CVLT), and Wisconsin Card Sorting Test (WCST). Demographic and clinical characteristics (eg, gender, frequency of METH use) were examined as predictors of performance. Subjects scored significantly lower than expected on one test of attention and one of fine motor function, but performed adequately on all other tests. There were no predictors of performance on attention; however, more frequent METH use was associated with better performance for males and worse for females on fine motor skills. The METH-dependent individuals in this population exhibit very limited cognitive impairment. The marked differences in education, Intellectual Quotient (IQ), and gender in our sample when compared to the published literature may contribute to these findings. Characterization of the impact of clinical and/or demographic features on cognitive deficits could be important in guiding the development of treatment interventions.

Price KL; DeSantis SM; Simpson AN; Tolliver BK; McRae-Clark AL; Saladin ME; Baker NL; Wagner MT; Brady KT

2011-09-01

366

The impact of clinical and demographic variables on cognitive performance in methamphetamine-dependent individuals in rural South Carolina.  

Science.gov (United States)

Inconsistencies in reports on methamphetamine (METH) associated cognitive dysfunction may be attributed, at least in part, to the diversity of study sample features (eg, clinical and demographic characteristics). The current study assessed cognitive function in a METH-dependent population from rural South Carolina, and the impact of demographic and clinical characteristics on performance. Seventy-one male (28.2%) and female (71.8%) METH-dependent subjects were administered a battery of neurocognitive tests including the Test of Memory Malingering (TOMM), Shipley Institute of Living Scale, Paced Auditory Serial Addition Test (PASAT), Symbol Digit Modalities Test (SDMT), Grooved Pegboard Test, California Verbal Learning Test (CVLT), and Wisconsin Card Sorting Test (WCST). Demographic and clinical characteristics (eg, gender, frequency of METH use) were examined as predictors of performance. Subjects scored significantly lower than expected on one test of attention and one of fine motor function, but performed adequately on all other tests. There were no predictors of performance on attention; however, more frequent METH use was associated with better performance for males and worse for females on fine motor skills. The METH-dependent individuals in this population exhibit very limited cognitive impairment. The marked differences in education, Intellectual Quotient (IQ), and gender in our sample when compared to the published literature may contribute to these findings. Characterization of the impact of clinical and/or demographic features on cognitive deficits could be important in guiding the development of treatment interventions. PMID:21838844

Price, Kimber L; DeSantis, Stacia M; Simpson, Annie N; Tolliver, Bryan K; McRae-Clark, Aimee L; Saladin, Michael E; Baker, Nathaniel L; Wagner, Mark T; Brady, Kathleen T

2011-07-18

367

Phase Transition in Unrestricted Random SAT  

CERN Document Server

For random CNF formulae with m clauses, n variables and an unrestricted number of literals per clause the transition from high to low satisfiability can be determined exactly for large n. The critical density m/n turns out to be strongly n-dependent, ccr = ln(2)/(1-p)^^n, where pn is the mean number of positive literals per clause.This is in contrast to restricted random SAT problems (random K-SAT), where the critical ratio m/n is a constant. All transition lines are calculated by the second moment method applied to the number of solutions N of a formula. In contrast to random K-SAT, the method does not fail for the unrestricted model, because long range interactions between solutions are not cut off by disorder.

Schuh, Bernd R

2012-01-01

368

Analysis of a Random Forests Model  

CERN Document Server

Random forests are a scheme proposed by Leo Breiman in the 00's for building a predictor ensemble with a set of decision trees that grow in randomly selected subspaces of data. Despite growing interest and practical use, there has been little exploration of the statistical properties of random forests, and little is known about the mathematical forces driving the algorithm. In this paper, we offer an in-depth analysis of a random forests model suggested by Breiman in 2004, which is very close to the original algorithm. We show in particular that the procedure is consistent and adapts to sparsity, in the sense that its rate of convergence depends only on the number of strong features and not on how many noise variables are present.

Biau, Grard

2010-01-01

369

Adeno-associated virus vectors show variable dependence on divalent cations for thermostability: implications for purification and handling.  

Science.gov (United States)

Recombinant adeno-associated virus (rAAV) shows significant promise as a vector for gene transfer in pre-clinical models of human disease, and is currently being evaluated in human clinical trials. As a consequence, increasing attention is being turned to the important tasks of optimizing rAAV titer, purity, and stability. We have observed dramatic variation in divalent cation dependence for thermostability of different rAAV vectors. To further investigate this observation, the thermostability of eight different vector constructs ranging in size from 73 to 107% of wild-type genome size (4.68 kilobases) was determined in the presence and absence of divalent cations. Virions containing smaller genomes (i.e., 95% wild type) were dependent on divalent cations for thermostability. Genome sequence also appeared to be a factor in the thermostability of the larger rAAV vectors. These observations are of both practical and theoretical significance. Divalent cations should be included in all buffer solutions used during rAAV purification and storage, and unnecessary heat exposure avoided. These data also demonstrate that different recombinants of a particular virus should not be assumed to possess the same thermostability profile. PMID:10724041

Turnbull, A E; Skulimowski, A; Smythe, J A; Alexander, I E

2000-03-01

370

Caffeine Expectancy Questionnaire (CaffEQ): construction, psychometric properties, and associations with caffeine use, caffeine dependence, and other related variables.  

UK PubMed Central (United Kingdom)

Expectancies for drug effects predict drug initiation, use, cessation, and relapse, and may play a causal role in drug effects (i.e., placebo effects). Surprisingly little is known about expectancies for caffeine even though it is the most widely used psychoactive drug in the world. In a series of independent studies, the nature and scope of caffeine expectancies among caffeine consumers and nonconsumers were assessed, and a comprehensive and psychometrically sound Caffeine Expectancy Questionnaire (CaffEQ) was developed. After 2 preliminary studies, the CaffEQ was administered to 1,046 individuals from the general population along with other measures of interest (e.g., caffeine use history, anxiety). Exploratory factor analysis of the CaffEQ yielded a 7-factor solution. Subsequently, an independent sample of 665 individuals completed the CaffEQ and other measures, and a subset (n = 440) completed the CaffEQ again approximately 2 weeks later. Confirmatory factor analysis revealed good model fit, and test-retest reliability was very good. The frequency and quantity of caffeine use were associated with greater expectancies for withdrawal/dependence, energy/work enhancement, appetite suppression, social/mood enhancement, and physical performance enhancement and lower expectancies for anxiety/negative physical effects and sleep disturbance. Caffeine expectancies predicted various caffeine- associated features of substance dependence (e.g., use despite harm, withdrawal incidence and severity, perceived difficulty stopping use, tolerance). Expectancies for caffeine consumed via coffee were stronger than for caffeine consumed via soft drinks or tea. The CaffEQ should facilitate the advancement of our knowledge of caffeine and drug use in general.

Huntley ED; Juliano LM

2012-09-01

371

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

372

Random matrices, random polynomials and Coulomb systems  

CERN Multimedia

It is well known that the joint probability density of the eigenvalues of Gaussian ensembles of random matrices may be interpreted as a Coulomb gas. We review these classical results for hermitian and complex random matrices, with special attention devoted to electrostatic analogies. We also discuss the joint probability density of the zeros of polynomials whose coefficients are complex Gaussian variables. This leads to a new two-dimensional solvable gas of interacting particles, with non-trivial interactions between particles.

Leboeuf, P

1999-01-01

373

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 g/kg/5minutes) was tested at two different paced heart rates (6065 bpm vs 100110 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 0.63.0 1.8 ms, P < 0.05), but at the high-rate STV did not change significantly (0.9 0.21.5 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 Bkgaard

2010-01-01

374

Male-dependent variability of fertilization and embryo development in two bovine in vitro fertilization systems and the effects of casein phosphopeptides (CPPs).  

UK PubMed Central (United Kingdom)

This study investigated the effects of semen from five different bulls and two different ejaculates of the same bull on penetration, cleavage, blastocyst formation, and cell allocation in bovine blastocysts produced in vitro. Casein phosphopeptides (CPPs) were tested for their ability to enhance fertilization and minimize variability among bulls and ejaculates. In Experiment 1, the BO-fertilization system was employed. Penetration and polyspermy both displayed great variation among bulls and between ejaculates, whereas no significant differences were observed in cleavage and blastocyst-formation rates. Similar variability was observed in penetration, polyspermy, cleavage, blastocyst-formation rates and cell allocation and distribution when the two fertilization systems, TALP and BO, were compared in Experiment 2. The BO-system supported penetration and polyspermy better (P < 0.05) than the TALP-system, whereas the TALP-system was superior (P < 0.05) in supporting cleavage and blastocyst formation. Significant interactions existed between bulls and the fertilization system employed. It is concluded that the success of in vitro fertilization is markedly dependent on individual bulls as well as on ejaculates from the same bull. CPPs are able to enhance penetration and embryo development in certain bulls or ejaculates and thus contribute to reducing the degree of individual variability, but they do not generally improve the success of bovine embryo production in vitro.

Kreysing U; Nagai T; Niemann H

1997-01-01

375

Male-dependent variability of fertilization and embryo development in two bovine in vitro fertilization systems and the effects of casein phosphopeptides (CPPs).  

Science.gov (United States)

This study investigated the effects of semen from five different bulls and two different ejaculates of the same bull on penetration, cleavage, blastocyst formation, and cell allocation in bovine blastocysts produced in vitro. Casein phosphopeptides (CPPs) were tested for their ability to enhance fertilization and minimize variability among bulls and ejaculates. In Experiment 1, the BO-fertilization system was employed. Penetration and polyspermy both displayed great variation among bulls and between ejaculates, whereas no significant differences were observed in cleavage and blastocyst-formation rates. Similar variability was observed in penetration, polyspermy, cleavage, blastocyst-formation rates and cell allocation and distribution when the two fertilization systems, TALP and BO, were compared in Experiment 2. The BO-system supported penetration and polyspermy better (P < 0.05) than the TALP-system, whereas the TALP-system was superior (P < 0.05) in supporting cleavage and blastocyst formation. Significant interactions existed between bulls and the fertilization system employed. It is concluded that the success of in vitro fertilization is markedly dependent on individual bulls as well as on ejaculates from the same bull. CPPs are able to enhance penetration and embryo development in certain bulls or ejaculates and thus contribute to reducing the degree of individual variability, but they do not generally improve the success of bovine embryo production in vitro. PMID:9402257

Kreysing, U; Nagai, T; Niemann, H

1997-01-01

376

Influence of some formulation variables on the optimization of pH-dependent, colon-targeted, sustained-release mesalamine microspheres.  

UK PubMed Central (United Kingdom)

The aim of this work was to understand the influence of different formulation variables on the optimization of pH-dependent, colon-targeted, sustained-release mesalamine microspheres prepared by O/O emulsion solvent evaporation method, employing pH-dependent Eudragit S and hydrophobic pH-independent ethylcellulose polymers. Formulation variables studied included concentration of Eudragit S in the internal phase and the ratios between; internal to external phase, drug to Eudragit S and Eudragit S to ethylcellulose to mesalamine. Prepared microspheres were evaluated by carrying out in vitro release studies and determination of particle size, production yield, and encapsulation efficiency. In addition, morphology of microspheres was examined using optical and scanning electron microscopy. Emulsion solvent evaporation method was found to be sensitive to the studied formulation variables. Particle size and encapsulation efficiency increased by increasing Eudragit S concentration in the internal phase, ratio of internal to external phase, and ratio of Eudragit S to the drug. Employing Eudragit S alone in preparation of the microspheres is only successful in forming acid-resistant microspheres with pulsatile release pattern at high pH. Eudragit S and ethylcellulose blend microspheres were able to control release under acidic condition and to extend drug release at high pH. The stability studies carried out at 40C/75% RH for 6 months proved the stability of the optimized formulation. From the results of this investigation, microencapsulation of mesalamine in microspheres using blend of Eudragit S and ethylcellulose could constitute a promising approach for site-specific and controlled delivery of drug in colon.

El-Bary AA; Aboelwafa AA; Al Sharabi IM

2012-03-01

377

Potassium Loss from Chlorhexidine-Treated Bacterial Pathogens is Time- and Concentration-Dependent and Variable Between Species.  

UK PubMed Central (United Kingdom)

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.

O'Driscoll NH; Labovitiadi O; Cushnie TP; Matthews KH; Lamb AJ

2013-08-01

378

Variable effects of parabrachial nucleus lesions on salt appetite in rats depending upon experimental paradigm and saline concentration.  

UK PubMed Central (United Kingdom)

Previous studies have demonstrated that bilateral lesions of the gustatory (medial) zone of the parabrachial nucleus (PBN) in the pons eliminate the salt (sodium chloride; NaCl) appetite induced in rats by treatment with the diuretic drug, furosemide. The present studies reexamined NaCl intake of rats with PBN lesions induced by ibotenic acid, using multiple models of salt appetite. The impairment of a conditioned taste aversion, an established consequence of PBN damage, was used as an initial screen with which to assess the effectiveness of the lesions. Rats with PBN lesions did not drink either 0.3 of a molar (M) solution of NaCl or 0.5 M NaCl in response to daily treatment with desoxycorticosterone acetate. These findings suggest that the excitatory stimulus of salt appetite mediated by mineralocorticoids is abolished by PBN lesions. In contrast, rats with PBN lesions drank some 0.5 M NaCl and more 0.3 M NaCl, in addition to water, in response to hypovolemia induced by subcutaneous injection of 30% polyethylene glycol solution. Those findings suggest that an excitatory stimulus of salt appetite, presumably mediated by Angiotensin II, is not abolished by PBN lesions. These and other observations indicate that lesions of the gustatory PBN in rats may or may not eliminate salt appetite, depending on which model is used and which concentration of NaCl solution is available.

Stricker EM; Grigson PS; Norgren R

2013-04-01

379

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.  

UK PubMed Central (United Kingdom)

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.

Ramrez-Vlez R; Romero M; Echeverri I; Ortega JG; Mosquera M; Salazar B; Girn SL; Saldarriaga W; Aguilar de Plata AC; Mateus JC

2011-01-01

380

No effect of short-term amino acid supplementation on variables related to skeletal muscle damage in 100 km ultra-runners - a randomized controlled trial  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background The purpose of this study was to investigate the effect of short-term supplementation of amino acids before and during a 100 km ultra-marathon on variables of skeletal muscle damage and muscle soreness. We hypothesized that the supplementation of amino acids before and during an ultra-marathon would lead to a reduction in the variables of skeletal muscle damage, a decrease in muscle soreness and an improved performance. Methods Twenty-eight experienced male ultra-runners were divided into two groups, one with amino acid supplementation and the other as a control group. The amino acid group was supplemented a total of 52.5 g of an amino acid concentrate before and during the 100 km ultra-marathon. Pre- and post-race, creatine kinase, urea and myoglobin were determined. At the same time, the athletes were asked for subjective feelings of muscle soreness. Results Race time was not different between the groups when controlled for personal best time in a 100 km ultra-marathon. The increases in creatine kinase, urea and myoglobin were not different in both groups. Subjective feelings of skeletal muscle soreness were not different between the groups. Conclusions We concluded that short-term supplementation of amino acids before and during a 100 km ultra-marathon had no effect on variables of skeletal muscle damage and muscle soreness.

Knechtle Beat; Knechtle Patrizia; Mrazek Claudia; Senn Oliver; Rosemann Thomas; Imoberdorf Reinhard; Ballmer Peter

2011-01-01

 
 
 
 
381

Effect of acamprosate on magnetic resonance spectroscopy measures of central glutamate in detoxified alcohol-dependent individuals: a randomized controlled experimental medicine study.  

UK PubMed Central (United Kingdom)

CONTEXT: Acamprosate is approved for the treatment of alcoholism, but its mechanism of action remains unclear. Results of animal studies suggest that a persistent hyperglutamatergic state contributes to the pathogenesis of alcoholism and that acamprosate may exert its actions by intervening in this process. Human translation of these findings is lacking. OBJECTIVE: To examine whether acamprosate modulates indices of central glutamate levels in recently abstinent alcohol-dependent patients as measured using proton nuclear magnetic resonance spectroscopy (H-MRS). DESIGN: A 4-week, double-blind, placebo-controlled, randomized controlled experimental medicine study, with H-MRS measures obtained on days 4 and 25. SETTING: An inpatient research unit at the NIH Clinical Center. Patients Thirty-three patients who met the DSM-IV criteria for alcohol dependence and who were admitted for medically supervised withdrawal from ongoing alcohol use. Intervention Four weeks of acamprosate (initial oral loading followed by 1998 mg daily) or matched placebo, initiated at the time of admission. MAIN OUTCOME MEASURES: The glutamate to creatine ratio as determined using single-voxel H-MRS in the anterior cingulate. Exploratory neuroendocrine, biochemical, and behavioral outcomes were also collected, as were safety- and tolerability-related measures. RESULTS: There was a highly significant suppression of the glutamate to creatine ratio across time by acamprosate (time treatment interaction: F?(,)?? = 13.5, P < .001). Cerebrospinal fluid levels of glutamate obtained in a subset of patients 4 weeks into abstinence were uncorrelated with the MRS measures and unaffected by treatment but were strongly correlated (R = 0.48, P < .001) with alcohol dependence severity. Other exploratory outcomes, including repeated dexamethasone-corticotropin-releasing hormone tests, and psychiatric ratings were unaffected. Among tolerability measures, gastrointestinal symptoms were significantly greater in acamprosate-treated individuals, in agreement with the established profile of acamprosate. CONCLUSION: The MRS measures of central glutamate are reduced across time when acamprosate therapy is initiated at the onset of alcohol abstinence. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00106106.

Umhau JC; Momenan R; Schwandt ML; Singley E; Lifshitz M; Doty L; Adams LJ; Vengeliene V; Spanagel R; Zhang Y; Shen J; George DT; Hommer D; Heilig M

2010-10-01

382

Relatively random: context effects on perceived randomness and predicted outcomes.  

UK PubMed Central (United Kingdom)

This article concerns the effect of context on people's judgments about sequences of chance outcomes. In Experiment 1, participants judged whether sequences were produced by random, mechanical processes (such as a roulette wheel) or skilled human action (such as basketball shots). Sequences with lower alternation rates were judged more likely to result from human action. However, this effect was highly context-dependent: A moderate alternation rate was judged more likely to indicate a random physical process when encountered among sequences with lower alternation rates than when embedded among sequences with higher alternation rates. Experiment 2 found the same effect for predictions of the next outcome following a streak: A streak of 3 at the end of the sequence was judged less likely to continue by participants who had encountered shorter terminal streaks in previous trials than by those who had encountered longer ones. These contrast effects (a) help to explain variability in the types of sequences that are judged to be random and that elicit the gambler's fallacy, and urge caution about attempts to establish universal parameterizations of these effects; (b) are congruent with theories of sequence judgment that emphasize the importance of people's actual experiences with sequences of different kinds; (c) provide a link between models of sequence judgment and broader accounts of psychophysical/economic judgment; and (d) may offer new insight into individual differences in randomness judgments and sequence predictions.

Matthews WJ

2013-09-01

383

Relatively random: context effects on perceived randomness and predicted outcomes.  

Science.gov (United States)

This article concerns the effect of context on people's judgments about sequences of chance outcomes. In Experiment 1, participants judged whether sequences were produced by random, mechanical processes (such as a roulette wheel) or skilled human action (such as basketball shots). Sequences with lower alternation rates were judged more likely to result from human action. However, this effect was highly context-dependent: A moderate alternation rate was judged more likely to indicate a random physical process when encountered among sequences with lower alternation rates than when embedded among sequences with higher alternation rates. Experiment 2 found the same effect for predictions of the next outcome following a streak: A streak of 3 at the end of the sequence was judged less likely to continue by participants who had encountered shorter terminal streaks in previous trials than by those who had encountered longer ones. These contrast effects (a) help to explain variability in the types of sequences that are judged to be random and that elicit the gambler's fallacy, and urge caution about attempts to establish universal parameterizations of these effects; (b) are congruent with theories of sequence judgment that emphasize the importance of people's actual experiences with sequences of different kinds; (c) provide a link between models of sequence judgment and broader accounts of psychophysical/economic judgment; and (d) may offer new insight into individual differences in randomness judgments and sequence predictions. PMID:23356242

Matthews, William J

2013-01-28

384

Genes at work in random bouts: stochastically discontinuous gene activity makes cell cycle duration and cell fate decisions variable, thus providing for stem cells plasticity.  

UK PubMed Central (United Kingdom)

Cell interdivision periods (IDP) in homogenous cell populations vary stochastically. Another aspect of probabilistic cell behavior is randomness in cell differentiation. These features are suggested to result from competing stochastic events of assembly/disassembly of the transcription pre-initiation complex (PIC) at gene promoters. The time needed to assemble a proper PIC from different proteins, which must be numerous enough to make their combination gene specific, may be comparable to the IDP. Nascent mRNA visualization at defined genes and inferences from protein level fluctuations in single cells suggest that some genes do operate in this way. The onset of mRNA production by such genes may miss the time windows provided by the cell cycle, resulting in cells differentiating into those in which the respective mRNAs are either present or absent. This creates a way to generate cell phenotype diversity in multicellular organisms.

Golubev A

2012-04-01

385

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

386

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; P. Pal; S. Chattopadhyay; B. K. Medya

2011-01-01

387

Can a soda-lime glass be used to demonstrate how patterns of strength dependence are influenced by pre-cementation and resin-cementation variables?  

UK PubMed Central (United Kingdom)

OBJECTIVES: 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. METHODS: The flexural modulus of a transparent soda-lime glass was determined by longitudinally sectioning into rectangular bar-shaped specimens and the flexural moduli of three resin-based materials (Venus Flow, Rely-X Veneer and Clearfil Majesty Posterior) was also determined. Disc shaped soda-lime glass specimens (n=240) were divided into ten groups and were alumina particle air abraded, hydrofluoric (HF) acid-etched and resin-cement coated prior to biaxial flexure strength testing. Sample sets were profilometrically evaluated to determine the surface texture. One-way analyses of variance (ANOVA) and post hoc all paired Tukey tests were performed at a significance level of P<0.05. The mean biaxial flexure strengths were plotted against resin-coating thickness and a regression analysis enabled estimation of the 'actual' magnitude of strengthening. RESULTS: The mean three-point flexural modulus of the soda-lime glass was 40.0 (1.0)GPa and the Venus Flow, Rely-X Veneer and Clearfil Majesty Posterior were 3.0 (0.2)GPa, 6.0 (0.2)GPa and 14.8 (1.6)GPa, respectively. At a theoretical 'zero' resin-coating thickness an increase in biaxial flexure strength of 20.1% (63.2MPa), 30.8% (68.8MPa) and 36.3% (71.7MPa), respectively was evident compared with the control (52.6 (5.5)MPa). CONCLUSIONS: Disc-shaped specimens cut from round stock facilitated rapid fabrication of discs with uniform surface condition and demonstrated strength dependence was influenced by precementation parameters and resin-cementation variables.

Hooi P; Addison O; Fleming GJ

2013-01-01

388

The phosphotransferase system-dependent sucrose utilization regulon in enteropathogenic Escherichia coli strains is located in a variable chromosomal region containing iap sequences.  

UK PubMed Central (United Kingdom)

The capacity to utilize sucrose as a carbon and energy source (Scr(+) phenotype) is a highly variable trait among Escherichia coli strains. In this study, seven enteropathogenic E. coli (EPEC) strains from different sources were studied for their capacity to grow using sucrose. Liquid media cultures showed that all analyzed strains have the Scr(+) phenotype and two distinct groups were defined: one of five and another of two strains displaying doubling times of 67 and 125 min, respectively. The genes conferring the Scr(+) phenotype in one of the fast-growing strains (T19) were cloned and sequenced. Comparative sequence analysis revealed that this strain possesses the scr regulon genes scrKYABR, encoding phosphoenolpyruvate:phosphotransferase system-dependent sucrose transport and utilization activities. Transcript level quantification revealed sucrose-dependent induction of scrK and scrR genes in fast-growing strains, whereas no transcripts were detected in slow-growing strains. Sequence comparison analysis revealed that the scr genes in strain T19 are almost identical to those present in the scr regulon of prototype EPEC E2348/69 and in both strains, the scr genes are inserted in the chromosomal intergenic region of hypothetical genes ygcE and ygcF. Comparison of the ygcE-ygcF intergenic region sequence of strains MG1655, enterohemorrhagic EDL933, uropathogenic ECFT073 and EPEC T19-E2348/69 revealed that the number of extragenic highly repeated iap sequences corresponded to nine, four, two and none, respectively. These results show that the iap sequence-containing chromosomal ygcE-ygcF intergenic region is highly variable in E. coli.

Trevio-Quintanilla LG; Escalante A; Caro AD; Martnez A; Gonzlez R; Puente JL; Bolvar F; Gosset G

2007-01-01

389

The phosphotransferase system-dependent sucrose utilization regulon in enteropathogenic Escherichia coli strains is located in a variable chromosomal region containing iap sequences.  

Science.gov (United States)

The capacity to utilize sucrose as a carbon and energy source (Scr(+) phenotype) is a highly variable trait among Escherichia coli strains. In this study, seven enteropathogenic E. coli (EPEC) strains from different sources were studied for their capacity to grow using sucrose. Liquid media cultures showed that all analyzed strains have the Scr(+) phenotype and two distinct groups were defined: one of five and another of two strains displaying doubling times of 67 and 125 min, respectively. The genes conferring the Scr(+) phenotype in one of the fast-growing strains (T19) were cloned and sequenced. Comparative sequence analysis revealed that this strain possesses the scr regulon genes scrKYABR, encoding phosphoenolpyruvate:phosphotransferase system-dependent sucrose transport and utilization activities. Transcript level quantification revealed sucrose-dependent induction of scrK and scrR genes in fast-growing strains, whereas no transcripts were detected in slow-growing strains. Sequence comparison analysis revealed that the scr genes in strain T19 are almost identical to those present in the scr regulon of prototype EPEC E2348/69 and in both strains, the scr genes are inserted in the chromosomal intergenic region of hypothetical genes ygcE and ygcF. Comparison of the ygcE-ygcF intergenic region sequence of strains MG1655, enterohemorrhagic EDL933, uropathogenic ECFT073 and EPEC T19-E2348/69 revealed that the number of extragenic highly repeated iap sequences corresponded to nine, four, two and none, respectively. These results show that the iap sequence-containing chromosomal ygcE-ygcF intergenic region is highly variable in E. coli. PMID:17693719

Trevio-Quintanilla, Luis Gerardo; Escalante, Adelfo; Caro, Alma Delia; Martnez, Alfredo; Gonzlez, Ricardo; Puente, Jos Luis; Bolvar, Francisco; Gosset, Guillermo

2007-01-01

390

Isotope partitioning in the adenosine 3',5'-monophosphate dependent protein kinase reaction indicates a steady-state random kinetic mechanism  

International Nuclear Information System (INIS)

Isotope partitioning beginning with the binary E.MgATP and E.N-acetyl-Leu-Arg-Arg-Ala-Ser-Leu-Gly (Ser-peptide) complexes indicates that the kinetic mechanism for the adenosine 3',5'-monophosphate dependent protein kinase is steady-state random. A total of 100% of the initial radioactive E.MgATP complex is trapped as phospho-Ser-peptide at infinite Ser-peptide concentration at both low and high concentration of uncomplexed Mg2+, suggesting that the off-rate of MgATP from the E.MgATP.Ser-peptide complex is slow relative to the catalytic steps. Km for Ser-peptide in the trapping reaction decreases from 17 microM at low Mg2+ to 2 microM at high Mg2+, indicating that Mg2+ decreases the off-rate for MgATP from the E.MgATP complex. A total of 100% of the radioactive E.Ser-peptide complex is trapped as phospho-Ser-peptide at low Mg2+, but only 40% is trapped at high Mg2+ in the presence of an infinite concentration of MgATP, suggesting that the off-rate for Ser-peptide from the central complex is much less than catalysis at low but not at high Mg2+. In support of this finding, the Ki for Leu-Arg-Arg-Ala-Ala-Leu-Gly (Ala-peptide) increases from 0.27 mM at low Mg2+ to 2.4 mM at high Mg2+. No trapping was observed at either high or low Mg2+ for the E.MgADP complex up to a phospho-Ser-peptide concentration of 5 mM. Thus, it is likely that in the slow-reaction direction the kinetic mechanism is rapid equilibrium.

1988-01-01

391

Limit theorems for Markov random fields  

International Nuclear Information System (INIS)

Markov Random Fields (MRF's) have been extensively applied in Statistical Mechanics as well as in Bayesian Image Analysis. MRF's are a special class of dependent random variables located at the vertices of a graph whose joint distribution includes a parameter called the temperature. When the number of vertices of the graph tends to infinity, the normalized distribution of statistics based on these random variables converge in distribution. It can happen that for certain values of the temperature, that the rate of growth of these normalizing constants change drastically. This feature is generally used to explain the phenomenon of phase transition as understood by physicist. In this dissertation the author will show that this drastic change in normalizing constants occurs even in the relatively smooth case when all the random variables are Gaussian. Hence any image analytic MRF ought to be checked for such discontinuous behavior before any analysis is performed. Mixed limit theorems in Bayesian Image Analysis seek to replace intensive simulations of MRF's with limit theorems that approximate the distribution of the MRF's as the number of sites increases. The problem of deriving mixed limit theorems for MRF's on a one dimensional lattice graph with an acceptor function that has a second moment has been studied by Chow. A mixed limit theorem for the integer lattice graph is derived when the acceptor function does not have a second moment as for instance when the acceptor function is a symmetric stable density of index 0

1991-01-01

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

A new method to detect transitory signatures and local time/space variability structures in the climate system: the scale-dependent correlation analysis  

Energy Technology Data Exchange (ETDEWEB)

The study of transitory signals and local variability structures in both/either time and space and their role as sources of climatic memory, is an important but often neglected topic in climate research despite its obvious importance and extensive coverage in the literature. Transitory signals arise either from non-linearities, in the climate system, transitory atmosphere-ocean couplings, and other processes in the climate system evolving after a critical threshold is crossed. These temporary interactions that, though intense, may not last long, can be responsible for a large amount of unexplained variability but are normally considered of limited relevance and often, discarded. With most of the current techniques at hand these typology of signatures are difficult to isolate because the low signal-to-noise ratio in midlatitudes, the limited recurrence of the transitory signals during a customary interval of data considered. Also, there is often a serious problem arising from the smoothing of local or transitory processes if statistical techniques are applied, that consider all the length of data available, rather than taking into account the size of the specific variability structure under investigation. Scale-dependent correlation (SDC) analysis is a new statistical method capable of highlighting the presence of transitory processes, these former being understood as temporary significant lag-dependent autocovariance in a single series, or covariance structures between two series. This approach, therefore, complements other approaches such as those resulting from the families of wavelet analysis, singular-spectrum analysis and recurrence plots. A main feature of SDC is its high-performance for short time series, its ability to characterize phase-relationships and thresholds in the bivariate domain. Ultimately, SDC helps tracking short-lagged relationships among processes that locally or temporarily couple and uncouple. The use of SDC is illustrated in the present paper by means of some synthetic time-series examples of increasing complexity, and it is compared with wavelet analysis in order to provide a well-known reference of its capabilities. A comparison between SDC and companion techniques is also addressed and results are exemplified for the specific case of some relevant El Nino-Southern Oscillation teleconnections. (orig.)

Rodo, Xavier; Rodriguez-Arias, Miquel-Angel [University of Barcelona, Laboratori de Recerca del Clima, Barcelona (Spain)

2006-10-15

394

Genetic variability in Gibberella fujikuroi and some related species of the genus Fusarium based on random amplification of polymorphic DNA (RAPD).  

UK PubMed Central (United Kingdom)

One of the most important rice pathogens is Fusarium moniliforme (perfect stage: Gibberella fujikuroi), the causal agent of the super-elongation ("bakanae") disease. Thirty-seven strains of this species from different geographical regions were analyzed for their ability to produce gibberellins (GA) and for genetic relatedness by random amplified polymorphic DNA (RAPD). All GA-producing isolates showed nearly identical RAPD patterns using 51 oligonucleotide nona- and deca-mers as arbitrary primers. On the other hand, large differences between GA-nonproducing isolates were obtained. Comparison of the RAPD patterns with those of the tester strains of the six known mating populations (A, B, C, D, E, F) of G. fujikuroi showed that all producer strains belong to mating population C and all nonproducer isolates to other mating populations. Evidence for the usefulness of the RAPD technique to distinguish between mating populations was provided by sexual crossings. Consensus phylogenetic trees based on RAPDs were constructed by the Phylogenetic Analysis Using Parsimony (PAUP) system. In combination with morphological analysis, RAPD can distinguish between different species of the genus Fusarium. These investigations may find an application in the diagnosis of unknown Fusarium spp. and in distinguishing isolates of G. fujikuroi within the section Liseola.

Voigt K; Schleier S; Brckner B

1995-05-01

395

Genetic variability in Gibberella fujikuroi and some related species of the genus Fusarium based on random amplification of polymorphic DNA (RAPD).  

Science.gov (United States)

One of the most important rice pathogens is Fusarium moniliforme (perfect stage: Gibberella fujikuroi), the causal agent of the super-elongation ("bakanae") disease. Thirty-seven strains of this species from different geographical regions were analyzed for their ability to produce gibberellins (GA) and for genetic relatedness by random amplified polymorphic DNA (RAPD). All GA-producing isolates showed nearly identical RAPD patterns using 51 oligonucleotide nona- and deca-mers as arbitrary primers. On the other hand, large differences between GA-nonproducing isolates were obtained. Comparison of the RAPD patterns with those of the tester strains of the six known mating populations (A, B, C, D, E, F) of G. fujikuroi showed that all producer strains belong to mating population C and all nonproducer isolates to other mating populations. Evidence for the usefulness of the RAPD technique to distinguish between mating populations was provided by sexual crossings. Consensus phylogenetic trees based on RAPDs were constructed by the Phylogenetic Analysis Using Parsimony (PAUP) system. In combination with morphological analysis, RAPD can distinguish between different species of the genus Fusarium. These investigations may find an application in the diagnosis of unknown Fusarium spp. and in distinguishing isolates of G. fujikuroi within the section Liseola. PMID:7553937

Voigt, K; Schleier, S; Brckner, B

1995-05-01

396

Detection of genetic variability in Basmati and non-Basmati rice varieties and their radiation induced mutants through random amplified polymorphic DNA (RAPD)  

International Nuclear Information System (INIS)

[en]Random Amplified Polymorphic DNA (RAPDs) markers were utilized to detect polymorphism between pure lines and commercially available Basmati rice varieties to assess variation which may be helpful in quality control and varietal identification (Basmati-370 and derived radiation induced mutants), differentiation of mutants and parents, and identification of RAPD markers co-segregating with important agronomic traits including plant height, days to flower and grain quality. Basmati varieties were distinguished from non-Basmati varieties with the help of five diagnostic markers which will be useful for detecting mixing of non-Basmati and Basmati rices, currently a serious marketing problem. Different Basmati cultivars were identified with the help of diagnostic RAPD markers which can be used in quality control as well as for ''fingerprinting'' of cultivars. Different radiation induced mutants were also successfully distinguished from the parents on the basis of variety specific and mutant specific markers which will be useful for varietal identification. In addition to this, other markers were also identified which can differentiate mutants from each other and are being, used for the fingerprinting of different mutants, particularly the dwarf mutants having similar appearance but different parentage. For identification of RAPD markers co-segregating with plant height and days to flower, 50 F2 plants and four F3 families were studied from a reciprocal cross made between Kashmir Basmati (tall and early) and Basmati-198 (dwarf and late). Segregating bands were observed within these populations, and indicating the possible use of RAPD markers for tagging gene(s) of agronomic importance in rice. (author)

1998-01-01

397

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

398

Once daily versus conventional dosing of pH-dependent mesalamine long-term to maintain quiescent ulcerative colitis: Preliminary results from a randomized trial  

Directory of Open Access Journals (Sweden)

Full Text Available Sunanda Kane1, William Holderman2, Peter Jacques2, Todd Miodek31Mayo Clinic College of Medicine, Rochester, MN, USA; 2Digestive Health Specialists, Tacoma, WA, USA; 3University of Chicago, Chicago, IL, USABackground and Aims: Multiple studies have demonstrated the efficacy of aminosalicylates in maintaining remission in ulcerative colitis (UC). A newer formulation of mesalamine can be administered once daily. We aimed to examine the efficacy and tolerability of pH-dependent mesalamine for long-term maintenance, and compare the rates of medication consumption between groups over a prolonged period.Methods: Subjects whose UC had been quiescent for at least 4 months, and who had been receiving mesalamine for maintenance only, were randomized to once daily or conventional dosing for 12 months. Disease activity and medication consumption was assessed every 3 months. The primary endpoint was the percentage of those with quiescent disease at 12 months.Results: We enrolled 20 patients, 12 to once daily and 8 to conventional dosing. Six of the 12 patients (50%) in the once daily group compared with 5 of the 8 patients (62.5%) in the conventional group experienced a flare (p = 0.31). Only 5 of the 12 (42%) patients in the once daily group were adherent compared with 3 of 8 patients (37.5%) in the conventional dosing group (p = NS). Median amount consumed in the once daily group was 63% (range 0%100%) and in the conventional group 55% (range 0%100%), (p > 0.5). None of the adherent subjects in the once daily group experienced a flare, while 6 out of 7 (86%) who were non-adherent experienced a flare (p <0.01). In the conventional dosing group, 1 in 3 adherent patients (33%) experienced a fl are compared with 4 out of 5 (80%) in the non-adherent group (p <0.01).Conclusion: Adherence, rather than medication regimen, appeared to be important in disease outcome at 12 months.Keywords: ulcerative colitis, mesalamine, aminosalicylates, remission

Sunanda Kane; William Holderman; Peter Jacques; Todd Miodek

2008-01-01

399

General anesthesia versus combined epidural/general anesthesia for elective lumbar spine disc surgery: A randomized clinical trial comparing the impact of the two methods upon the outcome variables  

Science.gov (United States)

Background: General anesthesia (GA) is the most frequently used technique for lumbar spine disc surgery. The aim of this study was to compare the intraoperative variables and postoperative outcome after GA and combined general/epidural anesthesia (CEG) in patients undergoing elective lumbar spine disk surgery. Methods: Eighty patients who underwent one or two level of laminectomy/discectomy during a 2 year period were enrolled in this randomized controlled trial (RCT). They were randomly selected to undergo GA or CEG. The data recorded during surgery were: The patients heart rate (HR), mean arterial blood pressure (MABP), amount of blood loss, and the medication used during anesthesia. The severity of pain score, total analgesic consumption, and complications were recorded in the postoperative period. Results: The MABP, HR, blood loss, and anesthetic medication were significantly lower in CEG group in comparison with that of GA group. In the postoperative period, the pain score and total analgesic requirement was lower in the CEG group and less complication were encountered in this group. Conclusion: The results of this study revealed that CEG have some advantages over GA in reducing the blood loss and anesthetic medication during the operation and it is also more effective in control of pain with fewer complications during the postoperative period.

Khajavi, Mohammad Reza; Asadian, Mohammad Amir; Imani, Farsad; Etezadi, Farhad; Moharari, Reza Shariat; Amirjamshidi, Abbas

2013-01-01

400

Hydraulic causes for time-dependent variability of PAH-contamination in a gravel aquifer; Hydraulische Ursachen der zeitlichen Varianz von PAK-Konzentrationen in einem Kiesgrundwasserleiter  

Energy Technology Data Exchange (ETDEWEB)

At a former industrial site for impregnation of wood for tracks, the groundwater of the Quaternary gravel aquifer is highly contaminated with polycyclic aromatic hydrocarbons (PAHs) which have shown very rapid fluctuations during the investigation periods. A comparison of two concentration time lines along the same streamline shows two different components, a parallel, area-wide component and a local, time-varying component of the concentration behaviour. These components also have a strong relationship between the different percentage occurrences of the PAHs at the measuring points. As one cause for the time-dependent variability, a correlation between a relatively rapid change of the groundwater level and the PAH-concentration has been observed. In addition, extreme rainfall events strongly influence the variation of the PAH-concentrations and lead to maximum concentration-peaks in the groundwater. These processes produce impulse-like inputs of the PAHs into the groundwater. A 1D-analytical model of the time dependent PAH-concentration variability indicates that impulse PAH-mobilisations from contamination sources at different locations are the dominant mobilisation processes at the investigation site. (orig.) [German] In einem Kiesgrundwasserleiter auf dem Standort eines ehemaligen Impraegnierwerks wurden im Grundwasser hohe Variationen im zeitlichen Verhalten der PAK-Kontamination beobachtet. Daraufhin sind diese Konzentrationsschwankungen detailliert analysiert worden. Beim Vergleich zweier Zeitreihen entlang der Fliessrichtung konnte der zeitliche Gang der PAK-Konzentrationen in eine gemeinsame grossflaechige und eine lokal/zeitversetzte Komponente unterschieden werden. Diese statistisch erfassten Komponenten lassen sich unter anderem auf die unterschiedliche Ausbildung der prozentualen Anteile der PAK-Substanzen an den Messstellen zurueckfuehren. Bei der Gegenueberstellung des gemessenen Konzentrationsgangs mit der hydraulischen Dynamik liess sich eine Beziehung zwischen rasch ablaufenden Grundwasserschwankungen und den Aenderungen in den PAK-Konzentrationen erkennen. Darueber hinaus war zu beobachten, dass starke Niederschlagsereignisse maximale PAK-Konzentrationen im Grundwasser verursachen und somit eine grosse Rolle fuer die zeitliche Variation der Konzentrationen spielen. Diese Ursache-Wirkungs-Beziehungen haben zudem den Charakter einer impulsartigen Mobilisierung der PAK im Grundwasser. Durch eine 1D-analytische Modellierung konnte ein Impulseintrag aus lokal unterschiedlichen Quellen als dominante Eintragsart fuer die PAK-Mobilisierung am Standort identifiziert werden. (orig.)

Zosseder, K. [Deutsches Zentrum fuer Luft und Raumfahrt (DLR), DFD-US, Wessling (Germany); Bender, S.; Wohnlich, S. [Ruhr-Universitaet Bochum (Germany). Institut fuer Geologie, Mineralogie und Geophysik

2009-06-15