Random matrix ensembles with random interactions: Results for ...

Indian Academy of Sciences (India)

... Public Lectures · Lecture Workshops · Refresher Courses · Symposia · Live Streaming. Home; Journals; Pramana – Journal of Physics; Volume 73; Issue 3. Random matrix ensembles with random interactions: Results for EGUE(2)-(4). Manan Vyas Manan Vyas. Volume 73 Issue 3 September 2009 pp 521-531 ...

Residual and Past Entropy for Concomitants of Ordered Random Variables of Morgenstern Family

Directory of Open Access Journals (Sweden)

M. M. Mohie EL-Din

2015-01-01

Full Text Available For a system, which is observed at time t, the residual and past entropies measure the uncertainty about the remaining and the past life of the distribution, respectively. In this paper, we have presented the residual and past entropy of Morgenstern family based on the concomitants of the different types of generalized order statistics (gos and give the linear transformation of such model. Characterization results for these dynamic entropies for concomitants of ordered random variables have been considered.

Robust Fuzzy Control for Fractional-Order Uncertain Hydroturbine Regulating System with Random Disturbances

Directory of Open Access Journals (Sweden)

Fengjiao Wu

2016-01-01

Full Text Available The robust fuzzy control for fractional-order hydroturbine regulating system is studied in this paper. First, the more practical fractional-order hydroturbine regulating system with uncertain parameters and random disturbances is presented. Then, on the basis of interval matrix theory and fractional-order stability theorem, a fuzzy control method is proposed for fractional-order hydroturbine regulating system, and the stability condition is expressed as a group of linear matrix inequalities. Furthermore, the proposed method has good robustness which can process external random disturbances and uncertain parameters. Finally, the validity and superiority are proved by the numerical simulations.

New Closed-Form Results on Ordered Statistics of Partial Sums of Gamma Random Variables and its Application to Performance Evaluation in the Presence of Nakagami Fading

KAUST Repository

Nam, Sung Sik

2017-06-19

Complex wireless transmission systems require multi-dimensional joint statistical techniques for performance evaluation. Here, we first present the exact closed-form results on order statistics of any arbitrary partial sums of Gamma random variables with the closedform results of core functions specialized for independent and identically distributed Nakagami-m fading channels based on a moment generating function-based unified analytical framework. These both exact closed-form results have never been published in the literature. In addition, as a feasible application example in which our new offered derived closed-form results can be applied is presented. In particular, we analyze the outage performance of the finger replacement schemes over Nakagami fading channels as an application of our method. Note that these analysis results are directly applicable to several applications, such as millimeter-wave communication systems in which an antenna diversity scheme operates using an finger replacement schemes-like combining scheme, and other fading scenarios. Note also that the statistical results can provide potential solutions for ordered statistics in any other research topics based on Gamma distributions or other advanced wireless communications research topics in the presence of Nakagami fading.

Order out of Randomness: Self-Organization Processes in Astrophysics

Science.gov (United States)

Aschwanden, Markus J.; Scholkmann, Felix; Béthune, William; Schmutz, Werner; Abramenko, Valentina; Cheung, Mark C. M.; Müller, Daniel; Benz, Arnold; Chernov, Guennadi; Kritsuk, Alexei G.; Scargle, Jeffrey D.; Melatos, Andrew; Wagoner, Robert V.; Trimble, Virginia; Green, William H.

2018-03-01

Self-organization is a property of dissipative nonlinear processes that are governed by a global driving force and a local positive feedback mechanism, which creates regular geometric and/or temporal patterns, and decreases the entropy locally, in contrast to random processes. Here we investigate for the first time a comprehensive number of (17) self-organization processes that operate in planetary physics, solar physics, stellar physics, galactic physics, and cosmology. Self-organizing systems create spontaneous " order out of randomness", during the evolution from an initially disordered system to an ordered quasi-stationary system, mostly by quasi-periodic limit-cycle dynamics, but also by harmonic (mechanical or gyromagnetic) resonances. The global driving force can be due to gravity, electromagnetic forces, mechanical forces (e.g., rotation or differential rotation), thermal pressure, or acceleration of nonthermal particles, while the positive feedback mechanism is often an instability, such as the magneto-rotational (Balbus-Hawley) instability, the convective (Rayleigh-Bénard) instability, turbulence, vortex attraction, magnetic reconnection, plasma condensation, or a loss-cone instability. Physical models of astrophysical self-organization processes require hydrodynamic, magneto-hydrodynamic (MHD), plasma, or N-body simulations. Analytical formulations of self-organizing systems generally involve coupled differential equations with limit-cycle solutions of the Lotka-Volterra or Hopf-bifurcation type.

Robust Fuzzy Control for Fractional-Order Uncertain Hydroturbine Regulating System with Random Disturbances

OpenAIRE

Fengjiao Wu; Guitao Zhang; Zhengzhong Wang

2016-01-01

The robust fuzzy control for fractional-order hydroturbine regulating system is studied in this paper. First, the more practical fractional-order hydroturbine regulating system with uncertain parameters and random disturbances is presented. Then, on the basis of interval matrix theory and fractional-order stability theorem, a fuzzy control method is proposed for fractional-order hydroturbine regulating system, and the stability condition is expressed as a group of linear matrix inequalities. ...

First-order corrections to random-phase approximation GW calculations in silicon and diamond

NARCIS (Netherlands)

Ummels, R.T.M.; Bobbert, P.A.; van Haeringen, W.

1998-01-01

We report on ab initio calculations of the first-order corrections in the screened interaction W to the random-phase approximation polarizability and to the GW self-energy, using a noninteracting Green's function, for silicon and diamond. It is found that the first-order vertex and self-consistency

Measuring order in disordered systems and disorder in ordered systems: Random matrix theory for isotropic and nematic liquid crystals and its perspective on pseudo-nematic domains

Science.gov (United States)

Zhao, Yan; Stratt, Richard M.

2018-05-01

Surprisingly long-ranged intermolecular correlations begin to appear in isotropic (orientationally disordered) phases of liquid crystal forming molecules when the temperature or density starts to close in on the boundary with the nematic (ordered) phase. Indeed, the presence of slowly relaxing, strongly orientationally correlated, sets of molecules under putatively disordered conditions ("pseudo-nematic domains") has been apparent for some time from light-scattering and optical-Kerr experiments. Still, a fully microscopic characterization of these domains has been lacking. We illustrate in this paper how pseudo-nematic domains can be studied in even relatively small computer simulations by looking for order-parameter tensor fluctuations much larger than one would expect from random matrix theory. To develop this idea, we show that random matrix theory offers an exact description of how the probability distribution for liquid-crystal order parameter tensors converges to its macroscopic-system limit. We then illustrate how domain properties can be inferred from finite-size-induced deviations from these random matrix predictions. A straightforward generalization of time-independent random matrix theory also allows us to prove that the analogous random matrix predictions for the time dependence of the order-parameter tensor are similarly exact in the macroscopic limit, and that relaxation behavior of the domains can be seen in the breakdown of the finite-size scaling required by that random-matrix theory.

Will electrical cyber-physical interdependent networks undergo first-order transition under random attacks?

Science.gov (United States)

Ji, Xingpei; Wang, Bo; Liu, Dichen; Dong, Zhaoyang; Chen, Guo; Zhu, Zhenshan; Zhu, Xuedong; Wang, Xunting

2016-10-01

Whether the realistic electrical cyber-physical interdependent networks will undergo first-order transition under random failures still remains a question. To reflect the reality of Chinese electrical cyber-physical system, the "partial one-to-one correspondence" interdependent networks model is proposed and the connectivity vulnerabilities of three realistic electrical cyber-physical interdependent networks are analyzed. The simulation results show that due to the service demands of power system the topologies of power grid and its cyber network are highly inter-similar which can effectively avoid the first-order transition. By comparing the vulnerability curves between electrical cyber-physical interdependent networks and its single-layer network, we find that complex network theory is still useful in the vulnerability analysis of electrical cyber-physical interdependent networks.

Neutron Transport in Spatially Random Media: An Assessment of the Accuracy of First Order Smoothing

International Nuclear Information System (INIS)

Williams, M.M.R.

2000-01-01

A formalism has been developed for studying the transmission of neutrons through a spatially stochastic medium. The stochastic components are represented by absorbing plates of randomly varying strength and random position. This type of geometry enables the Feinberg-Galanin-Horning method to be employed and leads to the solution of a coupled set of linear equations for the flux at the plate positions. The matrix of the coefficients contains members that are random and these are solved by simulation. That is, the strength and plate positions are sampled from uniform distributions and the equations solved many times (in this case 10 5 simulations are carried out). Probability distributions for the plate transmission and reflection factors are constructed from which the mean and variance can be computed.These essentially exact solutions enable closure approximations to be assessed for accuracy. To this end, we have compared the mean and variance obtained from the first order smoothing approximation of Keller with the exact results and have found excellent agreement for the mean values but note deviations of up to 40% for the variance. Nevertheless, for the problems considered here, first order smoothing appears to be of practical value and is very efficient numerically in comparison with simulation

SOERP, Statistics and 2. Order Error Propagation for Function of Random Variables

International Nuclear Information System (INIS)

Cox, N. D.; Miller, C. F.

1985-01-01

1 - Description of problem or function: SOERP computes second-order error propagation equations for the first four moments of a function of independently distributed random variables. SOERP was written for a rigorous second-order error propagation of any function which may be expanded in a multivariable Taylor series, the input variables being independently distributed. The required input consists of numbers directly related to the partial derivatives of the function, evaluated at the nominal values of the input variables and the central moments of the input variables from the second through the eighth. 2 - Method of solution: The development of equations for computing the propagation of errors begins by expressing the function of random variables in a multivariable Taylor series expansion. The Taylor series expansion is then truncated, and statistical operations are applied to the series in order to obtain equations for the moments (about the origin) of the distribution of the computed value. If the Taylor series is truncated after powers of two, the procedure produces second-order error propagation equations. 3 - Restrictions on the complexity of the problem: The maximum number of component variables allowed is 30. The IBM version will only process one set of input data per run

Fuzzy Random Walkers with Second Order Bounds: An Asymmetric Analysis

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Georgios Drakopoulos

2017-03-01

Full Text Available Edge-fuzzy graphs constitute an essential modeling paradigm across a broad spectrum of domains ranging from artificial intelligence to computational neuroscience and social network analysis. Under this model, fundamental graph properties such as edge length and graph diameter become stochastic and as such they are consequently expressed in probabilistic terms. Thus, algorithms for fuzzy graph analysis must rely on non-deterministic design principles. One such principle is Random Walker, which is based on a virtual entity and selects either edges or, like in this case, vertices of a fuzzy graph to visit. This allows the estimation of global graph properties through a long sequence of local decisions, making it a viable strategy candidate for graph processing software relying on native graph databases such as Neo4j. As a concrete example, Chebyshev Walktrap, a heuristic fuzzy community discovery algorithm relying on second order statistics and on the teleportation of the Random Walker, is proposed and its performance, expressed in terms of community coherence and number of vertex visits, is compared to the previously proposed algorithms of Markov Walktrap, Fuzzy Walktrap, and Fuzzy Newman–Girvan. In order to facilitate this comparison, a metric based on the asymmetric metrics of Tversky index and Kullback–Leibler divergence is used.

Piecewise linearisation of the first order loss function for families of arbitrarily distributed random variables

NARCIS (Netherlands)

Rossi, R.; Hendrix, E.M.T.

2014-01-01

We discuss the problem of computing optimal linearisation parameters for the first order loss function of a family of arbitrarily distributed random variable. We demonstrate that, in contrast to the problem in which parameters must be determined for the loss function of a single random variable,

Simulation-based production planning for engineer-to-order systems with random yield

NARCIS (Netherlands)

Akcay, Alp; Martagan, Tugce

2018-01-01

We consider an engineer-to-order production system with unknown yield. We model the yield as a random variable which represents the percentage output obtained from one unit of production quantity. We develop a beta-regression model in which the mean value of the yield depends on the unique

Does quasi-long-range order in the two-dimensional XY model really survive weak random phase fluctuations?

International Nuclear Information System (INIS)

Mudry, Christopher; Wen Xiaogang

1999-01-01

Effective theories for random critical points are usually non-unitary, and thus may contain relevant operators with negative scaling dimensions. To study the consequences of the existence of negative-dimensional operators, we consider the random-bond XY model. It has been argued that the XY model on a square lattice, when weakly perturbed by random phases, has a quasi-long-range ordered phase (the random spin wave phase) at sufficiently low temperatures. We show that infinitely many relevant perturbations to the proposed critical action for the random spin wave phase were omitted in all previous treatments. The physical origin of these perturbations is intimately related to the existence of broadly distributed correlation functions. We find that those relevant perturbations do enter the Renormalization Group equations, and affect critical behavior. This raises the possibility that the random XY model has no quasi-long-range ordered phase and no Kosterlitz-Thouless (KT) phase transition

Qualitatively Assessing Randomness in SVD Results

Science.gov (United States)

Lamb, K. W.; Miller, W. P.; Kalra, A.; Anderson, S.; Rodriguez, A.

2012-12-01

Singular Value Decomposition (SVD) is a powerful tool for identifying regions of significant co-variability between two spatially distributed datasets. SVD has been widely used in atmospheric research to define relationships between sea surface temperatures, geopotential height, wind, precipitation and streamflow data for myriad regions across the globe. A typical application for SVD is to identify leading climate drivers (as observed in the wind or pressure data) for a particular hydrologic response variable such as precipitation, streamflow, or soil moisture. One can also investigate the lagged relationship between a climate variable and the hydrologic response variable using SVD. When performing these studies it is important to limit the spatial bounds of the climate variable to reduce the chance of random co-variance relationships being identified. On the other hand, a climate region that is too small may ignore climate signals which have more than a statistical relationship to a hydrologic response variable. The proposed research seeks to identify a qualitative method of identifying random co-variability relationships between two data sets. The research identifies the heterogeneous correlation maps from several past results and compares these results with correlation maps produced using purely random and quasi-random climate data. The comparison identifies a methodology to determine if a particular region on a correlation map may be explained by a physical mechanism or is simply statistical chance.

Probability calculus of fractional order and fractional Taylor's series application to Fokker-Planck equation and information of non-random functions

International Nuclear Information System (INIS)

Jumarie, Guy

2009-01-01

A probability distribution of fractional (or fractal) order is defined by the measure μ{dx} = p(x)(dx) α , 0 α (D x α h α )f(x) provided by the modified Riemann Liouville definition, one can expand a probability calculus parallel to the standard one. A Fourier's transform of fractional order using the Mittag-Leffler function is introduced, together with its inversion formula; and it provides a suitable generalization of the characteristic function of fractal random variables. It appears that the state moments of fractional order are more especially relevant. The main properties of this fractional probability calculus are outlined, it is shown that it provides a sound approach to Fokker-Planck equation which are fractional in both space and time, and it provides new results in the information theory of non-random functions.

An MGF-based unified framework to determine the joint statistics of partial sums of ordered random variables

KAUST Repository

Nam, Sungsik

2010-11-01

Order statistics find applications in various areas of communications and signal processing. In this paper, we introduce an unified analytical framework to determine the joint statistics of partial sums of ordered random variables (RVs). With the proposed approach, we can systematically derive the joint statistics of any partial sums of ordered statistics, in terms of the moment generating function (MGF) and the probability density function (PDF). Our MGF-based approach applies not only when all the K ordered RVs are involved but also when only the Ks(Ks < K) best RVs are considered. In addition, we present the closed-form expressions for the exponential RV special case. These results apply to the performance analysis of various wireless communication systems over fading channels. © 2006 IEEE.

RTOG: Updated results of randomized trials

International Nuclear Information System (INIS)

Curran, Walter J.

1997-01-01

Objective: To review the background, rationale and available results for recently completed randomized comparative clinical trials of the Radiation Therapy Oncology Group (RTOG), including inter group trials in which the RTOG has been the managing group or a major participant. When available, laboratory studies will be correlated with clinical results

Numerical solution of second-order stochastic differential equations with Gaussian random parameters

Directory of Open Access Journals (Sweden)

Rahman Farnoosh

2014-07-01

Full Text Available In this paper, we present the numerical solution of ordinary differential equations (or SDEs, from each orderespecially second-order with time-varying and Gaussian random coefficients. We indicate a complete analysisfor second-order equations in specially case of scalar linear second-order equations (damped harmonicoscillators with additive or multiplicative noises. Making stochastic differential equations system from thisequation, it could be approximated or solved numerically by different numerical methods. In the case oflinear stochastic differential equations system by Computing fundamental matrix of this system, it could becalculated based on the exact solution of this system. Finally, this stochastic equation is solved by numericallymethod like E.M. and Milstein. Also its Asymptotic stability and statistical concepts like expectationand variance of solutions are discussed.

76 FR 2336 - Dynamic Random Access Memory Semiconductors From the Republic of Korea: Final Results of...

Science.gov (United States)

2011-01-13

... Semiconductors From the Republic of Korea: Final Results of Countervailing Duty Administrative Review AGENCY... administrative review of the countervailing duty order on dynamic random access memory semiconductors from the... to a change in the net subsidy rate. The final net subsidy rate for Hynix Semiconductor, Inc. is...

An MGF-based unified framework to determine the joint statistics of partial sums of ordered random variables

KAUST Repository

Nam, Sungsik; Alouini, Mohamed-Slim; Yang, Hongchuan

2010-01-01

Order statistics find applications in various areas of communications and signal processing. In this paper, we introduce an unified analytical framework to determine the joint statistics of partial sums of ordered random variables (RVs

First-order reversal curves of single domain particles: diluted random assemblages and chains

Science.gov (United States)

Egli, R.

2009-04-01

Exact magnetic models can be used to calculate first-order reversal curves (FORC) of single domain (SD) particle assemblages, as shown by Newell [2005] for the case of isolated Stoner-Wohlfarth particles. After overcoming experimental difficulties, a FORC diagram sharing many similarities to Newell's model has been measured on a lake sediment sample (see A.P. Chen et al., "Quantification of magnetofossils using first-order reversal curves", EGU General Assembly 2009, Abstracts Vol. 11, EGU2009-10719). This sample contains abundant magnetofossils, as shown by coercivity analysis and electron microscopy, therefore suggesting that well dispersed, intact magnetosome chains are the main SD carriers. Subtle differences between the reversible and the irreversible contributions of the measured FORC distribution suggest that magnetosome chains might not be correctly described by the Stoner-Wohlfarth model. To better understand the hysteresis properties of such chains, a simple magnetic model has been implemented, taking dipole-dipole interactions between particles within the same chain into account. The model results depend on the magnetosome elongation, the number of magnetosomes in a chain, and the gap between them. If the chain axis is subparallel to the applied field, the magnetic moment reverses by a pseudo-fanning mode, which is replaced by a pseudo-coherent rotation mode at greater angles. These reversal modes are intrinsically different from coherent rotation assumed Stoner-Wohlfarth model, resulting in FORC diagrams with a smaller reversible component. On the other hand, isolated authigenic SD particles can precipitate in the sediment matrix, as it might occur for pedogenic magnetite. In this case, an assembly of randomly located particles provides a possible model for the resulting FORC diagram. If the concentration of the particles is small, each particle is affected by a random interaction field whose statistical distribution can be calculated from first

Some Limit Properties of Random Transition Probability for Second-Order Nonhomogeneous Markov Chains Indexed by a Tree

Directory of Open Access Journals (Sweden)

Shi Zhiyan

2009-01-01

Full Text Available We study some limit properties of the harmonic mean of random transition probability for a second-order nonhomogeneous Markov chain and a nonhomogeneous Markov chain indexed by a tree. As corollary, we obtain the property of the harmonic mean of random transition probability for a nonhomogeneous Markov chain.

REGULAR METHOD FOR SYNTHESIS OF BASIC BENT-SQUARES OF RANDOM ORDER

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A. V. Sokolov

2016-01-01

Full Text Available The paper is devoted to the class construction of the most non-linear Boolean bent-functions of any length N = 2k (k = 2, 4, 6…, on the basis of their spectral representation – Agievich bent squares. These perfect algebraic constructions are used as a basis to build many new cryptographic primitives, such as generators of pseudo-random key sequences, crypto graphic S-boxes, etc. Bent-functions also find their application in the construction of C-codes in the systems with code division multiple access (CDMA to provide the lowest possible value of Peak-to-Average Power Ratio (PAPR k = 1, as well as for the construction of error-correcting codes and systems of orthogonal biphasic signals. All the numerous applications of bent-functions relate to the theory of their synthesis. However, regular methods for complete class synthesis of bent-functions of any length N = 2k are currently unknown. The paper proposes a regular synthesis method for the basic Agievich bent squares of any order n, based on a regular operator of dyadic shift. Classification for a complete set of spectral vectors of lengths (l = 8, 16, … based on a criterion of the maximum absolute value and set of absolute values of spectral components has been carried out in the paper. It has been shown that any spectral vector can be a basis for building bent squares. Results of the synthesis for the Agievich bent squares of order n = 8 have been generalized and it has been revealed that there are only 3 basic bent squares for this order, while the other 5 can be obtained with help the operation of step-cyclic shift. All the basic bent squares of order n = 16 have been synthesized that allows to construct the bent-functions of length N = 256. The obtained basic bent squares can be used either for direct synthesis of bent-functions and their practical application or for further research in order to synthesize new structures of bent squares of orders n = 16, 32, 64, …

Random textures of the order parameter of superfluid sup 3 He-B in aerogel

CERN Document Server

Fomin, Yu A

2002-01-01

The scheme for describing the properties of the superfluid sup 3 He in the aerogel is proposed in accordance with the Ginzburg and Landau theory. The aerogel effect on the order parameter is described by the random tensor field. This field exerts desorientation effect on the order parameter in the sup 3 He A-phase, but it does not influence the order parameter orientation in the B-phase, if there is no magnetic field. The change in the order parameter texture, originating in the B-phase in the aerogel in the magnetic field, is considered. Fluctuations of the sup 3 He-B anisotropy axis direction are correlated on the length, inversely proportional to the field intensity and having the macroscopic scale

The sink strengths of voids and the expected swelling for both random and ordered void distributions

International Nuclear Information System (INIS)

Quigley, T.M.; Murphy, S.M.; Bullough, R.; Wood, M.H.

1981-10-01

The sink strength of a void has been obtained when the void is a member of a random or ordered distribution of voids. The former sink strength derivation has employed the embedding model and the latter the cellular model. In each case the spatially varying size-effect interaction between the intrinsic point defects and the voids has been included together with the presence of other sink types in addition to the voids. The results are compared with previously published sink strengths that have made use of an approximate representation for the size-effect interactions, and indicate the importance of using the exact form of the interaction. In particular the bias for interstitials compared with vacancies of small voids is now much reduced and contamination of the surfaces of such voids no longer appears essential to facilitate the nucleation and growth of the voids. These new sink strengths have been used, in conjunction with recently published dislocation sink strengths, to calculate the expected swelling of materials containing network dislocations and voids. Results are presented for both the random and the void lattice situations. (author)

Diversity Order Results for MIMO Optical Wireless Communications

KAUST Repository

Sapenov, Yerzhan

2017-09-21

An optical wireless multiple-input multiple-output (MIMO) communication system employing intensity-modulation direct-detection (IM/DD) is considered. The maximal diversity order of the channel is characterized by studying the outage probability. Then, spatial repetition coding (RC) is shown to be diversity-optimal as it achieves the channel’s maximal diversity order. This diversity order is given by a simple expression which is suitable for any channel statistics of practical interest. The results are specialized to some practical channel statistics, and numerical results are provided to verify the results.

Diversity Order Results for MIMO Optical Wireless Communications

KAUST Repository

Sapenov, Yerzhan; Chaaban, Anas; Rezki, Zouheir; Abdallah, Mohamed; Qaraqe, Khalid; Alouini, Mohamed-Slim

2017-01-01

An optical wireless multiple-input multiple-output (MIMO) communication system employing intensity-modulation direct-detection (IM/DD) is considered. The maximal diversity order of the channel is characterized by studying the outage probability. Then, spatial repetition coding (RC) is shown to be diversity-optimal as it achieves the channel’s maximal diversity order. This diversity order is given by a simple expression which is suitable for any channel statistics of practical interest. The results are specialized to some practical channel statistics, and numerical results are provided to verify the results.

A stochastic collocation method for the second order wave equation with a discontinuous random speed

KAUST Repository

Motamed, Mohammad; Nobile, Fabio; Tempone, Raul

2012-01-01

In this paper we propose and analyze a stochastic collocation method for solving the second order wave equation with a random wave speed and subjected to deterministic boundary and initial conditions. The speed is piecewise smooth in the physical

A multi-tier higher order Conditional Random Field for land cover classification of multi-temporal multi-spectral Landsat imagery

CSIR Research Space (South Africa)

Salmon, BP

2015-07-01

Full Text Available In this paper the authors present a 2-tier higher order Conditional Random Field which is used for land cover classification. The Conditional Random Field is based on probabilistic messages being passed along a graph to compute efficiently...

The Schwinger Dyson equations and the algebra of constraints of random tensor models at all orders

International Nuclear Information System (INIS)

Gurau, Razvan

2012-01-01

Random tensor models for a generic complex tensor generalize matrix models in arbitrary dimensions and yield a theory of random geometries. They support a 1/N expansion dominated by graphs of spherical topology. Their Schwinger Dyson equations, generalizing the loop equations of matrix models, translate into constraints satisfied by the partition function. The constraints have been shown, in the large N limit, to close a Lie algebra indexed by colored rooted D-ary trees yielding a first generalization of the Virasoro algebra in arbitrary dimensions. In this paper we complete the Schwinger Dyson equations and the associated algebra at all orders in 1/N. The full algebra of constraints is indexed by D-colored graphs, and the leading order D-ary tree algebra is a Lie subalgebra of the full constraints algebra.

Competing order parameters in quenched random alloys: Fe/sub 1-x/Co/sub x/Cl2

International Nuclear Information System (INIS)

Wong, P.; Horn, P.M.; Birgeneau, R.J.; Safinya, C.R.; Shirane, G.

1980-01-01

A study is reported of the magnetic properties of the random alloy Fe/sub 1-x/Co/sub x/Cl 2 , which represents an archetypal example of a system with competing orthogonal spin anisotropies. Behavior similar to previous experiments and theoretical predictions is found, but with important qualitative and quantitative differences; in particular the phase transition in one variable is drastically altered by the existence of long-range order in the other variable. It is hypothesized that this is due to microscopic random-field effects

Presic-Boyd-Wong Type Results in Ordered Metric Spaces

Directory of Open Access Journals (Sweden)

Satish Shukla

2014-04-01

Full Text Available The purpose of this paper is to prove some Presic-Boyd-Wong type fixed point theorems in ordered metric spaces. The results of this paper generalize the famous results of Presic and Boyd-Wong in ordered metric spaces. We also initiate the homotopy result in product spaces. Some examples are provided which illustrate the results proved herein.

Radiation-induced segregation behavior in random and ordered face-centered cubic materials

International Nuclear Information System (INIS)

Bui, T.X.; Robertson, I.M.; Klatt, J.L.; Averback, R.S.; Kirk, M.A.

1993-01-01

Radiation-induced segregation has been studied in random solid solution alloys Ni-10%Al and Ni-6%Si, and in the ordered (L1 2 structure) intermetallics Ni 3 Si and Ni 3 Al. These materials were irradiated with 2 MeV He + ions at a temperature between 0.45 and 0.55T m and at an ion dose rate of approximately 1x10 -4 dpa per second. Subsequent Auger Electron Spectroscopy analysis showed that silicon segregated to the surface in the Ni-6% Si and Ni 3 Si alloys, and aluminum segregated away from the near surface region in the Ni-10% Al alloy. The Ni 3 Al samples exhibited no detectable segregation with respect to depth from the sample surface. The mechanisms that may give rise to this resistance to radiation induced segregation will be examined in terms of the mobility of the alloying constituents, ordering energies and atomic sizes. (orig.)

An MGF-based unified framework to determine the joint statistics of partial sums of ordered i.n.d. random variables

KAUST Repository

Nam, Sungsik

2014-08-01

The joint statistics of partial sums of ordered random variables (RVs) are often needed for the accurate performance characterization of a wide variety of wireless communication systems. A unified analytical framework to determine the joint statistics of partial sums of ordered independent and identically distributed (i.i.d.) random variables was recently presented. However, the identical distribution assumption may not be valid in several real-world applications. With this motivation in mind, we consider in this paper the more general case in which the random variables are independent but not necessarily identically distributed (i.n.d.). More specifically, we extend the previous analysis and introduce a new more general unified analytical framework to determine the joint statistics of partial sums of ordered i.n.d. RVs. Our mathematical formalism is illustrated with an application on the exact performance analysis of the capture probability of generalized selection combining (GSC)-based RAKE receivers operating over frequency-selective fading channels with a non-uniform power delay profile. © 1991-2012 IEEE.

Defining Higher-Order Turbulent Moment Closures with an Artificial Neural Network and Random Forest

Science.gov (United States)

McGibbon, J.; Bretherton, C. S.

2017-12-01

Unresolved turbulent advection and clouds must be parameterized in atmospheric models. Modern higher-order closure schemes depend on analytic moment closure assumptions that diagnose higher-order moments in terms of lower-order ones. These are then tested against Large-Eddy Simulation (LES) higher-order moment relations. However, these relations may not be neatly analytic in nature. Rather than rely on an analytic higher-order moment closure, can we use machine learning on LES data itself to define a higher-order moment closure?We assess the ability of a deep artificial neural network (NN) and random forest (RF) to perform this task using a set of observationally-based LES runs from the MAGIC field campaign. By training on a subset of 12 simulations and testing on remaining simulations, we avoid over-fitting the training data.Performance of the NN and RF will be assessed and compared to the Analytic Double Gaussian 1 (ADG1) closure assumed by Cloudy Layers Unified By Binormals (CLUBB), a higher-order turbulence closure currently used in the Community Atmosphere Model (CAM). We will show that the RF outperforms the NN and the ADG1 closure for the MAGIC cases within this diagnostic framework. Progress and challenges in using a diagnostic machine learning closure within a prognostic cloud and turbulence parameterization will also be discussed.

Solution Methods for Structures with Random Properties Subject to Random Excitation

DEFF Research Database (Denmark)

Köylüoglu, H. U.; Nielsen, Søren R. K.; Cakmak, A. S.

This paper deals with the lower order statistical moments of the response of structures with random stiffness and random damping properties subject to random excitation. The arising stochastic differential equations (SDE) with random coefficients are solved by two methods, a second order...... the SDE with random coefficients with deterministic initial conditions to an equivalent nonlinear SDE with deterministic coefficient and random initial conditions. In both methods, the statistical moment equations are used. Hierarchy of statistical moments in the markovian approach is closed...... by the cumulant neglect closure method applied at the fourth order level....

First-order system least-squares for second-order elliptic problems with discontinuous coefficients: Further results

Energy Technology Data Exchange (ETDEWEB)

Bloechle, B.; Manteuffel, T.; McCormick, S.; Starke, G.

1996-12-31

Many physical phenomena are modeled as scalar second-order elliptic boundary value problems with discontinuous coefficients. The first-order system least-squares (FOSLS) methodology is an alternative to standard mixed finite element methods for such problems. The occurrence of singularities at interface corners and cross-points requires that care be taken when implementing the least-squares finite element method in the FOSLS context. We introduce two methods of handling the challenges resulting from singularities. The first method is based on a weighted least-squares functional and results in non-conforming finite elements. The second method is based on the use of singular basis functions and results in conforming finite elements. We also share numerical results comparing the two approaches.

Creating, generating and comparing random network models with NetworkRandomizer.

Science.gov (United States)

Tosadori, Gabriele; Bestvina, Ivan; Spoto, Fausto; Laudanna, Carlo; Scardoni, Giovanni

2016-01-01

Biological networks are becoming a fundamental tool for the investigation of high-throughput data in several fields of biology and biotechnology. With the increasing amount of information, network-based models are gaining more and more interest and new techniques are required in order to mine the information and to validate the results. To fill the validation gap we present an app, for the Cytoscape platform, which aims at creating randomised networks and randomising existing, real networks. Since there is a lack of tools that allow performing such operations, our app aims at enabling researchers to exploit different, well known random network models that could be used as a benchmark for validating real, biological datasets. We also propose a novel methodology for creating random weighted networks, i.e. the multiplication algorithm, starting from real, quantitative data. Finally, the app provides a statistical tool that compares real versus randomly computed attributes, in order to validate the numerical findings. In summary, our app aims at creating a standardised methodology for the validation of the results in the context of the Cytoscape platform.

Ordered particles versus ordered pointers in the hybrid ordered plasma simulation (HOPS) code

International Nuclear Information System (INIS)

Anderson, D.V.; Shumaker, D.E.

1993-01-01

From a computational standpoint, particle simulation calculations for plasmas have not adapted well to the transitions from scalar to vector processing nor from serial to parallel environments. They have suffered from inordinate and excessive accessing of computer memory and have been hobbled by relatively inefficient gather-scatter constructs resulting from the use of indirect indexing. Lastly, the many-to-one mapping characteristic of the deposition phase has made it difficult to perform this in parallel. The authors' code sorts and reorders the particles in a spatial order. This allows them to greatly reduce the memory references, to run in directly indexed vector mode, and to employ domain decomposition to achieve parallelization. The field model solves pre-maxwell equations by interatively implicit methods. The OSOP (Ordered Storage Ordered Processing) version of HOPS keeps the particle tables ordered by rebuilding them after each particle pushing phase. Alternatively, the RSOP (Random Storage Ordered Processing) version keeps a table of pointers ordered by rebuilding them. Although OSOP is somewhat faster than RSOP in tests on vector-parallel machines, it is not clear this advantage will carry over to massively parallel computers

Reverse transcription using random pentadecamer primers increases yield and quality of resulting cDNA

DEFF Research Database (Denmark)

Stangegaard, Michael; Dufva, I.H.; Dufva, Hans Martin

2006-01-01

oligonucleotides (pentadecamers) consistently, yielded at least 2 fold as much cDNA as did random hexamers using either-poly(A) RNA or an amplified version of messenger RNA (aRNA) as a template. The cDNA generated using pentadecamers did not differ in size distribution or the amount of incorporated label compared...... with cDNA generated with random hexamers. The increased efficiency of priming using random pentadecamers resulted in reverse transcription of > 80% of the template aRNA, while random hexamers induced reverse transcription of only 40% of the template aRNA. This suggests a better coverage...... that random pentadecamers can replace random hexamers in reverse transcription reactions on both poly(A) RNA and amplified RNA, resulting in higher cDNA yields and quality....

Application of random coherence order selection in gradient-enhanced multidimensional NMR

International Nuclear Information System (INIS)

Bostock, Mark J.; Nietlispach, Daniel

2016-01-01

Development of multidimensional NMR is essential to many applications, for example in high resolution structural studies of biomolecules. Multidimensional techniques enable separation of NMR signals over several dimensions, improving signal resolution, whilst also allowing identification of new connectivities. However, these advantages come at a significant cost. The Fourier transform theorem requires acquisition of a grid of regularly spaced points to satisfy the Nyquist criterion, while frequency discrimination and acquisition of a pure phase spectrum require acquisition of both quadrature components for each time point in every indirect (non-acquisition) dimension, adding a factor of 2 N -1 to the number of free- induction decays which must be acquired, where N is the number of dimensions. Compressed sensing (CS) ℓ 1 -norm minimisation in combination with non-uniform sampling (NUS) has been shown to be extremely successful in overcoming the Nyquist criterion. Previously, maximum entropy reconstruction has also been used to overcome the limitation of frequency discrimination, processing data acquired with only one quadrature component at a given time interval, known as random phase detection (RPD), allowing a factor of two reduction in the number of points for each indirect dimension (Maciejewski et al. 2011 PNAS 108 16640). However, whilst this approach can be easily applied in situations where the quadrature components are acquired as amplitude modulated data, the same principle is not easily extended to phase modulated (P-/N-type) experiments where data is acquired in the form exp (iωt) or exp (-iωt), and which make up many of the multidimensional experiments used in modern NMR. Here we demonstrate a modification of the CS ℓ 1 -norm approach to allow random coherence order selection (RCS) for phase modulated experiments; we generalise the nomenclature for RCS and RPD as random quadrature detection (RQD). With this method, the power of RQD can be extended

Hidden temporal order unveiled in stock market volatility variance

Directory of Open Access Journals (Sweden)

Y. Shapira

2011-06-01

Full Text Available When analyzed by standard statistical methods, the time series of the daily return of financial indices appear to behave as Markov random series with no apparent temporal order or memory. This empirical result seems to be counter intuitive since investor are influenced by both short and long term past market behaviors. Consequently much effort has been devoted to unveil hidden temporal order in the market dynamics. Here we show that temporal order is hidden in the series of the variance of the stocks volatility. First we show that the correlation between the variances of the daily returns and means of segments of these time series is very large and thus cannot be the output of random series, unless it has some temporal order in it. Next we show that while the temporal order does not show in the series of the daily return, rather in the variation of the corresponding volatility series. More specifically, we found that the behavior of the shuffled time series is equivalent to that of a random time series, while that of the original time series have large deviations from the expected random behavior, which is the result of temporal structure. We found the same generic behavior in 10 different stock markets from 7 different countries. We also present analysis of specially constructed sequences in order to better understand the origin of the observed temporal order in the market sequences. Each sequence was constructed from segments with equal number of elements taken from algebraic distributions of three different slopes.

New Results On the Sum of Two Generalized Gaussian Random Variables

KAUST Repository

Soury, Hamza

2015-01-01

We propose in this paper a new method to compute the characteristic function (CF) of generalized Gaussian (GG) random variable in terms of the Fox H function. The CF of the sum of two independent GG random variables is then deduced. Based on this results, the probability density function (PDF) and the cumulative distribution function (CDF) of the sum distribution are obtained. These functions are expressed in terms of the bivariate Fox H function. Next, the statistics of the distribution of the sum, such as the moments, the cumulant, and the kurtosis, are analyzed and computed. Due to the complexity of bivariate Fox H function, a solution to reduce such complexity is to approximate the sum of two independent GG random variables by one GG random variable with suitable shape factor. The approximation method depends on the utility of the system so three methods of estimate the shape factor are studied and presented.

New Results on the Sum of Two Generalized Gaussian Random Variables

KAUST Repository

Soury, Hamza

2016-01-06

We propose in this paper a new method to compute the characteristic function (CF) of generalized Gaussian (GG) random variable in terms of the Fox H function. The CF of the sum of two independent GG random variables is then deduced. Based on this results, the probability density function (PDF) and the cumulative distribution function (CDF) of the sum distribution are obtained. These functions are expressed in terms of the bivariate Fox H function. Next, the statistics of the distribution of the sum, such as the moments, the cumulant, and the kurtosis, are analyzed and computed. Due to the complexity of bivariate Fox H function, a solution to reduce such complexity is to approximate the sum of two independent GG random variables by one GG random variable with suitable shape factor. The approximation method depends on the utility of the system so three methods of estimate the shape factor are studied and presented [1].

New Results on the Sum of Two Generalized Gaussian Random Variables

KAUST Repository

Soury, Hamza; Alouini, Mohamed-Slim

2016-01-01

We propose in this paper a new method to compute the characteristic function (CF) of generalized Gaussian (GG) random variable in terms of the Fox H function. The CF of the sum of two independent GG random variables is then deduced. Based on this results, the probability density function (PDF) and the cumulative distribution function (CDF) of the sum distribution are obtained. These functions are expressed in terms of the bivariate Fox H function. Next, the statistics of the distribution of the sum, such as the moments, the cumulant, and the kurtosis, are analyzed and computed. Due to the complexity of bivariate Fox H function, a solution to reduce such complexity is to approximate the sum of two independent GG random variables by one GG random variable with suitable shape factor. The approximation method depends on the utility of the system so three methods of estimate the shape factor are studied and presented [1].

Active control on high-order coherence and statistic characterization on random phase fluctuation of two classical point sources.

Science.gov (United States)

Hong, Peilong; Li, Liming; Liu, Jianji; Zhang, Guoquan

2016-03-29

Young's double-slit or two-beam interference is of fundamental importance to understand various interference effects, in which the stationary phase difference between two beams plays the key role in the first-order coherence. Different from the case of first-order coherence, in the high-order optical coherence the statistic behavior of the optical phase will play the key role. In this article, by employing a fundamental interfering configuration with two classical point sources, we showed that the high- order optical coherence between two classical point sources can be actively designed by controlling the statistic behavior of the relative phase difference between two point sources. Synchronous position Nth-order subwavelength interference with an effective wavelength of λ/M was demonstrated, in which λ is the wavelength of point sources and M is an integer not larger than N. Interestingly, we found that the synchronous position Nth-order interference fringe fingerprints the statistic trace of random phase fluctuation of two classical point sources, therefore, it provides an effective way to characterize the statistic properties of phase fluctuation for incoherent light sources.

Metaheuristic approaches to order sequencing on a unidirectional picking line

Directory of Open Access Journals (Sweden)

AP de Villiers

2013-06-01

Full Text Available In this paper the sequencing of orders on a unidirectional picking line is considered. The aim of the order sequencing is to minimise the number of cycles travelled by a picker within the picking line to complete all orders. A tabu search, simulated annealing, genetic algorithm, generalised extremal optimisation and a random local search are presented as possible solution approaches. Computational results based on real life data instances are presented for these metaheuristics and compared to the performance of a lower bound and the solutions used in practise. The random local search exhibits the best overall solution quality, however, the generalised extremal optimisation approach delivers comparable results in considerably shorter computational times.

Much of the variation in breast pathology quality assurance data in the UK can be explained by the random order in which cases arrive at individual centres, but some true outliers do exist.

Science.gov (United States)

Cross, Simon S; Stephenson, Timothy J; Harrison, Robert F

2011-10-01

To investigate the role of random temporal order of patient arrival at screening centres in the variability seen in rates of node positivity and breast cancer grade between centres in the NHS Breast Screening Programme. Computer simulations were performed of the variation in node positivity and breast cancer grade with the random temporal arrival of patients at screening centres based on national UK audit data. Cumulative mean graphs of these data were plotted. Confidence intervals for the parameters were generated, using the binomial distribution. UK audit data were plotted on these control limit graphs. The results showed that much of the variability in the audit data could be accounted for by the effects of random order of arrival of cases at the screening centres. Confidence intervals of 99.7% identified true outliers in the data. Much of the variation in breast pathology quality assurance data in the UK can be explained by the random order in which cases arrive at individual centres. Control charts with confidence intervals of 99.7% plotted against the number of reported cases are useful tools for identification of true outliers. 2011 Blackwell Publishing Limited.

IRFK2D: a computer program for simulating intrinsic random functions of order k

Science.gov (United States)

Pardo-Igúzquiza, Eulogio; Dowd, Peter A.

2003-07-01

IRFK2D is an ANSI Fortran-77 program that generates realizations of an intrinsic function of order k (with k equal to 0, 1 or 2) with a permissible polynomial generalized covariance model. The realizations may be non-conditional or conditioned to the experimental data. The turning bands method is used to generate realizations in 2D and 3D from simulations of an intrinsic random function of order k along lines that span the 2D or 3D space. The program generates two output files, the first containing the simulated values and the second containing the theoretical generalized variogram for different directions together with the theoretical model. The experimental variogram is calculated from the simulated values while the theoretical variogram is the specified generalized covariance model. The generalized variogram is used to assess the quality of the simulation as measured by the extent to which the generalized covariance is reproduced by the simulation. The examples given in this paper indicate that IRFK2D is an efficient implementation of the methodology.

Anisotropy of the monomer random walk in a polymer melt: local-order and connectivity effects

International Nuclear Information System (INIS)

Bernini, S; Leporini, D

2016-01-01

The random walk of a bonded monomer in a polymer melt is anisotropic due to local order and bond connectivity. We investigate both effects by molecular-dynamics simulations on melts of fully-flexible linear chains ranging from dimers (M  =  2) up to entangled polymers (M  =  200). The corresponding atomic liquid is also considered a reference system. To disentangle the influence of the local geometry and the bond arrangements, and to reveal their interplay, we define suitable measures of the anisotropy emphasising either the former or the latter aspect. Connectivity anisotropy, as measured by the correlation between the initial bond orientation and the direction of the subsequent monomer displacement, shows a slight enhancement due to the local order at times shorter than the structural relaxation time. At intermediate times—when the monomer displacement is comparable to the bond length—a pronounced peak and then decays slowly as t −1/2 , becoming negligible when the displacement is as large as about five bond lengths, i.e. about four monomer diameters or three Kuhn lengths. Local-geometry anisotropy, as measured by the correlation between the initial orientation of a characteristic axis of the Voronoi cell and the subsequent monomer dynamics, is affected at shorter times than the structural relaxation time by the cage shape with antagonistic disturbance by the connectivity. Differently, at longer times, the connectivity favours the persistence of the local-geometry anisotropy, which vanishes when the monomer displacement exceeds the bond length. Our results strongly suggest that the sole consideration of the local order is not enough to understand the microscopic origin of the rattling amplitude of the trapped monomer in the cage of the neighbours. (paper)

Transient modeling of non-Fickian transport and first-order reaction using continuous time random walk

Science.gov (United States)

Burnell, Daniel K.; Hansen, Scott K.; Xu, Jie

2017-09-01

Contaminants in groundwater may experience a broad spectrum of velocities and multiple rates of mass transfer between mobile and immobile zones during transport. These conditions may lead to non-Fickian plume evolution which is not well described by the advection-dispersion equation (ADE). Simultaneously, many groundwater contaminants are degraded by processes that may be modeled as first-order decay. It is now known that non-Fickian transport and reaction are intimately coupled, with reaction affecting the transport operator. However, closed-form solutions for these important scenarios have not been published for use in applications. In this paper, we present four new Green's function analytic solutions in the uncoupled, uncorrelated continuous time random walk (CTRW) framework for reactive non-Fickian transport, corresponding to the quartet of conservative tracer solutions presented by Kreft and Zuber (1978) for Fickian transport. These consider pulse injection for both resident and flux concentration combined with detection in both resident and flux concentration. A pair of solutions for resident concentration temporal pulses with detection in both flux and resident concentration is also presented. We also derive the relationship between flux and resident concentration for non-Fickian transport with first-order reaction for this CTRW formulation. An explicit discussion of employment of the new solutions to model transport with arbitrary upgradient boundary conditions as well as mobile-immobile mass transfer is then presented. Using the new solutions, we show that first-order reaction has no effect on the anomalous spatial spreading rate of concentration profiles, but produces breakthrough curves at fixed locations that appear to have been generated by Fickian transport. Under the assumption of a Pareto CTRW transition distribution, we present a variety of numerical simulations including results showing coherence of our analytic solutions and CTRW particle

Mixed results in the safety performance of computerized physician order entry.

Science.gov (United States)

Metzger, Jane; Welebob, Emily; Bates, David W; Lipsitz, Stuart; Classen, David C

2010-04-01

Computerized physician order entry is a required feature for hospitals seeking to demonstrate meaningful use of electronic medical record systems and qualify for federal financial incentives. A national sample of sixty-two hospitals voluntarily used a simulation tool designed to assess how well safety decision support worked when applied to medication orders in computerized order entry. The simulation detected only 53 percent of the medication orders that would have resulted in fatalities and 10-82 percent of the test orders that would have caused serious adverse drug events. It is important to ascertain whether actual implementations of computerized physician order entry are achieving goals such as improved patient safety.

A stochastic collocation method for the second order wave equation with a discontinuous random speed

KAUST Repository

Motamed, Mohammad

2012-08-31

In this paper we propose and analyze a stochastic collocation method for solving the second order wave equation with a random wave speed and subjected to deterministic boundary and initial conditions. The speed is piecewise smooth in the physical space and depends on a finite number of random variables. The numerical scheme consists of a finite difference or finite element method in the physical space and a collocation in the zeros of suitable tensor product orthogonal polynomials (Gauss points) in the probability space. This approach leads to the solution of uncoupled deterministic problems as in the Monte Carlo method. We consider both full and sparse tensor product spaces of orthogonal polynomials. We provide a rigorous convergence analysis and demonstrate different types of convergence of the probability error with respect to the number of collocation points for full and sparse tensor product spaces and under some regularity assumptions on the data. In particular, we show that, unlike in elliptic and parabolic problems, the solution to hyperbolic problems is not in general analytic with respect to the random variables. Therefore, the rate of convergence may only be algebraic. An exponential/fast rate of convergence is still possible for some quantities of interest and for the wave solution with particular types of data. We present numerical examples, which confirm the analysis and show that the collocation method is a valid alternative to the more traditional Monte Carlo method for this class of problems. © 2012 Springer-Verlag.

Challenges in higher order mode Raman amplifiers

DEFF Research Database (Denmark)

Rottwitt, Karsten; Nielsen, Kristian; Friis, Søren Michael Mørk

2015-01-01

A higher order Raman amplifier model that take random mode coupling into account ispresented. Mode dependent gain and signal power fluctuations at the output of the higher order modeRaman amplifier are discussed......A higher order Raman amplifier model that take random mode coupling into account ispresented. Mode dependent gain and signal power fluctuations at the output of the higher order modeRaman amplifier are discussed...

On the limit distribution of lower extreme generalized order statistics

Indian Academy of Sciences (India)

Abstract. In a wide subclass of generalized order statistics (gOs), which contains most of the known and important models of ordered random variables, weak conver- gence of lower extremes are developed. A recent result of extreme value theory of m−gOs (as well as the classical extreme value theory of ordinary order ...

Toward a Principled Sampling Theory for Quasi-Orders.

Science.gov (United States)

Ünlü, Ali; Schrepp, Martin

2016-01-01

Quasi-orders, that is, reflexive and transitive binary relations, have numerous applications. In educational theories, the dependencies of mastery among the problems of a test can be modeled by quasi-orders. Methods such as item tree or Boolean analysis that mine for quasi-orders in empirical data are sensitive to the underlying quasi-order structure. These data mining techniques have to be compared based on extensive simulation studies, with unbiased samples of randomly generated quasi-orders at their basis. In this paper, we develop techniques that can provide the required quasi-order samples. We introduce a discrete doubly inductive procedure for incrementally constructing the set of all quasi-orders on a finite item set. A randomization of this deterministic procedure allows us to generate representative samples of random quasi-orders. With an outer level inductive algorithm, we consider the uniform random extensions of the trace quasi-orders to higher dimension. This is combined with an inner level inductive algorithm to correct the extensions that violate the transitivity property. The inner level correction step entails sampling biases. We propose three algorithms for bias correction and investigate them in simulation. It is evident that, on even up to 50 items, the new algorithms create close to representative quasi-order samples within acceptable computing time. Hence, the principled approach is a significant improvement to existing methods that are used to draw quasi-orders uniformly at random but cannot cope with reasonably large item sets.

Toward a Principled Sampling Theory for Quasi-Orders

Science.gov (United States)

Ünlü, Ali; Schrepp, Martin

2016-01-01

Quasi-orders, that is, reflexive and transitive binary relations, have numerous applications. In educational theories, the dependencies of mastery among the problems of a test can be modeled by quasi-orders. Methods such as item tree or Boolean analysis that mine for quasi-orders in empirical data are sensitive to the underlying quasi-order structure. These data mining techniques have to be compared based on extensive simulation studies, with unbiased samples of randomly generated quasi-orders at their basis. In this paper, we develop techniques that can provide the required quasi-order samples. We introduce a discrete doubly inductive procedure for incrementally constructing the set of all quasi-orders on a finite item set. A randomization of this deterministic procedure allows us to generate representative samples of random quasi-orders. With an outer level inductive algorithm, we consider the uniform random extensions of the trace quasi-orders to higher dimension. This is combined with an inner level inductive algorithm to correct the extensions that violate the transitivity property. The inner level correction step entails sampling biases. We propose three algorithms for bias correction and investigate them in simulation. It is evident that, on even up to 50 items, the new algorithms create close to representative quasi-order samples within acceptable computing time. Hence, the principled approach is a significant improvement to existing methods that are used to draw quasi-orders uniformly at random but cannot cope with reasonably large item sets. PMID:27965601

Asymptotic results for the semi-Markovian random walk with delay

International Nuclear Information System (INIS)

Khaniyev, T.A.; Aliyev, R.T.

2006-12-01

In this study, the semi-Markovian random walk with a discrete interference of chance (X(t) ) is considered and under some weak assumptions the ergodicity of this process is discussed. Characteristic function of the ergodic distribution of X(t) is expressed by means of the probability characteristics of the boundary functionals (N,S N ). Some exact formulas for first and second moments of ergodic distribution of the process X(t) are obtained when the random variable ζ 1 - s, which is describing a discrete interference of chance, has Gamma distribution on the interval [0, ∞) with parameter (α,λ) . Based on these results, the asymptotic expansions with three terms for the first two moments of the ergodic distribution of the process X(t) are obtained, as λ → 0. (author)

Doppler Radar Vital Signs Detection Method Based on Higher Order Cyclostationary.

Science.gov (United States)

Yu, Zhibin; Zhao, Duo; Zhang, Zhiqiang

2017-12-26

Due to the non-contact nature, using Doppler radar sensors to detect vital signs such as heart and respiration rates of a human subject is getting more and more attention. However, the related detection-method research meets lots of challenges due to electromagnetic interferences, clutter and random motion interferences. In this paper, a novel third-order cyclic cummulant (TOCC) detection method, which is insensitive to Gaussian interference and non-cyclic signals, is proposed to investigate the heart and respiration rate based on continuous wave Doppler radars. The k -th order cyclostationary properties of the radar signal with hidden periodicities and random motions are analyzed. The third-order cyclostationary detection theory of the heart and respiration rate is studied. Experimental results show that the third-order cyclostationary approach has better estimation accuracy for detecting the vital signs from the received radar signal under low SNR, strong clutter noise and random motion interferences.

On the Limit Distribution of Lower Extreme Generalized Order Statistics

Indian Academy of Sciences (India)

In a wide subclass of generalized order statistics ( g O s ) , which contains most of the known and important models of ordered random variables, weak convergence of lower extremes are developed. A recent result of extreme value theory of m − g O s (as well as the classical extreme value theory of ordinary order statistics) ...

Higher order moments of a sum of random variables: remarks and applications.

Directory of Open Access Journals (Sweden)

Luisa Tibiletti

1996-02-01

Full Text Available The moments of a sum of random variables depend on both the pure moments of each random addendum and on the addendum mixed moments. In this note we introduce a simple measure to evaluate the relative impedance to attach to the latter. Once the pure moments are fixed, the functional relation between the random addenda leading to the extreme values is also provided. Applications to Finance, Decision Theory and Actuarial Sciences are also suggested.

Staggered chiral random matrix theory

International Nuclear Information System (INIS)

Osborn, James C.

2011-01-01

We present a random matrix theory for the staggered lattice QCD Dirac operator. The staggered random matrix theory is equivalent to the zero-momentum limit of the staggered chiral Lagrangian and includes all taste breaking terms at their leading order. This is an extension of previous work which only included some of the taste breaking terms. We will also present some results for the taste breaking contributions to the partition function and the Dirac eigenvalues.

Random Mutagenesis of the Aspergillus oryzae Genome Results in Fungal Antibacterial Activity

Directory of Open Access Journals (Sweden)

Cory A. Leonard

2013-01-01

Full Text Available Multidrug-resistant bacteria cause severe infections in hospitals and communities. Development of new drugs to combat resistant microorganisms is needed. Natural products of microbial origin are the source of most currently available antibiotics. We hypothesized that random mutagenesis of Aspergillus oryzae would result in secretion of antibacterial compounds. To address this hypothesis, we developed a screen to identify individual A. oryzae mutants that inhibit the growth of Methicillin-resistant Staphylococcus aureus (MRSA in vitro. To randomly generate A. oryzae mutant strains, spores were treated with ethyl methanesulfonate (EMS. Over 3000 EMS-treated A. oryzae cultures were tested in the screen, and one isolate, CAL220, exhibited altered morphology and antibacterial activity. Culture supernatant from this isolate showed antibacterial activity against Methicillin-sensitive Staphylococcus aureus, MRSA, and Pseudomonas aeruginosa, but not Klebsiella pneumonia or Proteus vulgaris. The results of this study support our hypothesis and suggest that the screen used is sufficient and appropriate to detect secreted antibacterial fungal compounds resulting from mutagenesis of A. oryzae. Because the genome of A. oryzae has been sequenced and systems are available for genetic transformation of this organism, targeted as well as random mutations may be introduced to facilitate the discovery of novel antibacterial compounds using this system.

Random Mutagenesis of the Aspergillus oryzae Genome Results in Fungal Antibacterial Activity

Science.gov (United States)

Leonard, Cory A.; Brown, Stacy D.; Hayman, J. Russell

2013-01-01

Multidrug-resistant bacteria cause severe infections in hospitals and communities. Development of new drugs to combat resistant microorganisms is needed. Natural products of microbial origin are the source of most currently available antibiotics. We hypothesized that random mutagenesis of Aspergillus oryzae would result in secretion of antibacterial compounds. To address this hypothesis, we developed a screen to identify individual A. oryzae mutants that inhibit the growth of Methicillin-resistant Staphylococcus aureus (MRSA) in vitro. To randomly generate A. oryzae mutant strains, spores were treated with ethyl methanesulfonate (EMS). Over 3000 EMS-treated A. oryzae cultures were tested in the screen, and one isolate, CAL220, exhibited altered morphology and antibacterial activity. Culture supernatant from this isolate showed antibacterial activity against Methicillin-sensitive Staphylococcus aureus, MRSA, and Pseudomonas aeruginosa, but not Klebsiella pneumonia or Proteus vulgaris. The results of this study support our hypothesis and suggest that the screen used is sufficient and appropriate to detect secreted antibacterial fungal compounds resulting from mutagenesis of A. oryzae. Because the genome of A. oryzae has been sequenced and systems are available for genetic transformation of this organism, targeted as well as random mutations may be introduced to facilitate the discovery of novel antibacterial compounds using this system. PMID:23983696

Random Mutagenesis of the Aspergillus oryzae Genome Results in Fungal Antibacterial Activity.

Science.gov (United States)

Leonard, Cory A; Brown, Stacy D; Hayman, J Russell

2013-01-01

Multidrug-resistant bacteria cause severe infections in hospitals and communities. Development of new drugs to combat resistant microorganisms is needed. Natural products of microbial origin are the source of most currently available antibiotics. We hypothesized that random mutagenesis of Aspergillus oryzae would result in secretion of antibacterial compounds. To address this hypothesis, we developed a screen to identify individual A. oryzae mutants that inhibit the growth of Methicillin-resistant Staphylococcus aureus (MRSA) in vitro. To randomly generate A. oryzae mutant strains, spores were treated with ethyl methanesulfonate (EMS). Over 3000 EMS-treated A. oryzae cultures were tested in the screen, and one isolate, CAL220, exhibited altered morphology and antibacterial activity. Culture supernatant from this isolate showed antibacterial activity against Methicillin-sensitive Staphylococcus aureus, MRSA, and Pseudomonas aeruginosa, but not Klebsiella pneumonia or Proteus vulgaris. The results of this study support our hypothesis and suggest that the screen used is sufficient and appropriate to detect secreted antibacterial fungal compounds resulting from mutagenesis of A. oryzae. Because the genome of A. oryzae has been sequenced and systems are available for genetic transformation of this organism, targeted as well as random mutations may be introduced to facilitate the discovery of novel antibacterial compounds using this system.

Random Fields

Science.gov (United States)

Vanmarcke, Erik

1983-03-01

Random variation over space and time is one of the few attributes that might safely be predicted as characterizing almost any given complex system. Random fields or "distributed disorder systems" confront astronomers, physicists, geologists, meteorologists, biologists, and other natural scientists. They appear in the artifacts developed by electrical, mechanical, civil, and other engineers. They even underlie the processes of social and economic change. The purpose of this book is to bring together existing and new methodologies of random field theory and indicate how they can be applied to these diverse areas where a "deterministic treatment is inefficient and conventional statistics insufficient." Many new results and methods are included. After outlining the extent and characteristics of the random field approach, the book reviews the classical theory of multidimensional random processes and introduces basic probability concepts and methods in the random field context. It next gives a concise amount of the second-order analysis of homogeneous random fields, in both the space-time domain and the wave number-frequency domain. This is followed by a chapter on spectral moments and related measures of disorder and on level excursions and extremes of Gaussian and related random fields. After developing a new framework of analysis based on local averages of one-, two-, and n-dimensional processes, the book concludes with a chapter discussing ramifications in the important areas of estimation, prediction, and control. The mathematical prerequisite has been held to basic college-level calculus.

An introduction to random interlacements

CERN Document Server

Drewitz, Alexander; Sapozhnikov, Artëm

2014-01-01

This book gives a self-contained introduction to the theory of random interlacements. The intended reader of the book is a graduate student with a background in probability theory who wants to learn about the fundamental results and methods of this rapidly emerging field of research. The model was introduced by Sznitman in 2007 in order to describe the local picture left by the trace of a random walk on a large discrete torus when it runs up to times proportional to the volume of the torus. Random interlacements is a new percolation model on the d-dimensional lattice. The main results covered by the book include the full proof of the local convergence of random walk trace on the torus to random interlacements and the full proof of the percolation phase transition of the vacant set of random interlacements in all dimensions. The reader will become familiar with the techniques relevant to working with the underlying Poisson Process and the method of multi-scale renormalization, which helps in overcoming the ch...

Olsalazine is contraindicated during pelvic radiation therapy: results of a double-blind, randomized clinical trial

International Nuclear Information System (INIS)

Martenson, James A.; Hyland, Glenn; Moertel, Charles G.; Mailliard, James A.; O'Fallon, Judith R.; Collins, Roger T.; Morton, Roscoe F.; Tewfik, Hamed H.; Moore, Randy L.; Frank, Albert R.; Urias, Rodolfo E.; Deming, Richard L.

1996-01-01

Purpose: A randomized clinical trial from Great Britain suggested a possible beneficial effect of acetylsalicylate in the prevention of radiation-induced bowel toxicity. Olsalazine is an orally administered drug designed to deliver 5-aminosalicylate to the large bowel with minimal systemic absorption. A randomized clinical trial was undertaken to assess the effectiveness of olsalazine in preventing acute diarrhea in patients receiving pelvic radiation therapy. Methods and Materials: Patients receiving pelvic radiation therapy were randomized, in double-blind fashion, to olsalazine 250 mg, two capsules twice daily, or an identical appearing placebo, two capsules twice daily. Patients were then evaluated weekly during radiation therapy for the primary study endpoint, diarrhea, as well as rectal bleeding, abdominal cramping, and tenesmus. Results: The study was closed early, after entry of 58 evaluable patients, when a preliminary analysis showed excessive diarrhea in patients randomized to olsalazine. The incidence and severity of diarrhea were worse in patients randomized to olsalazine (p 0.0036). Sixty percent of the patients randomized to olsalazine experienced Grade 3 or 4 diarrhea compared to only 14% randomized to placebo. There was also a trend toward higher incidence and greater severity of abdominal cramping in patients who were randomized to olsalazine (p = 0.084). Conclusion: Administration of olsalazine during pelvic radiation therapy resulted in an increased incidence and severity of diarrhea. Olsalazine is contraindicated in patients receiving pelvic radiation therapy

Iterative oscillation results for second-order differential equations with advanced argument

Directory of Open Access Journals (Sweden)

Irena Jadlovska

2017-07-01

Full Text Available This article concerns the oscillation of solutions to a linear second-order differential equation with advanced argument. Sufficient oscillation conditions involving limit inferior are given which essentially improve known results. We base our technique on the iterative construction of solution estimates and some of the recent ideas developed for first-order advanced differential equations. We demonstrate the advantage of our results on Euler-type advanced equation. Using MATLAB software, a comparison of the effectiveness of newly obtained criteria as well as the necessary iteration length in particular cases are discussed.

A Solution Method for Linear and Geometrically Nonlinear MDOF Systems with Random Properties subject to Random Excitation

DEFF Research Database (Denmark)

Micaletti, R. C.; Cakmak, A. S.; Nielsen, Søren R. K.

structural properties. The resulting state-space formulation is a system of ordinary stochastic differential equations with random coefficient and deterministic initial conditions which are subsequently transformed into ordinary stochastic differential equations with deterministic coefficients and random......A method for computing the lower-order moments of randomly-excited multi-degree-of-freedom (MDOF) systems with random structural properties is proposed. The method is grounded in the techniques of stochastic calculus, utilizing a Markov diffusion process to model the structural system with random...... initial conditions. This transformation facilitates the derivation of differential equations which govern the evolution of the unconditional statistical moments of response. Primary consideration is given to linear systems and systems with odd polynomial nonlinearities, for in these cases...

Randomness in preference orderings, outcomes and attribute tastes: An application to journey time risk

DEFF Research Database (Denmark)

Batley, Richard; Ibáñez Rivas, Juan Nicolás

2012-01-01

estimate a mean ‘reliability ratio’ (ratio of the value of standard deviation of journey time to the value of scheduled journey time) of 2.07, against a median of 0.85. The properties of the distribution of the reliability ratio suggest a predominant behaviour of aversion to journey time risk.......Within the broad area of probabilistic modelling of individual discrete choice, we develop three strands of discussion. First, we outline a theoretical framework for the modelling of individual discrete choice under risk, distinguishing between three specific sources of randomness; in preference...... orderings, in outcomes, and in attribute tastes. Second, we apply this theoretical modelling framework to the domain of journey time risk (or ‘reliability’), a subject which has acquired prominence in the transportation policies of many countries. Third, we apply the modelling framework empirically, based...

Ordering kinetics in quasi-one-dimensional Ising-like systems

International Nuclear Information System (INIS)

Mueller, M.; Paul, W.

1993-01-01

Results are presented of a Monte Carlo simulation of the kinetics of ordering in the two-dimensional nearest-neighbor Ising model in an L x M geometry with two free boundaries of length M much-gt L. This model can be viewed as representing an adsorbant on a stepped surface with mean terrace width L. The authors follow the ordering kinetics after quenches to temperatures 0.25 ≤T/T c ≤1 starting from a random initial configuration at a coverage of Θ=0.5 in the corresponding lattice gas picture. The systems evolve in time according to a Glauber kinetics with nonconserved order parameter. The equilibrium structure is given by a one-dimensional sequence of ordered domains. The ordering process evolves from a short initial two-dimensional ordering process through a crossover region to a quasi-one-dimensional behavior. The whole process is diffusive (inverse half-width of the structure factor peak 1/Δq parallel ∝ √t), in contrast to a model proposed by Kawasaki et al., where an intermediate logarithmic growth law is expected. All results are completely describable in the picture of an annihilating random walk (ARW) of domain walls. 36 refs., 16 figs

The Relationship of Dynamical Heterogeneity to the Adam-Gibbs and Random First-Order Transition Theories of Glass Formation

OpenAIRE

Starr, Francis W.; Douglas, Jack F.; Sastry, Srikanth

2013-01-01

We carefully examine common measures of dynamical heterogeneity for a model polymer melt and test how these scales compare with those hypothesized by the Adam and Gibbs (AG) and random first-order transition (RFOT) theories of relaxation in glass-forming liquids. To this end, we first analyze clusters of highly mobile particles, the string-like collective motion of these mobile particles, and clusters of relative low mobility. We show that the time scale of the high-mobility clusters and stri...

Strong result for real zeros of random algebraic polynomials

Directory of Open Access Journals (Sweden)

T. Uno

2001-01-01

Full Text Available An estimate is given for the lower bound of real zeros of random algebraic polynomials whose coefficients are non-identically distributed dependent Gaussian random variables. Moreover, our estimated measure of the exceptional set, which is independent of the degree of the polynomials, tends to zero as the degree of the polynomial tends to infinity.

Emergence of Lévy Walks from Second-Order Stochastic Optimization

Science.gov (United States)

Kuśmierz, Łukasz; Toyoizumi, Taro

2017-12-01

In natural foraging, many organisms seem to perform two different types of motile search: directed search (taxis) and random search. The former is observed when the environment provides cues to guide motion towards a target. The latter involves no apparent memory or information processing and can be mathematically modeled by random walks. We show that both types of search can be generated by a common mechanism in which Lévy flights or Lévy walks emerge from a second-order gradient-based search with noisy observations. No explicit switching mechanism is required—instead, continuous transitions between the directed and random motions emerge depending on the Hessian matrix of the cost function. For a wide range of scenarios, the Lévy tail index is α =1 , consistent with previous observations in foraging organisms. These results suggest that adopting a second-order optimization method can be a useful strategy to combine efficient features of directed and random search.

An Authenticated Key Agreement Scheme Based on Cyclic Automorphism Subgroups of Random Orders

Directory of Open Access Journals (Sweden)

Yang Jun

2017-01-01

Full Text Available Group-based cryptography is viewed as a modern cryptographic candidate solution to blocking quantum computer attacks, and key exchange protocols on the Internet are one of the primitives to ensure the security of communication. In 2016 Habeeb et al proposed a “textbook” key exchange protocol based on the semidirect product of two groups, which is insecure for use in real-world applications. In this paper, after discarding the unnecessary disguising notion of semidirect product in the protocol, we establish a simplified yet enhanced authenticated key agreement scheme based on cyclic automorphism subgroups of random orders by making hybrid use of certificates and symmetric-key encryption as challenge-and-responses in the public-key setting. Its passive security is formally analyzed, which is relative to the cryptographic hardness assumption of a computational number-theoretic problem. Cryptanalysis of this scheme shows that it is secure against the intruder-in-the-middle attack even in the worst case of compromising the signatures, and provides explicit key confirmation to both parties.

First- and second-order processing in transient stereopsis.

Science.gov (United States)

Edwards, M; Pope, D R; Schor, C M

2000-01-01

Large-field stimuli were used to investigate the interaction of first- and second-order pathways in transient-stereo processing. Stimuli consisted of sinewave modulations in either the mean luminance (first-order stimulus) or the contrast (second-order stimulus) of a dynamic-random-dot field. The main results of the present study are that: (1) Depth could be extracted with both the first-order and second-order stimuli; (2) Depth could be extracted from dichoptically mixed first- and second-order stimuli, however, the same stimuli, when presented as a motion sequence, did not result in a motion percept. Based upon these findings we conclude that the transient-stereo system processes both first- and second-order signals, and that these two signals are pooled prior to the extraction of transient depth. This finding of interaction between first- and second-order stereoscopic processing is different from the independence that has been found with the motion system.

Waiting time analysis for MX/G/1 priority queues with/without vacations under random order of service discipline

Directory of Open Access Journals (Sweden)

Norikazu Kawasaki

2000-01-01

Full Text Available We study MX/G/1 nonpreemptive and preemptive-resume priority queues with/without vacations under random order of service (ROS discipline within each class. By considering the conditional waiting times given the states of the system, which an arbitrary message observes upon arrival, we derive the Laplace-Stieltjes transforms of the waiting time distributions and explicitly obtain the first two moments. The relationship for the second moments under ROS and first-come first-served disciplines extends the one found previously by Takacs and Fuhrmann for non-priority single arrival queues.

Effects of a randomized intervention promoting healthy children's meals on children's ordering and dietary intake in a quick-service restaurant.

Science.gov (United States)

Anzman-Frasca, Stephanie; Braun, Abbey C; Ehrenberg, Sarah; Epstein, Leonard H; Gampp, April; Leone, Lucia A; Singh, Anita; Tauriello, Sara

2018-08-01

Children's consumption of restaurant foods is associated with higher energy intake and lower nutritional quality compared to foods prepared at home. The aim of this pilot study was to test whether an in-restaurant intervention promoting healthy children's meals (i.e. two meals that met nutrition recommendations and were thus healthier than typical children's meal offerings across leading restaurants) affected children's meal selection and intake. Families with 4-to-8-year-old children were recruited from one location of Anderson's Frozen Custard, a regional quick-service restaurant chain. Families were randomly assigned to return to the restaurant during an intervention or control period and were blinded to group assignment. All families received free meals. During the intervention period families also received placemats featuring two healthy "Kids' Meals of the Day" upon restaurant entry. After families finished dining, researchers recorded children's orders and collected leftovers for quantifying dietary intake via weighed plate waste. Poisson regression and chi-square tests were used to compare children's orders between study groups, and t-tests were used to test for differences in dietary intake among children ordering a promoted healthy entrée (main dish) versus those who did not. Fifty-eight families participated. Children who were exposed to the study placemats prior to ordering ordered a significantly greater number of healthy food components compared to controls (p = 0.03). Overall, in the intervention group, 21% of children ordered a healthy entrée or side dish, versus 7% of controls. Children who ordered one of the promoted healthy entrées consumed less saturated fat across the total meal compared to those who did not (p = 0.04). Manipulating the prominence of healthy choices in restaurants may shift children's meal selections. Future research should build on these initial promising results, aiming to increase the potency of the intervention

Multidemand Multisource Order Quantity Allocation with Multiple Transportation Alternatives

Directory of Open Access Journals (Sweden)

Jun Gang

2015-01-01

Full Text Available This paper focuses on a multidemand multisource order quantity allocation problem with multiple transportation alternatives. To solve this problem, a bilevel multiobjective programming model under a mixed uncertain environment is proposed. Two levels of decision makers are considered in the model. On the upper level, the purchaser aims to allocate order quantity to multiple suppliers for each demand node with the consideration of three objectives: total purchase cost minimization, total delay risk minimization, and total defect risk minimization. On the lower level, each supplier attempts to optimize the transportation alternatives with total transportation and penalty costs minimization as the objective. In contrast to prior studies, considering the information asymmetry in the bilevel decision, random and fuzzy random variables are used to model uncertain parameters of the construction company and the suppliers. To solve the bilevel model, a solution method based on Kuhn-Tucker conditions, sectional genetic algorithm, and fuzzy random simulation is proposed. Finally, the applicability of the proposed model and algorithm is evaluated through a practical case from a large scale construction project. The results show that the proposed model and algorithm are efficient in dealing with practical order quantity allocation problems.

Random Schroedinger operators and the theory of disordered systems: some rigorous results

International Nuclear Information System (INIS)

Kunz, H.; Souillard, B.

1981-01-01

The authors report results on a class of finite difference Schroedinger operators with stochastic potentials. The Hamiltonian is then H(V)=-Δ+V; where Δ is the discretized Laplacian and the potential V acts as a multiplication operator. The potential V is random. (Auth.)

Housing first reduces re-offending among formerly homeless adults with mental disorders: results of a randomized controlled trial.

Directory of Open Access Journals (Sweden)

Julian M Somers

Full Text Available BACKGROUND: Homelessness and mental illness have a strong association with public disorder and criminality. Experimental evidence indicates that Housing First (HF increases housing stability and perceived choice among those experiencing chronic homelessness and mental disorders. HF is also associated with lower residential costs than common alternative approaches. Few studies have examined the effect of HF on criminal behavior. METHODS: Individuals meeting criteria for homelessness and a current mental disorder were randomized to one of three conditions treatment as usual (reference; scattered site HF; and congregate HF. Administrative data concerning justice system events were linked in order to study prior histories of offending and to test the relationship between housing status and offending following randomization for up to two years. RESULTS: The majority of the sample (67% was involved with the justice system, with a mean of 8.07 convictions per person in the ten years prior to recruitment. The most common category of crime was "property offences" (mean=4.09. Following randomization, the scattered site HF condition was associated with significantly lower numbers of sentences than treatment as usual (Adjusted IRR=0.29; 95% CI 0.12-0.72. Congregate HF was associated with a marginally significant reduction in sentences compared to treatment as usual (Adjusted IRR=0.55; 95% CI: 0.26-1.14. CONCLUSIONS: This study is the first randomized controlled trial to demonstrate benefits of HF among a homeless sample with mental illness in the domain of public safety and crime. Our sample was frequently involved with the justice system, with great personal and societal costs. Further implementation of HF is strongly indicated, particularly in the scattered site format. Research examining interdependencies between housing, health, and the justice system is indicated. TRIAL REGISTRATION: ISRCTN57595077.

Approximate Forward Difference Equations for the Lower Order Non-Stationary Statistics of Geometrically Non-Linear Systems subject to Random Excitation

DEFF Research Database (Denmark)

Köylüoglu, H. U.; Nielsen, Søren R. K.; Cakmak, A. S.

Geometrically non-linear multi-degree-of-freedom (MDOF) systems subject to random excitation are considered. New semi-analytical approximate forward difference equations for the lower order non-stationary statistical moments of the response are derived from the stochastic differential equations...... of motion, and, the accuracy of these equations is numerically investigated. For stationary excitations, the proposed method computes the stationary statistical moments of the response from the solution of non-linear algebraic equations....

Average-case analysis of incremental topological ordering

DEFF Research Database (Denmark)

Ajwani, Deepak; Friedrich, Tobias

2010-01-01

Many applications like pointer analysis and incremental compilation require maintaining a topological ordering of the nodes of a directed acyclic graph (DAG) under dynamic updates. All known algorithms for this problem are either only analyzed for worst-case insertion sequences or only evaluated...... experimentally on random DAGs. We present the first average-case analysis of incremental topological ordering algorithms. We prove an expected runtime of under insertion of the edges of a complete DAG in a random order for the algorithms of Alpern et al. (1990) [4], Katriel and Bodlaender (2006) [18], and Pearce...

On nonlinear reduced order modeling

International Nuclear Information System (INIS)

Abdel-Khalik, Hany S.

2011-01-01

When applied to a model that receives n input parameters and predicts m output responses, a reduced order model estimates the variations in the m outputs of the original model resulting from variations in its n inputs. While direct execution of the forward model could provide these variations, reduced order modeling plays an indispensable role for most real-world complex models. This follows because the solutions of complex models are expensive in terms of required computational overhead, thus rendering their repeated execution computationally infeasible. To overcome this problem, reduced order modeling determines a relationship (often referred to as a surrogate model) between the input and output variations that is much cheaper to evaluate than the original model. While it is desirable to seek highly accurate surrogates, the computational overhead becomes quickly intractable especially for high dimensional model, n ≫ 10. In this manuscript, we demonstrate a novel reduced order modeling method for building a surrogate model that employs only 'local first-order' derivatives and a new tensor-free expansion to efficiently identify all the important features of the original model to reach a predetermined level of accuracy. This is achieved via a hybrid approach in which local first-order derivatives (i.e., gradient) of a pseudo response (a pseudo response represents a random linear combination of original model’s responses) are randomly sampled utilizing a tensor-free expansion around some reference point, with the resulting gradient information aggregated in a subspace (denoted by the active subspace) of dimension much less than the dimension of the input parameters space. The active subspace is then sampled employing the state-of-the-art techniques for global sampling methods. The proposed method hybridizes the use of global sampling methods for uncertainty quantification and local variational methods for sensitivity analysis. In a similar manner to

Global Attractivity Results for Mixed-Monotone Mappings in Partially Ordered Complete Metric Spaces

Directory of Open Access Journals (Sweden)

Kalabušić S

2009-01-01

Full Text Available We prove fixed point theorems for mixed-monotone mappings in partially ordered complete metric spaces which satisfy a weaker contraction condition than the classical Banach contraction condition for all points that are related by given ordering. We also give a global attractivity result for all solutions of the difference equation , where satisfies mixed-monotone conditions with respect to the given ordering.

Decomposition of conditional probability for high-order symbolic Markov chains

Science.gov (United States)

Melnik, S. S.; Usatenko, O. V.

2017-07-01

The main goal of this paper is to develop an estimate for the conditional probability function of random stationary ergodic symbolic sequences with elements belonging to a finite alphabet. We elaborate on a decomposition procedure for the conditional probability function of sequences considered to be high-order Markov chains. We represent the conditional probability function as the sum of multilinear memory function monomials of different orders (from zero up to the chain order). This allows us to introduce a family of Markov chain models and to construct artificial sequences via a method of successive iterations, taking into account at each step increasingly high correlations among random elements. At weak correlations, the memory functions are uniquely expressed in terms of the high-order symbolic correlation functions. The proposed method fills the gap between two approaches, namely the likelihood estimation and the additive Markov chains. The obtained results may have applications for sequential approximation of artificial neural network training.

Models of disordered media: some new results, including some new connections between composite-media, fluid-state, and random-flight theories

International Nuclear Information System (INIS)

Stell, G.

1983-01-01

Some new theoretical results on the microstructure of models of two-phase disordered media are given, as well as the new quantitative bounds on the thermal conductivity that follows for one such model (randomly centered spherical inclusions). A second set of results is then given for random flights, including random flights with hit expectancy prescribed in a unit hall around the flight origin. Finally, some interesting correspondences are demonstrated, via the Ornstein-Zernike equation, between random-flight results, liquid-state results and percolation-theory results. 27 references, 6 figures, 4 tables

Methods and optical fibers that decrease pulse degradation resulting from random chromatic dispersion

Science.gov (United States)

Chertkov, Michael; Gabitov, Ildar

2004-03-02

The present invention provides methods and optical fibers for periodically pinning an actual (random) accumulated chromatic dispersion of an optical fiber to a predicted accumulated dispersion of the fiber through relatively simple modifications of fiber-optic manufacturing methods or retrofitting of existing fibers. If the pinning occurs with sufficient frequency (at a distance less than or are equal to a correlation scale), pulse degradation resulting from random chromatic dispersion is minimized. Alternatively, pinning may occur quasi-periodically, i.e., the pinning distance is distributed between approximately zero and approximately two to three times the correlation scale.

Fluctuation microscopy: a probe of medium range order

International Nuclear Information System (INIS)

Treacy, M M J; Gibson, J M; Fan, L; Paterson, D J; McNulty, I

2005-01-01

Fluctuation microscopy is a hybrid diffraction-imaging technique that detects medium range order in amorphous materials by examining spatial fluctuations in coherent scattering. These fluctuations appear as speckle in images and diffraction patterns. The volume of material contributing to the speckle is determined by the point-spread function (the resolution) of the imaging optics and the sample thickness. The spatial periodicities being probed are related to the diffraction vector. Statistical analysis of the speckle allows the random and non-random (ordered) contributions to be discriminated. The image resolution that gives the maximum speckle contrast, as determined by the normalized variance of the image intensity, is determined by the characteristic length scale of the ordering. Because medium range ordering length scales can extend out to about the tenth coordination shell, fluctuation microscopy tends to be a low image resolution technique. This review presents the kinematical scattering theory underpinning fluctuation microscopy and a description of fluctuation electron microscopy as it has been employed in the transmission electron microscope for studying amorphous materials. Recent results using soft x-rays for studying nanoscale materials are also presented. We summarize outstanding issues and point to possible future directions for fluctuation microscopy as a technique

Optimal Order of Successive Office Hysteroscopy and Endometrial Biopsy for the Evaluation of Abnormal Uterine Bleeding: A Randomized Controlled Trial.

Science.gov (United States)

Sarkar, Papri; Mikhail, Emad; Schickler, Robyn; Plosker, Shayne; Imudia, Anthony N

2017-09-01

To estimate the optimal order of office hysteroscopy and endometrial biopsy when performed successively for evaluation of abnormal uterine bleeding. Patients undergoing successive office hysteroscopy and endometrial biopsy were included in a single-blind, prospective, randomized trial. The primary outcome was to evaluate the effect of order of procedures on patients' pain score. Prespecified secondary outcomes include procedure duration, hysteroscopic visualization of the uterine cavity, endometrial sample adequacy, and number of attempts at biopsy. Pain scores were assessed using a visual analog scale from 0 to 10 and endometrial sample adequacy was determined from the histopathology report. Hysteroscopy images were recorded. Sample size of 34 per group (n=68) was determined to be adequate to detect a difference of 20% in visual analog scale score between hysteroscopy first (group A) and biopsy first (group B) at α of 0.05 and 80% power. Between October 2015 and January 2017, 78 women were randomized to group A (n=40) and group B (n=38). There was no difference in global pain perception [7 (0-10) vs 7 (0-10); P=.57, 95% CI 5.8-7.1]. Procedure duration [3 (1-9) vs 3 (2-10), P=.32, 95% CI 3.3-4.1] and endometrial sample adequacy (78.9% vs 75.7%, P=.74) were similar in both groups. Group A patients had better endometrial visualization (Pabnormal uterine bleeding, the global pain perception, and time required are independent of the order in which procedures are performed. Performing hysteroscopy first ensures better image, whereas biopsy first yields adequate tissue sample with fewer attempts. ClinicalTrials.gov, NCT02472184.

Effect of calorie or exercise labels on menus on calories and macronutrients ordered and calories from specific foods in Hispanic participants: a randomized study.

Science.gov (United States)

Shah, Meena; Bouza, Brooke; Adams-Huet, Beverley; Jaffery, Manall; Esposito, Phil; Dart, Lyn

2016-12-01

The effect of menu labels on food choices is unknown in Hispanics. This study evaluated the impact of menu labels on calories and macronutrients ordered in Hispanics. 372 Hispanics (18-65 years) were randomly assigned to menus with no labels (NL) (n=127), rank-ordered calorie labels plus a statement on energy needs per meal (CL) (n=123), or rank-ordered exercise labels showing minutes of brisk walking necessary to burn the food calories (EL) (n=122). The menus had identical food choices. Participants were instructed to select foods from the assigned menu as if having lunch in a fast food restaurant. One-way analysis of variance found no difference in calories ordered (median (25th and 75th centiles)) by menu condition (NL: 785.0 (465.0, 1010.0) kcal; CL: 790.0 (510.0, 1020.0) kcal; EL: 752.5 (520.0, 1033.8) kcal; p=0.75). Calories from specific foods and macronutrient intake were not different by menu condition. Menu label use was 26.8% in the CL and 25.4% in the EL condition. Calories ordered were not different between those who used and those who did not use the labels. Regression analysis showed that perception of being overweight (p=0.02), selecting foods based on health value (p<0.0001), and meeting exercise guidelines (p<0.0001) were associated with fewer calories ordered. Logistic regression showed that selecting foods based on health value (p=0.01) was associated with higher food label use. Menu labels did not affect food choices in Hispanic participants. Future studies should determine if nutrition, exercise, and weight perception counseling prior to menu labels intervention would result in better food choices. NCT02804503; post-results. Copyright © 2016 American Federation for Medical Research.

Improving the Management Style of School Principals: Results from a Randomized Trial

Science.gov (United States)

Lassibille, Gérard

2016-01-01

Using information from a randomized experiment carried out over the course of two school years in Madagascar, this paper evaluates the impact of specific actions designed to streamline and tighten the work processes of public primary school directors. The results show that interventions at the school level, reinforced by interventions at the…

Partially ordered models

NARCIS (Netherlands)

Fernandez, R.; Deveaux, V.

2010-01-01

We provide a formal definition and study the basic properties of partially ordered chains (POC). These systems were proposed to model textures in image processing and to represent independence relations between random variables in statistics (in the later case they are known as Bayesian networks).

Spatial serial order processing in schizophrenia.

Science.gov (United States)

Fraser, David; Park, Sohee; Clark, Gina; Yohanna, Daniel; Houk, James C

2004-10-01

The aim of this study was to examine serial order processing deficits in 21 schizophrenia patients and 16 age- and education-matched healthy controls. In a spatial serial order working memory task, one to four spatial targets were presented in a randomized sequence. Subjects were required to remember the locations and the order in which the targets were presented. Patients showed a marked deficit in ability to remember the sequences compared with controls. Increasing the number of targets within a sequence resulted in poorer memory performance for both control and schizophrenia subjects, but the effect was much more pronounced in the patients. Targets presented at the end of a long sequence were more vulnerable to memory error in schizophrenia patients. Performance deficits were not attributable to motor errors, but to errors in target choice. The results support the idea that the memory errors seen in schizophrenia patients may be due to saturating the working memory network at relatively low levels of memory load.

Ordered Consumer Search

OpenAIRE

Armstrong, Mark

2016-01-01

The paper discusses situations in which consumers search through their options in a deliberate order, in contrast to more familiar models with random search. Topics include: network effects (consumers may be better off following the same search order as other consumers); the use of price and non-price advertising to direct search; the impact of consumers starting a new search with their previous supplier; the incentive sellers have to merge or co-locate with other sellers; and the incentive a...

On stochastic differential equations with random delay

International Nuclear Information System (INIS)

Krapivsky, P L; Luck, J M; Mallick, K

2011-01-01

We consider stochastic dynamical systems defined by differential equations with a uniform random time delay. The latter equations are shown to be equivalent to deterministic higher-order differential equations: for an nth-order equation with random delay, the corresponding deterministic equation has order n + 1. We analyze various examples of dynamical systems of this kind, and find a number of unusual behaviors. For instance, for the harmonic oscillator with random delay, the energy grows as exp((3/2) t 2/3 ) in reduced units. We then investigate the effect of introducing a discrete time step ε. At variance with the continuous situation, the discrete random recursion relations thus obtained have intrinsic fluctuations. The crossover between the fluctuating discrete problem and the deterministic continuous one as ε goes to zero is studied in detail on the example of a first-order linear differential equation

Analytic results for asymmetric random walk with exponential transition probabilities

International Nuclear Information System (INIS)

Gutkowicz-Krusin, D.; Procaccia, I.; Ross, J.

1978-01-01

We present here exact analytic results for a random walk on a one-dimensional lattice with asymmetric, exponentially distributed jump probabilities. We derive the generating functions of such a walk for a perfect lattice and for a lattice with absorbing boundaries. We obtain solutions for some interesting moment properties, such as mean first passage time, drift velocity, dispersion, and branching ratio for absorption. The symmetric exponential walk is solved as a special case. The scaling of the mean first passage time with the size of the system for the exponentially distributed walk is determined by the symmetry and is independent of the range

Sample size adjustments for varying cluster sizes in cluster randomized trials with binary outcomes analyzed with second-order PQL mixed logistic regression.

Science.gov (United States)

Candel, Math J J M; Van Breukelen, Gerard J P

2010-06-30

Adjustments of sample size formulas are given for varying cluster sizes in cluster randomized trials with a binary outcome when testing the treatment effect with mixed effects logistic regression using second-order penalized quasi-likelihood estimation (PQL). Starting from first-order marginal quasi-likelihood (MQL) estimation of the treatment effect, the asymptotic relative efficiency of unequal versus equal cluster sizes is derived. A Monte Carlo simulation study shows this asymptotic relative efficiency to be rather accurate for realistic sample sizes, when employing second-order PQL. An approximate, simpler formula is presented to estimate the efficiency loss due to varying cluster sizes when planning a trial. In many cases sampling 14 per cent more clusters is sufficient to repair the efficiency loss due to varying cluster sizes. Since current closed-form formulas for sample size calculation are based on first-order MQL, planning a trial also requires a conversion factor to obtain the variance of the second-order PQL estimator. In a second Monte Carlo study, this conversion factor turned out to be 1.25 at most. (c) 2010 John Wiley & Sons, Ltd.

Quantum random walks using quantum accelerator modes

International Nuclear Information System (INIS)

Ma, Z.-Y.; Burnett, K.; D'Arcy, M. B.; Gardiner, S. A.

2006-01-01

We discuss the use of high-order quantum accelerator modes to achieve an atom optical realization of a biased quantum random walk. We first discuss how one can create coexistent quantum accelerator modes, and hence how momentum transfer that depends on the atoms' internal state can be achieved. When combined with microwave driving of the transition between the states, a different type of atomic beam splitter results. This permits the realization of a biased quantum random walk through quantum accelerator modes

Order parameter fluctuations at a critical point - an exact result about percolation -

International Nuclear Information System (INIS)

Botet, Robert

2011-01-01

The order parameter of the system in the critical state, is expected to undergo large non-Gaussian fluctuations. However, almost nothing is known about the mathematical forms of the possible probability distributions of the order parameter. A remarkable exception is the site-percolation on the Bethe lattice, for which the complete order-parameter distribution has been recently derived at the critical point. Surprisingly, it appears to be the Kolmogorov-Smirnov distribution, well known in very different areas of mathematical statistics. In the present paper, we explain first how this special distribution could appear naturally in the context of the critical systems, under the assumption (still virtually unstudied) of the exponential distribution of the number of domains of a given size. In a second part, we present for the first time the complete derivation of the order-parameter distribution for the critical percolation model on the Bethe lattice, thus completing a recent publication announcing this result.

Emergent randomness in the Jaynes-Cummings model

International Nuclear Information System (INIS)

Garraway, B M; Stenholm, S

2008-01-01

We consider the well-known Jaynes-Cummings model and ask if it can display randomness. As a solvable Hamiltonian system, it does not display chaotic behaviour in the ordinary sense. Here, however, we look at the distribution of values taken up during the total time evolution. This evolution is determined by the eigenvalues distributed as the square roots of integers and leads to a seemingly erratic behaviour. That this may display a random Gaussian value distribution is suggested by an exactly provable result by Kac. In order to reach our conclusion we use the Kac model to develop tests for the emergence of a Gaussian. Even if the consequent double limits are difficult to evaluate numerically, we find definite indications that the Jaynes-Cummings case also produces a randomness in its value distributions. Numerical methods do not establish such a result beyond doubt, but our conclusions are definite enough to suggest strongly an unexpected randomness emerging in a dynamic time evolution

The Effects of the Bali Yoga Program for Breast Cancer Patients on Chemotherapy-Induced Nausea and Vomiting: Results of a Partially Randomized and Blinded Controlled Trial.

Science.gov (United States)

Anestin, Annélie S; Dupuis, Gilles; Lanctôt, Dominique; Bali, Madan

2017-10-01

Complementary and alternative medicine has been shown to be beneficial in reducing chemotherapy-induced nausea and vomiting. However, conclusive results are lacking in order to confirm its usefulness. The purpose of this study was to determine whether a standardized yoga intervention could reduce these adverse symptoms. This was a partially randomized and blinded controlled trial comparing a standardized yoga intervention with standard care. Eligible patients were adults diagnosed with stages I to III breast cancer receiving chemotherapy. Patients randomized to the experimental group participated in an 8-week yoga program. There was no significant difference between the experimental and control groups on chemotherapy-induced nausea and vomiting after 8 weeks. Results suggest the yoga program is not beneficial in managing these adverse symptoms. However, considering preliminary evidence suggesting yoga's beneficial impact in cancer symptom management, methodological limitations should be explored and additional studies should be conducted.

Educational needs of women in relation to postpartum religious orders

Directory of Open Access Journals (Sweden)

Marjan Beigi

2017-01-01

Full Text Available Introduction: Religious orders are one of the educational needs of the postpartum period. This study was conducted to determine the educational needs of postpartum religious orders.Materials and Methods: This cross-sectional study was conducted among 421 postpartum women and 15 specialists. Quota random sampling was conducted from January to March 2014 in Isfahan, Iran. Data analysis was performed using the Statistical Package for the Social Sciences software and statistical methods.Results: From the perspective of women and specialists, the results showed that the educational needs of women in postpartum religious orders is high.Conclusion: Considering the high educational need in the field of postpartum religious orders, it is necessary to integrate education in prenatal and postnatal health education programs.

Measurement model choice influenced randomized controlled trial results.

Science.gov (United States)

Gorter, Rosalie; Fox, Jean-Paul; Apeldoorn, Adri; Twisk, Jos

2016-11-01

In randomized controlled trials (RCTs), outcome variables are often patient-reported outcomes measured with questionnaires. Ideally, all available item information is used for score construction, which requires an item response theory (IRT) measurement model. However, in practice, the classical test theory measurement model (sum scores) is mostly used, and differences between response patterns leading to the same sum score are ignored. The enhanced differentiation between scores with IRT enables more precise estimation of individual trajectories over time and group effects. The objective of this study was to show the advantages of using IRT scores instead of sum scores when analyzing RCTs. Two studies are presented, a real-life RCT, and a simulation study. Both IRT and sum scores are used to measure the construct and are subsequently used as outcomes for effect calculation. The bias in RCT results is conditional on the measurement model that was used to construct the scores. A bias in estimated trend of around one standard deviation was found when sum scores were used, where IRT showed negligible bias. Accurate statistical inferences are made from an RCT study when using IRT to estimate construct measurements. The use of sum scores leads to incorrect RCT results. Copyright © 2016 Elsevier Inc. All rights reserved.

Ferrimagnetic Properties of Bond Dilution Mixed Blume-Capel Model with Random Single-Ion Anisotropy

International Nuclear Information System (INIS)

Liu Lei; Yan Shilei

2005-01-01

We study the ferrimagnetic properties of spin 1/2 and spin-1 systems by means of the effective field theory. The system is considered in the framework of bond dilution mixed Blume-Capel model (BCM) with random single-ion anisotropy. The investigation of phase diagrams and magnetization curves indicates the existence of induced magnetic ordering and single or multi-compensation points. Special emphasis is placed on the influence of bond dilution and random single-ion anisotropy on normal or induced magnetic ordering states and single or multi-compensation points. Normal magnetic ordering states take on new phase diagrams with increasing randomness (bond and anisotropy), while anisotropy induced magnetic ordering states are always occurrence no matter whether concentration of anisotropy is large or small. Existence and disappearance of compensation points rely strongly on bond dilution and random single-ion anisotropy. Some results have not been revealed in previous papers and predicted by Neel theory of ferrimagnetism.

Perturbation Solutions for Random Linear Structural Systems subject to Random Excitation using Stochastic Differential Equations

DEFF Research Database (Denmark)

Köyluoglu, H.U.; Nielsen, Søren R.K.; Cakmak, A.S.

1994-01-01

perturbation method using stochastic differential equations. The joint statistical moments entering the perturbation solution are determined by considering an augmented dynamic system with state variables made up of the displacement and velocity vector and their first and second derivatives with respect......The paper deals with the first and second order statistical moments of the response of linear systems with random parameters subject to random excitation modelled as white-noise multiplied by an envelope function with random parameters. The method of analysis is basically a second order...... to the random parameters of the problem. Equations for partial derivatives are obtained from the partial differentiation of the equations of motion. The zero time-lag joint statistical moment equations for the augmented state vector are derived from the Itô differential formula. General formulation is given...

Neutron scattering study of unstable magnetic long-range order in the random two-dimensional Ising antiferromagnets Rb/sub 2/Cosub(c)Mgsub(1-c)F/sub 4/

Energy Technology Data Exchange (ETDEWEB)

Ikeda, H; Suzuki, M [Ochanomizu Univ., Tokyo (Japan). Dept. of Physics; Hutchings, M T [UKAEA Atomic Energy Research Establishment, Harwell. Materials Physics Div.

1979-01-01

The spin correlation between two-dimensionally (2D) ordered antiferromagnetic layers in the random antiferromagnets Rb/sub 2/Cosub(c)Mgsub(1-c)F/sub 4/ depends strongly on the rate at which the sample is cooled through the Neel point Tsub(N) and decreases markedly with decreasing Co/sup 2 +/ ion concentration c. Preliminary data are presented which indicate that the order below sub(N) is metastable and relaxes to a fully correlated 3D ordered state on a finite, measurable, time-scale.

Self-correcting random number generator

Science.gov (United States)

Humble, Travis S.; Pooser, Raphael C.

2016-09-06

A system and method for generating random numbers. The system may include a random number generator (RNG), such as a quantum random number generator (QRNG) configured to self-correct or adapt in order to substantially achieve randomness from the output of the RNG. By adapting, the RNG may generate a random number that may be considered random regardless of whether the random number itself is tested as such. As an example, the RNG may include components to monitor one or more characteristics of the RNG during operation, and may use the monitored characteristics as a basis for adapting, or self-correcting, to provide a random number according to one or more performance criteria.

Randomized Oversampling for Generalized Multiscale Finite Element Methods

KAUST Repository

Calo, Victor M.

2016-03-23

In this paper, we develop efficient multiscale methods for flows in heterogeneous media. We use the generalized multiscale finite element (GMsFEM) framework. GMsFEM approximates the solution space locally using a few multiscale basis functions. This approximation selects an appropriate snapshot space and a local spectral decomposition, e.g., the use of oversampled regions, in order to achieve an efficient model reduction. However, the successful construction of snapshot spaces may be costly if too many local problems need to be solved in order to obtain these spaces. We use a moderate quantity of local solutions (or snapshot vectors) with random boundary conditions on oversampled regions with zero forcing to deliver an efficient methodology. Motivated by the randomized algorithm presented in [P. G. Martinsson, V. Rokhlin, and M. Tygert, A Randomized Algorithm for the approximation of Matrices, YALEU/DCS/TR-1361, Yale University, 2006], we consider a snapshot space which consists of harmonic extensions of random boundary conditions defined in a domain larger than the target region. Furthermore, we perform an eigenvalue decomposition in this small space. We study the application of randomized sampling for GMsFEM in conjunction with adaptivity, where local multiscale spaces are adaptively enriched. Convergence analysis is provided. We present representative numerical results to validate the method proposed.

Random ordinary differential equations and their numerical solution

CERN Document Server

Han, Xiaoying

2017-01-01

This book is intended to make recent results on the derivation of higher order numerical schemes for random ordinary differential equations (RODEs) available to a broader readership, and to familiarize readers with RODEs themselves as well as the closely associated theory of random dynamical systems. In addition, it demonstrates how RODEs are being used in the biological sciences, where non-Gaussian and bounded noise are often more realistic than the Gaussian white noise in stochastic differential equations (SODEs).   RODEs are used in many important applications and play a fundamental role in the theory of random dynamical systems.  They can be analyzed pathwise with deterministic calculus, but require further treatment beyond that of classical ODE theory due to the lack of smoothness in their time variable. Although classical numerical schemes for ODEs can be used pathwise for RODEs, they rarely attain their traditional order since the solutions of RODEs do not have sufficient smoothness to have Taylor ...

Random Mutagenesis of the Aspergillus oryzae Genome Results in Fungal Antibacterial Activity

OpenAIRE

Leonard, Cory A.; Brown, Stacy D.; Hayman, J. Russell

2013-01-01

Multidrug-resistant bacteria cause severe infections in hospitals and communities. Development of new drugs to combat resistant microorganisms is needed. Natural products of microbial origin are the source of most currently available antibiotics. We hypothesized that random mutagenesis of Aspergillus oryzae would result in secretion of antibacterial compounds. To address this hypothesis, we developed a screen to identify individual A. oryzae mutants that inhibit the growth of Methicillin-res...

Order acceptance in food processing systems with random raw material requirements

NARCIS (Netherlands)

Kilic, Onur A.; van Donk, Dirk Pieter; Wijngaard, Jacob; Tarim, S. Armagan

This study considers a food production system that processes a single perishable raw material into several products having stochastic demands. In order to process an order, the amount of raw material delivery from storage needs to meet the raw material requirement of the order. However, the amount

MiDAS ENCORE: Randomized Controlled Clinical Trial Report of 6-Month Results.

Science.gov (United States)

Staats, Peter S; Benyamin, Ramsin M

2016-02-01

Patients suffering from neurogenic claudication due to lumbar spinal stenosis (LSS) often experience moderate to severe pain and significant functional disability. Neurogenic claudication results from progressive degenerative changes in the spine, and most often affects the elderly. Both the MILD® procedure and epidural steroid injections (ESIs) offer interventional pain treatment options for LSS patients experiencing neurogenic claudication refractory to more conservative therapies. MILD provides an alternative to ESIs via minimally invasive lumbar decompression. Prospective, multi-center, randomized controlled clinical trial. Twenty-six US interventional pain management centers. To compare patient outcomes following treatment with either MILD (treatment group) or ESIs (active control group) in LSS patients with neurogenic claudication and verified ligamentum flavum hypertrophy. This prospective, multi-center, randomized controlled clinical trial includes 2 study arms with a 1-to-1 randomization ratio. A total of 302 patients were enrolled, with 149 randomized to MILD and 153 to the active control. Six-month follow-up has been completed and is presented in this report. In addition, one year follow-up will be conducted for patients in both study arms, and supplementary 2 year outcome data will be collected for patients in the MILD group only. Outcomes are assessed using the Oswestry Disability Index (ODI), numeric pain rating scale (NPRS) and Zurich Claudication Questionnaire (ZCQ). Primary efficacy is the proportion of ODI responders, tested for statistical superiority of the MILD group versus the active control group. ODI responders are defined as patients achieving the validated Minimal Important Change (MIC) of =10 point improvement in ODI from baseline to follow-up. Similarly, secondary efficacy includes proportion of NPRS and ZCQ responders using validated MIC thresholds. Primary safety is the incidence of device or procedure-related adverse events in each

Use of cinacalcet in nephrolithiasis associated with normocalcemic or hypercalcemic primary hyperparathyroidism: results of a prospective randomized pilot study

Directory of Open Access Journals (Sweden)

Simone Brardi

2015-03-01

Full Text Available Objectives: To evaluate, by means of a prospective randomized study, the efficacy of cinacalcet in the forms of nephrolithiasis associated with primary hyperparathyroidism in both the hypercalcemic and normocalcemic variant. Materials and Methods: Ten patients suffering from active nephrolithiasis associated with primary hyperparathyroidism (4 hypercalcemics and 6 normocalcemics, equally divided between males and females, were randomly but not blindly addressed to treatment with potassium citrate and allopurinol, or to the same therapeutic regimen in combination with cinacalcet. The dosage of cinacalcet was optimized for each patient in order to obtain a reduction of parathyroid hormone (PTH within normal limits while enabling the maintenance of adequate calcemic values. All study participants were given the same diet based on a reduction in sodium intake, oxalate-rich foods and animal protein with standardized intake of calcium and an increase in hydration. After a follow up period of 10 months , cinacalcet was associated to standard therapy and diet in patients who were not taken it, conversely cinacalcet was withdrawn in the remaining patients who remained on standard therapeutic regimen and diet. Follow up was continued for a second period of observation of the same duration of the first. Results: At the end of the period of treatment with cinacalcet, for both variants of hyperparathyroidism, a statistically significant reduction in the overall number and in the diameter of renal stones was found. Conclusions: This prospective randomized study shows the effectiveness of cinacalcet used in combination with a diet with normalized calcium intake, in reducing the number and size of urinary stones in hypercalemic and normocalcemic forms of primary hyperparathyroidism.

Exploring pseudo- and chaotic random Monte Carlo simulations

Science.gov (United States)

Blais, J. A. Rod; Zhang, Zhan

2011-07-01

Computer simulations are an increasingly important area of geoscience research and development. At the core of stochastic or Monte Carlo simulations are the random number sequences that are assumed to be distributed with specific characteristics. Computer-generated random numbers, uniformly distributed on (0, 1), can be very different depending on the selection of pseudo-random number (PRN) or chaotic random number (CRN) generators. In the evaluation of some definite integrals, the resulting error variances can even be of different orders of magnitude. Furthermore, practical techniques for variance reduction such as importance sampling and stratified sampling can be applied in most Monte Carlo simulations and significantly improve the results. A comparative analysis of these strategies has been carried out for computational applications in planar and spatial contexts. Based on these experiments, and on some practical examples of geodetic direct and inverse problems, conclusions and recommendations concerning their performance and general applicability are included.

Double scattering of light from Biophotonic Nanostructures with short-range order

Energy Technology Data Exchange (ETDEWEB)

Noh, Heeso; Liew, Seng Fatt; Saranathan, Vinodkumar; Prum, Richard O.; Mochrie, Simon G.J.; Dufresne, Eric R.; Cao, Hui (Yale)

2010-07-28

We investigate the physical mechanism for color production by isotropic nanostructures with short-range order in bird feather barbs. While the primary peak in optical scattering spectra results from constructive interference of singly-scattered light, many species exhibit secondary peaks with distinct characteristic. Our experimental and numerical studies show that these secondary peaks result from double scattering of light by the correlated structures. Without an analog in periodic or random structures, such a phenomenon is unique for short-range ordered structures, and has been widely used by nature for non-iridescent structural coloration.

Pseudo-random bit generator based on lag time series

Science.gov (United States)

García-Martínez, M.; Campos-Cantón, E.

2014-12-01

In this paper, we present a pseudo-random bit generator (PRBG) based on two lag time series of the logistic map using positive and negative values in the bifurcation parameter. In order to hidden the map used to build the pseudo-random series we have used a delay in the generation of time series. These new series when they are mapped xn against xn+1 present a cloud of points unrelated to the logistic map. Finally, the pseudo-random sequences have been tested with the suite of NIST giving satisfactory results for use in stream ciphers.

The Results of a Randomized Control Trial Evaluation of the SPARK Literacy Program

Science.gov (United States)

Jones, Curtis J.; Christian, Michael; Rice, Andrew

2016-01-01

The purpose of this report is to present the results of a two-year randomized control trial evaluation of the SPARK literacy program. SPARK is an early grade literacy program developed by Boys & Girls Clubs of Greater Milwaukee. In 2010, SPARK was awarded an Investing in Innovation (i3) Department of Education grant to further develop the…

On reflexivity of random walks in a random environment on a metric space

International Nuclear Information System (INIS)

Rozikov, U.A.

2002-11-01

In this paper, we consider random walks in random environments on a countable metric space when jumps of the walks of the fractions are finite. The transfer probabilities of the random walk from x is an element of G (where G is the considering metric space) are defined by vector p(x) is an element of R k , k>1, where {p(x), x is an element of G} is the set of independent and indentically distributed random vectors. For the random walk, a sufficient condition of nonreflexivity is obtained. Examples for metric spaces Z d free groups and free product of finite numbers cyclic groups of the second order and some other metric spaces are considered. (author)

Digital Fractional Order Controllers Realized by PIC Microprocessor: Experimental Results

OpenAIRE

Petras, I.; Grega, S.; Dorcak, L.

2003-01-01

This paper deals with the fractional-order controllers and their possible hardware realization based on PIC microprocessor and numerical algorithm coded in PIC Basic. The mathematical description of the digital fractional -order controllers and approximation in the discrete domain are presented. An example of realization of the particular case of digital fractional-order PID controller is shown and described.

Loss of long-range magnetic order in a nanoparticle assembly due to random anisotropy

International Nuclear Information System (INIS)

Binns, C; Howes, P B; Baker, S H; Marchetto, H; Potenza, A; Steadman, P; Dhesi, S S; Roy, M; Everard, M J; Rushforth, A

2008-01-01

We have used soft x-ray photoemission electron microscopy (XPEEM) combined with x-ray magnetic circular dichroism (XMCD) and DC SQUID (superconducting quantum interference device) magnetometry to probe the magnetic ground state in Fe thin films produced by depositing size-selected gas-phase Fe nanoparticles with a diameter of 1.7 nm (∼200 atoms) onto Si substrates. The depositions were carried out in ultrahigh vacuum conditions and thicknesses of the deposited film in the range 5-50 nm were studied. The magnetometry data are consistent with the film forming a correlated super-spin glass with a magnetic correlation length ∼5 nm. The XPEEM magnetic maps from the cluster-assembled films were compared to those for a conventional thin Fe film with a thickness of 20 nm produced by a molecular beam epitaxy (MBE) source. Whereas a normal magnetic domain structure is observed in the conventional MBE thin film, no domain structure could be observed in any of the nanoparticle films down to the resolution limit of the XMCD based XPEEM (100 nm) confirming the ground state indicated by the magnetometry measurements. This observation is consistent with the theoretical prediction that an arbitrarily weak random anisotropy field will destroy long-range magnetic order

Universal medium-range order of amorphous metal oxides.

Science.gov (United States)

Nishio, Kengo; Miyazaki, Takehide; Nakamura, Hisao

2013-10-11

We propose that the structure of amorphous metal oxides can be regarded as a dual-dense-random-packing structure, which is a superposition of the dense random packing of metal atoms and that of oxygen atoms. Our ab initio molecular dynamics simulations show that the medium-range order of amorphous HfO2, ZrO2, TiO2, In2O3, Ga2O3, Al2O3, and Cu2O is characterized by the pentagonal-bipyramid arrangement of metal atoms and that of oxygen atoms, and prove the validity of our dual-random-sphere-packing model. In other words, we find that the pentagonal medium-range order is universal independent of type of metal oxide.

Random packing of colloids and granular matter

NARCIS (Netherlands)

Wouterse, A.

2008-01-01

This thesis deals with the random packing of colloids and granular matter. A random packing is a stable disordered collection of touching particles, without long-range positional and orientational order. Experimental random packings of particles with the same shape but made of different materials

One-year results of a prospective randomized, evaluator-blinded, multicenter study comparing TVT and TVT Secur.

OpenAIRE

Andrada Hamer, Maria; Larsson, Per-Göran; Teleman, Pia; Bergqvist, Christina Eten; Persson, Jan

2012-01-01

INTRODUCTION AND HYPOTHESIS: The aim of this prospective randomized multicenter study was to compare retropubic tension-free vaginal tape (TVT) with TVT Secur in terms of efficacy and safety. METHODS: We set out to enrol 280 stress urinary incontinent (SUI) women with a half-time interim analysis of short-term cure and adverse events. The short-term results have previously been published. Of the133 randomized women, 125 underwent surgery, and 121 (TVT n = 61, TVT Secur n = 60)...

Simulation of Higher-Order Electrical Circuits with Stochastic Parameters via SDEs

Directory of Open Access Journals (Sweden)

BRANCIK, L.

2013-02-01

Full Text Available The paper deals with a technique for the simulation of higher-order electrical circuits with parameters varying randomly. The principle consists in the utilization of the theory of stochastic differential equations (SDE, namely the vector form of the ordinary SDEs. Random changes of both excitation voltage and some parameters of passive circuit elements are considered, and circuit responses are analyzed. The voltage and/or current responses are computed and represented in the form of the sample means accompanied by their confidence intervals to provide reliable estimates. The method is applied to analyze responses of the circuit models of optional orders, specially those consisting of a cascade connection of the RLGC networks. To develop the model equations the state-variable method is used, afterwards a corresponding vector SDE is formulated and a stochastic Euler numerical method applied. To verify the results the deterministic responses are also computed by the help of the PSpice simulator or the numerical inverse Laplace transforms (NILT procedure in MATLAB, while removing random terms from the circuit model.

Convergence to equilibrium under a random Hamiltonian

Science.gov (United States)

Brandão, Fernando G. S. L.; Ćwikliński, Piotr; Horodecki, Michał; Horodecki, Paweł; Korbicz, Jarosław K.; Mozrzymas, Marek

2012-09-01

We analyze equilibration times of subsystems of a larger system under a random total Hamiltonian, in which the basis of the Hamiltonian is drawn from the Haar measure. We obtain that the time of equilibration is of the order of the inverse of the arithmetic average of the Bohr frequencies. To compute the average over a random basis, we compute the inverse of a matrix of overlaps of operators which permute four systems. We first obtain results on such a matrix for a representation of an arbitrary finite group and then apply it to the particular representation of the permutation group under consideration.

Infinitely robust order and local order-parameter tulips in Apollonian networks with quenched disorder

Science.gov (United States)

Kaplan, C. Nadir; Hinczewski, Michael; Berker, A. Nihat

2009-06-01

For a variety of quenched random spin systems on an Apollonian network, including ferromagnetic and antiferromagnetic bond percolation and the Ising spin glass, we find the persistence of ordered phases up to infinite temperature over the entire range of disorder. We develop a renormalization-group technique that yields highly detailed information, including the exact distributions of local magnetizations and local spin-glass order parameters, which turn out to exhibit, as function of temperature, complex and distinctive tulip patterns.

The (mis)reporting of statistical results in psychology journals

OpenAIRE

Bakker, Marjan; Wicherts, Jelte M.

2011-01-01

In order to study the prevalence, nature (direction), and causes of reporting errors in psychology, we checked the consistency of reported test statistics, degrees of freedom, and p values in a random sample of high- and low-impact psychology journals. In a second study, we established the generality of reporting errors in a random sample of recent psychological articles. Our results, on the basis of 281 articles, indicate that around 18% of statistical results in the psychological literature...

Theory of Random Anisotropic Magnetic Alloys

DEFF Research Database (Denmark)

Lindgård, Per-Anker

1976-01-01

A mean-field-crystal-field theory is developed for random, multicomponent, anisotropic magnetic alloys. It is specially applicable to rare-earth alloys. A discussion is given of multicritical points and phase transitions between various states characterized by order parameters with different...... spatial directions or different ordering wave vectors. Theoretical predictions based on known parameters for the phase diagrams and magnetic moments for the binary rare-earth alloys of Tb, Dy, Ho, and Er, Tb-Tm, Nd-Pr, and pure double-hcp Nd agree qualitatively with the experimental observations...... fluctuation corrections in the mean-field results is also discussed....

[Intel random number generator-based true random number generator].

Science.gov (United States)

Huang, Feng; Shen, Hong

2004-09-01

To establish a true random number generator on the basis of certain Intel chips. The random numbers were acquired by programming using Microsoft Visual C++ 6.0 via register reading from the random number generator (RNG) unit of an Intel 815 chipset-based computer with Intel Security Driver (ISD). We tested the generator with 500 random numbers in NIST FIPS 140-1 and X(2) R-Squared test, and the result showed that the random number it generated satisfied the demand of independence and uniform distribution. We also compared the random numbers generated by Intel RNG-based true random number generator and those from the random number table statistically, by using the same amount of 7500 random numbers in the same value domain, which showed that the SD, SE and CV of Intel RNG-based random number generator were less than those of the random number table. The result of u test of two CVs revealed no significant difference between the two methods. Intel RNG-based random number generator can produce high-quality random numbers with good independence and uniform distribution, and solves some problems with random number table in acquisition of the random numbers.

On grey levels in random CAPTCHA generation

Science.gov (United States)

Newton, Fraser; Kouritzin, Michael A.

2011-06-01

A CAPTCHA is an automatically generated test designed to distinguish between humans and computer programs; specifically, they are designed to be easy for humans but difficult for computer programs to pass in order to prevent the abuse of resources by automated bots. They are commonly seen guarding webmail registration forms, online auction sites, and preventing brute force attacks on passwords. In the following, we address the question: How does adding a grey level to random CAPTCHA generation affect the utility of the CAPTCHA? We treat the problem of generating the random CAPTCHA as one of random field simulation: An initial state of background noise is evolved over time using Gibbs sampling and an efficient algorithm for generating correlated random variables. This approach has already been found to yield highly-readable yet difficult-to-crack CAPTCHAs. We detail how the requisite parameters for introducing grey levels are estimated and how we generate the random CAPTCHA. The resulting CAPTCHA will be evaluated in terms of human readability as well as its resistance to automated attacks in the forms of character segmentation and optical character recognition.

Experiments in order to reproduce cold fusion results

International Nuclear Information System (INIS)

Bimbot, R.; Blain, G.; Boureau, G.; Cieur, M.

1989-01-01

Three experiments have been performed in order to try and reproduce the cold fusion experiments reported by FLEISCHMANN and PONS (D 2 O electrolysis) and by the Frascati Group (D 2 absorption in Ti at liquid nitrogen temperature). In the two electrolysis experiments, a Pd cathode was used together with a Pt anode and a Pd (D 2 ) reference electrode, in acid and basic media. The electrolysis cell was surrounded by four neutron counters filled with an organic scintillator (NE213). The electronics made it possible to discriminate neutrons from gamma rays. The global efficiency for neutron detection was 20%, and the detection threshold was equal to 1 neutron/s/4π. A germanium detector (efficiency 70%) and a NaI crystal were used to record gamma ray spectra. In one of the experiments, tritium was measured in the solution before and after electrolysis. None of the two experiments showed neutron, gamma, or tritium production above background. In the third experiment, deuterium was absorbed in titanium by cooling at liquid nitrogen temperature, and desorbed by warming up at room temperature; both neutron and gamma emissions were recorded during these operations. The results of this experiment were also negative [fr

Random Walks on Homeo( S 1)

Science.gov (United States)

Malicet, Dominique

2017-12-01

In this paper, we study random walks {g_n=f_{n-1}\\ldots f_0} on the group Homeo ( S 1) of the homeomorphisms of the circle, where the homeomorphisms f k are chosen randomly, independently, with respect to a same probability measure {ν}. We prove that under the only condition that there is no probability measure invariant by {ν}-almost every homeomorphism, the random walk almost surely contracts small intervals. It generalizes what has been known on this subject until now, since various conditions on {ν} were imposed in order to get the phenomenon of contractions. Moreover, we obtain the surprising fact that the rate of contraction is exponential, even in the lack of assumptions of smoothness on the f k 's. We deduce various dynamical consequences on the random walk ( g n ): finiteness of ergodic stationary measures, distribution of the trajectories, asymptotic law of the evaluations, etc. The proof of the main result is based on a modification of the Ávila-Viana's invariance principle, working for continuous cocycles on a space fibred in circles.

Random sets and random fuzzy sets as ill-perceived random variables an introduction for Ph.D. students and practitioners

CERN Document Server

Couso, Inés; Sánchez, Luciano

2014-01-01

This short book provides a unified view of the history and theory of random sets and fuzzy random variables, with special emphasis on its use for representing higher-order non-statistical uncertainty about statistical experiments. The authors lay bare the existence of two streams of works using the same mathematical ground, but differing form their use of sets, according to whether they represent objects of interest naturally taking the form of sets, or imprecise knowledge about such objects. Random (fuzzy) sets can be used in many fields ranging from mathematical morphology, economics, artificial intelligence, information processing and statistics per se, especially in areas where the outcomes of random experiments cannot be observed with full precision. This book also emphasizes the link between random sets and fuzzy sets with some techniques related to the theory of imprecise probabilities. This small book is intended for graduate and doctoral students in mathematics or engineering, but also provides an i...

The treatment of disc herniation-induced sciatica with infliximab - Results of a randomized, controlled, 3-month follow-up study

NARCIS (Netherlands)

Korhonen, T; Karppinen, J; Paimela, L; Malmivaara, A; Lindgren, KA; Jarvinen, S; Niinimaki, J; Veeger, N; Seitsalo, S; Hurri, H

2005-01-01

Study Design. A randomized controlled trial. Objectives. To evaluate the efficacy of infliximab, a monoclonal antibody against tumor necrosis factor (TNF)-alpha in a randomized controlled setting. Summary of Background Data. Recently, we obtained encouraging results in an open-label study of

Stress concentrations in an impregnated fibre bundle with random fibre packing

OpenAIRE

Swolfs, Y.; Gorbatikh, L.; Romanov, V.; Orlova, S.; Lomov, S. V.; Verpoest, I.

2013-01-01

The stress redistribution after a single fibre break is a fundamental issue in longitudinal strength models for unidirectional composites. Current models assume hexagonal or square fibre packings. In the present work, random fibre packings were modelled using 3D finite element analysis and compared to ordered fibre packings. Significant differences in the stress redistribution are found. Compared to square and hexagonal packings, random fibre packings result in smaller stress concentration fa...

Quasi-human seniority-order algorithm for unequal circles packing

International Nuclear Information System (INIS)

Zhu, Dingju

2016-01-01

In the existing methods for solving unequal circles packing problems, the initial configuration is given arbitrarily or randomly, but the impact of different initial configurations for existing packing algorithm to the speed of existing packing algorithm solving unequal circles packing problems is very large. The quasi-human seniority-order algorithm proposed in this paper can generate a better initial configuration for existing packing algorithm to accelerate the speed of existing packing algorithm solving unequal circles packing problems. In experiments, the quasi-human seniority-order algorithm is applied to generate better initial configurations for quasi-physical elasticity methods to solve the unequal circles packing problems, and the experimental results show that the proposed quasi-human seniority-order algorithm can greatly improve the speed of solving the problem.

Correlation order, merging and diversification

NARCIS (Netherlands)

Dhaene, J.; Denuit, M.; Vanduffel, S.

2009-01-01

We investigate the influence of the dependence between random losses on the shortfall and on the diversification benefit that arises from merging these losses. We prove that increasing the dependence between losses, expressed in terms of correlation order, has an increasing effect on the shortfall,

Decisions with Uncertain Consequences-A Total Ordering on Loss-Distributions.

Science.gov (United States)

Rass, Stefan; König, Sandra; Schauer, Stefan

2016-01-01

Decisions are often based on imprecise, uncertain or vague information. Likewise, the consequences of an action are often equally unpredictable, thus putting the decision maker into a twofold jeopardy. Assuming that the effects of an action can be modeled by a random variable, then the decision problem boils down to comparing different effects (random variables) by comparing their distribution functions. Although the full space of probability distributions cannot be ordered, a properly restricted subset of distributions can be totally ordered in a practically meaningful way. We call these loss-distributions, since they provide a substitute for the concept of loss-functions in decision theory. This article introduces the theory behind the necessary restrictions and the hereby constructible total ordering on random loss variables, which enables decisions under uncertainty of consequences. Using data obtained from simulations, we demonstrate the practical applicability of our approach.

Randomized random walk on a random walk

International Nuclear Information System (INIS)

Lee, P.A.

1983-06-01

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)

N-state random switching based on quantum tunnelling

Science.gov (United States)

Bernardo Gavito, Ramón; Jiménez Urbanos, Fernando; Roberts, Jonathan; Sexton, James; Astbury, Benjamin; Shokeir, Hamzah; McGrath, Thomas; Noori, Yasir J.; Woodhead, Christopher S.; Missous, Mohamed; Roedig, Utz; Young, Robert J.

2017-08-01

In this work, we show how the hysteretic behaviour of resonant tunnelling diodes (RTDs) can be exploited for new functionalities. In particular, the RTDs exhibit a stochastic 2-state switching mechanism that could be useful for random number generation and cryptographic applications. This behaviour can be scaled to N-bit switching, by connecting various RTDs in series. The InGaAs/AlAs RTDs used in our experiments display very sharp negative differential resistance (NDR) peaks at room temperature which show hysteresis cycles that, rather than having a fixed switching threshold, show a probability distribution about a central value. We propose to use this intrinsic uncertainty emerging from the quantum nature of the RTDs as a source of randomness. We show that a combination of two RTDs in series results in devices with three-state outputs and discuss the possibility of scaling to N-state devices by subsequent series connections of RTDs, which we demonstrate for the up to the 4-state case. In this work, we suggest using that the intrinsic uncertainty in the conduction paths of resonant tunnelling diodes can behave as a source of randomness that can be integrated into current electronics to produce on-chip true random number generators. The N-shaped I-V characteristic of RTDs results in a two-level random voltage output when driven with current pulse trains. Electrical characterisation and randomness testing of the devices was conducted in order to determine the validity of the true randomness assumption. Based on the results obtained for the single RTD case, we suggest the possibility of using multi-well devices to generate N-state random switching devices for their use in random number generation or multi-valued logic devices.

An unbiased estimator of the variance of simple random sampling using mixed random-systematic sampling

OpenAIRE

Padilla, Alberto

2009-01-01

Systematic sampling is a commonly used technique due to its simplicity and ease of implementation. The drawback of this simplicity is that it is not possible to estimate the design variance without bias. There are several ways to circumvent this problem. One method is to suppose that the variable of interest has a random order in the population, so the sample variance of simple random sampling without replacement is used. By means of a mixed random - systematic sample, an unbiased estimator o...

Novel asymptotic results on the high-order statistics of the channel capacity over generalized fading channels

KAUST Repository

Yilmaz, Ferkan

2012-06-01

The exact analysis of the higher-order statistics of the channel capacity (i.e., higher-order ergodic capacity) often leads to complicated expressions involving advanced special functions. In this paper, we provide a generic framework for the computation of the higher-order statistics of the channel capacity over generalized fading channels. As such, this novel framework for the higher-order statistics results in simple, closed-form expressions which are shown to be asymptotically tight bounds in the high signal-to-noise ratio (SNR) regime of a variety of fading environment. In addition, it reveals the existence of differences (i.e., constant capacity gaps in log-domain) among different fading environments. By asymptotically tight bound we mean that the high SNR limit of the difference between the actual higher-order statistics of the channel capacity and its asymptotic bound (i.e., lower bound) tends to zero. The mathematical formalism is illustrated with some selected numerical examples that validate the correctness of our newly derived results. © 2012 IEEE.

A Monotonicity Result for the Range of a Perturbed Random Walk

OpenAIRE

Chen, Lung-Chi; Sun, Rongfeng

2012-01-01

We consider a discrete time simple symmetric random walk on Z^d, d>=1, where the path of the walk is perturbed by inserting deterministic jumps. We show that for any time n and any deterministic jumps that we insert, the expected number of sites visited by the perturbed random walk up to time n is always larger than or equal to that for the unperturbed walk. This intriguing problem arises from the study of a particle among a Poisson system of moving traps with sub-diffusive trap motion. In pa...

Random magnetism

International Nuclear Information System (INIS)

Tsallis, C.

1980-03-01

The 'ingredients' which control a phase transition in well defined system as well as in random ones (e.g. random magnetic systems) are listed and discussed within a somehow unifying perspective. Among these 'ingredients' we find the couplings and elements responsible for the cooperative phenomenon, the topological connectivity as well as possible topological incompatibilities, the influence of new degrees of freedom, the order parameter dimensionality, the ground state degeneracy and finally the 'quanticity' of the system. The general trends, though illustrated in magnetic systems, essentially hold for all phase transitions, and give a basis for connection of this area with Field theory, Theory of dynamical systems, etc. (Author) [pt

Random magnetism

International Nuclear Information System (INIS)

Tsallis, C.

1981-01-01

The 'ingredients' which control a phase transition in well defined systems as well as in random ones (e.q. random magnetic systems) are listed and discussed within a somehow unifying perspective. Among these 'ingredients' the couplings and elements responsible for the cooperative phenomenon, the topological connectivity as well as possible topological incompatibilities, the influence of new degrees of freedom, the order parameter dimensionality, the ground state degeneracy and finally the 'quanticity' of the system are found. The general trends, though illustrated in magnetic systems, essentially hold for all phase transitions, and give a basis for connection of this area with Field theory, Theory of dynamical systems, etc. (Author) [pt

Sampling large random knots in a confined space

International Nuclear Information System (INIS)

Arsuaga, J; Blackstone, T; Diao, Y; Hinson, K; Karadayi, E; Saito, M

2007-01-01

DNA knots formed under extreme conditions of condensation, as in bacteriophage P4, are difficult to analyze experimentally and theoretically. In this paper, we propose to use the uniform random polygon model as a supplementary method to the existing methods for generating random knots in confinement. The uniform random polygon model allows us to sample knots with large crossing numbers and also to generate large diagrammatically prime knot diagrams. We show numerically that uniform random polygons sample knots with large minimum crossing numbers and certain complicated knot invariants (as those observed experimentally). We do this in terms of the knot determinants or colorings. Our numerical results suggest that the average determinant of a uniform random polygon of n vertices grows faster than O(e n 2 )). We also investigate the complexity of prime knot diagrams. We show rigorously that the probability that a randomly selected 2D uniform random polygon of n vertices is almost diagrammatically prime goes to 1 as n goes to infinity. Furthermore, the average number of crossings in such a diagram is at the order of O(n 2 ). Therefore, the two-dimensional uniform random polygons offer an effective way in sampling large (prime) knots, which can be useful in various applications

Sampling large random knots in a confined space

Science.gov (United States)

Arsuaga, J.; Blackstone, T.; Diao, Y.; Hinson, K.; Karadayi, E.; Saito, M.

2007-09-01

DNA knots formed under extreme conditions of condensation, as in bacteriophage P4, are difficult to analyze experimentally and theoretically. In this paper, we propose to use the uniform random polygon model as a supplementary method to the existing methods for generating random knots in confinement. The uniform random polygon model allows us to sample knots with large crossing numbers and also to generate large diagrammatically prime knot diagrams. We show numerically that uniform random polygons sample knots with large minimum crossing numbers and certain complicated knot invariants (as those observed experimentally). We do this in terms of the knot determinants or colorings. Our numerical results suggest that the average determinant of a uniform random polygon of n vertices grows faster than O(e^{n^2}) . We also investigate the complexity of prime knot diagrams. We show rigorously that the probability that a randomly selected 2D uniform random polygon of n vertices is almost diagrammatically prime goes to 1 as n goes to infinity. Furthermore, the average number of crossings in such a diagram is at the order of O(n2). Therefore, the two-dimensional uniform random polygons offer an effective way in sampling large (prime) knots, which can be useful in various applications.

Sampling large random knots in a confined space

Energy Technology Data Exchange (ETDEWEB)

Arsuaga, J [Department of Mathematics, San Francisco State University, 1600 Holloway Ave, San Francisco, CA 94132 (United States); Blackstone, T [Department of Computer Science, San Francisco State University, 1600 Holloway Ave., San Francisco, CA 94132 (United States); Diao, Y [Department of Mathematics and Statistics, University of North Carolina at Charlotte, Charlotte, NC 28223 (United States); Hinson, K [Department of Mathematics and Statistics, University of North Carolina at Charlotte, Charlotte, NC 28223 (United States); Karadayi, E [Department of Mathematics, University of South Florida, 4202 E Fowler Avenue, Tampa, FL 33620 (United States); Saito, M [Department of Mathematics, University of South Florida, 4202 E Fowler Avenue, Tampa, FL 33620 (United States)

2007-09-28

DNA knots formed under extreme conditions of condensation, as in bacteriophage P4, are difficult to analyze experimentally and theoretically. In this paper, we propose to use the uniform random polygon model as a supplementary method to the existing methods for generating random knots in confinement. The uniform random polygon model allows us to sample knots with large crossing numbers and also to generate large diagrammatically prime knot diagrams. We show numerically that uniform random polygons sample knots with large minimum crossing numbers and certain complicated knot invariants (as those observed experimentally). We do this in terms of the knot determinants or colorings. Our numerical results suggest that the average determinant of a uniform random polygon of n vertices grows faster than O(e{sup n{sup 2}}). We also investigate the complexity of prime knot diagrams. We show rigorously that the probability that a randomly selected 2D uniform random polygon of n vertices is almost diagrammatically prime goes to 1 as n goes to infinity. Furthermore, the average number of crossings in such a diagram is at the order of O(n{sup 2}). Therefore, the two-dimensional uniform random polygons offer an effective way in sampling large (prime) knots, which can be useful in various applications.

Factors affecting medication-order processing time.

Science.gov (United States)

Beaman, M A; Kotzan, J A

1982-11-01

The factors affecting medication-order processing time at one hospital were studied. The order processing time was determined by directly observing the time to process randomly selected new drug orders on all three work shifts during two one-week periods. An order could list more than one drug for an individual patient. The observer recorded the nature, location, and cost of the drugs ordered, as well as the time to process the order. The time and type of interruptions also were noted. The time to process a drug order was classified as six dependent variables: (1) total time, (2) work time, (3) check time, (4) waiting time I--time from arrival on the dumbwaiter until work was initiated, (5) waiting time II--time between completion of the work and initiation of checking, and (6) waiting time III--time after the check was completed until the order left on the dumbwaiter. The significant predictors of each of the six dependent variables were determined using stepwise multiple regression. The total time to process a prescription order was 58.33 +/- 48.72 minutes; the urgency status of the order was the only significant determinant of total time. Urgency status also significantly predicted the three waiting-time variables. Interruptions and the number of drugs on the order were significant determinants of work time and check time. Each telephone interruption increased the work time by 1.72 minutes. While the results of this study cannot be generalized to other institutions, pharmacy managers can use the method of determining factors that affect medication-order processing time to identify problem areas in their institutions.

Mixed-order phase transition in a minimal, diffusion-based spin model.

Science.gov (United States)

Fronczak, Agata; Fronczak, Piotr

2016-07-01

In this paper we exactly solve, within the grand canonical ensemble, a minimal spin model with the hybrid phase transition. We call the model diffusion based because its Hamiltonian can be recovered from a simple dynamic procedure, which can be seen as an equilibrium statistical mechanics representation of a biased random walk. We outline the derivation of the phase diagram of the model, in which the triple point has the hallmarks of the hybrid transition: discontinuity in the average magnetization and algebraically diverging susceptibilities. At this point, two second-order transition curves meet in equilibrium with the first-order curve, resulting in a prototypical mixed-order behavior.

A weak zero-one law for sequences of random distance graphs

Energy Technology Data Exchange (ETDEWEB)

Zhukovskii, Maksim E [M. V. Lomonosov Moscow State University, Faculty of Mechanics and Mathematics, Moscow (Russian Federation)

2012-07-31

We study zero-one laws for properties of random distance graphs. Properties written in a first-order language are considered. For p(N) such that pN{sup {alpha}}{yields}{infinity} as N{yields}{infinity}, and (1-p)N{sup {alpha}} {yields} {infinity} as N {yields} {infinity} for any {alpha}>0, we succeed in refuting the law. In this connection, we consider a weak zero-one j-law. For this law, we obtain results for random distance graphs which are similar to the assertions concerning the classical zero-one law for random graphs. Bibliography: 18 titles.

Decisions with Uncertain Consequences-A Total Ordering on Loss-Distributions.

Directory of Open Access Journals (Sweden)

Stefan Rass

Full Text Available Decisions are often based on imprecise, uncertain or vague information. Likewise, the consequences of an action are often equally unpredictable, thus putting the decision maker into a twofold jeopardy. Assuming that the effects of an action can be modeled by a random variable, then the decision problem boils down to comparing different effects (random variables by comparing their distribution functions. Although the full space of probability distributions cannot be ordered, a properly restricted subset of distributions can be totally ordered in a practically meaningful way. We call these loss-distributions, since they provide a substitute for the concept of loss-functions in decision theory. This article introduces the theory behind the necessary restrictions and the hereby constructible total ordering on random loss variables, which enables decisions under uncertainty of consequences. Using data obtained from simulations, we demonstrate the practical applicability of our approach.

Cluster-randomized Studies in Educational Research: Principles and Methodological Aspects.

Science.gov (United States)

Dreyhaupt, Jens; Mayer, Benjamin; Keis, Oliver; Öchsner, Wolfgang; Muche, Rainer

2017-01-01

An increasing number of studies are being performed in educational research to evaluate new teaching methods and approaches. These studies could be performed more efficiently and deliver more convincing results if they more strictly applied and complied with recognized standards of scientific studies. Such an approach could substantially increase the quality in particular of prospective, two-arm (intervention) studies that aim to compare two different teaching methods. A key standard in such studies is randomization, which can minimize systematic bias in study findings; such bias may result if the two study arms are not structurally equivalent. If possible, educational research studies should also achieve this standard, although this is not yet generally the case. Some difficulties and concerns exist, particularly regarding organizational and methodological aspects. An important point to consider in educational research studies is that usually individuals cannot be randomized, because of the teaching situation, and instead whole groups have to be randomized (so-called "cluster randomization"). Compared with studies with individual randomization, studies with cluster randomization normally require (significantly) larger sample sizes and more complex methods for calculating sample size. Furthermore, cluster-randomized studies require more complex methods for statistical analysis. The consequence of the above is that a competent expert with respective special knowledge needs to be involved in all phases of cluster-randomized studies. Studies to evaluate new teaching methods need to make greater use of randomization in order to achieve scientifically convincing results. Therefore, in this article we describe the general principles of cluster randomization and how to implement these principles, and we also outline practical aspects of using cluster randomization in prospective, two-arm comparative educational research studies.

Random a-adic groups and random net fractals

Energy Technology Data Exchange (ETDEWEB)

Li Yin [Department of Mathematics, Nanjing University, Nanjing 210093 (China)], E-mail: Lyjerry7788@hotmail.com; Su Weiyi [Department of Mathematics, Nanjing University, Nanjing 210093 (China)], E-mail: suqiu@nju.edu.cn

2008-08-15

Based on random a-adic groups, this paper investigates the relationship between the existence conditions of a positive flow in a random network and the estimation of the Hausdorff dimension of a proper random net fractal. Subsequently we describe some particular random fractals for which our results can be applied. Finally the Mauldin and Williams theorem is shown to be very important example for a random Cantor set with application in physics as shown in E-infinity theory.

Ordering molecular genetic tests and reporting results: practices in laboratory and clinical settings.

Science.gov (United States)

Lubin, Ira M; Caggana, Michele; Constantin, Carolyn; Gross, Susan J; Lyon, Elaine; Pagon, Roberta A; Trotter, Tracy L; Wilson, Jean Amos; McGovern, Margaret M

2008-09-01

Previous studies have suggested that patient care may be compromised as a consequence of poor communication between clinicians and laboratory professionals in cases in which molecular genetic test results are reported. To understand better the contributing factors to such compromised care, we investigated both pre- and postanalytical processes using cystic fibrosis mutation analysis as our model. We found that although the majority of test requisition forms requested patient/family information that was necessary for the proper interpretation of test results, in many cases, these data were not provided by the individuals filling out the forms. We found instances in which result reports for simulated diagnostic testing described individuals as carriers where only a single mutation was found with no comment pertaining to a diagnosis of cystic fibrosis. Similarly, reports based on simulated scenarios for carrier testing were problematic when no mutations were identified, and the patient's race/ethnicity and family history were not discussed in reference to residual risk of disease. Remarkably, a pilot survey of obstetrician-gynecologists revealed that office staff, including secretaries, often helped order genetic tests and reported test results to patients, raising questions about what efforts are undertaken to ensure personnel competency. These findings are reviewed in light of what efforts should be taken to improve the quality of test-ordering and result-reporting practices.

78 FR 78694 - Orders: Supplemental Orders on Reporting by Regulated Entities of Stress Testing Results as of...

Science.gov (United States)

2013-12-27

... reporting under section 165(i)(2) of the Dodd-Frank Wall Street Reform and Consumer Protection Act (Dodd... testing. II. Orders For the convenience of the affected parties, the text of the Supplemental Orders... Reform and Consumer Protection Act (``Dodd-Frank Act'') requires certain financial companies with total...

How random is a random vector?

International Nuclear Information System (INIS)

Eliazar, Iddo

2015-01-01

Over 80 years ago Samuel Wilks proposed that the “generalized variance” of a random vector is the determinant of its covariance matrix. To date, the notion and use of the generalized variance is confined only to very specific niches in statistics. In this paper we establish that the “Wilks standard deviation” –the square root of the generalized variance–is indeed the standard deviation of a random vector. We further establish that the “uncorrelation index” –a derivative of the Wilks standard deviation–is a measure of the overall correlation between the components of a random vector. Both the Wilks standard deviation and the uncorrelation index are, respectively, special cases of two general notions that we introduce: “randomness measures” and “independence indices” of random vectors. In turn, these general notions give rise to “randomness diagrams”—tangible planar visualizations that answer the question: How random is a random vector? The notion of “independence indices” yields a novel measure of correlation for Lévy laws. In general, the concepts and results presented in this paper are applicable to any field of science and engineering with random-vectors empirical data.

How random is a random vector?

Science.gov (United States)

Eliazar, Iddo

2015-12-01

Over 80 years ago Samuel Wilks proposed that the "generalized variance" of a random vector is the determinant of its covariance matrix. To date, the notion and use of the generalized variance is confined only to very specific niches in statistics. In this paper we establish that the "Wilks standard deviation" -the square root of the generalized variance-is indeed the standard deviation of a random vector. We further establish that the "uncorrelation index" -a derivative of the Wilks standard deviation-is a measure of the overall correlation between the components of a random vector. Both the Wilks standard deviation and the uncorrelation index are, respectively, special cases of two general notions that we introduce: "randomness measures" and "independence indices" of random vectors. In turn, these general notions give rise to "randomness diagrams"-tangible planar visualizations that answer the question: How random is a random vector? The notion of "independence indices" yields a novel measure of correlation for Lévy laws. In general, the concepts and results presented in this paper are applicable to any field of science and engineering with random-vectors empirical data.

Improving predictions for collider observables by consistently combining fixed order calculations with resummed results in perturbation theory

International Nuclear Information System (INIS)

Schoenherr, Marek

2011-01-01

With the constantly increasing precision of experimental data acquired at the current collider experiments Tevatron and LHC the theoretical uncertainty on the prediction of multiparticle final states has to decrease accordingly in order to have meaningful tests of the underlying theories such as the Standard Model. A pure leading order calculation, defined in the perturbative expansion of said theory in the interaction constant, represents the classical limit to such a quantum field theory and was already found to be insufficient at past collider experiments, e.g. LEP or HERA. Such a leading order calculation can be systematically improved in various limits. If the typical scales of a process are large and the respective coupling constants are small, the inclusion of fixed-order higher-order corrections then yields quickly converging predictions with much reduced uncertainties. In certain regions of the phase space, still well within the perturbative regime of the underlying theory, a clear hierarchy of the inherent scales, however, leads to large logarithms occurring at every order in perturbation theory. In many cases these logarithms are universal and can be resummed to all orders leading to precise predictions in these limits. Multiparticle final states now exhibit both small and large scales, necessitating a description using both resummed and fixed-order results. This thesis presents the consistent combination of two such resummation schemes with fixed-order results. The main objective therefor is to identify and properly treat terms that are present in both formulations in a process and observable independent manner. In the first part the resummation scheme introduced by Yennie, Frautschi and Suura (YFS), resumming large logarithms associated with the emission of soft photons in massive QED, is combined with fixed-order next-to-leading matrix elements. The implementation of a universal algorithm is detailed and results are studied for various precision

Controllability Results For First Order Impulsive Stochastic Functional Differential Systems with State-Dependent Delay

Directory of Open Access Journals (Sweden)

C. Parthasarathy

2013-03-01

Full Text Available In this paper, we study the controllability results of first order impulsive stochastic differential and neutral differential systems with state-dependent delay by using semigroup theory. The controllability results are derived by the means of Leray-SchauderAlternative fixed point theorem. An example is provided to illustrate the theory.

Multidimensional coincidence point results for generalized $(\\psi ,\\theta ,\\varphi$-contraction on ordered metric spaces

Directory of Open Access Journals (Sweden)

Bhavana Deshpande

2017-11-01

Full Text Available The main objective of this research article is to establish some coincidence point theorem for $g$-non-decreasing mappings under generalized $(\\psi ,\\theta ,\\varphi $-contraction on a partially ordered metric space. Furthermore, we show how multidimensional results can be seen as a simple consequences of our unidimensional coincidence point theorem. Our results modify, improve, sharpen, enrich and generalize various known results.

All-order results for infrared and collinear singularities in massless gauge theories

CERN Document Server

Dixon, Lance J; Magnea, Lorenzo

2010-01-01

We review recent results concerning the all-order structure of infrared and collinear divergences in massless gauge theory amplitudes. While the exponentiation of these divergences for nonabelian gauge theories has been understood for a long time, in the past couple of years we have begun to unravel the all-order structure of the anomalous dimensions that build up the perturbative exponent. In the large-Nc limit, all infrared and collinear divergences are determined by just three functions; one of them, the cusp anomalous dimension, plays a key role also for non-planar contributions. Indeed, all infrared and collinear divergences of massless gauge theory amplitudes with any number of hard partons may be captured by a surprisingly simple expression constructed as a sum over color dipoles. Potential corrections to this expression, correlating four or more hard partons at three loops or beyond, are tightly constrained and are currently under study.

On the entropy of random surfaces with arbitrary genus

International Nuclear Information System (INIS)

Kostov, I.K.; Krzywicki, A.

1987-01-01

We calculate the susceptibility critical exponent γ for Polyakov random surfaces with arbitrary genus, using the Liouville theory to one-loop order. Some rigorous results obtained for special dimensionalities in a discrete version of the model are also noted. In all cases γ grows linearly with the genus of the surface. (orig.)

Cluster-randomized Studies in Educational Research: Principles and Methodological Aspects

Directory of Open Access Journals (Sweden)

Dreyhaupt, Jens

2017-05-01

Full Text Available An increasing number of studies are being performed in educational research to evaluate new teaching methods and approaches. These studies could be performed more efficiently and deliver more convincing results if they more strictly applied and complied with recognized standards of scientific studies. Such an approach could substantially increase the quality in particular of prospective, two-arm (intervention studies that aim to compare two different teaching methods. A key standard in such studies is randomization, which can minimize systematic bias in study findings; such bias may result if the two study arms are not structurally equivalent. If possible, educational research studies should also achieve this standard, although this is not yet generally the case. Some difficulties and concerns exist, particularly regarding organizational and methodological aspects. An important point to consider in educational research studies is that usually individuals cannot be randomized, because of the teaching situation, and instead whole groups have to be randomized (so-called “cluster randomization”. Compared with studies with individual randomization, studies with cluster randomization normally require (significantly larger sample sizes and more complex methods for calculating sample size. Furthermore, cluster-randomized studies require more complex methods for statistical analysis. The consequence of the above is that a competent expert with respective special knowledge needs to be involved in all phases of cluster-randomized studies.Studies to evaluate new teaching methods need to make greater use of randomization in order to achieve scientifically convincing results. Therefore, in this article we describe the general principles of cluster randomization and how to implement these principles, and we also outline practical aspects of using cluster randomization in prospective, two-arm comparative educational research studies.

Energy Contents of Frequently Ordered Restaurant Meals and Comparison with Human Energy Requirements and US Department of Agriculture Database Information: A Multisite Randomized Study

Science.gov (United States)

Urban, Lorien E.; Weber, Judith L.; Heyman, Melvin B.; Schichtl, Rachel L.; Verstraete, Sofia; Lowery, Nina S.; Das, Sai Krupa; Schleicher, Molly M.; Rogers, Gail; Economos, Christina; Masters, William A.; Roberts, Susan B.

2017-01-01

Background Excess energy intake from meals consumed away from home is implicated as a major contributor to obesity, and ~50% of US restaurants are individual or small-chain (non–chain) establishments that do not provide nutrition information. Objective To measure the energy content of frequently ordered meals in non–chain restaurants in three US locations, and compare with the energy content of meals from large-chain restaurants, energy requirements, and food database information. Design A multisite random-sampling protocol was used to measure the energy contents of the most frequently ordered meals from the most popular cuisines in non–chain restaurants, together with equivalent meals from large-chain restaurants. Setting Meals were obtained from restaurants in San Francisco, CA; Boston, MA; and Little Rock, AR, between 2011 and 2014. Main outcome measures Meal energy content determined by bomb calorimetry. Statistical analysis performed Regional and cuisine differences were assessed using a mixed model with restaurant nested within region×cuisine as the random factor. Paired t tests were used to evaluate differences between non–chain and chain meals, human energy requirements, and food database values. Results Meals from non–chain restaurants contained 1,205±465 kcal/meal, amounts that were not significantly different from equivalent meals from large-chain restaurants (+5.1%; P=0.41). There was a significant effect of cuisine on non–chain meal energy, and three of the four most popular cuisines (American, Italian, and Chinese) had the highest mean energy (1,495 kcal/meal). Ninety-two percent of meals exceeded typical energy requirements for a single eating occasion. Conclusions Non–chain restaurants lacking nutrition information serve amounts of energy that are typically far in excess of human energy requirements for single eating occasions, and are equivalent to amounts served by the large-chain restaurants that have previously been criticized

Competitive Employment for Youth with Autism Spectrum Disorders: Early Results from a Randomized Clinical Trial

Science.gov (United States)

Wehman, Paul H.; Schall, Carol M.; McDonough, Jennifer; Kregel, John; Brooke, Valerie; Molinelli, Alissa; Ham, Whitney; Graham, Carolyn W.; Riehle, J. Erin; Collins, Holly T.; Thiss, Weston

2014-01-01

For most youth with autism spectrum disorders (ASD), employment upon graduation from high school or college is elusive. Employment rates are reported in many studies to be very low despite many years of intensive special education services. This paper presented the preliminary results of a randomized clinical trial of Project SEARCH plus ASD…

Randomized controlled trial comparing TVT-O and TVT-S for the treatment of stress urinary incontinence: 2-year results.

Science.gov (United States)

Bianchi-Ferraro, Ana Maria H M; Jarmy-DiBella, Zsuzsanna I K; de Aquino Castro, Rodrigo; Bortolini, Maria Augusta T; Sartori, Marair G F; Girão, Manoel J B C

2014-10-01

The aim was to compare the efficacy and safety of single-incision sling TVT-Secur (TVT-S) and transobturator midurethral sling (TVT-O) for the treatment of stress urinary incontinence (SUI) over 2 years' follow-up. This is a randomized controlled trial in which women with SUI were randomly assigned to have either TVT-O (n = 56) or TVT-S (n = 66). Exclusion criteria included: voiding dysfunction, detrusor overactivity, and pelvic organ prolapse beyond the hymen. The primary outcomes were objective and subjective cure rates at a follow-up visit at 24 months, defined as a negative stress test and pad test as well as absence of self-reported SUI symptoms. Secondary endpoints included quality of life assessment using the King's Health Questionnaire (KHQ), and complication and reoperation rates. Analysis was performed using intention to treat, and statistical significance was fixed at 5% (p TVT-S and TVT-O groups were 77.3% and 83.6%, while subjective cure rates were 75.7% and 80.3% respectively, with no statistically significant differences between the techniques. There was a significant improvement in all KHQ domains in both groups (p TVT-O, while the long-term one was tape exposure observed in 5.3% of TVT-O and in 7.5% of TVT-S cases. The efficacy of the TVT-S was similar to that of the TVT-O after 2 years' assessment. This cohort will continue to be followed in order to maintain commitment to contributing data on long-term results.

Taxon ordering in phylogenetic trees by means of evolutionary algorithms

Directory of Open Access Journals (Sweden)

Cerutti Francesco

2011-07-01

Full Text Available Abstract Background In in a typical "left-to-right" phylogenetic tree, the vertical order of taxa is meaningless, as only the branch path between them reflects their degree of similarity. To make unresolved trees more informative, here we propose an innovative Evolutionary Algorithm (EA method to search the best graphical representation of unresolved trees, in order to give a biological meaning to the vertical order of taxa. Methods Starting from a West Nile virus phylogenetic tree, in a (1 + 1-EA we evolved it by randomly rotating the internal nodes and selecting the tree with better fitness every generation. The fitness is a sum of genetic distances between the considered taxon and the r (radius next taxa. After having set the radius to the best performance, we evolved the trees with (λ + μ-EAs to study the influence of population on the algorithm. Results The (1 + 1-EA consistently outperformed a random search, and better results were obtained setting the radius to 8. The (λ + μ-EAs performed as well as the (1 + 1, except the larger population (1000 + 1000. Conclusions The trees after the evolution showed an improvement both of the fitness (based on a genetic distance matrix, then close taxa are actually genetically close, and of the biological interpretation. Samples collected in the same state or year moved close each other, making the tree easier to interpret. Biological relationships between samples are also easier to observe.

E-learning in order to improve drug prescription for hospitalized older patients: a cluster-randomized controlled study.

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Franchi, Carlotta; Tettamanti, Mauro; Djade, Codjo Dgnefa; Pasina, Luca; Mannucci, Pier Mannuccio; Onder, Graziano; Gussoni, Gualberto; Manfellotto, Dario; Bonassi, Stefano; Salerno, Francesco; Nobili, Alessandro

2016-07-01

The aim of the study was to evaluate the effect of an e-learning educational program meant to foster the quality of drug prescription in hospitalized elderly patients. Twenty geriatric and internal medicine wards were randomized to intervention (e-learning educational program) or control (basic geriatric pharmacology notions). Logistic regression analysis was used in order to assess the effect of the intervention on the use of potentially inappropriate medication (PIM, primary outcome) at hospital discharge. Secondary outcomes were a reduced prevalence of at least one potential drug-drug interaction (DDI) and potentially severe DDI at discharge. Mortality rate and incidence of re-hospitalizations were other secondary outcomes assessed at the 12-month follow-up. A total of 697 patients (347 in the intervention and 350 in the control arms) were enrolled. No difference in the prevalence of PIM at discharge was found between arms (OR 1.29 95%CI 0.87-1.91). We also found no decrease in the prevalence of DDI (OR 0.67 95%CI 0.34-1.28) and potentially severe DDI (OR 0.86 95%CI 0.63-1.15) at discharge, nor in mortality rates and incidence of re-hospitalization at 12-month follow-up. This e-learning educational program had no clear effect on the quality of drug prescription and clinical outcomes in hospitalized elderly patients. Given the high prevalence of PIMs and potential DDIs recorded in the frame of this study, other approaches should be developed in order to improve the quality of drug prescription in this population. © 2016 The British Pharmacological Society.

On reporting results from randomized controlled trials with recurrent events

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Sobolev Boris G

2008-05-01

Full Text Available Abstract Background Evidence-based medicine has been advanced by the use of standards for reporting the design and methodology of randomized controlled trials (RCT. Indeed, without this information it is difficult to assess the quality of evidence from an RCT. Although a variety of statistical methods are available for the analysis of recurrent events, reporting the effect of an intervention on outcomes that recur is an area that remains poorly understood in clinical research. The purpose of this paper is to outline guidelines for reporting results from RCTs where the outcome of interest is a recurrent event. Methods We used a simulation study to relate an event process and results from analyses of the gamma-Poisson, independent-increment, conditional, and marginal Cox models. We reviewed the utility of regression models for the rate of a recurrent event by articulating the associated study questions, preenting the risk sets, and interpreting the regression coefficients. Results Based on a single data set produced by simulation, we reported and contrasted results from statistical methods for evaluating treatment effect from an RCT with a recurrent outcome. We showed that each model has different study questions, assumptions, risk sets, and rate ratio interpretation, and so inferences should consider the appropriateness of the model for the RCT. Conclusion Our guidelines for reporting results from an RCT involving a recurrent event suggest that the study question and the objectives of the trial, such as assessing comparable groups and estimating effect size, should determine the statistical methods. The guidelines should allow clinical researchers to report appropriate measures from an RCT for understanding the effect of intervention on the occurrence of a recurrent event.

The Ising model coupled to 2d orders

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Glaser, Lisa

2018-04-01

In this article we make first steps in coupling matter to causal set theory in the path integral. We explore the case of the Ising model coupled to the 2d discrete Einstein Hilbert action, restricted to the 2d orders. We probe the phase diagram in terms of the Wick rotation parameter β and the Ising coupling j and find that the matter and the causal sets together give rise to an interesting phase structure. The couplings give rise to five different phases. The causal sets take on random or crystalline characteristics as described in Surya (2012 Class. Quantum Grav. 29 132001) and the Ising model can be correlated or uncorrelated on the random orders and correlated, uncorrelated or anti-correlated on the crystalline orders. We find that at least one new phase transition arises, in which the Ising spins push the causal set into the crystalline phase.

2D vs. 3D imaging in laparoscopic surgery-results of a prospective randomized trial.

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Buia, Alexander; Stockhausen, Florian; Filmann, Natalie; Hanisch, Ernst

2017-12-01

3D imaging is an upcoming technology in laparoscopic surgery, and recent studies have shown that the modern 3D technique is superior in an experimental setting. However, the first randomized controlled clinical trial in this context dates back to 1998 and showed no significant difference between 2D and 3D visualization using the first 3D generation technique, which is now more than 15 years old. Positive results measured in an experimental setting considering 3D imaging on surgical performance led us to initiate a randomized controlled pragmatic clinical trial to validate our findings in daily clinical routine. Standard laparoscopic operations (cholecystectomy, appendectomy) were preoperatively randomized to a 2D or 3D imaging system. We used a surgical comfort scale (Likert scale) and the Raw NASA Workload TLX for the subjective assessment of 2D and 3D imaging; the duration of surgery was also measured. The results of 3D imaging were statistically significant better than 2D imaging concerning the parameters "own felt safety" and "task efficiency"; the difficulty level of the procedures in the 2D and 3D groups did not differ. Overall, the Raw NASA Workload TLX showed no significance between the groups. 3D imaging could be a possible advantage in laparoscopic surgery. The results of our clinical trial show increased personal felt safety and efficiency of the surgeon using a 3D imaging system. Overall of the procedures, the findings assessed using Likert scales in terms of own felt safety and task efficiency were statistically significant for 3D imaging. The individually perceived workload assessed with the Raw NASA TLX shows no difference. Although these findings are subjective impressions of the performing surgeons without a clear benefit for 3D technology in clinical outcome, we think that these results show the capability that 3D laparoscopy can have a positive impact while performing laparoscopic procedures.

Computer generation of random deviates

International Nuclear Information System (INIS)

Cormack, John

1991-01-01

The need for random deviates arises in many scientific applications. In medical physics, Monte Carlo simulations have been used in radiology, radiation therapy and nuclear medicine. Specific instances include the modelling of x-ray scattering processes and the addition of random noise to images or curves in order to assess the effects of various processing procedures. Reliable sources of random deviates with statistical properties indistinguishable from true random deviates are a fundamental necessity for such tasks. This paper provides a review of computer algorithms which can be used to generate uniform random deviates and other distributions of interest to medical physicists, along with a few caveats relating to various problems and pitfalls which can occur. Source code listings for the generators discussed (in FORTRAN, Turbo-PASCAL and Data General ASSEMBLER) are available on request from the authors. 27 refs., 3 tabs., 5 figs

Efficacy of an internet-based problem-solving training for teachers: results of a randomized controlled trial

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Ebert, D.D.; Lehr, D.; BoB, L.; Riper, H.; Cuijpers, P.; Andersson, G.; Thiart, H.; Heber, E.; Berking, M.

2014-01-01

Objective The primary purpose of this randomized controlled trial (RCT) was to evaluate the efficacy of internet-based problem-solving training (iPST) for employees in the educational sector (teachers) with depressive symptoms. The results of training were compared to those of a waitlist control

First-order phase transition in the quantum spin glass at T=0

Energy Technology Data Exchange (ETDEWEB)

Viana, J. Roberto; Nogueira, Yamilles; Sousa, J. Ricardo de

2003-05-26

The van Hemmen model with transverse and random longitudinal field is studied to analyze the tricritical behavior in the quantum Ising spin glass at T=0. The free energy and order parameter are calculated for two types of probability distributions: Gaussian and bimodal. We obtain the phase diagram in the {omega}-H plane, where {omega} and H are the transverse and random longitudinal fields, respectively. For the case of Gaussian distribution the phase transition is of second order, while the bimodal distribution we observe second-order transition for high-transverse field and first-order transition for small transverse field, with a tricritical point in the phase diagram.

First-order phase transition in the quantum spin glass at T=0

International Nuclear Information System (INIS)

Viana, J. Roberto; Nogueira, Yamilles; Sousa, J. Ricardo de

2003-01-01

The van Hemmen model with transverse and random longitudinal field is studied to analyze the tricritical behavior in the quantum Ising spin glass at T=0. The free energy and order parameter are calculated for two types of probability distributions: Gaussian and bimodal. We obtain the phase diagram in the Ω-H plane, where Ω and H are the transverse and random longitudinal fields, respectively. For the case of Gaussian distribution the phase transition is of second order, while the bimodal distribution we observe second-order transition for high-transverse field and first-order transition for small transverse field, with a tricritical point in the phase diagram

Sampling problems for randomly broken sticks

Energy Technology Data Exchange (ETDEWEB)

Huillet, Thierry [Laboratoire de Physique Theorique et Modelisation, CNRS-UMR 8089 et Universite de Cergy-Pontoise, 5 mail Gay-Lussac, 95031, Neuville sur Oise (France)

2003-04-11

Consider the random partitioning model of a population (represented by a stick of length 1) into n species (fragments) with identically distributed random weights (sizes). Upon ranking the fragments' weights according to ascending sizes, let S{sub m:n} be the size of the mth smallest fragment. Assume that some observer is sampling such populations as follows: drop at random k points (the sample size) onto this stick and record the corresponding numbers of visited fragments. We shall investigate the following sampling problems: (1) what is the sample size if the sampling is carried out until the first visit of the smallest fragment (size S{sub 1:n})? (2) For a given sample size, have all the fragments of the stick been visited at least once or not? This question is related to Feller's random coupon collector problem. (3) In what order are new fragments being discovered and what is the random number of samples separating the discovery of consecutive new fragments until exhaustion of the list? For this problem, the distribution of the size-biased permutation of the species' weights, as the sequence of their weights in their order of appearance is needed and studied.

Analyzes of students’ higher-order thinking skills of heat and temperature concept

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Slamet Budiarti, Indah; Suparmi, A.; Sarwanto; Harjana

2017-11-01

High order thinking skills refer to three highest domains of the revised Bloom Taxonomy. The aims of the research were to analyze the student’s higher-order thinking skills of heat and temperature concept. The samples were taken by purposive random sampling technique consisted of 85 high school students from 3 senior high schools in Jayapura city. The descriptive qualitative method was employed in this study. The data were collected by using tests and interviews regarding the subject matters of heat and temperature. Based on the results of data analysis, it was concluded that 68.24% of the students have a high order thinking skills in the analysis, 3.53% of the students have a high order thinking skills in evaluating, and 0% of the students have a high order thinking skills in creation.

Exact extreme-value statistics at mixed-order transitions.

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Bar, Amir; Majumdar, Satya N; Schehr, Grégory; Mukamel, David

2016-05-01

We study extreme-value statistics for spatially extended models exhibiting mixed-order phase transitions (MOT). These are phase transitions that exhibit features common to both first-order (discontinuity of the order parameter) and second-order (diverging correlation length) transitions. We consider here the truncated inverse distance squared Ising model, which is a prototypical model exhibiting MOT, and study analytically the extreme-value statistics of the domain lengths The lengths of the domains are identically distributed random variables except for the global constraint that their sum equals the total system size L. In addition, the number of such domains is also a fluctuating variable, and not fixed. In the paramagnetic phase, we show that the distribution of the largest domain length l_{max} converges, in the large L limit, to a Gumbel distribution. However, at the critical point (for a certain range of parameters) and in the ferromagnetic phase, we show that the fluctuations of l_{max} are governed by novel distributions, which we compute exactly. Our main analytical results are verified by numerical simulations.

Fuzzy stochastic generalized reliability studies on embankment systems based on first-order approximation theorem

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Wang Yajun

2008-12-01

Full Text Available In order to address the complex uncertainties caused by interfacing between the fuzziness and randomness of the safety problem for embankment engineering projects, and to evaluate the safety of embankment engineering projects more scientifically and reasonably, this study presents the fuzzy logic modeling of the stochastic finite element method (SFEM based on the harmonious finite element (HFE technique using a first-order approximation theorem. Fuzzy mathematical models of safety repertories were introduced into the SFEM to analyze the stability of embankments and foundations in order to describe the fuzzy failure procedure for the random safety performance function. The fuzzy models were developed with membership functions with half depressed gamma distribution, half depressed normal distribution, and half depressed echelon distribution. The fuzzy stochastic mathematical algorithm was used to comprehensively study the local failure mechanism of the main embankment section near Jingnan in the Yangtze River in terms of numerical analysis for the probability integration of reliability on the random field affected by three fuzzy factors. The result shows that the middle region of the embankment is the principal zone of concentrated failure due to local fractures. There is also some local shear failure on the embankment crust. This study provides a referential method for solving complex multi-uncertainty problems in engineering safety analysis.

Effects of mobility on ordering dynamics

International Nuclear Information System (INIS)

Baronchelli, Andrea; Pastor-Satorras, Romualdo

2009-01-01

Models of ordering dynamics allow us to understand natural systems in which an initially disordered population homogenizes some traits via local interactions. The simplest of these models, with wide applications ranging from evolutionary to social dynamics, are the Voter and Moran processes, usually defined in terms of static or randomly mixed individuals that interact with a neighbor to copy or modify a discrete trait. Here we study the effects of diffusion in Voter/Moran processes by proposing a generalization of ordering dynamics in a metapopulation framework, in which individuals are endowed with mobility and diffuse through a spatial structure represented as a graph of patches upon which interactions take place. We show that diffusion dramatically affects the time to reach the homogeneous state, independently of the underlying network's topology, while the final consensus emerges through different local/global mechanisms, depending on the mobility strength. Our results highlight the crucial role played by mobility in ordering processes and set up a general framework that allows its effect to be studied on a large class of models, with implications in the understanding of evolutionary and social phenomena. (letter)

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

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Wan Soo Rhee

1985-01-01

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.

Multi-Criteria Model for Determining Order Size

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Katarzyna Jakowska-Suwalska

2013-01-01

Full Text Available A multi-criteria model for determining the order size for materials used in production has been presented. It was assumed that the consumption rate of each material is a random variable with a known probability distribution. Using such a model, in which the purchase cost of materials ordered is limited, three criteria were considered: order size, probability of a lack of materials in the production process, and deviations in the order size from the consumption rate in past periods. Based on an example, it has been shown how to use the model to determine the order sizes for polyurethane adhesive and wood in a hard-coal mine. (original abstract

Super-resolving random-Gaussian apodized photon sieve.

Science.gov (United States)

Sabatyan, Arash; Roshaninejad, Parisa

2012-09-10

A novel apodized photon sieve is presented in which random dense Gaussian distribution is implemented to modulate the pinhole density in each zone. The random distribution in dense Gaussian distribution causes intrazone discontinuities. Also, the dense Gaussian distribution generates a substantial number of pinholes in order to form a large degree of overlap between the holes in a few innermost zones of the photon sieve; thereby, clear zones are formed. The role of the discontinuities on the focusing properties of the photon sieve is examined as well. Analysis shows that secondary maxima have evidently been suppressed, transmission has increased enormously, and the central maxima width is approximately unchanged in comparison to the dense Gaussian distribution. Theoretical results have been completely verified by experiment.

Pion radiation for high grade astrocytoma: results of a randomized study

International Nuclear Information System (INIS)

Pickles, Tom; Goodman, George B.; Rheaume, Dorianne E.; Duncan, Graeme G.; Fryer, Chris J.; Bhimji, Shamim; Ludgate, Charles; Syndikus, Isabel; Graham, Peter; Dimitrov, Mario; Bowen, Julie

1997-01-01

Purpose: This study attempted to compare within a randomized study the outcome of pion radiation therapy vs. conventional photon irradiation for the treatment of high-grade astrocytomas. Methods and Materials: Eighty-four patients were randomized to pion therapy (33-34.5 Gyπ), or conventional photon irradiation (60 Gy). Entry criteria included astrocytoma (modified Kernohan high Grade 3 or Grade 4), age 18-70, Karnofsky performance status (KPS) ≥50, ability to start irradiation within 30 days of surgery, unifocal tumor, and treatment volume < 850 cc. The high-dose volume in both arms was computed tomography enhancement plus a 2-cm margin. The study was designed with the power to detect a twofold difference between arms. Results: Eighty-one eligible patients were equally balanced for all known prognostic variables. Pion patients started radiation 7 days earlier on average than photon patients, but other treatment-related variables did not differ. There were no significant differences for either early or late radiation toxicity between treatment arms. Actuarial survival analysis shows no differences in terms of time to local recurrence or overall survival where median survival was 10 months in both arms (p = 0.22). The physician-assessed KPS and patient-assessed quality of life (QOL) measurements were generally maintained within 10 percentage points until shortly before tumor recurrence. There was no apparent difference in the serial KPS or QOL scores between treatment arms. Conclusion: In contrast to high linear energy transfer (LET) therapy for central nervous system tumors, such as neutron or neon therapy, the safety of pion therapy, which is of intermediate LET, has been reaffirmed. However, this study has demonstrated no therapeutic gain for pion therapy of glioblastoma

Modeling and optimizing of the random atomic spin gyroscope drift based on the atomic spin gyroscope

Energy Technology Data Exchange (ETDEWEB)

Quan, Wei; Lv, Lin, E-mail: lvlinlch1990@163.com; Liu, Baiqi [School of Instrument Science and Opto-Electronics Engineering, Beihang University, Beijing 100191 (China)

2014-11-15

In order to improve the atom spin gyroscope's operational accuracy and compensate the random error caused by the nonlinear and weak-stability characteristic of the random atomic spin gyroscope (ASG) drift, the hybrid random drift error model based on autoregressive (AR) and genetic programming (GP) + genetic algorithm (GA) technique is established. The time series of random ASG drift is taken as the study object. The time series of random ASG drift is acquired by analyzing and preprocessing the measured data of ASG. The linear section model is established based on AR technique. After that, the nonlinear section model is built based on GP technique and GA is used to optimize the coefficients of the mathematic expression acquired by GP in order to obtain a more accurate model. The simulation result indicates that this hybrid model can effectively reflect the characteristics of the ASG's random drift. The square error of the ASG's random drift is reduced by 92.40%. Comparing with the AR technique and the GP + GA technique, the random drift is reduced by 9.34% and 5.06%, respectively. The hybrid modeling method can effectively compensate the ASG's random drift and improve the stability of the system.

An adaptive random search for short term generation scheduling with network constraints.

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J A Marmolejo

Full Text Available This paper presents an adaptive random search approach to address a short term generation scheduling with network constraints, which determines the startup and shutdown schedules of thermal units over a given planning horizon. In this model, we consider the transmission network through capacity limits and line losses. The mathematical model is stated in the form of a Mixed Integer Non Linear Problem with binary variables. The proposed heuristic is a population-based method that generates a set of new potential solutions via a random search strategy. The random search is based on the Markov Chain Monte Carlo method. The main key of the proposed method is that the noise level of the random search is adaptively controlled in order to exploring and exploiting the entire search space. In order to improve the solutions, we consider coupling a local search into random search process. Several test systems are presented to evaluate the performance of the proposed heuristic. We use a commercial optimizer to compare the quality of the solutions provided by the proposed method. The solution of the proposed algorithm showed a significant reduction in computational effort with respect to the full-scale outer approximation commercial solver. Numerical results show the potential and robustness of our approach.

Diffusion of charged particles in strong large-scale random and regular magnetic fields

International Nuclear Information System (INIS)

Mel'nikov, Yu.P.

2000-01-01

The nonlinear collision integral for the Green's function averaged over a random magnetic field is transformed using an iteration procedure taking account of the strong random scattering of particles on the correlation length of the random magnetic field. Under this transformation the regular magnetic field is assumed to be uniform at distances of the order of the correlation length. The single-particle Green's functions of the scattered particles in the presence of a regular magnetic field are investigated. The transport coefficients are calculated taking account of the broadening of the cyclotron and Cherenkov resonances as a result of strong random scattering. The mean-free path lengths parallel and perpendicular to the regular magnetic field are found for a power-law spectrum of the random field. The analytical results obtained are compared with the experimental data on the transport ranges of solar and galactic cosmic rays in the interplanetary magnetic field. As a result, the conditions for the propagation of cosmic rays in the interplanetary space and a more accurate idea of the structure of the interplanetary magnetic field are determined

Search for a perfect generator of random numbers

International Nuclear Information System (INIS)

Musyck, E.

1977-01-01

Theoretical tests have been carried out by COVEYOU and MAC PHERSON to verify the applications of the LEHMER algorithm. In a similar way, a theoretical method is proposed to evaluate in a rigorous way the random character of numbers generated by a shift register. This theory introduces the concept of ''degree of randomness'' of the elements, taken in a definite order, of a shift register. It permits making the judicious choice of the elements of the shift register which will produce the bits of the random numbers. On the other hand, a calculation method is developed in order to verify the primitive character of any shift register of high complexity. A new test, called ''slice test'', of empirical and theoretical use is also described; it constitutes a significant contribution to the understanding of certain properties of pseudo-random sequences. As a practical example, a random number generator structure formed with 32 bits, built out of a shift register with 61 elements and 60 modulo-2 adder circuits was made. The author is convinced that this generator can be considered to be practically perfect for all empirical applications of random numbers, particularly for the solution of Monte-Carlo problems. (author)

Spiking and bursting patterns of fractional-order Izhikevich model

Science.gov (United States)

Teka, Wondimu W.; Upadhyay, Ranjit Kumar; Mondal, Argha

2018-03-01

Bursting and spiking oscillations play major roles in processing and transmitting information in the brain through cortical neurons that respond differently to the same signal. These oscillations display complex dynamics that might be produced by using neuronal models and varying many model parameters. Recent studies have shown that models with fractional order can produce several types of history-dependent neuronal activities without the adjustment of several parameters. We studied the fractional-order Izhikevich model and analyzed different kinds of oscillations that emerge from the fractional dynamics. The model produces a wide range of neuronal spike responses, including regular spiking, fast spiking, intrinsic bursting, mixed mode oscillations, regular bursting and chattering, by adjusting only the fractional order. Both the active and silent phase of the burst increase when the fractional-order model further deviates from the classical model. For smaller fractional order, the model produces memory dependent spiking activity after the pulse signal turned off. This special spiking activity and other properties of the fractional-order model are caused by the memory trace that emerges from the fractional-order dynamics and integrates all the past activities of the neuron. On the network level, the response of the neuronal network shifts from random to scale-free spiking. Our results suggest that the complex dynamics of spiking and bursting can be the result of the long-term dependence and interaction of intracellular and extracellular ionic currents.

Reconstructing random media

International Nuclear Information System (INIS)

Yeong, C.L.; Torquato, S.

1998-01-01

We formulate a procedure to reconstruct the structure of general random heterogeneous media from limited morphological information by extending the methodology of Rintoul and Torquato [J. Colloid Interface Sci. 186, 467 (1997)] developed for dispersions. The procedure has the advantages that it is simple to implement and generally applicable to multidimensional, multiphase, and anisotropic structures. Furthermore, an extremely useful feature is that it can incorporate any type and number of correlation functions in order to provide as much morphological information as is necessary for accurate reconstruction. We consider a variety of one- and two-dimensional reconstructions, including periodic and random arrays of rods, various distribution of disks, Debye random media, and a Fontainebleau sandstone sample. We also use our algorithm to construct heterogeneous media from specified hypothetical correlation functions, including an exponentially damped, oscillating function as well as physically unrealizable ones. copyright 1998 The American Physical Society

RANDNA: a random DNA sequence generator.

Science.gov (United States)

Piva, Francesco; Principato, Giovanni

2006-01-01

Monte Carlo simulations are useful to verify the significance of data. Genomic regularities, such as the nucleotide correlations or the not uniform distribution of the motifs throughout genomic or mature mRNA sequences, exist and their significance can be checked by means of the Monte Carlo test. The test needs good quality random sequences in order to work, moreover they should have the same nucleotide distribution as the sequences in which the regularities have been found. Random DNA sequences are also useful to estimate the background score of an alignment, that is a threshold below which the resulting score is merely due to chance. We have developed RANDNA, a free software which allows to produce random DNA or RNA sequences setting both their length and the percentage of nucleotide composition. Sequences having the same nucleotide distribution of exonic, intronic or intergenic sequences can be generated. Its graphic interface makes it possible to easily set the parameters that characterize the sequences being produced and saved in a text format file. The pseudo-random number generator function of Borland Delphi 6 is used, since it guarantees a good randomness, a long cycle length and a high speed. We have checked the quality of sequences generated by the software, by means of well-known tests, both by themselves and versus genuine random sequences. We show the good quality of the generated sequences. The software, complete with examples and documentation, is freely available to users from: http://www.introni.it/en/software.

Impact of an automated email notification system for results of tests pending at discharge: a cluster-randomized controlled trial.

Science.gov (United States)

Dalal, Anuj K; Roy, Christopher L; Poon, Eric G; Williams, Deborah H; Nolido, Nyryan; Yoon, Cathy; Budris, Jonas; Gandhi, Tejal; Bates, David W; Schnipper, Jeffrey L

2014-01-01

Physician awareness of the results of tests pending at discharge (TPADs) is poor. We developed an automated system that notifies responsible physicians of TPAD results via secure, network email. We sought to evaluate the impact of this system on self-reported awareness of TPAD results by responsible physicians, a necessary intermediary step to improve management of TPAD results. We conducted a cluster-randomized controlled trial at a major hospital affiliated with an integrated healthcare delivery network in Boston, Massachusetts. Adult patients with TPADs who were discharged from inpatient general medicine and cardiology services were assigned to the intervention or usual care arm if their inpatient attending physician and primary care physician (PCP) were both randomized to the same study arm. Patients of physicians randomized to discordant study arms were excluded. We surveyed these physicians 72 h after all TPAD results were finalized. The primary outcome was awareness of TPAD results by attending physicians. Secondary outcomes included awareness of TPAD results by PCPs, awareness of actionable TPAD results, and provider satisfaction. We analyzed data on 441 patients. We sent 441 surveys to attending physicians and 353 surveys to PCPs and received 275 and 152 responses from 83 different attending physicians and 112 different PCPs, respectively (attending physician survey response rate of 63%). Intervention attending physicians and PCPs were significantly more aware of TPAD results (76% vs 38%, adjusted/clustered OR 6.30 (95% CI 3.02 to 13.16), pemail notification represents a promising strategy for managing TPAD results, potentially mitigating an unresolved patient safety concern. ClinicalTrials.gov (NCT01153451).

Sensitivity analysis of ranked data: from order statistics to quantiles

NARCIS (Netherlands)

Heidergott, B.F.; Volk-Makarewicz, W.

2015-01-01

In this paper we provide the mathematical theory for sensitivity analysis of order statistics of continuous random variables, where the sensitivity is with respect to a distributional parameter. Sensitivity analysis of order statistics over a finite number of observations is discussed before

One step replica symmetry breaking and extreme order statistics of logarithmic REMs

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Xiangyu Cao, Yan V. Fyodorov, Pierre Le Doussal

2016-12-01

Full Text Available Building upon the one-step replica symmetry breaking formalism, duly understood and ramified, we show that the sequence of ordered extreme values of a general class of Euclidean-space logarithmically correlated random energy models (logREMs behave in the thermodynamic limit as a randomly shifted decorated exponential Poisson point process. The distribution of the random shift is determined solely by the large-distance ("infra-red", IR limit of the model, and is equal to the free energy distribution at the critical temperature up to a translation. the decoration process is determined solely by the small-distance ("ultraviolet", UV limit, in terms of the biased minimal process. Our approach provides connections of the replica framework to results in the probability literature and sheds further light on the freezing/duality conjecture which was the source of many previous results for log-REMs. In this way we derive the general and explicit formulae for the joint probability density of depths of the first and second minima (as well its higher-order generalizations in terms of model-specific contributions from UV as well as IR limits. In particular, we show that the second min statistics is largely independent of details of UV data, whose influence is seen only through the mean value of the gap. For a given log-correlated field this parameter can be evaluated numerically, and we provide several numerical tests of our theory using the circular model of $1/f$-noise.

A novel Random Walk algorithm with Compulsive Evolution for heat exchanger network synthesis

International Nuclear Information System (INIS)

Xiao, Yuan; Cui, Guomin

2017-01-01

Highlights: • A novel Random Walk Algorithm with Compulsive Evolution is proposed for HENS. • A simple and feasible evolution strategy is presented in RWCE algorithm. • The integer and continuous variables of HEN are optimized simultaneously in RWCE. • RWCE is demonstrated a relatively strong global search ability in HEN optimization. - Abstract: The heat exchanger network (HEN) synthesis can be characterized as highly combinatorial, nonlinear and nonconvex, contributing to unmanageable computational time and a challenge in identifying the global optimal network design. Stochastic methods are robust and show a powerful global optimizing ability. Based on the common characteristic of different stochastic methods, namely randomness, a novel Random Walk algorithm with Compulsive Evolution (RWCE) is proposed to achieve the best possible total annual cost of heat exchanger network with the relatively simple and feasible evolution strategy. A population of heat exchanger networks is first randomly initialized. Next, the heat load of heat exchanger for each individual is randomly expanded or contracted in order to optimize both the integer and continuous variables simultaneously and to obtain the lowest total annual cost. Besides, when individuals approach to local optima, there is a certain probability for them to compulsively accept the imperfect networks in order to keep the population diversity and ability of global optimization. The presented method is then applied to heat exchanger network synthesis cases from the literature to compare the best results published. RWCE consistently has a lower computed total annual cost compared to previously published results.

Multi-instantons and exact results II: specific cases, higher-order effects, and numerical calculations

International Nuclear Information System (INIS)

Zinn-Justin, Jean; Jentschura, Ulrich D.

2004-01-01

In this second part of the treatment of instantons in quantum mechanics, the focus is on specific calculations related to a number of quantum mechanical potentials with degenerate minima. We calculate the leading multi-instanton contributions to the partition function, using the formalism introduced in the first part of the treatise [Ann. Phys. (N. Y.) (previous issue) (2004)]. The following potentials are considered: (i) asymmetric potentials with degenerate minima, (ii) the periodic cosine potential, (iii) anharmonic oscillators with radial symmetry, and (iv) a specific potential which bears an analogy with the Fokker-Planck equation. The latter potential has the peculiar property that the perturbation series for the ground-state energy vanishes to all orders and is thus formally convergent (the ground-state energy, however, is non-zero and positive). For the potentials (ii), (iii), and (iv), we calculate the perturbative B-function as well as the instanton A-function to fourth order in g. We also consider the double-well potential in detail, and present some higher-order analytic as well as numerical calculations to verify explicitly the related conjectures up to the order of three instantons. Strategies analogous to those outlined here could result in new conjectures for problems where our present understanding is more limited

Order aggressiveness and order book dynamics

DEFF Research Database (Denmark)

Hall, Anthony D.; Hautsch, Nikolaus

2006-01-01

In this paper, we study the determinants of order aggressiveness and traders’ order submission strategy in an open limit order book market. Applying an order classification scheme, we model the most aggressive market orders, limit orders as well as cancellations on both sides of the market...... employing a six-dimensional autoregressive conditional intensity model. Using order book data from the Australian Stock Exchange, we find that market depth, the queued volume, the bid-ask spread, recent volatility, as well as recent changes in both the order flow and the price play an important role...... in explaining the determinants of order aggressiveness. Overall, our empirical results broadly confirm theoretical predictions on limit order book trading. However, we also find evidence for behavior that can be attributed to particular liquidity and volatility effects...

A Dietary Intervention in Urban African Americans: Results of the "Five Plus Nuts and Beans" Randomized Trial.

Science.gov (United States)

Miller, Edgar R; Cooper, Lisa A; Carson, Kathryn A; Wang, Nae-Yuh; Appel, Lawrence J; Gayles, Debra; Charleston, Jeanne; White, Karen; You, Na; Weng, Yingjie; Martin-Daniels, Michelle; Bates-Hopkins, Barbara; Robb, Inez; Franz, Whitney K; Brown, Emily L; Halbert, Jennifer P; Albert, Michael C; Dalcin, Arlene T; Yeh, Hsin-Chieh

2016-01-01

Unhealthy diets, often low in potassium, likely contribute to racial disparities in blood pressure. We tested the effectiveness of providing weekly dietary advice, assistance with selection of higher potassium grocery items, and a $30 per week food allowance on blood pressure and other outcomes in African American adults with hypertension. We conducted an 8-week RCT with two parallel arms between May 2012 and November 2013. We randomized 123 African Americans with controlled hypertension from an urban primary care clinic in Baltimore, Maryland, and implemented the trial in partnership with a community supermarket and the Baltimore City Health Department. Mean (SD) age was 58.6 (9.5) years; 71% were female; blood pressure was 131.3 (14.7)/77.2 (10.5) mmHg; BMI was 34.5 (8.2); and 28% had diabetes. Participants randomized to the active intervention group (Dietary Approaches to Stop Hypertension [DASH]-Plus) received coach-directed dietary advice and assistance with weekly online ordering and purchasing of high-potassium foods ($30/week) delivered by a community supermarket to a neighborhood library. Participants in the control group received a printed DASH diet brochure along with a debit account of equivalent value to that of the DASH-Plus group. The primary outcome was blood pressure change. Analyses were conducted in January to October 2014. Compared with the control group, the DASH-Plus group increased self-reported consumption of fruits and vegetables (mean=1.4, 95% CI=0.7, 2.1 servings/day); estimated intake of potassium (mean=0.4, 95% CI=0.1, 0.7 grams/day); and urine potassium excretion (mean=19%, 95% CI=1%, 38%). There was no significant effect on blood pressure. A program providing dietary advice, assistance with grocery ordering, and $30/week of high-potassium foods in African American patients with controlled hypertension in a community-based clinic did not reduce BP. However, the intervention increased consumption of fruits, vegetables, and urinary

Cost-effectiveness of family psychoeducation to prevent relapse in major depression: Results from a randomized controlled trial

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Shimodera Shinji

2012-05-01

Full Text Available Abstract Background Family psychoeducation is a relatively simple and straightforward intervention whose prophylactic effectiveness and cost-effectiveness is well-established for schizophrenia. We have recently demonstrated its effectiveness for unipolar depression, but its cost-effectiveness has never been examined. We hereby report a cost-effectiveness analysis alongside a randomized controlled trial in order to assess its cost-effectiveness for preventing relapse/recurrence in depression. Methods Fifty-seven patients diagnosed with major depression and undergoing its maintenance treatment, and their primary family members were randomized to treatment as usual (TAU only or to TAU plus family psychoeducation, which consisted of four 2-hour multiple-family sessions consisting of didactic lectures about depression (30 minutes and group discussion and problem solving (60–90 minutes. The economic analyses were undertaken from the perspective of the National Health Insurance (NHI, assuming the most reasonable price of US$50 per psychoeducation session per patient. The main outcome measures included relapse-free days and direct costs to the NHI. Results The intervention group enjoyed 272 (SD: 7.1 relapse-free days, while the control group spent 214 (SD: 90.8 relapse-free days (Cox proportional hazard ratio = 0.17, 95%CI: 0.04 to 0.75, p = 0.002. Cost-effectiveness acceptability curves suggested that the family psychoeducation has 90% or more chances of being cost-effective if the decision-maker is prepared to pay US$20 for one additional relapse-free day. This cost-effectiveness finding was robust when the price for family psychoeducation ranged between 50% to 150% of the baseline scenario in sensitivity analyses. If a relapse-free day is considered to be worth $30 or more, all the pricing scenarios have a close to 100% probability of being cost-effective. Conclusion Family psychoeducation is effective in the relapse prevention of

Discrete random walk models for space-time fractional diffusion

International Nuclear Information System (INIS)

Gorenflo, Rudolf; Mainardi, Francesco; Moretti, Daniele; Pagnini, Gianni; Paradisi, Paolo

2002-01-01

A physical-mathematical approach to anomalous diffusion may be based on generalized diffusion equations (containing derivatives of fractional order in space or/and time) and related random walk models. By space-time fractional diffusion equation we mean an evolution equation obtained from the standard linear diffusion equation by replacing the second-order space derivative with a Riesz-Feller derivative of order α is part of (0,2] and skewness θ (moduleθ≤{α,2-α}), and the first-order time derivative with a Caputo derivative of order β is part of (0,1]. Such evolution equation implies for the flux a fractional Fick's law which accounts for spatial and temporal non-locality. The fundamental solution (for the Cauchy problem) of the fractional diffusion equation can be interpreted as a probability density evolving in time of a peculiar self-similar stochastic process that we view as a generalized diffusion process. By adopting appropriate finite-difference schemes of solution, we generate models of random walk discrete in space and time suitable for simulating random variables whose spatial probability density evolves in time according to this fractional diffusion equation

Effects of the randomly distributed magnetic field on the phase diagrams of the Ising Nanowire II: Continuous distributions

International Nuclear Information System (INIS)

Akıncı, Ümit

2012-01-01

The effect of the random magnetic field distribution on the phase diagrams and ground state magnetizations of the Ising nanowire has been investigated with effective field theory with correlations. Gaussian distribution has been chosen as a random magnetic field distribution. The variation of the phase diagrams with that distribution parameters has been obtained and some interesting results have been found such as disappearance of the reentrant behavior and first order transitions which appear in the case of discrete distributions. Also for single and double Gaussian distributions, ground state magnetizations for different distribution parameters have been determined which can be regarded as separate partially ordered phases of the system. - Highlights: ► We give the phase diagrams of the Ising nanowire under the continuous randomly distributed magnetic field. ► Ground state magnetization values obtained. ► Different partially ordered phases observed.

Effect of order of draw of blood samples during phlebotomy on routine biochemistry results.

Science.gov (United States)

Sulaiman, Raashda A; Cornes, Michael P; Whitehead, Simon J; Othonos, Nadia; Ford, Clare; Gama, Rousseau

2011-11-01

To investigate whether incorrect order of draw of blood samples during phlebotomy causes in vitro potassium ethylenediaminetetraacetic acid EDTA (kEDTA) contamination of blood samples. Serum kEDTA, potassium, calcium, magnesium, alkaline phosphatase, zinc and iron concentrations were measured in blood samples drawn before and after collecting blood into kEDTA containing sample tubes by an experienced phlebotomist using the Sarstedt Safety Monovette system. EDTA was undetectable in all samples. The concentrations of other analytes were similar in blood samples drawn before and after collection of the EDTA blood sample. Order of draw of blood samples using the Sarstedt Safety Monovette system has no effect on serum biochemistry results, when samples are taken by an experienced phlebotomist.

Monomer-dimer problem on random planar honeycomb lattice

Energy Technology Data Exchange (ETDEWEB)

Ren, Haizhen [School of Mathematical Sciences, Xiamen University, Xiamen 361005, Fujian (China); Department of Mathematics, Qinghai Normal University, Xining 810008, Qinghai (China); Zhang, Fuji; Qian, Jianguo, E-mail: jqqian@xmu.edu.cn [School of Mathematical Sciences, Xiamen University, Xiamen 361005, Fujian (China)

2014-02-15

We consider the monomer-dimer (MD) problem on a random planar honeycomb lattice model, namely, the random multiple chain. This is a lattice system with non-periodic boundary condition, whose generating process is inspired by the growth of single walled zigzag carbon nanotubes. By applying algebraic and combinatorial techniques we establish a calculating expression of the MD partition function for bipartite graphs, which corresponds to the permanent of a matrix. Further, by using the transfer matrix argument we show that the computing problem of the permanent of high order matrix can be converted into some lower order matrices for this family of lattices, based on which we derive an explicit recurrence formula for evaluating the MD partition function of multiple chains and random multiple chains. Finally, we analyze the expectation of the number of monomer-dimer arrangements on a random multiple chain and the asymptotic behavior of the annealed MD entropy when the multiple chain becomes infinite in width and length, respectively.

Brain potentials index executive functions during random number generation.

Science.gov (United States)

Joppich, Gregor; Däuper, Jan; Dengler, Reinhard; Johannes, Sönke; Rodriguez-Fornells, Antoni; Münte, Thomas F

2004-06-01

The generation of random sequences is considered to tax different executive functions. To explore the involvement of these functions further, brain potentials were recorded in 16 healthy young adults while either engaging in random number generation (RNG) by pressing the number keys on a computer keyboard in a random sequence or in ordered number generation (ONG) necessitating key presses in the canonical order. Key presses were paced by an external auditory stimulus to yield either fast (1 press/800 ms) or slow (1 press/1300 ms) sequences in separate runs. Attentional demands of random and ordered tasks were assessed by the introduction of a secondary task (key-press to a target tone). The P3 amplitude to the target tone of this secondary task was reduced during RNG, reflecting the greater consumption of attentional resources during RNG. Moreover, RNG led to a left frontal negativity peaking 140 ms after the onset of the pacing stimulus, whenever the subjects produced a true random response. This negativity could be attributed to the left dorsolateral prefrontal cortex and was absent when numbers were repeated. This negativity was interpreted as an index for the inhibition of habitual responses. Finally, in response locked ERPs a negative component was apparent peaking about 50 ms after the key-press that was more prominent during RNG. Source localization suggested a medial frontal source. This effect was tentatively interpreted as a reflection of the greater monitoring demands during random sequence generation.

Consistency of self-reported alcohol consumption on randomized and sequential alcohol purchase tasks

Directory of Open Access Journals (Sweden)

Michael eAmlung

2012-07-01

Full Text Available Behavioral economic demand for addictive substances is commonly assessed via purchase tasks that measure estimated drug consumption at a range of prices. Purchase tasks typically use escalating prices in sequential order, which may influence performance by providing explicit price reference points. This study investigated the consistency of value preferences on two alcohol purchase tasks (APTs that used either a randomized or sequential price order (price range: free to $30 per drink in a sample of ninety-one young adult monthly drinkers. Randomization of prices significantly reduced relative response consistency (p < .01, although absolute consistency was high for both versions (>95%. Self-reported alcohol consumption across prices and indices of demand were highly similar across versions, although a few notable exceptions were found. These results suggest generally high consistency and overlapping performance between randomized and sequential price assessment. Implications for the behavioral economics literature and priorities for future research are discussed.

Comparison of tool feed influence in CNC polishing between a novel circular-random path and other pseudo-random paths.

Science.gov (United States)

Takizawa, Ken; Beaucamp, Anthony

2017-09-18

A new category of circular pseudo-random paths is proposed in order to suppress repetitive patterns and improve surface waviness on ultra-precision polished surfaces. Random paths in prior research had many corners, therefore deceleration of the polishing tool affected the surface waviness. The new random path can suppress velocity changes of the polishing tool and thus restrict degradation of the surface waviness, making it suitable for applications with stringent mid-spatial-frequency requirements such as photomask blanks for EUV lithography.

The covariance matrix of the Potts model: A random cluster analysis

International Nuclear Information System (INIS)

Borgs, C.; Chayes, J.T.

1996-01-01

We consider the covariance matrix, G mn = q 2 x ,m); δ(σ y ,n)>, of the d-dimensional q-states Potts model, rewriting it in the random cluster representation of Fortuin and Kasteleyn. In many of the q ordered phases, we identify the eigenvalues of this matrix both in terms of representations of the unbroken symmetry group of the model and in terms of random cluster connectivities and covariances, thereby attributing algebraic significance to these stochastic geometric quantities. We also show that the correlation length and the correlation length corresponding to the decay rate of one on the eigenvalues in the same as the inverse decay rate of the diameter of finite clusters. For dimension of d=2, we show that this correlation length and the correlation length of two-point function with free boundary conditions at the corresponding dual temperature are equal up to a factor of two. For systems with first-order transitions, this relation helps to resolve certain inconsistencies between recent exact and numerical work on correlation lengths at the self-dual point β o . For systems with second order transitions, this relation implies the equality of the correlation length exponents from above below threshold, as well as an amplitude ratio of two. In the course of proving the above results, we establish several properties of independent interest, including left continuity of the inverse correlation length with free boundary conditions and upper semicontinuity of the decay rate for finite clusters in all dimensions, and left continuity of the two-dimensional free boundary condition percolation probability at β o . We also introduce DLR equations for the random cluster model and use them to establish ergodicity of the free measure. In order to prove these results, we introduce a new class of events which we call decoupling events and two inequalities for these events

Self-dual random-plaquette gauge model and the quantum toric code

Science.gov (United States)

Takeda, Koujin; Nishimori, Hidetoshi

2004-05-01

We study the four-dimensional Z2 random-plaquette lattice gauge theory as a model of topological quantum memory, the toric code in particular. In this model, the procedure of quantum error correction works properly in the ordered (Higgs) phase, and phase boundary between the ordered (Higgs) and disordered (confinement) phases gives the accuracy threshold of error correction. Using self-duality of the model in conjunction with the replica method, we show that this model has exactly the same mathematical structure as that of the two-dimensional random-bond Ising model, which has been studied very extensively. This observation enables us to derive a conjecture on the exact location of the multicritical point (accuracy threshold) of the model, pc=0.889972…, and leads to several nontrivial results including bounds on the accuracy threshold in three dimensions.

Self-dual random-plaquette gauge model and the quantum toric code

International Nuclear Information System (INIS)

Takeda, Koujin; Nishimori, Hidetoshi

2004-01-01

We study the four-dimensional Z 2 random-plaquette lattice gauge theory as a model of topological quantum memory, the toric code in particular. In this model, the procedure of quantum error correction works properly in the ordered (Higgs) phase, and phase boundary between the ordered (Higgs) and disordered (confinement) phases gives the accuracy threshold of error correction. Using self-duality of the model in conjunction with the replica method, we show that this model has exactly the same mathematical structure as that of the two-dimensional random-bond Ising model, which has been studied very extensively. This observation enables us to derive a conjecture on the exact location of the multicritical point (accuracy threshold) of the model, p c =0.889972..., and leads to several nontrivial results including bounds on the accuracy threshold in three dimensions

On the joint statistics of stable random processes

International Nuclear Information System (INIS)

Hopcraft, K I; Jakeman, E

2011-01-01

A utilitarian continuous bi-variate random process whose first-order probability density function is a stable random variable is constructed. Results paralleling some of those familiar from the theory of Gaussian noise are derived. In addition to the joint-probability density for the process, these include fractional moments and structure functions. Although the correlation functions for stable processes other than Gaussian do not exist, we show that there is coherence between values adopted by the process at different times, which identifies a characteristic evolution with time. The distribution of the derivative of the process, and the joint-density function of the value of the process and its derivative measured at the same time are evaluated. These enable properties to be calculated analytically such as level crossing statistics and those related to the random telegraph wave. When the stable process is fractal, the proportion of time it spends at zero is finite and some properties of this quantity are evaluated, an optical interpretation for which is provided. (paper)

Dimer coverings on random multiple chains of planar honeycomb lattices

International Nuclear Information System (INIS)

Ren, Haizhen; Zhang, Fuji; Qian, Jianguo

2012-01-01

We study dimer coverings on random multiple chains. A multiple chain is a planar honeycomb lattice constructed by successively fusing copies of a ‘straight’ condensed hexagonal chain at the bottom of the previous one in two possible ways. A random multiple chain is then generated by admitting the Bernoulli distribution on the two types of fusing, which describes a zeroth-order Markov process. We determine the expectation of the number of the pure dimer coverings (perfect matchings) over the ensemble of random multiple chains by the transfer matrix approach. Our result shows that, with only two exceptions, the average of the logarithm of this expectation (i.e., the annealed entropy per dimer) is asymptotically nonzero when the fusing process goes to infinity and the length of the hexagonal chain is fixed, though it is zero when the fusing process and the length of the hexagonal chain go to infinity simultaneously. Some numerical results are provided to support our conclusion, from which we can see that the asymptotic behavior fits well to the theoretical results. We also apply the transfer matrix approach to the quenched entropy and reveal that the quenched entropy of random multiple chains has a close connection with the well-known Lyapunov exponent of random matrices. Using the theory of Lyapunov exponents we show that, for some random multiple chains, the quenched entropy per dimer is strictly smaller than the annealed one when the fusing process goes to infinity. Finally, we determine the expectation of the free energy per dimer over the ensemble of the random multiple chains in which the three types of dimers in different orientations are distinguished, and specify a series of non-random multiple chains whose free energy per dimer is asymptotically equal to this expectation. (paper)

Numerical study of microphase separation in gels and random media

International Nuclear Information System (INIS)

Uchida, Nariya

2004-01-01

Microphase separation in gels and random media is numerically studied using a Ginzburg-Landau model. A random field destroys long-range orientational (lamellar) order and gives rise to a disordered bicontinuous morphology. The dependence of the correlation length on the field strength is distinct from that of random-field magnets

Structural changes in the ordering processes of macromolecular compounds

International Nuclear Information System (INIS)

Kobayashi, M.; Tashiro, K.

1998-01-01

In order to clarify the microscopically-viewed relationship between the conformational ordering process and the aggregation process of the macromolecular chains in the phase transitions from melt to solid or from solution to gel, the time-resolved Fourier-transform infrared spectra and small-angle X-ray or neutron scattering data have been analyzed in an organized manner. Two concrete examples were presented. (1) In the gelation phenomenon of syndiotactic polystyrene-organic solvent system, the ordered TTGG conformation is formed and develops with time. This conformational ordering is accelerated by the aggregation of these chain segments, resulting in the formation of macroscopic gel network. (2) In the isothermal crystallization process from the melt of polyethylene, the following ordering mechanism was revealed. The conformationally-disordered short trans conformers appear at first in the random coils of the melt. These disordered trans sequences grow to longer and more regular trans sequences of the orthorhombic-type crystal and then the isolated lamellae are formed. Afterwards, the stacked lamellar structure is developed without change of lamellar thickness but with small decrease in the long period, indicating an insertion of new lamellae between the already produced lamellar layers

Theoretical model of the density of states of random binary alloys

International Nuclear Information System (INIS)

Zekri, N.; Brezini, A.

1991-09-01

A theoretical formulation of the density of states for random binary alloys is examined based on a mean field treatment. The present model includes both diagonal and off-diagonal disorder and also short-range order. Extensive results are reported for various concentrations and compared to other calculations. (author). 22 refs, 6 figs

Reliability-based design optimization via high order response surface method

International Nuclear Information System (INIS)

Li, Hong Shuang

2013-01-01

To reduce the computational effort of reliability-based design optimization (RBDO), the response surface method (RSM) has been widely used to evaluate reliability constraints. We propose an efficient methodology for solving RBDO problems based on an improved high order response surface method (HORSM) that takes advantage of an efficient sampling method, Hermite polynomials and uncertainty contribution concept to construct a high order response surface function with cross terms for reliability analysis. The sampling method generates supporting points from Gauss-Hermite quadrature points, which can be used to approximate response surface function without cross terms, to identify the highest order of each random variable and to determine the significant variables connected with point estimate method. The cross terms between two significant random variables are added to the response surface function to improve the approximation accuracy. Integrating the nested strategy, the improved HORSM is explored in solving RBDO problems. Additionally, a sampling based reliability sensitivity analysis method is employed to reduce the computational effort further when design variables are distributional parameters of input random variables. The proposed methodology is applied on two test problems to validate its accuracy and efficiency. The proposed methodology is more efficient than first order reliability method based RBDO and Monte Carlo simulation based RBDO, and enables the use of RBDO as a practical design tool.

Reporting of Positive Results in Randomized Controlled Trials of Mindfulness-Based Mental Health Interventions.

Directory of Open Access Journals (Sweden)

Stephanie Coronado-Montoya

Full Text Available A large proportion of mindfulness-based therapy trials report statistically significant results, even in the context of very low statistical power. The objective of the present study was to characterize the reporting of "positive" results in randomized controlled trials of mindfulness-based therapy. We also assessed mindfulness-based therapy trial registrations for indications of possible reporting bias and reviewed recent systematic reviews and meta-analyses to determine whether reporting biases were identified.CINAHL, Cochrane CENTRAL, EMBASE, ISI, MEDLINE, PsycInfo, and SCOPUS databases were searched for randomized controlled trials of mindfulness-based therapy. The number of positive trials was described and compared to the number that might be expected if mindfulness-based therapy were similarly effective compared to individual therapy for depression. Trial registries were searched for mindfulness-based therapy registrations. CINAHL, Cochrane CENTRAL, EMBASE, ISI, MEDLINE, PsycInfo, and SCOPUS were also searched for mindfulness-based therapy systematic reviews and meta-analyses.108 (87% of 124 published trials reported ≥1 positive outcome in the abstract, and 109 (88% concluded that mindfulness-based therapy was effective, 1.6 times greater than the expected number of positive trials based on effect size d = 0.55 (expected number positive trials = 65.7. Of 21 trial registrations, 13 (62% remained unpublished 30 months post-trial completion. No trial registrations adequately specified a single primary outcome measure with time of assessment. None of 36 systematic reviews and meta-analyses concluded that effect estimates were overestimated due to reporting biases.The proportion of mindfulness-based therapy trials with statistically significant results may overstate what would occur in practice.

ACORN—A new method for generating sequences of uniformly distributed Pseudo-random Numbers

Science.gov (United States)

Wikramaratna, R. S.

1989-07-01

A new family of pseudo-random number generators, the ACORN ( additive congruential random number) generators, is proposed. The resulting numbers are distributed uniformly in the interval [0, 1). The ACORN generators are defined recursively, and the ( k + 1)th order generator is easily derived from the kth order generator. Some theorems concerning the period length are presented and compared with existing results for linear congruential generators. A range of statistical tests are applied to the ACORN generators, and their performance is compared with that of the linear congruential generators and the Chebyshev generators. The tests show the ACORN generators to be statistically superior to the Chebyshev generators, while being statistically similar to the linear congruential generators. However, the ACORN generators execute faster than linear congruential generators for the same statistical faithfulness. The main advantages of the ACORN generator are speed of execution, long period length, and simplicity of coding.

Study on the Light Scattering from Random Rough Surfaces by Kirrhoff Approximation

Directory of Open Access Journals (Sweden)

Keding Yan

2014-07-01

Full Text Available In order to study the space distribution characteristics of light scattering from random rough surfaces, the linear filtering method is used to generate a series of Gaussian randomly rough surfaces, and the Kirchhoff Approximation is used to calculate the scattered light intensity distribution from random metal and dielectric rough surfaces. The three characteristics of the scattered light intensity distribution peak, the intensity distribution width and the position of peak are reviewed. Numerical calculation results show that significant differences between scattering characteristics of metal surfaces and the dielectric surfaces exist. The light scattering characteristics are jointly influenced by the slope distribution and reflectance of surface element. The scattered light intensity distribution is affected by common influence of surface local slope distribution and surface local reflectivity. The results can provide a basis theory for the research to lidar target surface scattering characteristics.

Random balance designs for the estimation of first order global sensitivity indices

International Nuclear Information System (INIS)

Tarantola, S.; Gatelli, D.; Mara, T.A.

2006-01-01

We present two methods for the estimation of main effects in global sensitivity analysis. The methods adopt Satterthwaite's application of random balance designs in regression problems, and extend it to sensitivity analysis of model output for non-linear, non-additive models. Finite as well as infinite ranges for model input factors are allowed. The methods are easier to implement than any other method available for global sensitivity analysis, and reduce significantly the computational cost of the analysis. We test their performance on different test cases, including an international benchmark on safety assessment for nuclear waste disposal originally carried out by OECD/NEA

Adjuvant Hormone Therapy May Improve Survival in Epithelial Ovarian Cancer: Results of the AHT Randomized Trial.

Science.gov (United States)

Eeles, Rosalind A; Morden, James P; Gore, Martin; Mansi, Janine; Glees, John; Wenczl, Miklos; Williams, Christopher; Kitchener, Henry; Osborne, Richard; Guthrie, David; Harper, Peter; Bliss, Judith M

2015-12-10

To assess the effects of adjuvant hormone therapy (AHT) on survival and disease outcome in women with epithelial ovarian cancer. Participants were premenopausal and postmenopausal women who had been diagnosed with epithelial ovarian cancer (any International Federation of Gynecology and Obstetrics stage) 9 or fewer months previously. Ineligible patients included those with deliberately preserved ovarian function, with a history of a hormone-dependent malignancy, or with any contraindications to hormone-replacement therapy. Patients were centrally randomly assigned in a 1:1 ratio to either AHT for 5 years after random assignment or no AHT (control). Main outcome measures were overall survival (OS), defined as time from random assignment to death (any cause), and relapse-free survival, defined as time from random assignment to relapse or death (any cause). Patients who continued, alive and relapse free, were censored at their last known follow-up. A total of 150 patients (n = 75, AHT; n = 75, control) were randomly assigned from 1990 to 1995 from 19 centers in the United Kingdom, Spain, and Hungary; all patients were included in intention-to-treat analyses. The median follow-up in alive patients is currently 19.1 years. Of the 75 patients with AHT, 53 (71%) have died compared with 68 (91%) of 75 patients in the control group. OS was significantly improved in patients who were receiving AHT (hazard ratio, 0.63; 95% CI, 0.44 to 0.90; P = .011). A similar effect was seen for relapse-free survival (hazard ratio, 0.67; 95% CI, 0.47 to 0.97; P = .032). Effects remained after adjustment for known prognostic factors. These results show that women who have severe menopausal symptoms after ovarian cancer treatment can safely take hormone-replacement therapy, and this may, in fact, infer benefits in terms of OS in addition to known advantages in terms of quality of life. © 2015 by American Society of Clinical Oncology.

THERAPEUTIC EQUIVALENCE OF ORIGINAL CLOPIDOGREL (PLAVIX AND ITS GENERIC (EGITROMB. RESULTS OF COMPARATIVE RANDOMIZED CROSS-OVER BLIND STUDY

Directory of Open Access Journals (Sweden)

V. V. Yakusevich

2011-01-01

Full Text Available Aim. To study therapeutic equivalence (efficacy, safety and tolerability of original clopidogrel (Plavix and its generic (Egitromb in patients of high cardiovascular risk. Material and methods. Thirty one patients with coronary heart disease and indications for clopidogrel therapy were involved into the randomized cross-over blind study. Half of the patients received original clopidogrel (75 mg daily during the first 2 weeks and then they received generic clopidogrel in the same dose during next 2 weeks. Another half of the patients received the drugs in reverse order. Antiplatelet activity of Plavix and Egitromb was estimated by effects on ADP-induced platelet aggregation initially and after 2 weeks of treatment with each drug. Study blinding was provided by the following approach: doctors of cardiology clinic performed clinical monitoring and drug distribution; coded blood samples for platelet aggregation assessment were studied in independent laboratory of thrombosis; statistical data analysis was performed by biostatistics expert in other research center. Results. 2-week therapy with each drug led to a significant decrease of ADP-induced platelet aggregation which remained low after switching from original drug to generic and vice versa. Aggregation dynamics did not depend on the first administered drug. There were no significant differences between aggregation changes as a result of treatment with original or generic drug. No one adverse event was observed in association with both drugs therapy. Conclusion. Generic drug Egitromb (Egis, Hungary and original clopidogrel Plavix (Sanofi-Aventis, France have equivalent antiplatelet effect.

Autonomous Byte Stream Randomizer

Science.gov (United States)

Paloulian, George K.; Woo, Simon S.; Chow, Edward T.

2013-01-01

Net-centric networking environments are often faced with limited resources and must utilize bandwidth as efficiently as possible. In networking environments that span wide areas, the data transmission has to be efficient without any redundant or exuberant metadata. The Autonomous Byte Stream Randomizer software provides an extra level of security on top of existing data encryption methods. Randomizing the data s byte stream adds an extra layer to existing data protection methods, thus making it harder for an attacker to decrypt protected data. Based on a generated crypto-graphically secure random seed, a random sequence of numbers is used to intelligently and efficiently swap the organization of bytes in data using the unbiased and memory-efficient in-place Fisher-Yates shuffle method. Swapping bytes and reorganizing the crucial structure of the byte data renders the data file unreadable and leaves the data in a deconstructed state. This deconstruction adds an extra level of security requiring the byte stream to be reconstructed with the random seed in order to be readable. Once the data byte stream has been randomized, the software enables the data to be distributed to N nodes in an environment. Each piece of the data in randomized and distributed form is a separate entity unreadable on its own right, but when combined with all N pieces, is able to be reconstructed back to one. Reconstruction requires possession of the key used for randomizing the bytes, leading to the generation of the same cryptographically secure random sequence of numbers used to randomize the data. This software is a cornerstone capability possessing the ability to generate the same cryptographically secure sequence on different machines and time intervals, thus allowing this software to be used more heavily in net-centric environments where data transfer bandwidth is limited.

Cluster Tails for Critical Power-Law Inhomogeneous Random Graphs

Science.gov (United States)

van der Hofstad, Remco; Kliem, Sandra; van Leeuwaarden, Johan S. H.

2018-04-01

Recently, the scaling limit of cluster sizes for critical inhomogeneous random graphs of rank-1 type having finite variance but infinite third moment degrees was obtained in Bhamidi et al. (Ann Probab 40:2299-2361, 2012). It was proved that when the degrees obey a power law with exponent τ \\in (3,4), the sequence of clusters ordered in decreasing size and multiplied through by n^{-(τ -2)/(τ -1)} converges as n→ ∞ to a sequence of decreasing non-degenerate random variables. Here, we study the tails of the limit of the rescaled largest cluster, i.e., the probability that the scaling limit of the largest cluster takes a large value u, as a function of u. This extends a related result of Pittel (J Combin Theory Ser B 82(2):237-269, 2001) for the Erdős-Rényi random graph to the setting of rank-1 inhomogeneous random graphs with infinite third moment degrees. We make use of delicate large deviations and weak convergence arguments.

An experimental comparison of triggered and random pulse train uncertainties

International Nuclear Information System (INIS)

Henzlova, Daniela; Menlove, Howard O.; Swinhoe, Martyn T.

2010-01-01

response) have used only one of the two analysis methods for the nuclear material assay. The aim of this study is to provide a systematic comparison of the precision of the measured S, D, T rates and 240 Pu effective mass obtained using the above mentioned pulse train sampling techniques. In order to perform this task, a LANL developed list mode based data acquisition system is used, where the entire pulse train is recorded and subsequently analyzed. The list mode acquisition brings an essential advantage for this type of comparison, since the very same pulse train can be analyzed using signal-triggered as well as randomly triggered counting gates. The aim of this study is not only to compare the precision of signal-triggered versus random triggered sampling techniques, but also to investigate the influence of fast accidental sampling on the precision of signal-triggered results. In addition the different random sampling techniques used in safeguards are investigated. For this purpose we implement two types of random sampling - non-overlapping gates (Feynrnan approach) and periodic overlapping gates (fast accidentals). In the following sections the equations utilized in the pulse train analysis are described, experimental setup and measurement techniques are discussed and finally the results are summarized and discussed.

Complexity Analysis and DSP Implementation of the Fractional-Order Lorenz Hyperchaotic System

Directory of Open Access Journals (Sweden)

Shaobo He

2015-12-01

Full Text Available The fractional-order hyperchaotic Lorenz system is solved as a discrete map by applying the Adomian decomposition method (ADM. Lyapunov Characteristic Exponents (LCEs of this system are calculated according to this deduced discrete map. Complexity of this system versus parameters are analyzed by LCEs, bifurcation diagrams, phase portraits, complexity algorithms. Results show that this system has rich dynamical behaviors. Chaos and hyperchaos can be generated by decreasing fractional order q in this system. It also shows that the system is more complex when q takes smaller values. SE and C 0 complexity algorithms provide a parameter choice criteria for practice applications of fractional-order chaotic systems. The fractional-order system is implemented by digital signal processor (DSP, and a pseudo-random bit generator is designed based on the implemented system, which passes the NIST test successfully.

"Big Bang" as a result result of the curvature-driven first-order phase transition in the early cold Universe

Science.gov (United States)

Pashitskii, E. A.; Pentegov, V. I.

We suggest that the "Big Bang" may be a result of the first-order phase transition driven by changing scalar curvature of the 4D space-time in the expanding cold Universe, filled with nonlinear scalar field φ and neutral matter with equation of state p = vɛ (where p and ɛ are pressure and energy density of matter). We consider a Lagrangian for scalar field in curved space-time with nonlinearity φ, which along with the quadratic term -ΣR|φ|2 (where Σ is interaction constant and R is scalar curvature) contains a term ΣR(φ +φ+) linear in φ. Due to this term the condition for the extrema of the potential energy of the scalar field is given by a cubic equation. Provided v > 1/3 the scalar curvature R = [κ(3v-1)ɛ - 4Γ (where κ and Γ are Einstein's gravitational and cosmological constants) decreases along with decreasing " in the process of the Universe's expansion, and at some critical value Rc < 0 a first-order phase transition occurs, driven by an "external field" parameter proportional to R. Given certain conditions the critical radius of the early Universe at the point of the first-order phase transition may reach arbitrary large values, so this scenario of unrestricted "inflation" of the Universe may be called "hyperinflation". Beyond the point of phase transition the system is rolling down into the potential minimum releasing the potential energy of scalar field with subsequent powerful heating of the Universe playing the role of "Big Bang".

Rain dance: the role of randomization in clinical trials

Directory of Open Access Journals (Sweden)

Diniz JB

2016-07-01

Full Text Available Juliana Belo Diniz,1 Victor Fossaluza,2 Carlos Alberto de Bragança Pereira,1,2 Sergio Wechsler2 1Institute of Psychiatry, Clinics Hospital University of São Paulo Medical School, 2Department of Statistics, Institute of Mathematics and Statistics, University of São Paulo, São Paulo, Brazil Abstract: Randomized clinical trials are the gold standard for testing efficacy of treatment interventions. However, although randomization protects against deliberately biased samples, it does not guarantee random imbalances will not occur. Methods of intentional allocation that can overcome such deficiency of randomization have been developed, but are less frequently applied than randomization. Initially, we introduce a fictitious case example to revise and discuss the reasons of researchers' resistance to intentionally allocate instead of simply randomizing. We then introduce a real case example to evaluate the performance of an intentional protocol for allocation based on compositional data balance. A real case of allocation of 50 patients in two arms was compared with an optimal allocation of global instead of sequential arrivals. Performance was measured by a weighted average of Aitchison distances, between arms, of prognostic factors. To compare the intentional allocation with simple random allocation, 50,000 arrival orderings of 50 patients were simulated. To each one of the orders, both kinds of allocations into two arms were considered. Intentional allocation performed as well as optimal allocation in the case considered. In addition, out of the 50,000 simulated orders, 61% of them performed better with intentional allocation than random allocation. Hence, we conclude that intentional allocation should be encouraged in the design of future interventional clinical trials as a way to prevent unbalanced samples. Our sequential method is a viable alternative to overcome technical difficulties for study designs that require sequential inclusion of

Encouraging GPs to undertake screening and a brief intervention in order to reduce problem drinking: a randomized controlled trial

DEFF Research Database (Denmark)

Hansen, Lars Jørgen; Olivarius, Niels de Fine; Beich, Anders

1999-01-01

intervention, problem drinking, randomized controlled trial, family practice, marketing of health services......intervention, problem drinking, randomized controlled trial, family practice, marketing of health services...

Exchange bias mechanism in FM/FM/AF spin valve systems in the presence of random unidirectional anisotropy field at the AF interface: The role played by the interface roughness due to randomness

Science.gov (United States)

Yüksel, Yusuf

2018-05-01

We propose an atomistic model and present Monte Carlo simulation results regarding the influence of FM/AF interface structure on the hysteresis mechanism and exchange bias behavior for a spin valve type FM/FM/AF magnetic junction. We simulate perfectly flat and roughened interface structures both with uncompensated interfacial AF moments. In order to simulate rough interface effect, we introduce the concept of random exchange anisotropy field induced at the interface, and acting on the interface AF spins. Our results yield that different types of the random field distributions of anisotropy field may lead to different behavior of exchange bias.

Random matrix theory in nuclear structure: past, present and future

International Nuclear Information System (INIS)

Kota, V.K.B.

2012-01-01

Random matrix theory (RMT) introduced by Wigner in 50's to describe statistical properties of slow-neutron resonances in heavy nuclei such as 232 Th, was developed further in the 60's by Dyson, Mehta, Porter and others and in the 70's by French, Pandey, Bohigas and others. Going beyond this, the demonstration that level fluctuations of quantum analogues of classically chaotic few-degrees-of-freedom systems follow random matrix theory (integrable systems follow Poisson as shown by Berry) in 1984 by Bohigas and others on one hand and the recognition from 1995 onwards that two-body random matrix ensembles derived from shell model have wide ranging applications on the other, defined new directions in RMT applications in nuclear physics. Growth points in RMT in nuclear physics are: (i) analysis of nuclear data looking for order-chaos transitions and symmetry (Time-reversal, Parity, Isospin) breaking; (ii) analysis of shell model driven embedded (or two-body) random matrix ensembles giving statistical properties generated by random interactions in the presence of a mean-field; (iii) statistical nuclear spectroscopy generated by embedded ensembles for level densities, occupancies, GT strengths, transition strength sums and so on; (iv) the new paradigm of regular structures generated by random interactions as brought out by studies using various nuclear models; (v) random matrix theory for nuclear reactions with particular reference to open quantum systems; (vi) RMT results from nuclear physics to atomic physics, mesoscopic physics and quantum information science. Topics (i)-(vi) emphasizing recent results are discussed. (author)

Fourth-Order Spatial Correlation of Thermal Light

International Nuclear Information System (INIS)

Wen Feng; Zhang Xun; Sun Jia; Song Jian-Ping; Zhang Yan-Peng; Xue Xin-Xin

2014-01-01

We investigate the fourth-order spatial correlation properties of pseudo-thermal light in the photon counting regime, and apply the Klyshko advanced-wave picture to describe the process of four-photon coincidence counting measurement. We deduce the theory of a proof-of-principle four-photon coincidence counting configuration, and find that if the four randomly radiated photons come from the same radiation area and are indistinguishable in principle, the fourth-order correlation of them is 24 times larger than that when four photons come from different radiation areas. In addition, we also show that the higher-order spatial correlation function can be decomposed into multiple lower-order correlation functions, and the contrast and visibility of low-order correlation peaks are less than those of higher orders, while the resolutions all are identical. This study may be useful for better understanding the four-photon interference and multi-channel correlation imaging

Nudging physician prescription decisions by partitioning the order set: results of a vignette-based study.

Science.gov (United States)

Tannenbaum, David; Doctor, Jason N; Persell, Stephen D; Friedberg, Mark W; Meeker, Daniella; Friesema, Elisha M; Goldstein, Noah J; Linder, Jeffrey A; Fox, Craig R

2015-03-01

Healthcare professionals are rapidly adopting electronic health records (EHRs). Within EHRs, seemingly innocuous menu design configurations can influence provider decisions for better or worse. The purpose of this study was to examine whether the grouping of menu items systematically affects prescribing practices among primary care providers. We surveyed 166 primary care providers in a research network of practices in the greater Chicago area, of whom 84 responded (51% response rate). Respondents and non-respondents were similar on all observable dimensions except that respondents were more likely to work in an academic setting. The questionnaire consisted of seven clinical vignettes. Each vignette described typical signs and symptoms for acute respiratory infections, and providers chose treatments from a menu of options. For each vignette, providers were randomly assigned to one of two menu partitions. For antibiotic-inappropriate vignettes, the treatment menu either listed over-the-counter (OTC) medications individually while grouping prescriptions together, or displayed the reverse partition. For antibiotic-appropriate vignettes, the treatment menu either listed narrow-spectrum antibiotics individually while grouping broad-spectrum antibiotics, or displayed the reverse partition. The main outcome was provider treatment choice. For antibiotic-inappropriate vignettes, we categorized responses as prescription drugs or OTC-only options. For antibiotic-appropriate vignettes, we categorized responses as broad- or narrow-spectrum antibiotics. Across vignettes, there was an 11.5 percentage point reduction in choosing aggressive treatment options (e.g., broad-spectrum antibiotics) when aggressive options were grouped compared to when those same options were listed individually (95% CI: 2.9 to 20.1%; p = .008). Provider treatment choice appears to be influenced by the grouping of menu options, suggesting that the layout of EHR order sets is not an arbitrary exercise

The "Healthy Habits, Healthy Girls" randomized controlled trial for girls: study design, protocol, and baseline results.

Science.gov (United States)

Leme, Ana Carolina Barco; Philippi, Sonia Tucunduva

2015-07-01

The purpose of this article is to describe the study design, protocol, and baseline results of the "Healthy Habits, Healthy Girls" program. The intervention is being evaluated through a randomized controlled trial in 10 public schools in the city of São Paulo, Brazil. Data on the following variables were collected and assessed at baseline and will be reevaluated at 7 and 12 months: body mass index, waist circumference, dietary intake, nutrition, physical activity, social cognitive mediators, physical activity level, sedentary behaviors, self-rated physical status, and overall self-esteem. According to the baseline results, 32.4% and 23.4% of girls were overweight in the intervention and control groups, respectively, and in both groups a higher percentage failed to meet daily recommendations for moderate and vigorous physical activity and maximum screen time (TV, computer, mobile devices). There were no significant differences between the groups for most of the variables, except age (p = 0.000) and waist circumference (p = 0.014). The study showed a gap in the Brazilian literature on protocols for randomized controlled trials to prevent obesity among youth. The current study may thus be an important initial contribution to the field.

Ordered array of CoPc-vacancies filled with single-molecule rotors

Science.gov (United States)

Xie, Zheng-Bo; Wang, Ya-Li; Tao, Min-Long; Sun, Kai; Tu, Yu-Bing; Yuan, Hong-Kuan; Wang, Jun-Zhong

2018-05-01

We report the highly ordered array of CoPc-vacancies and the single-molecule rotors inside the vacancies. When CoPc molecules are deposited on Cd(0001) at low-temperature, three types of molecular vacancies appeared randomly in the CoPc monolayer. Annealing the sample to higher temperature leads to the spontaneous phase separation and self-organized arrangement of the vacancies. Highly ordered arrays of two-molecule vacancies and single-molecule vacancies have been obtained. In particular, there is a rotating CoPc molecule inside each single-molecule vacancy, which constitutes the array of single-molecule rotors. These results provide a new routine to fabricate the nano-machines on a large scale.

Birth order, neuroticism, and psychoticism among Iranian children.

Science.gov (United States)

Makaremi, A

1992-12-01

To investigate the effects of birth order, parents' education, and parents' occupation on four dimensions of the Junior Eysenck Personality Questionnaire, 262 elementary school students (100 boys and 162 girls) were selected randomly from four elementary schools in Shiraz. Analyses showed the main effects of birth order were significant on Neuroticism and Lie scales. Further, the effects of mothers' occupation on the Lie scale and fathers' education on the Neuroticism scale were significant.

On randomly interrupted diffusion

International Nuclear Information System (INIS)

Luczka, J.

1993-01-01

Processes driven by randomly interrupted Gaussian white noise are considered. An evolution equation for single-event probability distributions in presented. Stationary states are considered as a solution of a second-order ordinary differential equation with two imposed conditions. A linear model is analyzed and its stationary distributions are explicitly given. (author). 10 refs

Random and systematic beam modulator errors in dynamic intensity modulated radiotherapy

International Nuclear Information System (INIS)

Parsai, Homayon; Cho, Paul S; Phillips, Mark H; Giansiracusa, Robert S; Axen, David

2003-01-01

This paper reports on the dosimetric effects of random and systematic modulator errors in delivery of dynamic intensity modulated beams. A sliding-widow type delivery that utilizes a combination of multileaf collimators (MLCs) and backup diaphragms was examined. Gaussian functions with standard deviations ranging from 0.5 to 1.5 mm were used to simulate random positioning errors. A clinical example involving a clival meningioma was chosen with optic chiasm and brain stem as limiting critical structures in the vicinity of the tumour. Dose calculations for different modulator fluctuations were performed, and a quantitative analysis was carried out based on cumulative and differential dose volume histograms for the gross target volume and surrounding critical structures. The study indicated that random modulator errors have a strong tendency to reduce minimum target dose and homogeneity. Furthermore, it was shown that random perturbation of both MLCs and backup diaphragms in the order of σ = 1 mm can lead to 5% errors in prescribed dose. In comparison, when MLCs or backup diaphragms alone was perturbed, the system was more robust and modulator errors of at least σ = 1.5 mm were required to cause dose discrepancies greater than 5%. For systematic perturbation, even errors in the order of ±0.5 mm were shown to result in significant dosimetric deviations

Mobile access to virtual randomization for investigator-initiated trials.

Science.gov (United States)

Deserno, Thomas M; Keszei, András P

2017-08-01

Background/aims Randomization is indispensable in clinical trials in order to provide unbiased treatment allocation and a valid statistical inference. Improper handling of allocation lists can be avoided using central systems, for example, human-based services. However, central systems are unaffordable for investigator-initiated trials and might be inaccessible from some places, where study subjects need allocations. We propose mobile access to virtual randomization, where the randomization lists are non-existent and the appropriate allocation is computed on demand. Methods The core of the system architecture is an electronic data capture system or a clinical trial management system, which is extended by an R interface connecting the R server using the Java R Interface. Mobile devices communicate via the representational state transfer web services. Furthermore, a simple web-based setup allows configuring the appropriate statistics by non-statisticians. Our comprehensive R script supports simple randomization, restricted randomization using a random allocation rule, block randomization, and stratified randomization for un-blinded, single-blinded, and double-blinded trials. For each trial, the electronic data capture system or the clinical trial management system stores the randomization parameters and the subject assignments. Results Apps are provided for iOS and Android and subjects are randomized using smartphones. After logging onto the system, the user selects the trial and the subject, and the allocation number and treatment arm are displayed instantaneously and stored in the core system. So far, 156 subjects have been allocated from mobile devices serving five investigator-initiated trials. Conclusion Transforming pre-printed allocation lists into virtual ones ensures the correct conduct of trials and guarantees a strictly sequential processing in all trial sites. Covering 88% of all randomization models that are used in recent trials, virtual randomization

Random balance designs for the estimation of first order global sensitivity indices

Energy Technology Data Exchange (ETDEWEB)

Tarantola, S. [Joint Research Centre, European Commission, Institute of the Protection and Security of the Citizen, TP 361, Via E. Fermi 1, 21020 Ispra (Vatican City State, Holy See,) (Italy)]. E-mail: stefano.tarantola@jrc.it; Gatelli, D. [Joint Research Centre, European Commission, Institute of the Protection and Security of the Citizen, TP 361, Via E. Fermi 1, 21020 Ispra (VA) (Italy); Mara, T.A. [Laboratory of Industrial engineering, University of Reunion Island, BP 7151, 15 avenue Rene Cassin, 97 715 Saint-Denis (France)

2006-06-15

We present two methods for the estimation of main effects in global sensitivity analysis. The methods adopt Satterthwaite's application of random balance designs in regression problems, and extend it to sensitivity analysis of model output for non-linear, non-additive models. Finite as well as infinite ranges for model input factors are allowed. The methods are easier to implement than any other method available for global sensitivity analysis, and reduce significantly the computational cost of the analysis. We test their performance on different test cases, including an international benchmark on safety assessment for nuclear waste disposal originally carried out by OECD/NEA.

Random coil chemical shifts in acidic 8 M urea: Implementation of random coil shift data in NMRView

International Nuclear Information System (INIS)

Schwarzinger, Stephan; Kroon, Gerard J.A.; Foss, Ted R.; Wright, Peter E.; Dyson, H. Jane

2000-01-01

Studies of proteins unfolded in acid or chemical denaturant can help in unraveling events during the earliest phases of protein folding. In order for meaningful comparisons to be made of residual structure in unfolded states, it is necessary to use random coil chemical shifts that are valid for the experimental system under study. We present a set of random coil chemical shifts obtained for model peptides under experimental conditions used in studies of denatured proteins. This new set, together with previously published data sets, has been incorporated into a software interface for NMRView, allowing selection of the random coil data set that fits the experimental conditions best

Human papillomavirus-based cervical cancer prevention: long-term results of a randomized screening trial.

Science.gov (United States)

Denny, Lynette; Kuhn, Louise; Hu, Chih-Chi; Tsai, Wei-Yann; Wright, Thomas C

2010-10-20

Screen-and-treat approaches to cervical cancer prevention are an attractive option for low-resource settings, but data on their long-term efficacy are lacking. We evaluated the efficacy of two screen-and-treat approaches through 36 months of follow-up in a randomized trial. A total of 6637 unscreened South African women aged 35-65 years who were tested for the presence of high-risk human papillomavirus (HPV) DNA in cervical samples underwent visual inspection of the cervix using acetic acid staining and HIV serotesting. Of these, 6555 were randomly assigned to three study arms: 1) HPV-and-treat, in which all women with a positive HPV DNA test result underwent cryotherapy; 2) visual inspection-and-treat, in which all women with a positive visual inspection test result underwent cryotherapy; or 3) control, in which further evaluation or treatment was delayed for 6 months. All women underwent colposcopy with biopsy at 6 months. All women who were HPV DNA- or visual inspection-positive at enrollment, and a subset of all other women had extended follow-up to 36 months (n = 3639) with yearly colposcopy. The endpoint-cervical intraepithelial neoplasia grade 2 or worse (CIN2+)-was analyzed using actuarial life-table methods. All statistical tests were two-sided. After 36 months, there was a sustained statistically significant decrease in the cumulative detection of CIN2+ in the HPV-and-treat arm compared with the control arm (1.5% vs 5.6%, difference = 4.1%, 95% confidence interval [CI] = 2.8% to 5.3%, P cryotherapy.

Alzheimer random walk

Science.gov (United States)

Odagaki, Takashi; Kasuya, Keisuke

2017-09-01

Using the Monte Carlo simulation, we investigate a memory-impaired self-avoiding walk on a square lattice in which a random walker marks each of sites visited with a given probability p and makes a random walk avoiding the marked sites. Namely, p = 0 and p = 1 correspond to the simple random walk and the self-avoiding walk, respectively. When p> 0, there is a finite probability that the walker is trapped. We show that the trap time distribution can well be fitted by Stacy's Weibull distribution b(a/b){a+1}/{b}[Γ({a+1}/{b})]-1x^a\\exp(-a/bx^b)} where a and b are fitting parameters depending on p. We also find that the mean trap time diverges at p = 0 as p- α with α = 1.89. In order to produce sufficient number of long walks, we exploit the pivot algorithm and obtain the mean square displacement and its Flory exponent ν(p) as functions of p. We find that the exponent determined for 1000 step walks interpolates both limits ν(0) for the simple random walk and ν(1) for the self-avoiding walk as [ ν(p) - ν(0) ] / [ ν(1) - ν(0) ] = pβ with β = 0.388 when p ≪ 0.1 and β = 0.0822 when p ≫ 0.1. Contribution to the Topical Issue "Continuous Time Random Walk Still Trendy: Fifty-year History, Current State and Outlook", edited by Ryszard Kutner and Jaume Masoliver.

Residual Defect Density in Random Disks Deposits.

Science.gov (United States)

Topic, Nikola; Pöschel, Thorsten; Gallas, Jason A C

2015-08-03

We investigate the residual distribution of structural defects in very tall packings of disks deposited randomly in large channels. By performing simulations involving the sedimentation of up to 50 × 10(9) particles we find all deposits to consistently show a non-zero residual density of defects obeying a characteristic power-law as a function of the channel width. This remarkable finding corrects the widespread belief that the density of defects should vanish algebraically with growing height. A non-zero residual density of defects implies a type of long-range spatial order in the packing, as opposed to only local ordering. In addition, we find deposits of particles to involve considerably less randomness than generally presumed.

Monte Carlo studies of two-dimensional random-anisotropy magnets

Science.gov (United States)

Denholm, D. R.; Sluckin, T. J.

1993-07-01

We have carried out a systematic set of Monte Carlo simulations of the Harris-Plischke-Zuckermann lattice model of random magnetic anisotropy on a two-dimensional square lattice, using the classical Metropolis algorithm. We have considered varying temperature T, external magnetic field H (both in the reproducible and irreproducible limits), time scale of the simulation τ in Monte Carlo steps and anisotropy ratio D/J. In the absence of randomness this model reduces to the XY model in two dimensions, which possesses the familiar Kosterlitz-Thouless low-temperature phase with algebraic but no long-range order. In the presence of random anisotropy we find evidence of a low-temperature phase with some disordered features, which might be identified with a spin-glass phase. The low-temperature Kosterlitz-Thouless phase survives at intermediate temperatures for low randomness, but is no longer present for large D/J. We have also studied the high-H approach to perfect order, for which there are theoretical predictions due to Chudnovsky.

Pseudo-random number generator based on asymptotic deterministic randomness

Science.gov (United States)

Wang, Kai; Pei, Wenjiang; Xia, Haishan; Cheung, Yiu-ming

2008-06-01

A novel approach to generate the pseudorandom-bit sequence from the asymptotic deterministic randomness system is proposed in this Letter. We study the characteristic of multi-value correspondence of the asymptotic deterministic randomness constructed by the piecewise linear map and the noninvertible nonlinearity transform, and then give the discretized systems in the finite digitized state space. The statistic characteristics of the asymptotic deterministic randomness are investigated numerically, such as stationary probability density function and random-like behavior. Furthermore, we analyze the dynamics of the symbolic sequence. Both theoretical and experimental results show that the symbolic sequence of the asymptotic deterministic randomness possesses very good cryptographic properties, which improve the security of chaos based PRBGs and increase the resistance against entropy attacks and symbolic dynamics attacks.

Pseudo-random number generator based on asymptotic deterministic randomness

International Nuclear Information System (INIS)

Wang Kai; Pei Wenjiang; Xia Haishan; Cheung Yiuming

2008-01-01

A novel approach to generate the pseudorandom-bit sequence from the asymptotic deterministic randomness system is proposed in this Letter. We study the characteristic of multi-value correspondence of the asymptotic deterministic randomness constructed by the piecewise linear map and the noninvertible nonlinearity transform, and then give the discretized systems in the finite digitized state space. The statistic characteristics of the asymptotic deterministic randomness are investigated numerically, such as stationary probability density function and random-like behavior. Furthermore, we analyze the dynamics of the symbolic sequence. Both theoretical and experimental results show that the symbolic sequence of the asymptotic deterministic randomness possesses very good cryptographic properties, which improve the security of chaos based PRBGs and increase the resistance against entropy attacks and symbolic dynamics attacks

Peri-apatite coating decreases uncemented tibial component migration: long-term RSA results of a randomized controlled trial and limitations of short-term results.

Science.gov (United States)

Van Hamersveld, Koen T; Marang-Van De Mheen, Perla J; Nelissen, Rob G H H; Toksvig-Larsen, Sören

2018-05-09

Background and purpose - Biological fixation of uncemented knee prostheses can be improved by applying hydroxyapatite coating around the porous surface via a solution deposition technique called Peri-Apatite (PA). The 2-year results of a randomized controlled trial, evaluating the effect of PA, revealed several components with continuous migration in the second postoperative year, particularly in the uncoated group. To evaluate whether absence of early stabilization is diagnostic of loosening, we now present long-term follow-up results. Patients and methods - 60 patients were randomized to PA-coated or uncoated (porous only) total knee arthroplasty of which 58 were evaluated with radiostereometric analysis (RSA) performed at baseline, at 3 months postoperatively and at 1, 2, 5, 7, and 10 years. A linear mixed-effects model was used to analyze the repeated measurements. Results - PA-coated components had a statistically significantly lower mean migration at 10 years of 0.94 mm (95% CI 0.72-1.2) compared with the uncoated group showing a mean migration of 1.72 mm (95% CI 1.4-2.1). Continuous migration in the second postoperative year was seen in 7 uncoated components and in 1 PA-coated component. All of these implants stabilized after 2 years except for 2 uncoated components. Interpretation - Peri-apatite enhances stabilization of uncemented components. The number of components that stabilized after 2 years emphasizes the importance of longer follow-up to determine full stabilization and risk of loosening in uncemented components with biphasic migration profiles.

Topological orders in rigid states

International Nuclear Information System (INIS)

Wen, X.G.

1990-01-01

The authors study a new kind of ordering topological order in rigid states (the states with no local gapless excitations). This paper concentrates on characterization of the different topological orders. As an example the authors discuss in detail chiral spin states of 2+1 dimensional spin systems. Chiral spin states are described by the topological Chern-Simons theories in the continuum limit. The authors show that the topological orders can be characterized by a non-Abelian gauge structure over the moduli space which parametrizes a family of the model Hamiltonians supporting topologically ordered ground states. In 2 + 1 dimensions, the non-Abelian gauge structure determines possible fractional statistics of the quasi-particle excitations over the topologically ordered ground states. The dynamics of the low lying global excitations is shown to be independent of random spatial dependent perturbations. The ground state degeneracy and the non-Abelian gauge structures discussed in this paper are very robust, even against those perturbations that break translation symmetry. The authors also discuss the symmetry properties of the degenerate ground states of chiral spin states. The authors find that some degenerate ground states of chiral spin states on torus carry non-trivial quantum numbers of the 90 degrees rotation

ROPE: Recoverable Order-Preserving Embedding of Natural Language

Energy Technology Data Exchange (ETDEWEB)

Widemann, David P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wang, Eric X. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Thiagarajan, Jayaraman J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

2016-02-11

We present a novel Recoverable Order-Preserving Embedding (ROPE) of natural language. ROPE maps natural language passages from sparse concatenated one-hot representations to distributed vector representations of predetermined fixed length. We use Euclidean distance to return search results that are both grammatically and semantically similar. ROPE is based on a series of random projections of distributed word embeddings. We show that our technique typically forms a dictionary with sufficient incoherence such that sparse recovery of the original text is possible. We then show how our embedding allows for efficient and meaningful natural search and retrieval on Microsoft’s COCO dataset and the IMDB Movie Review dataset.

Evidence of significant bias in an elementary random number generator

International Nuclear Information System (INIS)

Borgwaldt, H.; Brandl, V.

1981-03-01

An elementary pseudo random number generator for isotropically distributed unit vectors in 3-dimensional space has ben tested for bias. This generator uses the IBM-suplied routine RANDU and a transparent rejection technique. The tests show clearly that non-randomness in the pseudo random numbers generated by the primary IBM generator leads to bias in the order of 1 percent in estimates obtained from the secondary random number generator. FORTRAN listings of 4 variants of the random number generator called by a simple test programme and output listings are included for direct reference. (orig.) [de

Some results of the spectra of random Schroedinger operators and their application to random point interaction models in one and three dimensions

International Nuclear Information System (INIS)

Kirsch, W.; Martinelli, F.

1981-01-01

After the derivation of weak conditions under which the potential for the Schroedinger operator is well defined the authers state an ergodicity assumption of this potential which ensures that the spectrum of this operator is a fixed non random set. Then random point interaction Hamiltonians are considered in this framework. Finally the authors consider a model where for sufficiently small fluctuations around the equilibrium positions a finite number of gaps appears. (HSI)

The relationship of dynamical heterogeneity to the Adam-Gibbs and random first-order transition theories of glass formation.

Science.gov (United States)

Starr, Francis W; Douglas, Jack F; Sastry, Srikanth

2013-03-28

We carefully examine common measures of dynamical heterogeneity for a model polymer melt and test how these scales compare with those hypothesized by the Adam and Gibbs (AG) and random first-order transition (RFOT) theories of relaxation in glass-forming liquids. To this end, we first analyze clusters of highly mobile particles, the string-like collective motion of these mobile particles, and clusters of relative low mobility. We show that the time scale of the high-mobility clusters and strings is associated with a diffusive time scale, while the low-mobility particles' time scale relates to a structural relaxation time. The difference of the characteristic times for the high- and low-mobility particles naturally explains the well-known decoupling of diffusion and structural relaxation time scales. Despite the inherent difference of dynamics between high- and low-mobility particles, we find a high degree of similarity in the geometrical structure of these particle clusters. In particular, we show that the fractal dimensions of these clusters are consistent with those of swollen branched polymers or branched polymers with screened excluded-volume interactions, corresponding to lattice animals and percolation clusters, respectively. In contrast, the fractal dimension of the strings crosses over from that of self-avoiding walks for small strings, to simple random walks for longer, more strongly interacting, strings, corresponding to flexible polymers with screened excluded-volume interactions. We examine the appropriateness of identifying the size scales of either mobile particle clusters or strings with the size of cooperatively rearranging regions (CRR) in the AG and RFOT theories. We find that the string size appears to be the most consistent measure of CRR for both the AG and RFOT models. Identifying strings or clusters with the "mosaic" length of the RFOT model relaxes the conventional assumption that the "entropic droplets" are compact. We also confirm the

A random spatial network model based on elementary postulates

Science.gov (United States)

Karlinger, Michael R.; Troutman, Brent M.

1989-01-01

A model for generating random spatial networks that is based on elementary postulates comparable to those of the random topology model is proposed. In contrast to the random topology model, this model ascribes a unique spatial specification to generated drainage networks, a distinguishing property of some network growth models. The simplicity of the postulates creates an opportunity for potential analytic investigations of the probabilistic structure of the drainage networks, while the spatial specification enables analyses of spatially dependent network properties. In the random topology model all drainage networks, conditioned on magnitude (number of first-order streams), are equally likely, whereas in this model all spanning trees of a grid, conditioned on area and drainage density, are equally likely. As a result, link lengths in the generated networks are not independent, as usually assumed in the random topology model. For a preliminary model evaluation, scale-dependent network characteristics, such as geometric diameter and link length properties, and topologic characteristics, such as bifurcation ratio, are computed for sets of drainage networks generated on square and rectangular grids. Statistics of the bifurcation and length ratios fall within the range of values reported for natural drainage networks, but geometric diameters tend to be relatively longer than those for natural networks.

Drop Spreading with Random Viscosity

Science.gov (United States)

Xu, Feng; Jensen, Oliver

2016-11-01

Airway mucus acts as a barrier to protect the lung. However as a biological material, its physical properties are known imperfectly and can be spatially heterogeneous. In this study we assess the impact of these uncertainties on the rate of spreading of a drop (representing an inhaled aerosol) over a mucus film. We model the film as Newtonian, having a viscosity that depends linearly on the concentration of a passive solute (a crude proxy for mucin proteins). Given an initial random solute (and hence viscosity) distribution, described as a Gaussian random field with a given correlation structure, we seek to quantify the uncertainties in outcomes as the drop spreads. Using lubrication theory, we describe the spreading of the drop in terms of a system of coupled nonlinear PDEs governing the evolution of film height and the vertically-averaged solute concentration. We perform Monte Carlo simulations to predict the variability in the drop centre location and width (1D) or area (2D). We show how simulation results are well described (at much lower computational cost) by a low-order model using a weak disorder expansion. Our results show for example how variability in the drop location is a non-monotonic function of the solute correlation length increases. Engineering and Physical Sciences Research Council.

Brief Strategic Family Therapy Versus Treatment as Usual: Results of a Multisite Randomized Trial for Substance Using Adolescents

Science.gov (United States)

Robbins, Michael S.; Feaster, Daniel J.; Horigian, Viviana E.; Rohrbaugh, Michael; Shoham, Varda; Bachrach, Ken; Miller, Michael; Burlew, Kathleen A.; Hodgkins, Candy; Carrion, Ibis; Vandermark, Nancy; Schindler, Eric; Werstlein, Robert; Szapocznik, José

2012-01-01

Objective To determine the effectiveness of brief strategic family therapy (BSFT; an evidence-based family therapy) compared to treatment as usual (TAU) as provided in community-based adolescent outpatient drug abuse programs. Method A randomized effectiveness trial in the National Drug Abuse Treatment Clinical Trials Network compared BSFT to TAU with a multiethnic sample of adolescents (213 Hispanic, 148 White, and 110 Black) referred for drug abuse treatment at 8 community treatment agencies nationwide. Randomization encompassed both adolescents’ families (n = 480) and the agency therapists (n = 49) who provided either TAU or BSFT services. The primary outcome was adolescent drug use, assessed monthly via adolescent self-report and urinalysis for up to 1 year post randomization. Secondary outcomes included treatment engagement (≥2 sessions), retention (≥8 sessions), and participants’ reports of family functioning 4, 8, and 12 months following randomization. Results No overall differences between conditions were observed in the trajectories of self-reports of adolescent drug use. However, the median number of days of self-reported drug use was significantly higher, χ2(1) = 5.40, p family members in treatment and in improving parent reports of family functioning, χ2(2) = 9.10, p < .011. Conclusions We discuss challenges in treatment implementation in community settings and provide recommendations for further research. PMID:21967492

Protein domain organisation: adding order

Directory of Open Access Journals (Sweden)

Kummerfeld Sarah K

2009-01-01

Full Text Available Abstract Background Domains are the building blocks of proteins. During evolution, they have been duplicated, fused and recombined, to produce proteins with novel structures and functions. Structural and genome-scale studies have shown that pairs or groups of domains observed together in a protein are almost always found in only one N to C terminal order and are the result of a single recombination event that has been propagated by duplication of the multi-domain unit. Previous studies of domain organisation have used graph theory to represent the co-occurrence of domains within proteins. We build on this approach by adding directionality to the graphs and connecting nodes based on their relative order in the protein. Most of the time, the linear order of domains is conserved. However, using the directed graph representation we have identified non-linear features of domain organization that are over-represented in genomes. Recognising these patterns and unravelling how they have arisen may allow us to understand the functional relationships between domains and understand how the protein repertoire has evolved. Results We identify groups of domains that are not linearly conserved, but instead have been shuffled during evolution so that they occur in multiple different orders. We consider 192 genomes across all three kingdoms of life and use domain and protein annotation to understand their functional significance. To identify these features and assess their statistical significance, we represent the linear order of domains in proteins as a directed graph and apply graph theoretical methods. We describe two higher-order patterns of domain organisation: clusters and bi-directionally associated domain pairs and explore their functional importance and phylogenetic conservation. Conclusion Taking into account the order of domains, we have derived a novel picture of global protein organization. We found that all genomes have a higher than expected

Influence of short range ordering and clustering on transport properties

International Nuclear Information System (INIS)

Vigier, G.; Pelletier, J.M.

1982-01-01

The influence of short range ordering and clustering phenomena on the electrical resistivity p and the thermopower S is investigated both theoretically and experimentally. According to the considered alloys either increases or decreases of transport properties may be observed when deviations from a random distribution of solute atoms occur. These observations are explained with a model based on free electrons and Born approximations the importance of the potential choice is underlined; two kinds of description of the structure factor are investigated. A good semiquantitative agreement is obtained between computed results and experimental observations

Optical detection of random features for high security applications

Science.gov (United States)

Haist, T.; Tiziani, H. J.

1998-02-01

Optical detection of random features in combination with digital signatures based on public key codes in order to recognize counterfeit objects will be discussed. Without applying expensive production techniques objects are protected against counterfeiting. Verification is done off-line by optical means without a central authority. The method is applied for protecting banknotes. Experimental results for this application are presented. The method is also applicable for identity verification of a credit- or chip-card holder.

Robustness of Dengue Complex Network under Targeted versus Random Attack

Directory of Open Access Journals (Sweden)

Hafiz Abid Mahmood Malik

2017-01-01

Full Text Available Dengue virus infection is one of those epidemic diseases that require much consideration in order to save the humankind from its unsafe impacts. According to the World Health Organization (WHO, 3.6 billion individuals are at risk because of the dengue virus sickness. Researchers are striving to comprehend the dengue threat. This study is a little commitment to those endeavors. To observe the robustness of the dengue network, we uprooted the links between nodes randomly and targeted by utilizing different centrality measures. The outcomes demonstrated that 5% targeted attack is equivalent to the result of 65% random assault, which showed the topology of this complex network validated a scale-free network instead of random network. Four centrality measures (Degree, Closeness, Betweenness, and Eigenvector have been ascertained to look for focal hubs. It has been observed through the results in this study that robustness of a node and links depends on topology of the network. The dengue epidemic network presented robust behaviour under random attack, and this network turned out to be more vulnerable when the hubs of higher degree have higher probability to fail. Moreover, representation of this network has been projected, and hub removal impact has been shown on the real map of Gombak (Malaysia.

Mean Abnormal Result Rate: Proof of Concept of a New Metric for Benchmarking Selectivity in Laboratory Test Ordering.

Science.gov (United States)

Naugler, Christopher T; Guo, Maggie

2016-04-01

There is a need to develop and validate new metrics to access the appropriateness of laboratory test requests. The mean abnormal result rate (MARR) is a proposed measure of ordering selectivity, the premise being that higher mean abnormal rates represent more selective test ordering. As a validation of this metric, we compared the abnormal rate of lab tests with the number of tests ordered on the same requisition. We hypothesized that requisitions with larger numbers of requested tests represent less selective test ordering and therefore would have a lower overall abnormal rate. We examined 3,864,083 tests ordered on 451,895 requisitions and found that the MARR decreased from about 25% if one test was ordered to about 7% if nine or more tests were ordered, consistent with less selectivity when more tests were ordered. We then examined the MARR for community-based testing for 1,340 family physicians and found both a wide variation in MARR as well as an inverse relationship between the total tests ordered per year per physician and the physician-specific MARR. The proposed metric represents a new utilization metric for benchmarking relative selectivity of test orders among physicians. © American Society for Clinical Pathology, 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Static correlation beyond the random phase approximation

DEFF Research Database (Denmark)

Olsen, Thomas; Thygesen, Kristian Sommer

2014-01-01

derived from Hedin's equations (Random Phase Approximation (RPA), Time-dependent Hartree-Fock (TDHF), Bethe-Salpeter equation (BSE), and Time-Dependent GW) all reproduce the correct dissociation limit. We also show that the BSE improves the correlation energies obtained within RPA and TDHF significantly...... and confirms that BSE greatly improves the RPA and TDHF results despite the fact that the BSE excitation spectrum breaks down in the dissociation limit. In contrast, second order screened exchange gives a poor description of the dissociation limit, which can be attributed to the fact that it cannot be derived...

Effect of randomness on multi-frequency aeroelastic responses resolved by Unsteady Adaptive Stochastic Finite Elements

International Nuclear Information System (INIS)

Witteveen, Jeroen A.S.; Bijl, Hester

2009-01-01

The Unsteady Adaptive Stochastic Finite Elements (UASFE) method resolves the effect of randomness in numerical simulations of single-mode aeroelastic responses with a constant accuracy in time for a constant number of samples. In this paper, the UASFE framework is extended to multi-frequency responses and continuous structures by employing a wavelet decomposition pre-processing step to decompose the sampled multi-frequency signals into single-frequency components. The effect of the randomness on the multi-frequency response is then obtained by summing the results of the UASFE interpolation at constant phase for the different frequency components. Results for multi-frequency responses and continuous structures show a three orders of magnitude reduction of computational costs compared to crude Monte Carlo simulations in a harmonically forced oscillator, a flutter panel problem, and the three-dimensional transonic AGARD 445.6 wing aeroelastic benchmark subject to random fields and random parameters with various probability distributions.

A randomized phase II dose-response exercise trial among colon cancer survivors: Purpose, study design, methods, and recruitment results.

Science.gov (United States)

Brown, Justin C; Troxel, Andrea B; Ky, Bonnie; Damjanov, Nevena; Zemel, Babette S; Rickels, Michael R; Rhim, Andrew D; Rustgi, Anil K; Courneya, Kerry S; Schmitz, Kathryn H

2016-03-01

Observational studies indicate that higher volumes of physical activity are associated with improved disease outcomes among colon cancer survivors. The aim of this report is to describe the purpose, study design, methods, and recruitment results of the courage trial, a National Cancer Institute (NCI) sponsored, phase II, randomized, dose-response exercise trial among colon cancer survivors. The primary objective of the courage trial is to quantify the feasibility, safety, and physiologic effects of low-dose (150 min·week(-1)) and high-dose (300 min·week(-1)) moderate-intensity aerobic exercise compared to usual-care control group over six months. The exercise groups are provided with in-home treadmills and heart rate monitors. Between January and July 2015, 1433 letters were mailed using a population-based state cancer registry; 126 colon cancer survivors inquired about participation, and 39 were randomized onto the study protocol. Age was associated with inquiry about study participation (Pclinical, or geographic characteristics were associated with study inquiry or randomization. The final trial participant was randomized in August 2015. Six month endpoint data collection was completed in February 2016. The recruitment of colon cancer survivors into an exercise trial is feasible. The findings from this trial will inform key design aspects for future phase 2 and phase 3 randomized controlled trials to examine the efficacy of exercise to improve clinical outcomes among colon cancer survivors. Copyright © 2016 Elsevier Inc. All rights reserved.

Least squares estimation in a simple random coefficient autoregressive model

DEFF Research Database (Denmark)

Johansen, S; Lange, T

2013-01-01

The question we discuss is whether a simple random coefficient autoregressive model with infinite variance can create the long swings, or persistence, which are observed in many macroeconomic variables. The model is defined by yt=stρyt−1+εt,t=1,…,n, where st is an i.i.d. binary variable with p...... we prove the curious result that View the MathML source. The proof applies the notion of a tail index of sums of positive random variables with infinite variance to find the order of magnitude of View the MathML source and View the MathML source and hence the limit of View the MathML source...

Ab initio lattice stability of fcc and hcp Fe-Mn random alloys

International Nuclear Information System (INIS)

Gebhardt, T; Music, D; Hallstedt, B; Schneider, J M; Ekholm, M; Abrikosov, I A; Vitos, L

2010-01-01

We have studied the lattice stability of face centred cubic (fcc) versus hexagonal close packed (hcp) Fe-Mn random alloys using ab initio calculations. In the calculations we considered the antiferromagnetic order of local moments, which for fcc alloys models the magnetic configuration of this phase at room temperature (below its Neel temperature) as well as their complete disorder, corresponding to paramagnetic fcc and hcp alloys. For both cases, the results are consistent with our thermodynamic calculations, obtained within the Calphad approach. For the room temperature magnetic configuration, the cross-over of the total energies of the hcp phase and the fcc phase of Fe-Mn alloys is at the expected Mn content, whereas for the magnetic configuration above the fcc Neel temperature, the hcp lattice is more stable within the whole composition range studied. The increase of the total energy difference between hcp and antiferromagnetic fcc due to additions of Mn as well as the stabilizing effect of antiferromagnetic ordering on the fcc phase are well displayed. These results are of relevance for understanding the deformation mechanisms of these random alloys.

Ab initio lattice stability of fcc and hcp Fe-Mn random alloys

Energy Technology Data Exchange (ETDEWEB)

Gebhardt, T; Music, D; Hallstedt, B; Schneider, J M [Materials Chemistry, RWTH Aachen University, D-52056 Aachen (Germany); Ekholm, M; Abrikosov, I A [Department of Physics, Chemistry and Biology (IFM), Linkoeping University, SE-581 83 Linkoeping (Sweden); Vitos, L, E-mail: gebhardt@mch.rwth-aachen.d [Department of Materials Science and Engineering, Applied Materials Physics, oyal Institute of Technology, SE-10044 Stockholm (Sweden)

2010-07-28

We have studied the lattice stability of face centred cubic (fcc) versus hexagonal close packed (hcp) Fe-Mn random alloys using ab initio calculations. In the calculations we considered the antiferromagnetic order of local moments, which for fcc alloys models the magnetic configuration of this phase at room temperature (below its Neel temperature) as well as their complete disorder, corresponding to paramagnetic fcc and hcp alloys. For both cases, the results are consistent with our thermodynamic calculations, obtained within the Calphad approach. For the room temperature magnetic configuration, the cross-over of the total energies of the hcp phase and the fcc phase of Fe-Mn alloys is at the expected Mn content, whereas for the magnetic configuration above the fcc Neel temperature, the hcp lattice is more stable within the whole composition range studied. The increase of the total energy difference between hcp and antiferromagnetic fcc due to additions of Mn as well as the stabilizing effect of antiferromagnetic ordering on the fcc phase are well displayed. These results are of relevance for understanding the deformation mechanisms of these random alloys.

Skew-orthogonal polynomials and random matrix theory

CERN Document Server

Ghosh, Saugata

2009-01-01

Orthogonal polynomials satisfy a three-term recursion relation irrespective of the weight function with respect to which they are defined. This gives a simple formula for the kernel function, known in the literature as the Christoffel-Darboux sum. The availability of asymptotic results of orthogonal polynomials and the simple structure of the Christoffel-Darboux sum make the study of unitary ensembles of random matrices relatively straightforward. In this book, the author develops the theory of skew-orthogonal polynomials and obtains recursion relations which, unlike orthogonal polynomials, depend on weight functions. After deriving reduced expressions, called the generalized Christoffel-Darboux formulas (GCD), he obtains universal correlation functions and non-universal level densities for a wide class of random matrix ensembles using the GCD. The author also shows that once questions about higher order effects are considered (questions that are relevant in different branches of physics and mathematics) the ...

Universality in random-walk models with birth and death

International Nuclear Information System (INIS)

Bender, C.M.; Boettcher, S.; Meisinger, P.N.

1995-01-01

Models of random walks are considered in which walkers are born at one site and die at all other sites. Steady-state distributions of walkers exhibit dimensionally dependent critical behavior as a function of the birth rate. Exact analytical results for a hyperspherical lattice yield a second-order phase transition with a nontrivial critical exponent for all positive dimensions D≠2, 4. Numerical studies of hypercubic and fractal lattices indicate that these exact results are universal. This work elucidates the adsorption transition of polymers at curved interfaces. copyright 1995 The American Physical Society

Cryptographic pseudo-random sequence from the spatial chaotic map

International Nuclear Information System (INIS)

Sun Fuyan; Liu Shutang

2009-01-01

A scheme for pseudo-random binary sequence generation based on the spatial chaotic map is proposed. In order to face the challenge of using the proposed PRBS in cryptography, the proposed PRBS is subjected to statistical tests which are the well-known FIPS-140-1 in the area of cryptography, and correlation properties of the proposed sequences are investigated. The proposed PRBS successfully passes all these tests. Results of statistical testing of the sequences are found encouraging. The results of statistical tests suggest strong candidature for cryptographic applications.

Modeling superhydrophobic surfaces comprised of random roughness

Science.gov (United States)

Samaha, M. A.; Tafreshi, H. Vahedi; Gad-El-Hak, M.

2011-11-01

We model the performance of superhydrophobic surfaces comprised of randomly distributed roughness that resembles natural surfaces, or those produced via random deposition of hydrophobic particles. Such a fabrication method is far less expensive than ordered-microstructured fabrication. The present numerical simulations are aimed at improving our understanding of the drag reduction effect and the stability of the air-water interface in terms of the microstructure parameters. For comparison and validation, we have also simulated the flow over superhydrophobic surfaces made up of aligned or staggered microposts for channel flows as well as streamwise or spanwise ridge configurations for pipe flows. The present results are compared with other theoretical and experimental studies. The numerical simulations indicate that the random distribution of surface roughness has a favorable effect on drag reduction, as long as the gas fraction is kept the same. The stability of the meniscus, however, is strongly influenced by the average spacing between the roughness peaks, which needs to be carefully examined before a surface can be recommended for fabrication. Financial support from DARPA, contract number W91CRB-10-1-0003, is acknowledged.

Direct test of the Gaussian auxiliary field ansatz in nonconserved order parameter phase ordering dynamics

Science.gov (United States)

Yeung, Chuck

2018-06-01

The assumption that the local order parameter is related to an underlying spatially smooth auxiliary field, u (r ⃗,t ) , is a common feature in theoretical approaches to non-conserved order parameter phase separation dynamics. In particular, the ansatz that u (r ⃗,t ) is a Gaussian random field leads to predictions for the decay of the autocorrelation function which are consistent with observations, but distinct from predictions using alternative theoretical approaches. In this paper, the auxiliary field is obtained directly from simulations of the time-dependent Ginzburg-Landau equation in two and three dimensions. The results show that u (r ⃗,t ) is equivalent to the distance to the nearest interface. In two dimensions, the probability distribution, P (u ) , is well approximated as Gaussian except for small values of u /L (t ) , where L (t ) is the characteristic length-scale of the patterns. The behavior of P (u ) in three dimensions is more complicated; the non-Gaussian region for small u /L (t ) is much larger than that in two dimensions but the tails of P (u ) begin to approach a Gaussian form at intermediate times. However, at later times, the tails of the probability distribution appear to decay faster than a Gaussian distribution.

Birth order and post-traumatic stress disorder.

Science.gov (United States)

Green, Ben; Griffiths, Emily C

2014-01-01

To compare the birth order of patients with post-traumatic stress disorder (PTSD) and adjustment disorder (AD) with population norms. 83 PTSD patients and 104 AD control patients from a psychiatric trauma clinic were diagnosed according to DCR-10 guidelines. A family history was taken as to number of siblings, and their birth order. We compared the distribution of birth order for each patient group against birth order distributions expected by chance for the same years of birth using UK population-level birth order from the Office for National Statistics. Psychiatric patients with PTSD were more likely to be from a large family, specifically to be the fifth child or later (OR 4.78, p birth order between AD patients and the general population. People with PTSD are more likely to be the youngest children from large families than expected from a random sample of people born in the same years. This association with birth order was not found for another psychiatric diagnosis AD from the same clinic. We discuss possible psychosocial and biological causes, and implications for further research.

Random analysis of bearing capacity of square footing using the LAS procedure

Science.gov (United States)

Kawa, Marek; Puła, Wojciech; Suska, Michał

2016-09-01

In the present paper, a three-dimensional problem of bearing capacity of square footing on random soil medium is analyzed. The random fields of strength parameters c and φ are generated using LAS procedure (Local Average Subdivision, Fenton and Vanmarcke 1990). The procedure used is re-implemented by the authors in Mathematica environment in order to combine it with commercial program. Since the procedure is still tested the random filed has been assumed as one-dimensional: the strength properties of soil are random in vertical direction only. Individual realizations of bearing capacity boundary-problem with strength parameters of medium defined the above procedure are solved using FLAC3D Software. The analysis is performed for two qualitatively different cases, namely for the purely cohesive and cohesive-frictional soils. For the latter case the friction angle and cohesion have been assumed as independent random variables. For these two cases the random square footing bearing capacity results have been obtained for the range of fluctuation scales from 0.5 m to 10 m. Each time 1000 Monte Carlo realizations have been performed. The obtained results allow not only the mean and variance but also the probability density function to be estimated. An example of application of this function for reliability calculation has been presented in the final part of the paper.

NMR determination of the order parameter in proton and deuteron glasses

International Nuclear Information System (INIS)

Blinc, R.; Dolinsek, J.; Zalar, B.

1989-01-01

The inhomogeneous broadening of the ND + deuteron, O-D--O deuteron and 87 Rb quadrapole perturbed NMR spectra in Rb 0.56 (ND 4 ) 0.44 D 2 PO 4 is used for a direct determination of the Edwards-Anderson pseudo-spin glass order parameter. The data provide strong support for a model where the basic difference between magnetic spin glasses and proton or deuteron glasses is the presence of an inherent random field resulting from substitutional disorder which linearly couples to the O-D--O pseudo spins. In these systems we do not deal with a transition from a paraelectric to a pseudo-spin glass phase but rather with a transition from an ergodic pseudo-spin glass phase with a single order parameter q to a non-ergodic pseudo-spin glass phase with an infinite number of order parameters. (author). 11 refs.; 6 figs

A theoretical and numerical study of polarimetric scattering and emission from random rough surfaces with anisotropic directional spectrum

Science.gov (United States)

Yueh, S. H.; Kwok, R.

1993-01-01

In this paper, theoretical and numerical results of the polarimetric scattering and emission from random rough surfaces with anisotropic directional spectrum are presented for the remote sensing of ocean and soil surfaces. The polarimetric scattered field for rough dielectric surfaces is derived to the second order by the small perturbation method (SPM). It is found that the second-order scattered field is coherent in nature, and its coefficients for different polarizations present the lowest-order corrections to the Fresnel reflection coefficients of the surfaces. In addition, the cross-polarized (HV and VH) components of the coherent fields are reciprocal and not zero for surfaces with anisotropic directional spectrum when the azimuth angle of the incident direction is not aligned with the symmetry directions of surfaces. In order to verify the energy conservation condition of the theoretical results, which is important if the theory is to be applied to the passive polarimetry of rough surfaces, a Monte Carlo simulation is performed to numerically calculate the polarimetric reflectivities of one-dimensional random rough surfaces which are generated with a prescribed power-law spectrum in the spectral domain and transformed to the spatial domain by the FFT. The surfaces simulated by this approach are periodic with the period corresponding to the low-wavenumber cutoff. To calculate the scattering from periodic dielectric surfaces, the authors present a new numerical technique which applies the Floquet theorem to reduce the problem to one period and does not require the evaluation of one-dimensional periodic Green's function used in the conventional method of moment formulation. Once the scattering coefficients are obtained, the polarimetric Stokes vectors for the emission from the random surfaces are then calculated according to the Kirchhoff's law and are illustrated as functions of relative azimuth observation and row directions. The second-order SPM is also

Random clustering ferns for multimodal object recognition

OpenAIRE

Villamizar Vergel, Michael Alejandro; Garrell Zulueta, Anais; Sanfeliu Cortés, Alberto; Moreno-Noguer, Francesc

2017-01-01

The final publication is available at link.springer.com We propose an efficient and robust method for the recognition of objects exhibiting multiple intra-class modes, where each one is associated with a particular object appearance. The proposed method, called random clustering ferns, combines synergically a single and real-time classifier, based on the boosted assembling of extremely randomized trees (ferns), with an unsupervised and probabilistic approach in order to recognize efficient...

Reducing thermal conductivity of binary alloys below the alloy limit via chemical ordering

International Nuclear Information System (INIS)

Duda, John C; English, Timothy S; Jordan, Donald A; Norris, Pamela M; Soffa, William A

2011-01-01

Substitutional solid solutions that exist in both ordered and disordered states will exhibit markedly different physical properties depending on their exact crystallographic configuration. Many random substitutional solid solutions (alloys) will display a tendency to order given the appropriate kinetic and thermodynamic conditions. Such order-disorder transitions will result in major crystallographic reconfigurations, where the atomic basis, symmetry, and periodicity of the alloy change dramatically. Consequently, the dominant scattering mechanism in ordered alloys will be different than that in disordered alloys. In this study, we present a hypothesis that ordered alloys can exhibit lower thermal conductivities than their disordered counterparts at elevated temperatures. To validate this hypothesis, we investigate the phononic transport properties of disordered and ordered AB Lennard-Jones alloys via non-equilibrium molecular dynamics and harmonic lattice dynamics calculations. It is shown that the thermal conductivity of an ordered alloy is the same as the thermal conductivity of the disordered alloy at ∼0.6T melt and lower than that of the disordered alloy above 0.8T melt .

Post-stratification based on a choice of a randomization device

Directory of Open Access Journals (Sweden)

Sarjinder Singh

2014-06-01

Full Text Available In this paper, we use the idea of post-stratification based on the respondents’ choice of a particular randomization device in order to estimate the population proportion of a sensitive characteristic. The proposed idea gives full freedom to the respondents and is expected to result in greater cooperation from them as well as to provide some increase in the relative efficiency of the newly proposed estimator.

Local Treatment of Unresectable Colorectal Liver Metastases: Results of a Randomized Phase II Trial.

Science.gov (United States)

Ruers, Theo; Van Coevorden, Frits; Punt, Cornelis J A; Pierie, Jean-Pierre E N; Borel-Rinkes, Inne; Ledermann, Jonathan A; Poston, Graeme; Bechstein, Wolf; Lentz, Marie-Ange; Mauer, Murielle; Folprecht, Gunnar; Van Cutsem, Eric; Ducreux, Michel; Nordlinger, Bernard

2017-09-01

Tumor ablation is often employed for unresectable colorectal liver metastases. However, no survival benefit has ever been demonstrated in prospective randomized studies. Here, we investigate the long-term benefits of such an aggressive approach. In this randomized phase II trial, 119 patients with unresectable colorectal liver metastases (n  38%) was met. We now report on long-term OS results. All statistical tests were two-sided. The analyses were according to intention to treat. At a median follow up of 9.7 years, 92 of 119 (77.3%) patients had died: 39 of 60 (65.0%) in the combined modality arm and 53 of 59 (89.8%) in the systemic treatment arm. Almost all patients died of progressive disease (35 patients in the combined modality arm, 49 patients in the systemic treatment arm). There was a statistically significant difference in OS in favor of the combined modality arm (hazard ratio [HR] = 0.58, 95% confidence interval [CI] = 0.38 to 0.88, P = .01). Three-, five-, and eight-year OS were 56.9% (95% CI = 43.3% to 68.5%), 43.1% (95% CI = 30.3% to 55.3%), 35.9% (95% CI = 23.8% to 48.2%), respectively, in the combined modality arm and 55.2% (95% CI = 41.6% to 66.9%), 30.3% (95% CI = 19.0% to 42.4%), 8.9% (95% CI = 3.3% to 18.1%), respectively, in the systemic treatment arm. Median OS was 45.6 months (95% CI = 30.3 to 67.8 months) in the combined modality arm vs 40.5 months (95% CI = 27.5 to 47.7 months) in the systemic treatment arm. This phase II trial is the first randomized study demonstrating that aggressive local treatment can prolong OS in patients with unresectable colorectal liver metastases. © The Author 2017. Published by Oxford University Press.

Existence and controllability results for damped second order impulsive functional differential systems with state-dependent delay

Directory of Open Access Journals (Sweden)

M. Mallika Arjunan

2014-01-01

Full Text Available In this paper, we investigate the existence and controllability of mild solutions for a damped second order impulsive functional differential equation with state-dependent delay in Banach spaces. The results are obtained by using Sadovskii's fixed point theorem combined with the theories of a strongly continuous cosine family of bounded linear operators. Finally, an example is provided to illustrate the main results.

2D gravity, random surfaces and all that

International Nuclear Information System (INIS)

Ambjoern, J.

1990-11-01

I review the recent progress in 2d gravity and discuss the new numerical simulations for 2d gravity and for random surfaces in d>2. The random surface theories of interest in d>2 have extrinsic curvature terms, and for a finite value of the extrinsic curvature coupling there seems to be a second order phase transition where the string tension scales. (orig.)

Fractional Brownian motions via random walk in the complex plane and via fractional derivative. Comparison and further results on their Fokker-Planck equations

International Nuclear Information System (INIS)

Jumarie, Guy

2004-01-01

There are presently two different models of fractional Brownian motions available in the literature: the Riemann-Liouville fractional derivative of white noise on the one hand, and the complex-valued Brownian motion of order n defined by using a random walk in the complex plane, on the other hand. The paper provides a comparison between these two approaches, and in addition, takes this opportunity to contribute some complements. These two models are more or less equivalent on the theoretical standpoint for fractional order between 0 and 1/2, but their practical significances are quite different. Otherwise, for order larger than 1/2, the fractional derivative model has no counterpart in the complex plane. These differences are illustrated by an example drawn from mathematical finance. Taylor expansion of fractional order provides the expression of fractional difference in terms of finite difference, and this allows us to improve the derivation of Fokker-Planck equation and Kramers-Moyal expansion, and to get more insight in their relation with stochastic differential equations of fractional order. In the case of multi-fractal systems, the Fokker-Planck equation can be solved by using path integrals, and the fractional dynamic equations of the state moments of the stochastic system can be easily obtained. By combining fractional derivative and complex white noise of order n, one obtains a family of complex-valued fractional Brownian motions which exhibits long-range dependence. The conclusion outlines suggestions for further research, mainly regarding Lorentz transformation of fractional noises

Shear- and magnetic-field-induced ordering in magnetic nanoparticle dispersion from small-angle neutron scattering

International Nuclear Information System (INIS)

Krishnamurthy, V.V.; Bhandar, A.S.; Piao, M.; Zoto, I.; Lane, A.M.; Nikles, D.E.; Wiest, J.M.; Mankey, G.J.; Porcar, L.; Glinka, C.J.

2003-01-01

Small-angle neutron scattering experiments have been performed to investigate orientational ordering of a dispersion of rod-shaped ferromagnetic nanoparticles under the influence of shear flow and static magnetic field. In this experiment, the flow and flow gradient directions are perpendicular to the direction of the applied magnetic field. The scattering intensity is isotropic in zero-shear-rate or zero-applied-field conditions, indicating that the particles are randomly oriented. Anisotropic scattering is observed both in a shear flow and in a static magnetic field, showing that both flow and field induce orientational order in the dispersion. The anisotropy increases with the increase of field and with the increase of shear rate. Three states of order have been observed with the application of both shear flow and magnetic field. At low shear rates, the particles are aligned in the field direction. When increasing shear rate is applied, the particles revert to random orientations at a characteristic shear rate that depends on the strength of the applied magnetic field. Above the characteristic shear rate, the particles align along the flow direction. The experimental results agree qualitatively with the predictions of a mean field model

The additive congruential random number generator--A special case of a multiple recursive generator

Science.gov (United States)

Wikramaratna, Roy S.

2008-07-01

This paper considers an approach to generating uniformly distributed pseudo-random numbers which works well in serial applications but which also appears particularly well-suited for application on parallel processing systems. Additive Congruential Random Number (ACORN) generators are straightforward to implement for arbitrarily large order and modulus; if implemented using integer arithmetic, it becomes possible to generate identical sequences on any machine. Previously published theoretical analysis has demonstrated that a kth order ACORN sequence approximates to being uniformly distributed in up to k dimensions, for any given k. ACORN generators can be constructed to give period lengths exceeding any given number (for example, with period length in excess of 230p, for any given p). Results of empirical tests have demonstrated that, if p is greater than or equal to 2, then the ACORN generator can be used successfully for generating double precision uniform random variates. This paper demonstrates that an ACORN generator is a particular case of a multiple recursive generator (and, therefore, also a special case of a matrix generator). Both these latter approaches have been widely studied, and it is to be hoped that the results given in the present paper will lead to greater confidence in using the ACORN generators.

Enhancing Motion-In-Depth Perception of Random-Dot Stereograms.

Science.gov (United States)

Zhang, Di; Nourrit, Vincent; De Bougrenet de la Tocnaye, Jean-Louis

2018-07-01

Random-dot stereograms have been widely used to explore the neural mechanisms underlying binocular vision. Although they are a powerful tool to stimulate motion-in-depth (MID) perception, published results report some difficulties in the capacity to perceive MID generated by random-dot stereograms. The purpose of this study was to investigate whether the performance of MID perception could be improved using an appropriate stimulus design. Sixteen inexperienced observers participated in the experiment. A training session was carried out to improve the accuracy of MID detection before the experiment. Four aspects of stimulus design were investigated: presence of a static reference, background texture, relative disparity, and stimulus contrast. Participants' performance in MID direction discrimination was recorded and compared to evaluate whether varying these factors helped MID perception. Results showed that only the presence of background texture had a significant effect on MID direction perception. This study provides suggestions for the design of 3D stimuli in order to facilitate MID perception.

Numerical Inversion for the Multiple Fractional Orders in the Multiterm TFDE

OpenAIRE

Sun, Chunlong; Li, Gongsheng; Jia, Xianzheng

2017-01-01

The fractional order in a fractional diffusion model is a key parameter which characterizes the anomalous diffusion behaviors. This paper deals with an inverse problem of determining the multiple fractional orders in the multiterm time-fractional diffusion equation (TFDE for short) from numerics. The homotopy regularization algorithm is applied to solve the inversion problem using the finite data at one interior point in the space domain. The inversion fractional orders with random noisy data...

Random walks with shape prior for cochlea segmentation in ex vivo μCT

DEFF Research Database (Denmark)

Ruiz Pujadas, Esmeralda; Kjer, Hans Martin; Piella, Gemma

2016-01-01

Purpose Cochlear implantation is a safe and effective surgical procedure to restore hearing in deaf patients. However, the level of restoration achieved may vary due to differences in anatomy, implant type and surgical access. In order to reduce the variability of the surgical outcomes, we...... propose a new framework for cochlea segmentation in ex vivo μCT images using random walks where a distance-based shape prior is combined with a region term estimated by a Gaussian mixture model. The prior is also weighted by a confidence map to adjust its influence according to the strength of the image...... contour. Random walks is performed iteratively, and the prior mask is aligned in every iteration. Results We tested the proposed approach in ten μCT data sets and compared it with other random walks-based segmentation techniques such as guided random walks (Eslami et al. in Med Image Anal 17...

ATG-Fresenius treatment and low-dose tacrolimus: results of a randomized controlled trial in liver transplantation.

Science.gov (United States)

Benítez, C E; Puig-Pey, I; López, M; Martínez-Llordella, M; Lozano, J J; Bohne, F; Londoño, M C; García-Valdecasas, J C; Bruguera, M; Navasa, M; Rimola, A; Sánchez-Fueyo, A

2010-10-01

We report the results of a prospective randomized controlled trial in liver transplantation assessing the efficacy and safety of antithymocyte globulin (ATG-Fresenius) plus tacrolimus monotherapy at gradually decreasing doses. Patients were randomized to either: (a) standard-dose tacrolimus plus steroids;or (b) peritransplant ATG-Fresenius plus reduced-dose tacrolimus monotherapy followed by weaning of tacrolimus starting 3 months after transplantation. The primary end-point was the achievement of very low-dose tacrolimus (every-other-day or once daily dose with Fresenius group but no benefits in terms of improved renal function, lower metabolic complications or increased prevalence of tolerance-related biomarkers were observed. In conclusion, the use of ATG-Fresenius and tacrolimus at gradually decreasing doses was associated with a high rate of rejection, did not allow for the administration of very low doses of tacrolimus and failed to provide detectable clinical benefits. ClinicalTrials.gov identifier: NCT00436722. © 2010 The Authors Journal compilation © 2010 The American Society of Transplantation and the American Society of Transplant Surgeons.

Order-disorder transition of vortex matter in Mg0.95B2

International Nuclear Information System (INIS)

Oliveira, A.A.M.; Sharma, P.A.; Hur, N.; Cheong, S-W.; Ortiz, W.A.

2008-01-01

Third-harmonic susceptibility has been employed to probe the order-disorder transition of vortex matter of a good-quality sample of MgB 2 with random disorder. In the major part of the temperature interval, the measured boundary line can be adjusted by a power-law function, in accordance with theoretical models for the melting of the ordered phase of a 3D vortex-glass. For larger temperatures, however, thermally-induced depinning anticipates disorder, which is also predictable for the vortex matter behavior of a clean system with small amounts of randomly distributed disorder, as is the case of the Mg 0.95 B 2 sample studied here

Partner-Assisted Emotional Disclosure for Patients with GI Cancer: Results from a Randomized Controlled Trial

Science.gov (United States)

Porter, Laura S.; Keefe, Francis J.; Baucom, Donald H.; Hurwitz, Herbert; Moser, Barry; Patterson, Emily; Kim, Hong Jin

2009-01-01

Background For patients with cancer who are married or in an intimate relationship, their relationships with their partners play a critical role in their adaptation to their illness. However, cancer patients and their partners often have difficulty in talking with each other about their cancer-related concerns. Difficulties in communication may ultimately compromise both the patient-partner relationship and the patient's psychological adjustment. The present study tested the efficacy of a novel partner-assisted emotional disclosure intervention in a sample of patients with gastrointestinal (GI) cancer. Methods 130 patients with GI cancer and their partners were randomly assigned to receive four sessions of either partner-assisted emotional disclosure or a couples cancer education/support intervention. Patients and partners completed measures of relationship quality, intimacy with their partner, and psychological distress before randomization and at the end of the intervention sessions. Data were analyzed using multilevel modeling. Results Compared to an education/support condition, the partner-assisted emotional disclosure condition led to improvements in relationship quality and intimacy for couples in which the patient initially reported higher levels of holding back from discussing cancer-related concerns. Conclusions Partner-assisted emotional disclosure is a novel intervention that builds on both the private emotional disclosure and the cognitive-behavioral marital literature. The results of this study suggest that this intervention may be beneficial for couples in which the patient tends to hold back from discussing concerns. Future research on methods of enhancing the effects of partner-assisted emotional disclosure is warranted. PMID:19731357

Breast-conserving therapy with partial or whole breast irradiation: Ten-year results of the Budapest randomized trial

International Nuclear Information System (INIS)

Polgár, Csaba; Fodor, János; Major, Tibor; Sulyok, Zoltán; Kásler, Miklós

2013-01-01

Background and purpose: To report the long-term results of a single-institution randomized study comparing the results of breast-conserving treatment with partial breast irradiation (PBI) or conventional whole breast irradiation (WBI). Patients and methods: Between 1998 and 2004, 258 selected women with pT1 pN0-1mi M0, grade 1–2, non-lobular breast cancer without the presence of extensive intraductal component and resected with negative margins were randomized after BCS to receive 50 Gy WBI (n = 130) or PBI (n = 128). The latter consisted of either 7 × 5.2 Gy high-dose-rate (HDR) multi-catheter brachytherapy (BT; n = 88) or 50 Gy electron beam (EB) irradiation (n = 40). Primary endpoint was local recurrence (LR) as a first event. Secondary endpoints were overall survival (OS), cancer-specific survival (CSS), disease-free survival (DFS), and cosmetic results. Results: After a median follow up of 10.2 years, the ten-year actuarial rate of LR was 5.9% and 5.1% in PBI and WBI arms, respectively (p = 0.77). There was no significant difference in the ten-year probability of OS (80% vs 82%), CSS (94% vs 92%), and DFS (85% vs 84%), either. The rate of excellent-good cosmetic result was 81% in the PBI, and 63% in the control group (p < 0.01). Conclusions: Partial breast irradiation delivered by interstitial HDR BT or EB for a selected group of early-stage breast cancer patients produces similar ten-year results to those achieved with conventional WBI. Significantly better cosmetic outcome can be achieved with HDR BT implants compared with the outcome after WBI

Random unitary operations and quantum Darwinism

International Nuclear Information System (INIS)

Balaneskovic, Nenad

2016-01-01

We study the behavior of Quantum Darwinism (Zurek, Nature Physics 5, 181-188 (2009)) within the iterative, random unitary operations qubit-model of pure decoherence (Novotn'y et al, New Jour. Phys. 13, 053052 (2011)). We conclude that Quantum Darwinism, which describes the quantum mechanical evolution of an open system from the point of view of its environment, is not a generic phenomenon, but depends on the specific form of initial states and on the type of system-environment interactions. Furthermore, we show that within the random unitary model the concept of Quantum Darwinism enables one to explicitly construct and specify artificial initial states of environment that allow to store information about an open system of interest and its pointer-basis with maximal efficiency. Furthermore, we investigate the behavior of Quantum Darwinism after introducing dissipation into the iterative random unitary qubit model with pure decoherence in accord with V. Scarani et al (Phys. Rev. Lett. 88, 097905 (2002)) and reconstruct the corresponding dissipative attractor space. We conclude that in Zurek's qubit model Quantum Darwinism depends on the order in which pure decoherence and dissipation act upon an initial state of the entire system. We show explicitly that introducing dissipation into the random unitary evolution model in general suppresses Quantum Darwinism (regardless of the order in which decoherence and dissipation are applied) for all positive non-zero values of the dissipation strength parameter, even for those initial state configurations which, in Zurek's qubit model and in the random unitary model with pure decoherence, would lead to Quantum Darwinism. Finally, we discuss what happens with Quantum Darwinism after introducing into the iterative random unitary qubit model with pure decoherence (asymmetric) dissipation and dephasing, again in accord with V. Scarani et al (Phys. Rev. Lett. 88, 097905 (2002)), and reconstruct the corresponding

Examination of Cognitive Function During Six Months of Calorie Restriction: Results of a Randomized Controlled Trial

Science.gov (United States)

Martin, Corby K.; Anton, Stephen D.; Han, Hongmei; York-Crowe, Emily; Redman, Leanne M.; Ravussin, Eric; Williamson, Donald A.

2009-01-01

Background Calorie restriction increases longevity in many organisms, and calorie restriction or its mimetic might increase longevity in humans. It is unclear if calorie restriction/dieting contributes to cognitive impairment. During this randomized controlled trial, the effect of 6 months of calorie restriction on cognitive functioning was tested. Methods Participants (n = 48) were randomized to one of four groups: (1) control (weight maintenance), (2) calorie restriction (CR; 25% restriction), (3) CR plus structured exercise (CR + EX, 12.5% restriction plus 12.5% increased energy expenditure via exercise), or (4) low-calorie diet (LCD; 890 kcal/d diet until 15% weight loss, followed by weight maintenance). Cognitive tests (verbal memory, visual memory, attention/concentration) were conducted at baseline and months 3 and 6. Mixed linear models tested if cognitive function changed significantly from baseline to months 3 and 6, and if this change differed by group. Correlation analysis was used to determine if average daily energy deficit (quantified from change in body energy stores) was associated with change in cognitive test performance for the three dieting groups combined. Results No consistent pattern of verbal memory, visual retention/memory, or attention/concentration deficits emerged during the trial. Daily energy deficit was not significantly associated with change in cognitive test performance. Conclusions This randomized controlled trial suggests that calorie restriction/dieting was not associated with a consistent pattern of cognitive impairment. These conclusions must be interpreted in the context of study limitations, namely small sample size and limited statistical power. Previous reports of cognitive impairment might reflect sampling biases or information processing biases. PMID:17518698

Joint Ordering and Pricing Decisions for New Repeat-Purchase Products

Directory of Open Access Journals (Sweden)

Xiang Wu

2015-01-01

Full Text Available This paper studies ordering and pricing problems for new repeat-purchase products. We incorporate the repeat-purchase rate and price effects into the Bass model to characterize the demand pattern. We consider two decision models: (1 two-stage decision model, in which the sales division chooses a price to maximize the gross profit and the purchasing division determines an optimal ordering decision to minimize the total cost under a given demand subsequently, and (2 joint decision model, in which the firm makes ordering and pricing decisions simultaneously to maximize the profit. We combine the generalized Bass model with dynamic lot sizing model to formulate the joint decision model. We apply both models to a specific imported food provided by an online fresh produce retailer in Central China, solve them by Gaussian Random-Walk and Wagner-Whitin based algorithms, and observe three results. First, joint pricing and ordering decisions bring more significant profits than making pricing and ordering decisions sequentially. Second, a great initiative in adoption significantly increases price premium and profit. Finally, the optimal price shows a U-shape (i.e., decreases first and increases later relationship and the profit increases gradually with the repeat-purchase rate when it is still not very high.

A new simple technique for improving the random properties of chaos-based cryptosystems

Science.gov (United States)

Garcia-Bosque, M.; Pérez-Resa, A.; Sánchez-Azqueta, C.; Celma, S.

2018-03-01

A new technique for improving the security of chaos-based stream ciphers has been proposed and tested experimentally. This technique manages to improve the randomness properties of the generated keystream by preventing the system to fall into short period cycles due to digitation. In order to test this technique, a stream cipher based on a Skew Tent Map algorithm has been implemented on a Virtex 7 FPGA. The randomness of the keystream generated by this system has been compared to the randomness of the keystream generated by the same system with the proposed randomness-enhancement technique. By subjecting both keystreams to the National Institute of Standards and Technology (NIST) tests, we have proved that our method can considerably improve the randomness of the generated keystreams. In order to incorporate our randomness-enhancement technique, only 41 extra slices have been needed, proving that, apart from effective, this method is also efficient in terms of area and hardware resources.

Random walk of passive tracers among randomly moving obstacles.

Science.gov (United States)

Gori, Matteo; Donato, Irene; Floriani, Elena; Nardecchia, Ilaria; Pettini, Marco

2016-04-14

This study is mainly motivated by the need of understanding how the diffusion behavior of a biomolecule (or even of a larger object) is affected by other moving macromolecules, organelles, and so on, inside a living cell, whence the possibility of understanding whether or not a randomly walking biomolecule is also subject to a long-range force field driving it to its target. By means of the Continuous Time Random Walk (CTRW) technique the topic of random walk in random environment is here considered in the case of a passively diffusing particle among randomly moving and interacting obstacles. The relevant physical quantity which is worked out is the diffusion coefficient of the passive tracer which is computed as a function of the average inter-obstacles distance. The results reported here suggest that if a biomolecule, let us call it a test molecule, moves towards its target in the presence of other independently interacting molecules, its motion can be considerably slowed down.

Determinants of translation speed are randomly distributed across transcripts resulting in a universal scaling of protein synthesis times

Science.gov (United States)

Sharma, Ajeet K.; Ahmed, Nabeel; O'Brien, Edward P.

2018-02-01

Ribosome profiling experiments have found greater than 100-fold variation in ribosome density along mRNA transcripts, indicating that individual codon elongation rates can vary to a similar degree. This wide range of elongation times, coupled with differences in codon usage between transcripts, suggests that the average codon translation-rate per gene can vary widely. Yet, ribosome run-off experiments have found that the average codon translation rate for different groups of transcripts in mouse stem cells is constant at 5.6 AA/s. How these seemingly contradictory results can be reconciled is the focus of this study. Here, we combine knowledge of the molecular factors shown to influence translation speed with genomic information from Escherichia coli, Saccharomyces cerevisiae and Homo sapiens to simulate the synthesis of cytosolic proteins in these organisms. The model recapitulates a near constant average translation rate, which we demonstrate arises because the molecular determinants of translation speed are distributed nearly randomly amongst most of the transcripts. Consequently, codon translation rates are also randomly distributed and fast-translating segments of a transcript are likely to be offset by equally probable slow-translating segments, resulting in similar average elongation rates for most transcripts. We also show that the codon usage bias does not significantly affect the near random distribution of codon translation rates because only about 10 % of the total transcripts in an organism have high codon usage bias while the rest have little to no bias. Analysis of Ribo-Seq data and an in vivo fluorescent assay supports these conclusions.

Spatial analysis of "crazy quilts", a class of potentially random aesthetic artefacts.

Directory of Open Access Journals (Sweden)

Gesche Westphal-Fitch

Full Text Available Human artefacts in general are highly structured and often display ordering principles such as translational, reflectional or rotational symmetry. In contrast, human artefacts that are intended to appear random and non symmetrical are very rare. Furthermore, many studies show that humans find it extremely difficult to recognize or reproduce truly random patterns or sequences. Here, we attempt to model two-dimensional decorative spatial patterns produced by humans that show no obvious order. "Crazy quilts" represent a historically important style of quilt making that became popular in the 1870s, and lasted about 50 years. Crazy quilts are unusual because unlike most human artefacts, they are specifically intended to appear haphazard and unstructured. We evaluate the degree to which this intention was achieved by using statistical techniques of spatial point pattern analysis to compare crazy quilts with regular quilts from the same region and era and to evaluate the fit of various random distributions to these two quilt classes. We found that the two quilt categories exhibit fundamentally different spatial characteristics: The patch areas of crazy quilts derive from a continuous random distribution, while area distributions of regular quilts consist of Gaussian mixtures. These Gaussian mixtures derive from regular pattern motifs that are repeated and we suggest that such a mixture is a distinctive signature of human-made visual patterns. In contrast, the distribution found in crazy quilts is shared with many other naturally occurring spatial patterns. Centroids of patches in the two quilt classes are spaced differently and in general, crazy quilts but not regular quilts are well-fitted by a random Strauss process. These results indicate that, within the constraints of the quilt format, Victorian quilters indeed achieved their goal of generating random structures.

Spatial analysis of "crazy quilts", a class of potentially random aesthetic artefacts.

Science.gov (United States)

Westphal-Fitch, Gesche; Fitch, W Tecumseh

2013-01-01

Human artefacts in general are highly structured and often display ordering principles such as translational, reflectional or rotational symmetry. In contrast, human artefacts that are intended to appear random and non symmetrical are very rare. Furthermore, many studies show that humans find it extremely difficult to recognize or reproduce truly random patterns or sequences. Here, we attempt to model two-dimensional decorative spatial patterns produced by humans that show no obvious order. "Crazy quilts" represent a historically important style of quilt making that became popular in the 1870s, and lasted about 50 years. Crazy quilts are unusual because unlike most human artefacts, they are specifically intended to appear haphazard and unstructured. We evaluate the degree to which this intention was achieved by using statistical techniques of spatial point pattern analysis to compare crazy quilts with regular quilts from the same region and era and to evaluate the fit of various random distributions to these two quilt classes. We found that the two quilt categories exhibit fundamentally different spatial characteristics: The patch areas of crazy quilts derive from a continuous random distribution, while area distributions of regular quilts consist of Gaussian mixtures. These Gaussian mixtures derive from regular pattern motifs that are repeated and we suggest that such a mixture is a distinctive signature of human-made visual patterns. In contrast, the distribution found in crazy quilts is shared with many other naturally occurring spatial patterns. Centroids of patches in the two quilt classes are spaced differently and in general, crazy quilts but not regular quilts are well-fitted by a random Strauss process. These results indicate that, within the constraints of the quilt format, Victorian quilters indeed achieved their goal of generating random structures.

[Stimulation of wound healing by tetrachlordecaoxide. Results of a randomized double-blind study].

Science.gov (United States)

Hinz, J; Hautzinger, H; Helling, J; Schirren, G; Sell, G; Stahl, K W; Kühne, F W

1984-05-10

In 38 patients with chronic therapeutically resistant wounds, which, in 25 cases, had been existing for more than one year, Tetrachlorodecaoxide ( TCDO ) in a water solution containing glycerin was analyzed for its capacity to induce wound healing and compared in this respect to the standard in moist wound treatment, physiological sodium chloride. The results of the clinical trial demonstrate that the TCDO solution is significantly superior to physiological saline in local wound treatment regarding the degree of wound smear reduction, the formation of wound granulation tissue, the stimulation of epithelisation on the wound borders and the shrinking of the wound surface. The differences in therapeutic efficiency are so large that, in spite of the relatively small patient samples (21 + 17) it was possible to verify the superiority of a method for wound treatment in a randomized double blind clinical trial.

Effects of dilution on the magnetic ordering of a two-dimensional lattice of dipolar magnets

International Nuclear Information System (INIS)

Patchedjiev, S M; Whitehead, J P; De'Bell, K

2005-01-01

Monte Carlo simulations are used to study the effects of dilution by random vacancies on the phenomenon of order arising from disorder in an ultrathin magnetic film. At very low concentrations of vacancies, both the collinear ordered phase observed in the undiluted system and the microvortex state are observed, and the boundary on which the reorientation transition between these states occurs is found to be consistent with the predictions of earlier work. However, even at vacancy densities as low as 0.5% there is evidence that the vacancies result in a energy landscape with a number of very nearly degenerate minima

POLICY IMPLICATIONS OF ADJUSTING RANDOMIZED TRIAL DATA FOR ECONOMIC EVALUATIONS: A DEMONSTRATION FROM THE ASCUS-LSIL TRIAGE STUDY

Science.gov (United States)

Campos, Nicole G.; Castle, Philip E.; Schiffman, Mark; Kim, Jane J.

2013-01-01

Background Although the randomized controlled trial (RCT) is widely considered the most reliable method for evaluation of health care interventions, challenges to both internal and external validity exist. Thus, the efficacy of an intervention in a trial setting does not necessarily represent the real-world performance that decision makers seek to inform comparative effectiveness studies and economic evaluations. Methods Using data from the ASCUS-LSIL Triage Study (ALTS), we performed a simplified economic evaluation of age-based management strategies to detect cervical intraepithelial neoplasia grade 3 (CIN3) among women who were referred to the study with low-grade squamous intraepithelial lesions (LSIL). We used data from the trial itself to adjust for 1) potential lead time bias and random error that led to variation in the observed prevalence of CIN3 by study arm, and 2) potential ascertainment bias among providers in the most aggressive management arm. Results We found that using unadjusted RCT data may result in counterintuitive cost-effectiveness results when random error and/or bias are present. Following adjustment, the rank order of management strategies changed for two of the three age groups we considered. Conclusion Decision analysts need to examine study design, available trial data and cost-effectiveness results closely in order to detect evidence of potential bias. Adjustment for random error and bias in RCTs may yield different policy conclusions relative to unadjusted trial data. PMID:22147881

Operator Spreading in Random Unitary Circuits

Science.gov (United States)

Nahum, Adam; Vijay, Sagar; Haah, Jeongwan

2018-04-01

Random quantum circuits yield minimally structured models for chaotic quantum dynamics, which are able to capture, for example, universal properties of entanglement growth. We provide exact results and coarse-grained models for the spreading of operators by quantum circuits made of Haar-random unitaries. We study both 1 +1 D and higher dimensions and argue that the coarse-grained pictures carry over to operator spreading in generic many-body systems. In 1 +1 D , we demonstrate that the out-of-time-order correlator (OTOC) satisfies a biased diffusion equation, which gives exact results for the spatial profile of the OTOC and determines the butterfly speed vB. We find that in 1 +1 D , the "front" of the OTOC broadens diffusively, with a width scaling in time as t1 /2. We address fluctuations in the OTOC between different realizations of the random circuit, arguing that they are negligible in comparison to the broadening of the front within a realization. Turning to higher dimensions, we show that the averaged OTOC can be understood exactly via a remarkable correspondence with a purely classical droplet growth problem. This implies that the width of the front of the averaged OTOC scales as t1 /3 in 2 +1 D and as t0.240 in 3 +1 D (exponents of the Kardar-Parisi-Zhang universality class). We support our analytic argument with simulations in 2 +1 D . We point out that, in two or higher spatial dimensions, the shape of the spreading operator at late times is affected by underlying lattice symmetries and, in general, is not spherical. However, when full spatial rotational symmetry is present in 2 +1 D , our mapping implies an exact asymptotic form for the OTOC, in terms of the Tracy-Widom distribution. For an alternative perspective on the OTOC in 1 +1 D , we map it to the partition function of an Ising-like statistical mechanics model. As a result of special structure arising from unitarity, this partition function reduces to a random walk calculation which can be

Image compression-encryption algorithms by combining hyper-chaotic system with discrete fractional random transform

Science.gov (United States)

Gong, Lihua; Deng, Chengzhi; Pan, Shumin; Zhou, Nanrun

2018-07-01

Based on hyper-chaotic system and discrete fractional random transform, an image compression-encryption algorithm is designed. The original image is first transformed into a spectrum by the discrete cosine transform and the resulting spectrum is compressed according to the method of spectrum cutting. The random matrix of the discrete fractional random transform is controlled by a chaotic sequence originated from the high dimensional hyper-chaotic system. Then the compressed spectrum is encrypted by the discrete fractional random transform. The order of DFrRT and the parameters of the hyper-chaotic system are the main keys of this image compression and encryption algorithm. The proposed algorithm can compress and encrypt image signal, especially can encrypt multiple images once. To achieve the compression of multiple images, the images are transformed into spectra by the discrete cosine transform, and then the spectra are incised and spliced into a composite spectrum by Zigzag scanning. Simulation results demonstrate that the proposed image compression and encryption algorithm is of high security and good compression performance.

Higher order Cambell techniques for neutron flux measurement. Pt. 1

International Nuclear Information System (INIS)

Lux, I.; Baranyai, A.

1982-01-01

An exact mathematical description of arbitrary high order Campbell techniques for measuring particle fluxes is given. The nth order Campbell technique assumes the measurement of the moments of the outcoming voltage up to the nth one. A simple relation is derived among the various moments of the total measured voltage and of the detector signal caused by one incident particle. It is proven that in the monoparticle case combination of the measured moments up to the order n provides an expression proportional to the particle flux and to the nth moment of the detector signal. Generalization to several different particles is given and it is shown that if the flux of the particle causing the largest detector signal is measured with a relative error epsilon in the dc method and the error is due to the signals of other particles, then in the nth order campbelling the error will be of order epsilonsup(n). The effect of a random background on the measured voltage is also investigated and it is established that the nth order campbelling supresses the noise according to the nth power of the relative amplitude of the noise to the signal. The results concerning constant fluxes are generalized to time dependent particle fluxes and a method assuming a Fourier transform of the measured quantities is proposed for their determination. (orig.)

Dynamic analysis of a pumped-storage hydropower plant with random power load

Science.gov (United States)

Zhang, Hao; Chen, Diyi; Xu, Beibei; Patelli, Edoardo; Tolo, Silvia

2018-02-01

This paper analyzes the dynamic response of a pumped-storage hydropower plant in generating mode. Considering the elastic water column effects in the penstock, a linearized reduced order dynamic model of the pumped-storage hydropower plant is used in this paper. As the power load is always random, a set of random generator electric power output is introduced to research the dynamic behaviors of the pumped-storage hydropower plant. Then, the influences of the PI gains on the dynamic characteristics of the pumped-storage hydropower plant with the random power load are analyzed. In addition, the effects of initial power load and PI parameters on the stability of the pumped-storage hydropower plant are studied in depth. All of the above results will provide theoretical guidance for the study and analysis of the pumped-storage hydropower plant.

First-principles studies of Te line-ordered alloys in a MoS2 monolayer

Science.gov (United States)

Andriambelaza, N. F.; Mapasha, R. E.; Chetty, N.

2018-04-01

The thermodynamic stability, structural and electronic properties of Te line-ordered alloys are investigated using density functional theory (DFT) methods. Thirty four possible Te line-ordered alloy configurations are found in a 5×5 supercell of a MoS2 monolayer. The calculated formation energies show that the Te line-ordered alloy configurations are thermodynamically stable at 0 K and agree very well with the random alloys. The lowest energy configurations at each concentration correspond to the configuration where the Te atom rows are far apart from each other (avoiding clustering) within the supercell. The variation of the lattice constant at different concentrations obey Vegard's law. The Te line-ordered alloys fine tune the band gap of a MoS2 monolayer although deviating from linearity behavior. Our results suggest that the Te line-ordered alloys can be an effective way to modulate the band gap of a MoS2 monolayer for nanoelectronic, optoelectronic and nanophotonic applications.

Rounding by disorder of first-order quantum phase transitions: emergence of quantum critical points.

Science.gov (United States)

Goswami, Pallab; Schwab, David; Chakravarty, Sudip

2008-01-11

We give a heuristic argument for disorder rounding of a first-order quantum phase transition into a continuous phase transition. From both weak and strong disorder analysis of the N-color quantum Ashkin-Teller model in one spatial dimension, we find that, for N > or =3, the first-order transition is rounded to a continuous transition and the physical picture is the same as the random transverse field Ising model for a limited parameter regime. The results are strikingly different from the corresponding classical problem in two dimensions where the fate of the renormalization group flows is a fixed point corresponding to N-decoupled pure Ising models.

Finite Time Control for Fractional Order Nonlinear Hydroturbine Governing System via Frequency Distributed Model

Directory of Open Access Journals (Sweden)

Bin Wang

2016-01-01

Full Text Available This paper studies the application of frequency distributed model for finite time control of a fractional order nonlinear hydroturbine governing system (HGS. Firstly, the mathematical model of HGS with external random disturbances is introduced. Secondly, a novel terminal sliding surface is proposed and its stability to origin is proved based on the frequency distributed model and Lyapunov stability theory. Furthermore, based on finite time stability and sliding mode control theory, a robust control law to ensure the occurrence of the sliding motion in a finite time is designed for stabilization of the fractional order HGS. Finally, simulation results show the effectiveness and robustness of the proposed scheme.

Sex difference in human fingertip recognition of micron-level randomness as unpleasant.

Science.gov (United States)

Nakatani, M; Kawasoe, T; Denda, M

2011-08-01

We investigated sex difference in evaluation, using the human fingertip, of the tactile impressions of three different micron-scale patterns laser-engraved on plastic plates. There were two ordered (periodical) patterns consisting of ripples on a scale of a few micrometres and one pseudo-random (non-periodical) pattern; these patterns were considered to mimic the surface geometry of healthy and damaged human hair, respectively. In the first experiment, 10 women and 10 men ran a fingertip over each surface and determined which of the three plates felt most unpleasant. All 10 female participants reported the random pattern, but not the ordered patterns, as unpleasant, whereas the majority of the male participants did not. In the second experiment, 9 of 10 female participants continued to report the pseudo-random pattern as unpleasant even after their fingertip had been coated with a collodion membrane. In the third experiment, participants were asked to evaluate the magnitude of the tactile impression for each pattern. The results again indicated that female participants tend to report a greater magnitude of unpleasantness than male participants. Our findings indicate that the female participants could readily detect microgeometric surface characteristics and that they evaluated the random pattern as more unpleasant. Possible physical and perceptual mechanisms involved are discussed. © 2011 The Authors. ICS © 2011 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

Simulation of quantum systems with random walks: A new algorithm for charged systems

International Nuclear Information System (INIS)

Ceperley, D.

1983-01-01

Random walks with branching have been used to calculate exact properties of the ground state of quantum many-body systems. In this paper, a more general Green's function identity is derived which relates the potential energy, a trial wavefunction, and a trial density matrix to the rules of a branched random walk. It is shown that an efficient algorithm requires a good trial wavefunction, a good trial density matrix, and a good sampling of this density matrix. An accurate density matrix is constructed for Coulomb systems using the path integral formula. The random walks from this new algorithm diffuse through phase space an order of magnitude faster than the previous Green's Function Monte Carlo method. In contrast to the simple diffusion Monte Carlo algorithm, it is exact method. Representative results are presented for several molecules

Higher order optical aberrations and visual acuity in a randomized controlled trial comparing transepithelial versus epithelium-off corneal crosslinking for progressive keratoconus

Directory of Open Access Journals (Sweden)

Godefrooij DA

2017-10-01

Full Text Available Daniel A Godefrooij, Mustapha El Kandoussi, Nienke Soeters, Robert PL Wisse Utrecht Cornea Research Group, Department of Ophthalmology, University Medical Center Utrecht, Utrecht, the Netherlands Purpose: The purpose of this study was to compare the effects of transepithelial crosslinking (trans-CXL versus epithelium-off crosslinking (epi-off CXL for progressive keratoconus with respect to the development of higher order aberrations (HOAs and their effects on visual acuity.Materials and methods: A total of 61 patients were randomized and examined preoperatively and 1, 3, 6, and 12 months postoperatively in an academic referral center. Total corneal HOAs were compared between the two treatment groups using mixed linear modeling. Types of HOAs (coma, trefoil, and spherical aberration that differed between groups were entered in a multivariable analysis to test their effect on uncorrected distance visual acuity (UDVA and corrected distance visual acuity (CDVA.Results: The epi-off CXL group had more flattening in maximal keratometry compared to the trans-CXL group (P=0.02. UDVA did not differ significantly between the groups (P=0.59; however, CDVA was significantly more improved in the trans-CXL group (P=0.02. Horizontal trefoil improved more in the epi-off group compared to the trans-CXL group (P=0.04, whereas the other HOAs were virtually unchanged in both groups. Differences in changes in HOAs between the two groups had no effect on either UCVA (P=0.76 or CDVA (P=0.96.Conclusion: Although HOAs are clinically relevant determinants of vision quality in keratoconus patients, the change in total HOAs post treatment did not differ between the trans-CXL and epi-off CXL groups. Only horizontal trefoil differed significantly post treatment between the trans-CXL and epi-off CXL groups. However, this difference did not independently affect either UDVA or CDVA. Trans-CXL provides no benefit over epi-off CXL regarding visual relevant HOAs. Keywords

Random matrices and random difference equations

International Nuclear Information System (INIS)

Uppuluri, V.R.R.

1975-01-01

Mathematical models leading to products of random matrices and random difference equations are discussed. A one-compartment model with random behavior is introduced, and it is shown how the average concentration in the discrete time model converges to the exponential function. This is of relevance to understanding how radioactivity gets trapped in bone structure in blood--bone systems. The ideas are then generalized to two-compartment models and mammillary systems, where products of random matrices appear in a natural way. The appearance of products of random matrices in applications in demography and control theory is considered. Then random sequences motivated from the following problems are studied: constant pulsing and random decay models, random pulsing and constant decay models, and random pulsing and random decay models

Birth order and mortality in two ethno-linguistic groups: Register-based evidence from Finland.

Science.gov (United States)

Saarela, Jan; Cederström, Agneta; Rostila, Mikael

2016-06-01

Previous research has documented an association between birth order and suicide, although no study has examined whether it depends on the cultural context. Our aim was to study the association between birth order and cause-specific mortality in Finland, and whether it varies by ethno-linguistic affiliation. We used data from the Finnish population register, representing a 5% random sample of all Finnish speakers and a 20% random sample of Swedish speakers, who lived in Finland in any year 1987-2011. For each person, there was a link to all children who were alive in 1987. In total, there were 254,059 siblings in 96,387 sibling groups, and 9797 deaths. We used Cox regressions stratified by each siblings group and estimated all-cause and cause-specific mortality risks during the period 1987-2011. In line with previous research from Sweden, deaths from suicide were significantly associated with birth order. As compared to first-born, second-born had a suicide risk of 1.27, third-born of 1.35, and fourth- or higher-born of 1.72, while other causes of death did not display an evident and consistent birth-order pattern. Results for the Finnish-speaking siblings groups were almost identical to those based on both ethno-linguistic groups. In the Swedish-speaking siblings groups, there was no increase in the suicide risk by birth order, but a statistically not significant tendency towards an association with other external causes of death and deaths from cardiovascular diseases. Our findings provided evidence for an association between birth order and suicide among Finnish speakers in Finland, while no such association was found for Swedish speakers, suggesting that the birth order effect might depend on the cultural context. Copyright © 2016 Elsevier Ltd. All rights reserved.

Nonparametric Bayesian predictive distributions for future order statistics

Science.gov (United States)

Richard A. Johnson; James W. Evans; David W. Green

1999-01-01

We derive the predictive distribution for a specified order statistic, determined from a future random sample, under a Dirichlet process prior. Two variants of the approach are treated and some limiting cases studied. A practical application to monitoring the strength of lumber is discussed including choices of prior expectation and comparisons made to a Bayesian...

Bayesian calibration of simultaneity in audiovisual temporal order judgments.

Directory of Open Access Journals (Sweden)

Shinya Yamamoto

Full Text Available After repeated exposures to two successive audiovisual stimuli presented in one frequent order, participants eventually perceive a pair separated by some lag time in the same order as occurring simultaneously (lag adaptation. In contrast, we previously found that perceptual changes occurred in the opposite direction in response to tactile stimuli, conforming to bayesian integration theory (bayesian calibration. We further showed, in theory, that the effect of bayesian calibration cannot be observed when the lag adaptation was fully operational. This led to the hypothesis that bayesian calibration affects judgments regarding the order of audiovisual stimuli, but that this effect is concealed behind the lag adaptation mechanism. In the present study, we showed that lag adaptation is pitch-insensitive using two sounds at 1046 and 1480 Hz. This enabled us to cancel lag adaptation by associating one pitch with sound-first stimuli and the other with light-first stimuli. When we presented each type of stimulus (high- or low-tone in a different block, the point of simultaneity shifted to "sound-first" for the pitch associated with sound-first stimuli, and to "light-first" for the pitch associated with light-first stimuli. These results are consistent with lag adaptation. In contrast, when we delivered each type of stimulus in a randomized order, the point of simultaneity shifted to "light-first" for the pitch associated with sound-first stimuli, and to "sound-first" for the pitch associated with light-first stimuli. The results clearly show that bayesian calibration is pitch-specific and is at work behind pitch-insensitive lag adaptation during temporal order judgment of audiovisual stimuli.

Breast-conserving therapy with partial or whole breast irradiation: ten-year results of the Budapest randomized trial.

Science.gov (United States)

Polgár, Csaba; Fodor, János; Major, Tibor; Sulyok, Zoltán; Kásler, Miklós

2013-08-01

To report the long-term results of a single-institution randomized study comparing the results of breast-conserving treatment with partial breast irradiation (PBI) or conventional whole breast irradiation (WBI). Between 1998 and 2004, 258 selected women with pT1 pN0-1mi M0, grade 1-2, non-lobular breast cancer without the presence of extensive intraductal component and resected with negative margins were randomized after BCS to receive 50 Gy WBI (n=130) or PBI (n=128). The latter consisted of either 7 × 5.2 Gy high-dose-rate (HDR) multi-catheter brachytherapy (BT; n=88) or 50 Gy electron beam (EB) irradiation (n=40). Primary endpoint was local recurrence (LR) as a first event. Secondary endpoints were overall survival (OS), cancer-specific survival (CSS), disease-free survival (DFS), and cosmetic results. After a median follow up of 10.2 years, the ten-year actuarial rate of LR was 5.9% and 5.1% in PBI and WBI arms, respectively (p=0.77). There was no significant difference in the ten-year probability of OS (80% vs 82%), CSS (94% vs 92%), and DFS (85% vs 84%), either. The rate of excellent-good cosmetic result was 81% in the PBI, and 63% in the control group (p<0.01). Partial breast irradiation delivered by interstitial HDR BT or EB for a selected group of early-stage breast cancer patients produces similar ten-year results to those achieved with conventional WBI. Significantly better cosmetic outcome can be achieved with HDR BT implants compared with the outcome after WBI. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Hierarchical random additive process and logarithmic scaling of generalized high order, two-point correlations in turbulent boundary layer flow

Science.gov (United States)

Yang, X. I. A.; Marusic, I.; Meneveau, C.

2016-06-01

Townsend [Townsend, The Structure of Turbulent Shear Flow (Cambridge University Press, Cambridge, UK, 1976)] hypothesized that the logarithmic region in high-Reynolds-number wall-bounded flows consists of space-filling, self-similar attached eddies. Invoking this hypothesis, we express streamwise velocity fluctuations in the inertial layer in high-Reynolds-number wall-bounded flows as a hierarchical random additive process (HRAP): uz+=∑i=1Nzai . Here u is the streamwise velocity fluctuation, + indicates normalization in wall units, z is the wall normal distance, and ai's are independently, identically distributed random additives, each of which is associated with an attached eddy in the wall-attached hierarchy. The number of random additives is Nz˜ln(δ /z ) where δ is the boundary layer thickness and ln is natural log. Due to its simplified structure, such a process leads to predictions of the scaling behaviors for various turbulence statistics in the logarithmic layer. Besides reproducing known logarithmic scaling of moments, structure functions, and correlation function [" close="]3/2 uz(x ) uz(x +r ) >, new logarithmic laws in two-point statistics such as uz4(x ) > 1 /2, 1/3, etc. can be derived using the HRAP formalism. Supporting empirical evidence for the logarithmic scaling in such statistics is found from the Melbourne High Reynolds Number Boundary Layer Wind Tunnel measurements. We also show that, at high Reynolds numbers, the above mentioned new logarithmic laws can be derived by assuming the arrival of an attached eddy at a generic point in the flow field to be a Poisson process [Woodcock and Marusic, Phys. Fluids 27, 015104 (2015), 10.1063/1.4905301]. Taken together, the results provide new evidence supporting the essential ingredients of the attached eddy hypothesis to describe streamwise velocity fluctuations of large, momentum transporting eddies in wall-bounded turbulence, while observed deviations suggest the need for further extensions of the

Fractional Processes and Fractional-Order Signal Processing Techniques and Applications

CERN Document Server

Sheng, Hu; Qiu, TianShuang

2012-01-01

Fractional processes are widely found in science, technology and engineering systems. In Fractional Processes and Fractional-order Signal Processing, some complex random signals, characterized by the presence of a heavy-tailed distribution or non-negligible dependence between distant observations (local and long memory), are introduced and examined from the ‘fractional’ perspective using simulation, fractional-order modeling and filtering and realization of fractional-order systems. These fractional-order signal processing (FOSP) techniques are based on fractional calculus, the fractional Fourier transform and fractional lower-order moments. Fractional Processes and Fractional-order Signal Processing: • presents fractional processes of fixed, variable and distributed order studied as the output of fractional-order differential systems; • introduces FOSP techniques and the fractional signals and fractional systems point of view; • details real-world-application examples of FOSP techniques to demonstr...

Increased 1-year continuation of DMPA among women randomized to self-administration: results from a randomized controlled trial at Planned Parenthood.

Science.gov (United States)

Kohn, Julia E; Simons, Hannah R; Della Badia, Lisa; Draper, Elissa; Morfesis, Johanna; Talmont, Elizabeth; Beasley, Anitra; McDonald, Melanie; Westhoff, Carolyn L

2018-03-01

Self-administration of subcutaneous depot medroxyprogesterone acetate (DMPA-sc) is feasible, acceptable, and effective. Our objective was to compare one-year continuation of DMPA-sc between women randomized to self-administration versus clinic administration. We randomized 401 females ages 15-44 requesting DMPA at clinics in Texas and New Jersey to self-administration or clinic administration in a 1:1 allocation. Clinic staff taught participants randomized to self-administration to self-inject and observed the first injection; participants received instructions, a sharps container, and three doses for home use. Participants randomized to clinic administration received usual care. All participants received DMPA-sc at no cost and injection reminders via text message or email. We conducted follow-up surveys at six and 12 months. Three hundred thirty-six participants (84%) completed the 12-month survey; 316 completed both follow-up surveys (an 80% response rate excluding eight withdrawals). Participants ranged in age from 16-44. One-year DMPA continuous use was 69% in the self-administration group and 54% in the clinic group (p=.005). There were three self-reported pregnancies during the study period, all occurred in the clinic group; all three women had discontinued DMPA and one reported her pregnancy as intended. Among the self-administration group, 97% reported that self-administration was very or somewhat easy; 87% would recommend self-administration of DMPA-sc to a friend. Among the clinic group, 52% reported interest in self-administration in the future. Satisfaction was similar between groups. No serious adverse events were reported. DMPA self-administration improves contraceptive continuation and is a feasible and acceptable option for women and adolescents. Self-administration of subcutaneous DMPA can improve contraceptive access, autonomy, and continuation, and is a feasible and acceptable option for women and adolescents. It should be made widely available

Fast physical random bit generation with chaotic semiconductor lasers

Science.gov (United States)

Uchida, Atsushi; Amano, Kazuya; Inoue, Masaki; Hirano, Kunihito; Naito, Sunao; Someya, Hiroyuki; Oowada, Isao; Kurashige, Takayuki; Shiki, Masaru; Yoshimori, Shigeru; Yoshimura, Kazuyuki; Davis, Peter

2008-12-01

Random number generators in digital information systems make use of physical entropy sources such as electronic and photonic noise to add unpredictability to deterministically generated pseudo-random sequences. However, there is a large gap between the generation rates achieved with existing physical sources and the high data rates of many computation and communication systems; this is a fundamental weakness of these systems. Here we show that good quality random bit sequences can be generated at very fast bit rates using physical chaos in semiconductor lasers. Streams of bits that pass standard statistical tests for randomness have been generated at rates of up to 1.7 Gbps by sampling the fluctuating optical output of two chaotic lasers. This rate is an order of magnitude faster than that of previously reported devices for physical random bit generators with verified randomness. This means that the performance of random number generators can be greatly improved by using chaotic laser devices as physical entropy sources.

Determination of spatially dependent transfer function of zero power reactor by using pseudo-random incentive

International Nuclear Information System (INIS)

Kostic, Lj.

1973-01-01

Specially constructed fast reactivity oscillator was stimulating the zero power reactor by a stimulus which caused pseudo-random reactivity changes. Measuring system included stochastic oscillator BCR-1 supplied by pseudo-random pulses from noise generator GBS-16, instrumental tape-recorder, system for data acquisition and digital computer ZUSE-Z-23. For measuring the spatially dependent transfer function, reactor response was measured at a number of different positions of stochastic oscillator and ionization chamber. In order to keep the reactor system linear, experiment was limited to small reactivity fluctuations. Experimental results were compared to theoretical ones

The potts chain in a random field: an exact solution

International Nuclear Information System (INIS)

Riera, R.; Chaves, C.M.G.F.; Santos, Raimundo R. dos.

1984-01-01

An exact solution is presented for the one-dimensional q-state Potts model in a quenched random field. The ferromagnetic phase is unstable against any small random field perturbation. The correlation function and the Edwards-Anderson order parameter Q are discussed. For finite q only the phase with Q ≠ 0 is present. (Author) [pt

Metal-Insulator Transition Driven by Vacancy Ordering in GeSbTe Phase Change Materials.

Science.gov (United States)

Bragaglia, Valeria; Arciprete, Fabrizio; Zhang, Wei; Mio, Antonio Massimiliano; Zallo, Eugenio; Perumal, Karthick; Giussani, Alessandro; Cecchi, Stefano; Boschker, Jos Emiel; Riechert, Henning; Privitera, Stefania; Rimini, Emanuele; Mazzarello, Riccardo; Calarco, Raffaella

2016-04-01

Phase Change Materials (PCMs) are unique compounds employed in non-volatile random access memory thanks to the rapid and reversible transformation between the amorphous and crystalline state that display large differences in electrical and optical properties. In addition to the amorphous-to-crystalline transition, experimental results on polycrystalline GeSbTe alloys (GST) films evidenced a Metal-Insulator Transition (MIT) attributed to disorder in the crystalline phase. Here we report on a fundamental advance in the fabrication of GST with out-of-plane stacking of ordered vacancy layers by means of three distinct methods: Molecular Beam Epitaxy, thermal annealing and application of femtosecond laser pulses. We assess the degree of vacancy ordering and explicitly correlate it with the MIT. We further tune the ordering in a controlled fashion attaining a large range of resistivity. Employing ordered GST might allow the realization of cells with larger programming windows.

Metal - Insulator Transition Driven by Vacancy Ordering in GeSbTe Phase Change Materials

Science.gov (United States)

Bragaglia, Valeria; Arciprete, Fabrizio; Zhang, Wei; Mio, Antonio Massimiliano; Zallo, Eugenio; Perumal, Karthick; Giussani, Alessandro; Cecchi, Stefano; Boschker, Jos Emiel; Riechert, Henning; Privitera, Stefania; Rimini, Emanuele; Mazzarello, Riccardo; Calarco, Raffaella

2016-04-01

Phase Change Materials (PCMs) are unique compounds employed in non-volatile random access memory thanks to the rapid and reversible transformation between the amorphous and crystalline state that display large differences in electrical and optical properties. In addition to the amorphous-to-crystalline transition, experimental results on polycrystalline GeSbTe alloys (GST) films evidenced a Metal-Insulator Transition (MIT) attributed to disorder in the crystalline phase. Here we report on a fundamental advance in the fabrication of GST with out-of-plane stacking of ordered vacancy layers by means of three distinct methods: Molecular Beam Epitaxy, thermal annealing and application of femtosecond laser pulses. We assess the degree of vacancy ordering and explicitly correlate it with the MIT. We further tune the ordering in a controlled fashion attaining a large range of resistivity. Employing ordered GST might allow the realization of cells with larger programming windows.

Is balneotherapy effective for fibromyalgia? Results from a 6-month double-blind randomized clinical trial.

Science.gov (United States)

Fioravanti, Antonella; Manica, Patrizia; Bortolotti, Roberto; Cevenini, Gabriele; Tenti, Sara; Paolazzi, Giuseppe

2018-05-05

The aim of this study was to assess the efficacy and tolerability of balneotherapy (BT) in patients with primary fibromyalgia syndrome (FS). In a prospective, randomized, controlled, double-blind trial with a 6-month follow-up, 100 FS patients were randomized to receive a cycle of BT with highly mineralized sulfate water (BT group) or with tap water (control group). Clinical assessments were performed at screening visit, at basal time, and after treatment (2 weeks, 3 and 6 months). The primary outcome measures were the change of global pain on the Visual Analogue Scale (VAS) and Fibromyalgia Impact Questionnaire total score (FIQ-Total) from baseline to 15 days. Secondary outcomes included Widespread Pain Index, Symptom Severity Scale Score, Short Form Health Survey, State-Trait Anxiety Inventory (STAI), and Center for Epidemiologic Studies Depression Scale. We performed an intent-to-treat analysis. The Kolmogorov-Smirnov test was applied to verify the normality distribution of all quantitative variables and the Student's t test to compare sample data. In the BT group, we observed a significant improvement of VAS and FIQ-Total at the end of the treatment that persisted until 6 months, while no significant differences were found in the control group. The differences between groups were significant for primary parameters at each time point. Similar results were obtained for the other secondary outcomes except for the STAI outcome. Adverse events were reported by 10 patients in the BT group and by 22 patients in the control group. Our results support the short- and long-term therapeutic efficacy of BT in FS. NCT02548065.

Chaos, complexity, and random matrices

Science.gov (United States)

Cotler, Jordan; Hunter-Jones, Nicholas; Liu, Junyu; Yoshida, Beni

2017-11-01

Chaos and complexity entail an entropic and computational obstruction to describing a system, and thus are intrinsically difficult to characterize. In this paper, we consider time evolution by Gaussian Unitary Ensemble (GUE) Hamiltonians and analytically compute out-of-time-ordered correlation functions (OTOCs) and frame potentials to quantify scrambling, Haar-randomness, and circuit complexity. While our random matrix analysis gives a qualitatively correct prediction of the late-time behavior of chaotic systems, we find unphysical behavior at early times including an O(1) scrambling time and the apparent breakdown of spatial and temporal locality. The salient feature of GUE Hamiltonians which gives us computational traction is the Haar-invariance of the ensemble, meaning that the ensemble-averaged dynamics look the same in any basis. Motivated by this property of the GUE, we introduce k-invariance as a precise definition of what it means for the dynamics of a quantum system to be described by random matrix theory. We envision that the dynamical onset of approximate k-invariance will be a useful tool for capturing the transition from early-time chaos, as seen by OTOCs, to late-time chaos, as seen by random matrix theory.

Randomizer for High Data Rates

Science.gov (United States)

Garon, Howard; Sank, Victor J.

2018-01-01

NASA as well as a number of other space agencies now recognize that the current recommended CCSDS randomizer used for telemetry (TM) is too short. When multiple applications of the PN8 Maximal Length Sequence (MLS) are required in order to fully cover a channel access data unit (CADU), spectral problems in the form of elevated spurious discretes (spurs) appear. Originally the randomizer was called a bit transition generator (BTG) precisely because it was thought that its primary value was to insure sufficient bit transitions to allow the bit/symbol synchronizer to lock and remain locked. We, NASA, have shown that the old BTG concept is a limited view of the real value of the randomizer sequence and that the randomizer also aids in signal acquisition as well as minimizing the potential for false decoder lock. Under the guidelines we considered here there are multiple maximal length sequences under GF(2) which appear attractive in this application. Although there may be mitigating reasons why another MLS sequence could be selected, one sequence in particular possesses a combination of desired properties which offsets it from the others.

A Methodological Study of Order Effects in Reporting Relational Aggression Experiences.

Science.gov (United States)

Serico, Jennifer M; NeMoyer, Amanda; Goldstein, Naomi E S; Houck, Mark; Leff, Stephen S

2018-03-01

Unlike the overt nature of physical aggression, which lends itself to simpler and more direct methods of investigation, the often-masked nature of relational aggression has led to difficulties and debate regarding the most effective tools of study. Given concerns with the accuracy of third-party relational aggression reports, especially as individuals age, self-report measures may be particularly useful when assessing experiences with relational aggression. However, it is important to recognize validity concerns-in particular, the potential effects of item order presentation-associated with self-report of relational aggression perpetration and victimization. To investigate this issue, surveys were administered and completed by 179 young adults randomly assigned to one of four survey conditions reflecting manipulation of item order. Survey conditions included presentation of (a) perpetration items only, (b) victimization items only, (c) perpetration items followed by victimization items, and (d) victimization items followed by perpetration items. Results revealed that participants reported perpetrating relational aggression significantly more often when asked only about perpetration or when asked about perpetration before victimization, compared with participants who were asked about victimization before perpetration. Item order manipulation did not result in significant differences in self-reported victimization experiences. Results of this study indicate a need for greater consideration of item order when conducting research using self-report data and the importance of additional investigation into which form of item presentation elicits the most accurate self-report information.

[Work-Related Medical Rehabilitation in Cancer Rehabilitation - Short-Term Results from a Cluster-Randomized Multicenter-Trial].

Science.gov (United States)

Wienert, Julian; Bethge, Matthias

2018-05-25

Rehabilitation programs that support return to work become increasingly relevant for cancer survivors. In Germany, such programs were established as work-related medical rehabilitation (WMR). The study investigated whether WMR leads to better results compared to medical rehabilitation (MR). We report effects on secondary outcomes when the rehabilitation program was completed. Clusters of participants were randomly assigned to WMR or MR. Patients of working age and an elevated risk of not returning to work were included. The grade of implementation was assessed by dose delivered and dose received. Study outcomes were assessed using scales measuring functioning and symptoms, coping with illness as well as self-reported work ability. Treatment effects were estimated using mixed linear models. From 232 planned randomized intervention groups, 165 (71%) were realized. In total, 476 patients were included. Mean age of participants was 50.7 years (SD=7.3). Most frequent primary diagnoses were malignant neoplasms of the breast. Participants in the WMR program reported significantly better outcomes regarding quality of life (SMD=0.17-0.25), fatigue (SMD=0.18-0.27), coping with illness (SMD=0.17-0.22), and self-reported work-ability (SMD=0.16) compared to participants in MR program (all p<0.05). The results indicate a positive effect in favor of WMR for cancer patients with an elevated risk of not returning to work at the end of their treatment. © Georg Thieme Verlag KG Stuttgart · New York.

Random ray-tracing and graphic analysing of charged particle trajectories

International Nuclear Information System (INIS)

Lin Xiaomei; Mao Naifeng; Chen Jingxian

1990-01-01

In order to describe the optical properties of a charged particle beam realistically, the random sampling of initial conditions of particles in ray-tracing is discussed. The emission surface of particles may be a plane, a cylindrical surface or a spherical surface. The distribution functions may be expressed analytically or numerically. In order to analyse the properties of the charged particle beam systematically by use of the results from ray-tracing efficiently, the graphic processing and analysing of particle trajectories are also discussed, including the spline function fitting of trajectories, the graphic drafting of trajectories and beam envelopes, the determining of image dimensions and the correspinding positions, and also the graphic drafting of particle distributions on arbitrary cross sections

Quantum Random Networks for Type 2 Quantum Computers

National Research Council Canada - National Science Library

Allara, David L; Hasslacher, Brosl

2006-01-01

Random boolean networks (RBNs) have been studied theoretically and computationally in order to be able to use their remarkable self-healing and large basins of altercation properties as quantum computing architectures, especially...

Parallel random number generator for inexpensive configurable hardware cells

Science.gov (United States)

Ackermann, J.; Tangen, U.; Bödekker, B.; Breyer, J.; Stoll, E.; McCaskill, J. S.

2001-11-01

A new random number generator ( RNG) adapted to parallel processors has been created. This RNG can be implemented with inexpensive hardware cells. The correlation between neighboring cells is suppressed with smart connections. With such connection structures, sequences of pseudo-random numbers are produced. Numerical tests including a self-avoiding random walk test and the simulation of the order parameter and energy of the 2D Ising model give no evidence for correlation in the pseudo-random sequences. Because the new random number generator has suppressed the correlation between neighboring cells which is usually observed in cellular automaton implementations, it is applicable for extended time simulations. It gives an immense speed-up factor if implemented directly in configurable hardware, and has recently been used for long time simulations of spatially resolved molecular evolution.

Recommendations and illustrations for the evaluation of photonic random number generators

Science.gov (United States)

Hart, Joseph D.; Terashima, Yuta; Uchida, Atsushi; Baumgartner, Gerald B.; Murphy, Thomas E.; Roy, Rajarshi

2017-09-01

The never-ending quest to improve the security of digital information combined with recent improvements in hardware technology has caused the field of random number generation to undergo a fundamental shift from relying solely on pseudo-random algorithms to employing optical entropy sources. Despite these significant advances on the hardware side, commonly used statistical measures and evaluation practices remain ill-suited to understand or quantify the optical entropy that underlies physical random number generation. We review the state of the art in the evaluation of optical random number generation and recommend a new paradigm: quantifying entropy generation and understanding the physical limits of the optical sources of randomness. In order to do this, we advocate for the separation of the physical entropy source from deterministic post-processing in the evaluation of random number generators and for the explicit consideration of the impact of the measurement and digitization process on the rate of entropy production. We present the Cohen-Procaccia estimate of the entropy rate h (𝜖 ,τ ) as one way to do this. In order to provide an illustration of our recommendations, we apply the Cohen-Procaccia estimate as well as the entropy estimates from the new NIST draft standards for physical random number generators to evaluate and compare three common optical entropy sources: single photon time-of-arrival detection, chaotic lasers, and amplified spontaneous emission.

Recommendations and illustrations for the evaluation of photonic random number generators

Directory of Open Access Journals (Sweden)

Joseph D. Hart

2017-09-01

Full Text Available The never-ending quest to improve the security of digital information combined with recent improvements in hardware technology has caused the field of random number generation to undergo a fundamental shift from relying solely on pseudo-random algorithms to employing optical entropy sources. Despite these significant advances on the hardware side, commonly used statistical measures and evaluation practices remain ill-suited to understand or quantify the optical entropy that underlies physical random number generation. We review the state of the art in the evaluation of optical random number generation and recommend a new paradigm: quantifying entropy generation and understanding the physical limits of the optical sources of randomness. In order to do this, we advocate for the separation of the physical entropy source from deterministic post-processing in the evaluation of random number generators and for the explicit consideration of the impact of the measurement and digitization process on the rate of entropy production. We present the Cohen-Procaccia estimate of the entropy rate h(,τ as one way to do this. In order to provide an illustration of our recommendations, we apply the Cohen-Procaccia estimate as well as the entropy estimates from the new NIST draft standards for physical random number generators to evaluate and compare three common optical entropy sources: single photon time-of-arrival detection, chaotic lasers, and amplified spontaneous emission.

Positioning of chromosomes in human spermatozoa is determined by ordered centromere arrangement.

Directory of Open Access Journals (Sweden)

Olga S Mudrak

Full Text Available The intranuclear positioning of chromosomes (CHRs is a well-documented fact; however, mechanisms directing such ordering remain unclear. Unlike somatic cells, human spermatozoa contain distinct spatial markers and have asymmetric nuclei which make them a unique model for localizing CHR territories and matching peri-centromere domains. In this study, we established statistically preferential longitudinal and lateral positioning for eight CHRs. Both parameters demonstrated a correlation with the CHR gene densities but not with their sizes. Intranuclear non-random positioning of the CHRs was found to be driven by a specific linear order of centromeres physically interconnected in continuous arrays. In diploid spermatozoa, linear order of peri-centromeres was identical in two genome sets and essentially matched the arrangement established for haploid cells. We propose that the non-random longitudinal order of CHRs in human spermatozoa is generated during meiotic stages of spermatogenesis. The specific arrangement of sperm CHRs may serve as an epigenetic basis for differential transcription/replication and direct spatial CHR organization during early embryogenesis.

The Impact of an Ergonomics Intervention on Psychosocial Factors and Musculoskeletal Symptoms among Thai Hospital Orderlies.

Science.gov (United States)

Chanchai, Withaya; Songkham, Wanpen; Ketsomporn, Pranom; Sappakitchanchai, Punnarat; Siriwong, Wattasit; Robson, Mark Gregory

2016-05-03

(1) BACKGROUND: Musculoskeletal disorders have a multifactorial etiology that is not only associated with physical risk factors, but also psychosocial risk factors; (2) OBJECTIVE: This study evaluated the effects of an ergonomic intervention on musculoskeletal disorders and psychosocial risk factors; (3) MATERIAL AND METHODS: This study took a participatory ergonomic (PE) approach with a randomized controlled trial (RCT) conducted at tertiary care hospitals during July to December 2014. A group of hospital orderlies in Thailand were randomly selected for examination. Fifty orderlies were placed in a case group and another 50 orderlies were placed in the control group. The Nordic Musculoskeletal Disorders Questionnaire (NMQ) and the Copenhagen Psychosocial Questionnaire (COPSOQ) were used for data collection before and after the intervention program; (4) RESULTS: The most commonly reported problem among hospital orderlies was found to be lower back symptoms (82%). The study found significant differences in prevalence rates of reported musculoskeletal conditions in the arm, upper back, and lower back regions before and after intervention. Findings showed that psychosocial risk factors were affected by the intervention. COPSOQ psychosocial risk factors were significantly different pre/post intervention. These variables included: work pace, influence at work, meaning of work, predictability, rewards, role conflicts, and social support from supervisors. No other psychosocial risk factors were found to be significant; (5) CONCLUSIONS: Positive results were observed following the intervention in the work environment, particularly in terms of reducing physical work environment risk factors for musculoskeletal disorders and increasing promotion factors of the psychosocial work environment.

The Impact of an Ergonomics Intervention on Psychosocial Factors and Musculoskeletal Symptoms among Thai Hospital Orderlies

Directory of Open Access Journals (Sweden)

Withaya Chanchai

2016-05-01

Full Text Available (1 Background: Musculoskeletal disorders have a multifactorial etiology that is not only associated with physical risk factors, but also psychosocial risk factors; (2 Objective: This study evaluated the effects of an ergonomic intervention on musculoskeletal disorders and psychosocial risk factors; (3 Material and Methods: This study took a participatory ergonomic (PE approach with a randomized controlled trial (RCT conducted at tertiary care hospitals during July to December 2014. A group of hospital orderlies in Thailand were randomly selected for examination. Fifty orderlies were placed in a case group and another 50 orderlies were placed in the control group. The Nordic Musculoskeletal Disorders Questionnaire (NMQ and the Copenhagen Psychosocial Questionnaire (COPSOQ were used for data collection before and after the intervention program; (4 Results: The most commonly reported problem among hospital orderlies was found to be lower back symptoms (82%. The study found significant differences in prevalence rates of reported musculoskeletal conditions in the arm, upper back, and lower back regions before and after intervention. Findings showed that psychosocial risk factors were affected by the intervention. COPSOQ psychosocial risk factors were significantly different pre/post intervention. These variables included: work pace, influence at work, meaning of work, predictability, rewards, role conflicts, and social support from supervisors. No other psychosocial risk factors were found to be significant; (5 Conclusions: Positive results were observed following the intervention in the work environment, particularly in terms of reducing physical work environment risk factors for musculoskeletal disorders and increasing promotion factors of the psychosocial work environment.

Off-label use of recombinant factor VIIa for treatment of haemorrhage: results from randomized clinical trials

DEFF Research Database (Denmark)

Johansson, Per Ingemar

2008-01-01

) for evidence of such an approach. Methods In October 2007, a review of RCT involving rFVIIa for non-haemophilic indications was performed. The effect of rFVIIa on blood loss and transfusion requirements was recorded. Results Seventeen RCTs were identified concerning different bleeding conditions, for example......, secondary to surgery, infection and stem cell transplantation. Three pilot studies reported a significant reduction in transfusion requirements and/or blood loss in the rFVIIa-treated groups, but these have not been confirmed in large randomized trials. No difference in thromboembolic complications between...

Random walk on random walks

NARCIS (Netherlands)

Hilário, M.; Hollander, den W.Th.F.; Sidoravicius, V.; Soares dos Santos, R.; Teixeira, A.

2014-01-01

In this paper we study a random walk in a one-dimensional dynamic random environment consisting of a collection of independent particles performing simple symmetric random walks in a Poisson equilibrium with density ¿¿(0,8). At each step the random walk performs a nearest-neighbour jump, moving to

Staple Line Reinforcement During Laparoscopic Sleeve Gastrectomy: Absorbable Monofilament, Barbed Suture, Fibrin Glue, or Nothing? Results of a Prospective Randomized Study.

Science.gov (United States)

Carandina, S; Tabbara, M; Bossi, M; Valenti, A; Polliand, C; Genser, L; Barrat, Christophe

2016-02-01

Laparoscopic sleeve gastrectomy (LSG) is associated with serious complications, such as staple line (SL) leaks and bleeding. In order to prevent the occurrence of these complications, surgeons have advocated the need to strengthen the staple line. The aim of this randomized controlled study was to compare the efficacy of three different ways of strengthening of the SL in LSG in preventing surgical post-operative complications. Between April 2012 and December 2014, 600 patients (pts) scheduled for LSG were prospectively randomized into groups without SL reinforcement (group A) or with SL reinforcement including fibrin glue coverage (group B), or oversewn SL with imbricating absorbable (Monocryl™; group C) or barbed (V lock®) running suture (group D). Primary endpoints were post-operative leaks, bleeding, and stenosis, while secondary outcomes consisted of the time to perform the staple line reinforcement (SLR) and total operative time. Mean SLR operative time was lower for group B (3.4 ± 1.3 min) compared with that for groups C (26.8 ± 8.5 min) and D (21.1 ± 8.4 min) (p running suture or with fibrin glue, is an unrewarding surgical act with the sole effect of prolonging the operative time.

Impact of sending email reminders of the legal requirement for posting results on ClinicalTrials.gov: cohort embedded pragmatic randomized controlled trial.

Science.gov (United States)

Maruani, Annabel; Boutron, Isabelle; Baron, Gabriel; Ravaud, Philippe

2014-09-19

To evaluate the impact of sending an email to responsible parties of completed trials that do not comply with the Food and Drug Administration Amendments Act 801 legislation, to remind them of the legal requirement to post results. Cohort embedded pragmatic randomized controlled trial. Trials registered on ClinicalTrials.gov. 190 out of 379 trials randomly selected by computer generated randomization list to receive the intervention (personalized emails structured as a survey and sent by one of us to responsible parties of the trials, indirectly reminding them of the legal requirement and potential penalties for non-compliance). The primary outcome was the proportion of results posted on ClinicalTrials.gov at three months. The secondary outcome was the proportion posted at six months. In a second step, two assessors blinded to the intervention group collected the date of the first results being received on ClinicalTrials.gov. A post hoc sensitivity analysis excluding trials wrongly included was performed. Among 379 trials included, 190 were randomized to receive the email intervention. The rate of posting of results did not differ at three months between trials with or without the intervention: 36/190 (19%) v 24/189 (13%), respectively (relative risk 1.5, 95% confidence interval 0.9 to 2.4, P=0.096) but did at six months: 46/190 (24%) v 27/189 (14%), 1.7, 1.1 to 2.6, P=0.014. In the sensitivity analysis, which excluded 48/379 trials (13%), 26/190 (14%) and 22/189 (12%), respectively, results were significant at three months (relative risk 5.1, 1.1 to 22.9, P=0.02) and at six months (4.1, 1.3 to 10.6, P=0.001). Sending email reminders about the FDA's legal requirement to post results at ClinicalTrials.gov improved significantly the posting rate at six months but not at three months.Trial registration ClinicalTrials.gov NCT01658254. © Maruani et al 2014.

First-principles studies of chromium line-ordered alloys in a molybdenum disulfide monolayer

Science.gov (United States)

Andriambelaza, N. F.; Mapasha, R. E.; Chetty, N.

2017-08-01

Density functional theory calculations have been performed to study the thermodynamic stability, structural and electronic properties of various chromium (Cr) line-ordered alloy configurations in a molybdenum disulfide (MoS2) hexagonal monolayer for band gap engineering. Only the molybdenum (Mo) sites were substituted at each concentration in this study. For comparison purposes, different Cr line-ordered alloy and random alloy configurations were studied and the most thermodynamically stable ones at each concentration were identified. The configurations formed by the nearest neighbor pair of Cr atoms are energetically most favorable. The line-ordered alloys are constantly lower in formation energy than the random alloys at each concentration. An increase in Cr concentration reduces the lattice constant of the MoS2 system following the Vegard’s law. From density of states analysis, we found that the MoS2 band gap is tunable by both the Cr line-ordered alloys and random alloys with the same magnitudes. The reduction of the band gap is mainly due to the hybridization of the Cr 3d and Mo 4d orbitals at the vicinity of the band edges. The band gap engineering and magnitudes (1.65 eV to 0.86 eV) suggest that the Cr alloys in a MoS2 monolayer are good candidates for nanotechnology devices.

Collapse of the random-phase approximation: Examples and counter-examples from the shell model

International Nuclear Information System (INIS)

Johnson, Calvin W.; Stetcu, Ionel

2009-01-01

The Hartree-Fock approximation to the many-fermion problem can break exact symmetries, and in some cases by changing a parameter in the interaction one can drive the Hartree-Fock minimum from a symmetry-breaking state to a symmetry-conserving state (also referred to as a 'phase transition' in the literature). The order of the transition is important when one applies the random-phase approximation (RPA) to the of the Hartree-Fock wave function: if first order, RPA is stable through the transition, but if second-order, then the RPA amplitudes become large and lead to unphysical results. The latter is known as 'collapse' of the RPA. While the difference between first- and second-order transitions in the RPA was first pointed out by Thouless, we present for the first time nontrivial examples of both first- and second-order transitions in a uniform model, the interacting shell-model, where we can compare to exact numerical results.

Numerical Inversion for the Multiple Fractional Orders in the Multiterm TFDE

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Chunlong Sun

2017-01-01

Full Text Available The fractional order in a fractional diffusion model is a key parameter which characterizes the anomalous diffusion behaviors. This paper deals with an inverse problem of determining the multiple fractional orders in the multiterm time-fractional diffusion equation (TFDE for short from numerics. The homotopy regularization algorithm is applied to solve the inversion problem using the finite data at one interior point in the space domain. The inversion fractional orders with random noisy data give good approximations to the exact order demonstrating the efficiency of the inversion algorithm and numerical stability of the inversion problem.

Vacuum instability in a random electric field

International Nuclear Information System (INIS)

Krive, I.V.; Pastur, L.A.

1984-01-01

The reaction of the vacuum on an intense spatially homogeneous random electric field is investigated. It is shown that a stochastic electric field always causes a breakdown of the boson vacuum, and the number of pairs of particles which are created by the electric field increases exponentially in time. For the choice of potential field in the form of a dichotomic random process we find in explicit form the dependence of the average number of pairs of particles on the time of the action of the source of the stochastic field. For the fermion vacuum the average number of pairs of particles which are created by the field in the lowest order of perturbation theory in the amplitude of the random field is independent of time

Method for Evaluation of Outage Probability on Random Access Channel in Mobile Communication Systems

Science.gov (United States)

Kollár, Martin

2012-05-01

In order to access the cell in all mobile communication technologies a so called random-access procedure is used. For example in GSM this is represented by sending the CHANNEL REQUEST message from Mobile Station (MS) to Base Transceiver Station (BTS) which is consequently forwarded as an CHANNEL REQUIRED message to the Base Station Controller (BSC). If the BTS decodes some noise on the Random Access Channel (RACH) as random access by mistake (so- called ‘phantom RACH') then it is a question of pure coincidence which èstablishment cause’ the BTS thinks to have recognized. A typical invalid channel access request or phantom RACH is characterized by an IMMEDIATE ASSIGNMENT procedure (assignment of an SDCCH or TCH) which is not followed by sending an ESTABLISH INDICATION from MS to BTS. In this paper a mathematical model for evaluation of the Power RACH Busy Threshold (RACHBT) in order to guaranty in advance determined outage probability on RACH is described and discussed as well. It focuses on Global System for Mobile Communications (GSM) however the obtained results can be generalized on remaining mobile technologies (ie WCDMA and LTE).

Some Tests of Random Walk Hypothesis for Bulgarian Foreign Exchange Rates

OpenAIRE

Nikolai Gueorguiev

1993-01-01

The objective of this paper is to check if the exchange rate in newly emerged, relatively thin foreign exchange markets, follows a random walk pattern. The findings of the current study cast doubts on random walk presence in Bulgarian exchange rates against major international currencies. It turns out that the series of daily returns are stationary but correlated and therefore can be modelled better by higher-order ARIMA processes than by random walk.

Spatial Analysis of “Crazy Quilts”, a Class of Potentially Random Aesthetic Artefacts

Science.gov (United States)

Westphal-Fitch, Gesche; Fitch, W. Tecumseh

2013-01-01

Human artefacts in general are highly structured and often display ordering principles such as translational, reflectional or rotational symmetry. In contrast, human artefacts that are intended to appear random and non symmetrical are very rare. Furthermore, many studies show that humans find it extremely difficult to recognize or reproduce truly random patterns or sequences. Here, we attempt to model two-dimensional decorative spatial patterns produced by humans that show no obvious order. “Crazy quilts” represent a historically important style of quilt making that became popular in the 1870s, and lasted about 50 years. Crazy quilts are unusual because unlike most human artefacts, they are specifically intended to appear haphazard and unstructured. We evaluate the degree to which this intention was achieved by using statistical techniques of spatial point pattern analysis to compare crazy quilts with regular quilts from the same region and era and to evaluate the fit of various random distributions to these two quilt classes. We found that the two quilt categories exhibit fundamentally different spatial characteristics: The patch areas of crazy quilts derive from a continuous random distribution, while area distributions of regular quilts consist of Gaussian mixtures. These Gaussian mixtures derive from regular pattern motifs that are repeated and we suggest that such a mixture is a distinctive signature of human-made visual patterns. In contrast, the distribution found in crazy quilts is shared with many other naturally occurring spatial patterns. Centroids of patches in the two quilt classes are spaced differently and in general, crazy quilts but not regular quilts are well-fitted by a random Strauss process. These results indicate that, within the constraints of the quilt format, Victorian quilters indeed achieved their goal of generating random structures. PMID:24066095

Warehouse Order-Picking Process. Review

Directory of Open Access Journals (Sweden)

E. V. Korobkov

2015-01-01

Full Text Available This article describes basic warehousing activities, namely: movement, information storage and transfer, as well as connections between typical warehouse operations (reception, transfer, assigning storage position and put-away, order-picking, hoarding and sorting, cross-docking, shipping. It presents a classification of the warehouse order-picking systems in terms of manual labor on offer as well as external (marketing channels, consumer’s demand structure, supplier’s replenishment structure and inventory level, total production demand, economic situation and internal (mechanization level, information accessibility, warehouse dimensionality, method of dispatch for shipping, zoning, batching, storage assignment method, routing method factors affecting the designing systems complexity. Basic optimization considerations are described. There is a literature review on the following sub-problems of planning and control of orderpicking processes.A layout design problem has been taken in account at two levels — external (facility layout problem and internal (aisle configuration problem. For a problem of distributing goods or stock keeping units the following methods are emphasized: random, nearest open storage position, and dedicated (COI-based, frequency-based distribution, as well as class-based and familygrouped (complimentary- and contact-based one. Batching problem can be solved by two main methods, i.e. proximity order batching (seed and saving algorithms and time-window order batching. There are two strategies for a zoning problem: progressive and synchronized, and also a special case of zoning — bucket brigades method. Hoarding/sorting problem is briefly reviewed. Order-picking routing problem will be thoroughly described in the next article of the cycle “Warehouse order-picking process”.

The (mis)reporting of statistical results in psychology journals.

Science.gov (United States)

Bakker, Marjan; Wicherts, Jelte M

2011-09-01

In order to study the prevalence, nature (direction), and causes of reporting errors in psychology, we checked the consistency of reported test statistics, degrees of freedom, and p values in a random sample of high- and low-impact psychology journals. In a second study, we established the generality of reporting errors in a random sample of recent psychological articles. Our results, on the basis of 281 articles, indicate that around 18% of statistical results in the psychological literature are incorrectly reported. Inconsistencies were more common in low-impact journals than in high-impact journals. Moreover, around 15% of the articles contained at least one statistical conclusion that proved, upon recalculation, to be incorrect; that is, recalculation rendered the previously significant result insignificant, or vice versa. These errors were often in line with researchers' expectations. We classified the most common errors and contacted authors to shed light on the origins of the errors.

Randomized controlled trial of perioperative antimicrobial therapy based on the results of preoperative bile cultures in patients undergoing biliary reconstruction.

Science.gov (United States)

Okamura, Kunishige; Tanaka, Kimitaka; Miura, Takumi; Nakanishi, Yoshitsugu; Noji, Takehiro; Nakamura, Toru; Tsuchikawa, Takahiro; Okamura, Keisuke; Shichinohe, Toshiaki; Hirano, Satoshi

2017-07-01

The high frequency of surgical site infections (SSIs) after hepato-pancreato-biliary (HPB) surgery is a problem that needs to be addressed. This prospective, randomized, controlled study examined whether perioperative prophylactic use of antibiotics based on preoperative bile culture results in HPB surgery could decrease SSI. Participants comprised 126 patients who underwent HPB (bile duct, gallbladder, ampullary, or pancreatic) cancer surgery with biliary reconstruction at Hokkaido University Hospital between August 2008 and March 2013 (UMIN Clinical Trial Registry #00001278). Before surgery, subjects were randomly allocated to a targeted group administered antibiotics based on bile culture results or a standard group administered cefmetazole. The primary endpoint was SSI rates within 30 days after surgery. Secondary endpoint was SSI rates for each operative procedure. Of the 126 patients, 124 were randomly allocated (targeted group, n = 62; standard group, n = 62). Frequency of SSI after surgery was significantly lower in the targeted group (27 patients, 43.5%) than in the standard group (44 patients, 71.0%; P = 0.002). Among patients who underwent pancreaticoduodenectomy and hepatectomy, SSI occurred significantly less frequently in the targeted group (P = 0.001 and P = 0.025, respectively). This study demonstrated that preoperative bile culture-targeted administration of prophylactic antibiotics decreased SSIs following HBP surgery with biliary reconstruction. © 2017 Japanese Society of Hepato-Biliary-Pancreatic Surgery.

RandomSpot: A web-based tool for systematic random sampling of virtual slides.

Science.gov (United States)

Wright, Alexander I; Grabsch, Heike I; Treanor, Darren E

2015-01-01

This paper describes work presented at the Nordic Symposium on Digital Pathology 2014, Linköping, Sweden. Systematic random sampling (SRS) is a stereological tool, which provides a framework to quickly build an accurate estimation of the distribution of objects or classes within an image, whilst minimizing the number of observations required. RandomSpot is a web-based tool for SRS in stereology, which systematically places equidistant points within a given region of interest on a virtual slide. Each point can then be visually inspected by a pathologist in order to generate an unbiased sample of the distribution of classes within the tissue. Further measurements can then be derived from the distribution, such as the ratio of tumor to stroma. RandomSpot replicates the fundamental principle of traditional light microscope grid-shaped graticules, with the added benefits associated with virtual slides, such as facilitated collaboration and automated navigation between points. Once the sample points have been added to the region(s) of interest, users can download the annotations and view them locally using their virtual slide viewing software. Since its introduction, RandomSpot has been used extensively for international collaborative projects, clinical trials and independent research projects. So far, the system has been used to generate over 21,000 sample sets, and has been used to generate data for use in multiple publications, identifying significant new prognostic markers in colorectal, upper gastro-intestinal and breast cancer. Data generated using RandomSpot also has significant value for training image analysis algorithms using sample point coordinates and pathologist classifications.

Randomized Clinical Trial Comparing Proton Beam Radiation Therapy with Transarterial Chemoembolization for Hepatocellular Carcinoma: Results of an Interim Analysis

Energy Technology Data Exchange (ETDEWEB)

Bush, David A., E-mail: dbush@llu.edu [Department of Radiation Medicine, Loma Linda University Medical Center, Loma Linda, California (United States); Smith, Jason C. [Department of Diagnostic Radiology, Loma Linda University Medical Center, Loma Linda, California (United States); Slater, Jerry D. [Department of Radiation Medicine, Loma Linda University Medical Center, Loma Linda, California (United States); Volk, Michael L. [Transplantation Institute and Liver Center, Loma Linda University Medical Center, Loma Linda, California (United States); Reeves, Mark E. [VA Loma Linda Health Care System, Loma Linda, California (United States); Cheng, Jason [Transplantation Institute and Liver Center, Loma Linda University Medical Center, Loma Linda, California (United States); Grove, Roger [Department of Radiation Medicine, Loma Linda University Medical Center, Loma Linda, California (United States); Vera, Michael E. de [Transplantation Institute and Liver Center, Loma Linda University Medical Center, Loma Linda, California (United States)

2016-05-01

Purpose: To describe results of a planned interim analysis of a prospective, randomized clinical trial developed to compare treatment outcomes among patients with newly diagnosed hepatocellular carcinoma (HCC). Methods and Materials: Eligible subjects had either clinical or pathologic diagnosis of HCC and met either Milan or San Francisco transplant criteria. Patients were randomly assigned to transarterial chemoembolization (TACE) or to proton beam radiation therapy. Patients randomized to TACE received at least 1 TACE with additional TACE for persistent disease. Proton beam radiation therapy was delivered to all areas of gross disease to a total dose of 70.2 Gy in 15 daily fractions over 3 weeks. The primary endpoint was progression-free survival, with secondary endpoints of overall survival, local tumor control, and treatment-related toxicities as represented by posttreatment days of hospitalization. Results: At the time of this analysis 69 subjects were available for analysis. Of these, 36 were randomized to TACE and 33 to proton. Total days of hospitalization within 30 days of TACE/proton was 166 and 24 days, respectively (P<.001). Ten TACE and 12 proton patients underwent liver transplantation after treatment. Viable tumor identified in the explanted livers after TACE/proton averaged 2.4 and 0.9 cm, respectively. Pathologic complete response after TACE/proton was 10%/25% (P=.38). The 2-year overall survival for all patients was 59%, with no difference between treatment groups. Median survival time was 30 months (95% confidence interval 20.7-39.3 months). There was a trend toward improved 2-year local tumor control (88% vs 45%, P=.06) and progression-free survival (48% vs 31%, P=.06) favoring the proton beam treatment group. Conclusions: This interim analysis indicates similar overall survival rates for proton beam radiation therapy and TACE. There is a trend toward improved local tumor control and progression-free survival with proton beam. There are

Time-delayed fronts from biased random walks

International Nuclear Information System (INIS)

Fort, Joaquim; Pujol, Toni

2007-01-01

We generalize a previous model of time-delayed reaction-diffusion fronts (Fort and Mendez 1999 Phys. Rev. Lett. 82 867) to allow for a bias in the microscopic random walk of particles or individuals. We also present a second model which takes the time order of events (diffusion and reproduction) into account. As an example, we apply them to the human invasion front across the USA in the 19th century. The corrections relative to the previous model are substantial. Our results are relevant to physical and biological systems with anisotropic fronts, including particle diffusion in disordered lattices, population invasions, the spread of epidemics, etc

Synthesis of results of randomized controlled trials of contrast media

International Nuclear Information System (INIS)

Kinnison, M.L.; Powe, N.R.; Steinberg, E.P.

1988-01-01

The authors review 100 randomized controlled trials (RCTs) that examine the safety or efficacy of new low-osmolality contrast media (LOM) and focus on the 43 RCTs judged to be of the highest quality. These RCTs showed no consistent differences in nephrotoxicity between high- and low-osmolality contrast media. Certain cardiovascular parameters were altered less with low-osmolality agents during intracardiac injection, but the clinical significance of these differences in unclear. Heat and pain sensations occurred less often with low-osmolality contrast media. No differences were noted in the incidence of nausea, vomiting, urticaria, or bronchospasm. Even with numerous RCTs comparing these media, physicians still must make economically significant choices about contrast media without sufficient data about their relative safety

Random model of two-level atoms interacting with electromagnetic field

International Nuclear Information System (INIS)

Kireev, A.N.; Meleshko, A.N.

1983-12-01

A phase transition has been studied in a random system of two-level atoms interacting with an electromagnetic field. It is shown that superradiation can arise when there is short-range order in a spin-subsystem. The existence of long-range order is irrelevant for this phase transition

Spherically symmetric random walks. II. Dimensionally dependent critical behavior

International Nuclear Information System (INIS)

Bender, C.M.; Boettcher, S.; Meisinger, P.N.

1996-01-01

A recently developed model of random walks on a D-dimensional hyperspherical lattice, where D is not restricted to integer values, is extended to include the possibility of creating and annihilating random walkers. Steady-state distributions of random walkers are obtained for all dimensions D approx-gt 0 by solving a discrete eigenvalue problem. These distributions exhibit dimensionally dependent critical behavior as a function of the birth rate. This remarkably simple model exhibits a second-order phase transition with a universal, nontrivial critical exponent for all dimensions D approx-gt 0. copyright 1996 The American Physical Society

Protein domain organisation: adding order.

Science.gov (United States)

Kummerfeld, Sarah K; Teichmann, Sarah A

2009-01-29

Domains are the building blocks of proteins. During evolution, they have been duplicated, fused and recombined, to produce proteins with novel structures and functions. Structural and genome-scale studies have shown that pairs or groups of domains observed together in a protein are almost always found in only one N to C terminal order and are the result of a single recombination event that has been propagated by duplication of the multi-domain unit. Previous studies of domain organisation have used graph theory to represent the co-occurrence of domains within proteins. We build on this approach by adding directionality to the graphs and connecting nodes based on their relative order in the protein. Most of the time, the linear order of domains is conserved. However, using the directed graph representation we have identified non-linear features of domain organization that are over-represented in genomes. Recognising these patterns and unravelling how they have arisen may allow us to understand the functional relationships between domains and understand how the protein repertoire has evolved. We identify groups of domains that are not linearly conserved, but instead have been shuffled during evolution so that they occur in multiple different orders. We consider 192 genomes across all three kingdoms of life and use domain and protein annotation to understand their functional significance. To identify these features and assess their statistical significance, we represent the linear order of domains in proteins as a directed graph and apply graph theoretical methods. We describe two higher-order patterns of domain organisation: clusters and bi-directionally associated domain pairs and explore their functional importance and phylogenetic conservation. Taking into account the order of domains, we have derived a novel picture of global protein organization. We found that all genomes have a higher than expected degree of clustering and more domain pairs in forward and

Scavenging and recombination kinetics in a radiation spur: The successive ordered scavenging events

Science.gov (United States)

Al-Samra, Eyad H.; Green, Nicholas J. B.

2018-03-01

This study describes stochastic models to investigate the successive ordered scavenging events in a spur of four radicals, a model system based on a radiation spur. Three simulation models have been developed to obtain the probabilities of the ordered scavenging events: (i) a Monte Carlo random flight (RF) model, (ii) hybrid simulations in which the reaction rate coefficient is used to generate scavenging times for the radicals and (iii) the independent reaction times (IRT) method. The results of these simulations are found to be in agreement with one another. In addition, a detailed master equation treatment is also presented, and used to extract simulated rate coefficients of the ordered scavenging reactions from the RF simulations. These rate coefficients are transient, the rate coefficients obtained for subsequent reactions are effectively equal, and in reasonable agreement with the simple correction for competition effects that has recently been proposed.

Pseudo random number generator based on quantum chaotic map

Science.gov (United States)

Akhshani, A.; Akhavan, A.; Mobaraki, A.; Lim, S.-C.; Hassan, Z.

2014-01-01

For many years dissipative quantum maps were widely used as informative models of quantum chaos. In this paper, a new scheme for generating good pseudo-random numbers (PRNG), based on quantum logistic map is proposed. Note that the PRNG merely relies on the equations used in the quantum chaotic map. The algorithm is not complex, which does not impose high requirement on computer hardware and thus computation speed is fast. In order to face the challenge of using the proposed PRNG in quantum cryptography and other practical applications, the proposed PRNG is subjected to statistical tests using well-known test suites such as NIST, DIEHARD, ENT and TestU01. The results of the statistical tests were promising, as the proposed PRNG successfully passed all these tests. Moreover, the degree of non-periodicity of the chaotic sequences of the quantum map is investigated through the Scale index technique. The obtained result shows that, the sequence is more non-periodic. From these results it can be concluded that, the new scheme can generate a high percentage of usable pseudo-random numbers for simulation and other applications in scientific computing.

A modified hybrid uncertain analysis method for dynamic response field of the LSOAAC with random and interval parameters

Science.gov (United States)

Zi, Bin; Zhou, Bin

2016-07-01

For the prediction of dynamic response field of the luffing system of an automobile crane (LSOAAC) with random and interval parameters, a hybrid uncertain model is introduced. In the hybrid uncertain model, the parameters with certain probability distribution are modeled as random variables, whereas, the parameters with lower and upper bounds are modeled as interval variables instead of given precise values. Based on the hybrid uncertain model, the hybrid uncertain dynamic response equilibrium equation, in which different random and interval parameters are simultaneously included in input and output terms, is constructed. Then a modified hybrid uncertain analysis method (MHUAM) is proposed. In the MHUAM, based on random interval perturbation method, the first-order Taylor series expansion and the first-order Neumann series, the dynamic response expression of the LSOAAC is developed. Moreover, the mathematical characteristics of extrema of bounds of dynamic response are determined by random interval moment method and monotonic analysis technique. Compared with the hybrid Monte Carlo method (HMCM) and interval perturbation method (IPM), numerical results show the feasibility and efficiency of the MHUAM for solving the hybrid LSOAAC problems. The effects of different uncertain models and parameters on the LSOAAC response field are also investigated deeply, and numerical results indicate that the impact made by the randomness in the thrust of the luffing cylinder F is larger than that made by the gravity of the weight in suspension Q . In addition, the impact made by the uncertainty in the displacement between the lower end of the lifting arm and the luffing cylinder a is larger than that made by the length of the lifting arm L .

Radiotherapy with or without hyperthermia in the treatment of superficial localized breast cancer: results from five randomized controlled trials

International Nuclear Information System (INIS)

Vernon, Clare C.; Hand, Jeffrey W.; Field, Stanley B.; Machin, David; Whaley, Jill B.; Zee, Jacoba van der; Putten, Wim L.J. van; Rhoon, Gerard C. van; Dijk, Jan D.P. van; Gonzalez, Dionisio Gonzalez; Liu, F.-F.; Goodman, Phyllis; Sherar, Michael

1996-01-01

Purpose: Claims for the value of hyperthermia as an adjunct to radiotherapy in the treatment of cancer have mostly been based on small Phase I or II trials. To test the benefit of this form of treatment, randomized Phase III trials were needed. Methods and Materials: Five randomized trials addressing this question were started between 1988 and 1991. In these trials, patients were eligible if they had advanced primary or recurrent breast cancer, and local radiotherapy was indicated in preference to surgery. In addition, heating of the lesions and treatment with a prescribed (re)irradiation schedule had to be feasible and informed consent was obtained. The primary endpoint of all trials was local complete response. Slow recruitment led to a decision to collaborate and combine the trial results in one analysis, and report them simultaneously in one publication. Interim analyses were carried out and the trials were closed to recruitment when a previously agreed statistically significant difference in complete response rate was observed in the two larger trials. Results: We report on pretreatment characteristics, the treatments received, the local response observed, duration of response, time to local failure, distant progression and survival, and treatment toxicity of the 306 patients randomized. The overall CR rate for RT alone was 41% and for the combined treatment arm was 59%, giving, after stratification by trial, an odds ratio of 2.3. Not all trials demonstrated an advantage for the combined treatment, although the 95% confidence intervals of the different trials all contain the pooled odds ratio. The greatest effect was observed in patients with recurrent lesions in previously irradiated areas, where further irradiation was limited to low doses. Conclusion: The combined result of the five trials has demonstrated the efficacy of hyperthermia as an adjunct to radiotherapy for treatment of recurrent breast cancer. The implication of these encouraging results is that

A Randomization Procedure for "Trickle-Process" Evaluations

Science.gov (United States)

Goldman, Jerry

1977-01-01

This note suggests a solution to the problem of achieving randomization in experimental settings where units deemed eligible for treatment "trickle in," that is, appear at any time. The solution permits replication of the experiment in order to test for time-dependent effects. (Author/CTM)

Some common random fixed point theorems for contractive type conditions in cone random metric spaces

Directory of Open Access Journals (Sweden)

Saluja Gurucharan S.

2016-08-01

Full Text Available In this paper, we establish some common random fixed point theorems for contractive type conditions in the setting of cone random metric spaces. Our results unify, extend and generalize many known results from the current existing literature.

Efficacy of Souvenaid in mild Alzheimer's disease: results from a randomized, controlled trial

NARCIS (Netherlands)

Scheltens, P.; Twisk, J.W.; Blesa, R.; Scarpini, E.; von Arnim, C.A.F.; Bongers, A.; Harrison, J.; Swinkels, S.H.N.; Stam, C.J.; de Waal, H.; Wurtman, R.J.; Wieggers, R.L.; Vellas, B.; Kamphuis, P.J.G.H.

2012-01-01

Souvenaid aims to improve synapse formation and function. An earlier study in patients with Alzheimer's disease (AD) showed that Souvenaid increased memory performance after 12 weeks in drug-naïve patients with mild AD. The Souvenir II study was a 24-week, randomized, controlled, double-blind,

A single dose of oxytocin nasal spray improves higher-order social cognition in schizophrenia.

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Guastella, Adam J; Ward, Philip B; Hickie, Ian B; Shahrestani, Sara; Hodge, Marie Antoinette Redoblado; Scott, Elizabeth M; Langdon, Robyn

2015-11-01

Schizophrenia is associated with significant impairments in both higher and lower order social cognitive performance and these impairments contribute to poor social functioning. People with schizophrenia report poor social functioning to be one of their greatest unmet treatment needs. Recent studies have suggested the potential of oxytocin as such a treatment, but mixed results render it uncertain what aspects of social cognition are improved by oxytocin and, subsequently, how oxytocin might best be applied as a therapeutic. The aim of this study was to determine whether a single dose of oxytocin improved higher-order and lower-order social cognition performance for patients with schizophrenia across a well-established battery of social cognition tests. Twenty-one male patients received both a single dose of oxytocin nasal spray (24IU) and a placebo, two weeks apart in a randomized within-subjects placebo controlled design. Following each administration, participants completed the social cognition tasks, as well as a test of general neurocognition. Results revealed that oxytocin particularly enhanced performance on higher order social cognition tasks, with no effects on general neurocognition. Results for individual tasks showed most improvement on tests measuring appreciation of indirect hints and recognition of social faux pas. These results suggest that oxytocin, if combined to enhance social cognition learning, may be beneficial when targeted at higher order social cognition domains. This study also suggests that these higher order tasks, which assess social cognitive processing in a social communication context, may provide useful markers of response to oxytocin in schizophrenia. Copyright © 2015 Elsevier B.V. All rights reserved.

Prospective randomized clinical studies involving reirradiation. Lessons learned

International Nuclear Information System (INIS)

Nieder, Carsten; Langendijk, Johannes A.; Guckenberger, Matthias; Grosu, Anca L.

2016-01-01

Reirradiation is a potentially useful option for many patients with recurrent cancer. The purpose of this study was to review all recently published randomized trials in order to identify methodological strengths and weaknesses, comment on the results, clinical implications and open questions, and give advice for the planning of future trials. Systematic review of trials published between 2000 and 2015 (databases searched were PubMed, Scopus and Web of Science). We reviewed 9 trials, most of which addressed reirradiation of head and neck tumours. The median number of patients was 69. Trial design, primary endpoint and statistical hypotheses varied widely. The results contribute mainly to decision making for reirradiation of nasopharynx cancer and bone metastases. The trials with relatively long median follow-up confirm that serious toxicity remains a concern after high cumulative total doses. Multi-institutional collaboration is encouraged to complete sufficiently large trials. Despite a paucity of large randomized studies, reirradiation has been adopted in different clinical scenarios by many institutions. Typically, the patients have been assessed by multidisciplinary tumour boards and advanced technologies are used to create highly conformal dose distributions. (orig.) [de

From Bloch to random lasing in ZnO self-assembled nanostructures

DEFF Research Database (Denmark)

Garcia-Fernandez, Pedro David; Cefe, López

2013-01-01

In this paper, we present measurements on UV lasing in ZnO ordered and disordered nanostructures. Bloch lasing is achieved in the ordered structures by exploiting very low group-velocity Bloch modes in ZnO photonic crystals. In the second case, random lasing is observed in ZnO photonic glasses. We...... study the lasing threshold in both cases and its dependence on the structural parameters. Finally, we present the transition from Bloch to random lasing by deliberately doping a ZnO inverse photonic crystal with a controlled amount of lattice vacancies effectively converting it into a translationally...

Continuous-time quantum random walks require discrete space

International Nuclear Information System (INIS)

Manouchehri, K; Wang, J B

2007-01-01

Quantum random walks are shown to have non-intuitive dynamics which makes them an attractive area of study for devising quantum algorithms for long-standing open problems as well as those arising in the field of quantum computing. In the case of continuous-time quantum random walks, such peculiar dynamics can arise from simple evolution operators closely resembling the quantum free-wave propagator. We investigate the divergence of quantum walk dynamics from the free-wave evolution and show that, in order for continuous-time quantum walks to display their characteristic propagation, the state space must be discrete. This behavior rules out many continuous quantum systems as possible candidates for implementing continuous-time quantum random walks

Continuous-time quantum random walks require discrete space

Science.gov (United States)

Manouchehri, K.; Wang, J. B.

2007-11-01

Quantum random walks are shown to have non-intuitive dynamics which makes them an attractive area of study for devising quantum algorithms for long-standing open problems as well as those arising in the field of quantum computing. In the case of continuous-time quantum random walks, such peculiar dynamics can arise from simple evolution operators closely resembling the quantum free-wave propagator. We investigate the divergence of quantum walk dynamics from the free-wave evolution and show that, in order for continuous-time quantum walks to display their characteristic propagation, the state space must be discrete. This behavior rules out many continuous quantum systems as possible candidates for implementing continuous-time quantum random walks.

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

NARCIS (Netherlands)

J.L. Geluk (Jaap); L. Peng (Liang); C.G. de Vries (Casper)

1999-01-01

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

Stability of a nonlinear second order equation under parametric bounded noise excitation

International Nuclear Information System (INIS)

Wiebe, Richard; Xie, Wei-Chau

2016-01-01

The motivation for the following work is a structural column under dynamic axial loads with both deterministic (harmonic transmitted forces from the surrounding structure) and random (wind and/or earthquake) loading components. The bounded noise used herein is a sinusoid with an argument composed of a random (Wiener) process deviation about a mean frequency. By this approach, a noise parameter may be used to investigate the behavior through the spectrum from simple harmonic forcing, to a bounded random process with very little harmonic content. The stability of both the trivial and non-trivial stationary solutions of an axially-loaded column (which is modeled as a second order nonlinear equation) under parametric bounded noise excitation is investigated by use of Lyapunov exponents. Specifically the effect of noise magnitude, amplitude of the forcing, and damping on stability of a column is investigated. First order averaging is employed to obtain analytical approximations of the Lyapunov exponents of the trivial solution. For the non-trivial stationary solution however, the Lyapunov exponents are obtained via Monte Carlo simulation as the stability equations become analytically intractable. (paper)

Heavy-traffic limits for polling models with exhaustive service and non-FCFS service orders

NARCIS (Netherlands)

P. Vis (Petra); R. Bekker (Rene); R.D. van der Mei (Rob)

2015-01-01

htmlabstractWe study cyclic polling models with exhaustive service at each queue under a variety of non-FCFS (first-come-first-served) local service orders, namely last-come-first-served with and without preemption, random-order-of-service, processor sharing, the multi-class priority scheduling with

Restoration of dimensional reduction in the random-field Ising model at five dimensions

Science.gov (United States)

Fytas, Nikolaos G.; Martín-Mayor, Víctor; Picco, Marco; Sourlas, Nicolas

2017-04-01

The random-field Ising model is one of the few disordered systems where the perturbative renormalization group can be carried out to all orders of perturbation theory. This analysis predicts dimensional reduction, i.e., that the critical properties of the random-field Ising model in D dimensions are identical to those of the pure Ising ferromagnet in D -2 dimensions. It is well known that dimensional reduction is not true in three dimensions, thus invalidating the perturbative renormalization group prediction. Here, we report high-precision numerical simulations of the 5D random-field Ising model at zero temperature. We illustrate universality by comparing different probability distributions for the random fields. We compute all the relevant critical exponents (including the critical slowing down exponent for the ground-state finding algorithm), as well as several other renormalization-group invariants. The estimated values of the critical exponents of the 5D random-field Ising model are statistically compatible to those of the pure 3D Ising ferromagnet. These results support the restoration of dimensional reduction at D =5 . We thus conclude that the failure of the perturbative renormalization group is a low-dimensional phenomenon. We close our contribution by comparing universal quantities for the random-field problem at dimensions 3 ≤D equality at all studied dimensions.

Sugars, obesity, and cardiovascular disease: results from recent randomized control trials.

Science.gov (United States)

Rippe, James M; Angelopoulos, Theodore J

2016-11-01

The relationship between sugar consumption and various health-related sequelas is controversial. Some investigators have argued that excessive sugar consumption is associated with increased risk of obesity, coronary heart disease, diabetes (T2D), metabolic syndrome, non-alcoholic fatty liver disease, and stimulation of reward pathways in the brain potentially causing excessive caloric consumption. These concerns have influenced organizations such as the World Health Organization, the Scientific Advisory Committee on Nutrition in England not to exceed 5 % of total energy and the Dietary Guidelines for Americans Advisory Committee 2015 to recommend upper limits of sugar consumption not to exceed 10 % of calories. Data from many randomized control trials (RCTs) do not support linkages between sugar consumption at normal levels within the human diet and various adverse metabolic and health-related effects. Fructose and glucose are typically consumed together in roughly equal proportions from high-fructose corn syrup (also known as isoglucose in Europe) or sucrose. The purpose of this review is to present data from recent RCTs and findings from recent systematic reviews and meta-analyses related to sugar consumption and its putative health effects. This review evaluates findings from recent randomized controlled trials, systematic reviews and meta-analyses into the relationship of sugar consumption and a range of health-related issues including energy-regulating hormones, obesity, cardiovascular disease, diabetes, and accumulation of liver fat and neurologic responses. Data from these sources do not support linkages between sugar consumption at normal levels within the human diet and various adverse metabolic and health-related effects.

Survival after relapse in patients with endometrial cancer : results from a randomized trial

NARCIS (Netherlands)

Creutzberg, CL; van Putten, WLJ; Koper, PC; Lybeert, MLM; Jobsen, JJ; Warlam-Rodenhuis, CC; De Winter, KAJ; Lutgens, LCHW; van den Bergh, ACM; van der Steen-Banasik, E; Beerman, H; van Lent, M

Objective. The aim of this study was to determine the rates of local control and survival after relapse in patients with stage I endometrial cancer treated in the multicenter randomized PORTEC trial. Methods, The PORTEC trial included 715 patients with stage I endometrial cancer, either grade I or 2

Mainstreaming Remedial Mathematics Students in Introductory Statistics: Results Using a Randomized Controlled Trial

Science.gov (United States)

Logue, Alexandra W.; Watanabe-Rose, Mari

2014-01-01

This study used a randomized controlled trial to determine whether students, assessed by their community colleges as needing an elementary algebra (remedial) mathematics course, could instead succeed at least as well in a college-level, credit-bearing introductory statistics course with extra support (a weekly workshop). Researchers randomly…

10-year results of a new low-monomer cement: follow-up of a randomized RSA study.

Science.gov (United States)

Söderlund, Per; Dahl, Jon; Röhrl, Stephan; Nivbrant, Bo; Nilsson, Kjell G

2012-12-01

The properties and performance of a new low-monomer cement were examined in this prospective randomized, controlled RSA study. 5-year data have already been published, showing no statistically significant differences compared to controls. In the present paper we present the 10-year results. 44 patients were originally randomized to receive total hip replacement with a Lubinus SPII titanium-aluminum-vanadium stem cemented either with the new Cemex Rx bone cement or with control bone cement, Palacos R. Patients were examined using RSA, Harris hip score, and conventional radiographs. At 10 years, 33 hips could be evaluated clinically and 30 hips could be evaluated with RSA (16 Cemex and 14 Palacos). 9 patients had died and 4 patients were too old or infirm to be investigated. Except for 1 hip that was revised for infection after less than 5 years, no further hips were revised before the 10-year follow-up. There were no statistically significant clinical differences between the groups. The Cemex cement had magnitudes of migration similar to or sometimes lower than those of Palacos cement. In both groups, most hips showed extensive radiolucent lines, probably due to the use of titanium alloy stems. At 10 years, the Cemex bone cement tested performed just as well as the control (Palacos bone cement).

Further results on global state feedback stabilization of nonlinear high-order feedforward systems.

Science.gov (United States)

Xie, Xue-Jun; Zhang, Xing-Hui

2014-03-01

In this paper, by introducing a combined method of sign function, homogeneous domination and adding a power integrator, and overcoming several troublesome obstacles in the design and analysis, the problem of state feedback control for a class of nonlinear high-order feedforward systems with the nonlinearity's order being relaxed to an interval rather than a fixed point is solved. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

Microwave single-scattering properties of randomly oriented soft-ice hydrometeors

Directory of Open Access Journals (Sweden)

D. Casella

2008-11-01

Full Text Available Large ice hydrometeors are usually present in intense convective clouds and may significantly affect the upwelling radiances that are measured by satellite-borne microwave radiometers – especially, at millimeter-wavelength frequencies. Thus, interpretation of these measurements (e.g., for precipitation retrieval requires knowledge of the single scattering properties of ice particles. On the other hand, shape and internal structure of these particles (especially, the larger ones is very complex and variable, and therefore it is necessary to resort to simplifying assumptions in order to compute their single-scattering parameters.

In this study, we use the discrete dipole approximation (DDA to compute the absorption and scattering efficiencies and the asymmetry factor of two kinds of quasi-spherical and non-homogeneous soft-ice particles in the frequency range 50–183 GHz. Particles of the first kind are modeled as quasi-spherical ice particles having randomly distributed spherical air inclusions. Particles of the second kind are modeled as random aggregates of ice spheres having random radii. In both cases, particle densities and dimensions are coherent with the snow hydrometeor category that is utilized by the University of Wisconsin – Non-hydrostatic Modeling System (UW-NMS cloud-mesoscale model. Then, we compare our single-scattering results for randomly-oriented soft-ice hydrometeors with corresponding ones that make use of: a effective-medium equivalent spheres, b solid-ice equivalent spheres, and c randomly-oriented aggregates of ice cylinders. Finally, we extend to our particles the scattering formulas that have been developed by other authors for randomly-oriented aggregates of ice cylinders.

Controls/CFD Interdisciplinary Research Software Generates Low-Order Linear Models for Control Design From Steady-State CFD Results

Science.gov (United States)

Melcher, Kevin J.

1997-01-01

The NASA Lewis Research Center is developing analytical methods and software tools to create a bridge between the controls and computational fluid dynamics (CFD) disciplines. Traditionally, control design engineers have used coarse nonlinear simulations to generate information for the design of new propulsion system controls. However, such traditional methods are not adequate for modeling the propulsion systems of complex, high-speed vehicles like the High Speed Civil Transport. To properly model the relevant flow physics of high-speed propulsion systems, one must use simulations based on CFD methods. Such CFD simulations have become useful tools for engineers that are designing propulsion system components. The analysis techniques and software being developed as part of this effort are an attempt to evolve CFD into a useful tool for control design as well. One major aspect of this research is the generation of linear models from steady-state CFD results. CFD simulations, often used during the design of high-speed inlets, yield high resolution operating point data. Under a NASA grant, the University of Akron has developed analytical techniques and software tools that use these data to generate linear models for control design. The resulting linear models have the same number of states as the original CFD simulation, so they are still very large and computationally cumbersome. Model reduction techniques have been successfully applied to reduce these large linear models by several orders of magnitude without significantly changing the dynamic response. The result is an accurate, easy to use, low-order linear model that takes less time to generate than those generated by traditional means. The development of methods for generating low-order linear models from steady-state CFD is most complete at the one-dimensional level, where software is available to generate models with different kinds of input and output variables. One-dimensional methods have been extended

Using computerized provider order entry to enforce documentation of tests with pending results at hospital discharge.

Science.gov (United States)

Cadwallader, J; Asirwa, C; Li, X; Kesterson, J; Tierney, W M; Were, M C

2012-01-01

Small numbers of tests with pending results are documented in hospital discharge summaries leading to breakdown in communication and medical errors due to inadequate followup. Evaluate effect of using a computerized provider order entry (CPOE) system to enforce documentation of tests with pending results into hospital discharge summaries. We assessed the percent of all tests with pending results and those with actionable results that were documented before (n = 182 discharges) and after (n = 203 discharges) implementing the CPOE-enforcement tool. We also surveyed providers (n = 52) about the enforcement functionality. Documentation of all tests with pending results improved from 12% (87/701 tests) before to 22% (178/812 tests) (p = 0.02) after implementation. Documentation of tests with eventual actionable results increased from 0% (0/24) to 50% (14/28)(ppending results into discharge summaries significantly increased documentation rates, especially of actionable tests. However, gaps in documentation still exist.

Extinction order and altered community structure rapidly disrupt ecosystem functioning.

Science.gov (United States)

Larsen, Trond H; Williams, Neal M; Kremen, Claire

2005-05-01

By causing extinctions and altering community structure, anthropogenic disturbances can disrupt processes that maintain ecosystem integrity. However, the relationship between community structure and ecosystem functioning in natural systems is poorly understood. Here we show that habitat loss appeared to disrupt ecosystem functioning by affecting extinction order, species richness and abundance. We studied pollination by bees in a mosaic of agricultural and natural habitats in California and dung burial by dung beetles on recently created islands in Venezuela. We found that large-bodied bee and beetle species tended to be both most extinction-prone and most functionally efficient, contributing to rapid functional loss. Simulations confirmed that extinction order led to greater disruption of function than predicted by random species loss. Total abundance declined with richness and also appeared to contribute to loss of function. We demonstrate conceptually and empirically how the non-random response of communities to disturbance can have unexpectedly large functional consequences.

Partially ordered sets, transfinite topology and the dimension of Cantorian-fractal spacetime

Energy Technology Data Exchange (ETDEWEB)

Marek-Crnjac, L. [Institute of Mathematics and Physics, University of Maribor (Slovenia)], E-mail: leila.marek@guest.arnes.si

2009-11-15

We introduce partially ordered sets and relate them to random Cantor sets of E-infinity theory. Subsequently we derive the dimensionality of Cantorian-fractal spacetime using posets and E-infinity transfinite Cantor sets.

Home parenteral nutrition increases fat free mass in patients with incurable gastrointestinal cancer. Results of a randomized controlled trial

DEFF Research Database (Denmark)

Obling, Sine Roelsgaard; Wilson, Benedicte Vibjerg; Pfeiffer, Per

2018-01-01

, the primary endpoint being fat free mass (FFM) and secondary: muscle function, quality of life and overall survival. Design and methods: In a single centre open-label randomised controlled trial, patients with incurable gastrointestinal cancer, nutritionally at risk, were randomly assigned to either; a) best...... FFM. Secondary outcomes were muscle strength, quality of life and survival. Results: Eligible for inclusion were 234 patients, 47 of these accepted enrolment; 25 were randomized to non-sHPN and 22 to sHPN according to performance status, age and diagnoses. Median age was 66.9 (41.5-88.2), BMI 21.3 (14.......8-35.7) and (91%) were receiving palliative chemotherapy. Median FFM and fat free mass index increased in the sHPN group. At 12 weeks a significant difference (p FFM. Handgrip strength increased in both groups...

Energy Contents of Frequently Ordered Restaurant Meals and Comparison with Human Energy Requirements and U.S. Department of Agriculture Database Information: A Multisite Randomized Study.

Science.gov (United States)

Urban, Lorien E; Weber, Judith L; Heyman, Melvin B; Schichtl, Rachel L; Verstraete, Sofia; Lowery, Nina S; Das, Sai Krupa; Schleicher, Molly M; Rogers, Gail; Economos, Christina; Masters, William A; Roberts, Susan B

2016-04-01

Excess energy intake from meals consumed away from home is implicated as a major contributor to obesity, and ∼50% of US restaurants are individual or small-chain (non-chain) establishments that do not provide nutrition information. To measure the energy content of frequently ordered meals in non-chain restaurants in three US locations, and compare with the energy content of meals from large-chain restaurants, energy requirements, and food database information. A multisite random-sampling protocol was used to measure the energy contents of the most frequently ordered meals from the most popular cuisines in non-chain restaurants, together with equivalent meals from large-chain restaurants. Meals were obtained from restaurants in San Francisco, CA; Boston, MA; and Little Rock, AR, between 2011 and 2014. Meal energy content determined by bomb calorimetry. Regional and cuisine differences were assessed using a mixed model with restaurant nested within region×cuisine as the random factor. Paired t tests were used to evaluate differences between non-chain and chain meals, human energy requirements, and food database values. Meals from non-chain restaurants contained 1,205±465 kcal/meal, amounts that were not significantly different from equivalent meals from large-chain restaurants (+5.1%; P=0.41). There was a significant effect of cuisine on non-chain meal energy, and three of the four most popular cuisines (American, Italian, and Chinese) had the highest mean energy (1,495 kcal/meal). Ninety-two percent of meals exceeded typical energy requirements for a single eating occasion. Non-chain restaurants lacking nutrition information serve amounts of energy that are typically far in excess of human energy requirements for single eating occasions, and are equivalent to amounts served by the large-chain restaurants that have previously been criticized for providing excess energy. Restaurants in general, rather than specific categories of restaurant, expose patrons to

Magnetic ordering in arrays of one-dimensional nanoparticle chains

International Nuclear Information System (INIS)

Serantes, D; Baldomir, D; Pereiro, M; Hernando, B; Prida, V M; Sanchez Llamazares, J L; Zhukov, A; Ilyn, M; Gonzalez, J

2009-01-01

The magnetic order in parallel-aligned one-dimensional (1D) chains of magnetic nanoparticles is studied using a Monte Carlo technique. If the easy anisotropy axes are collinear along the chains a macroscopic mean-field approach indicates antiferromagnetic (AFM) order even when no interparticle interactions are taken into account, which evidences that a mean-field treatment is inadequate for the study of the magnetic order in these highly anisotropic systems. From the direct microscopic analysis of the evolution of the magnetic moments, we observe spontaneous intra-chain ferromagnetic (FM)-type and inter-chain AFM-type ordering at low temperatures (although not completely regular) for the easy-axes collinear case, whereas a random distribution of the anisotropy axes leads to a sort of intra-chain AFM arrangement with no inter-chain regular order. When the magnetic anisotropy is neglected a perfectly regular intra-chain FM-like order is attained. Therefore it is shown that the magnetic anisotropy, and particularly the spatial distribution of the easy axes, is a key parameter governing the magnetic ordering type of 1D-nanoparticle chains.

Monte Carlo simulation of the three-state vector Potts model on a three-dimensional random lattice

International Nuclear Information System (INIS)

Jianbo Zhang; Heping Ying

1991-09-01

We have performed a numerical simulation of the three-state vector Potts model on a three-dimensional random lattice. The averages of energy density, magnetization, specific heat and susceptibility of the system in the N 3 (N=8,10,12) lattices were calculated. The results show that a first order nature of the Z(3) symmetry breaking transition appears, as characterized by a thermal hysterisis in the energy density as well as an abrupt drop of magnetization being sharper and discontinuous with increasing of volume in the cross-over region. The results obtained on the random lattice were consistent with those obtained on the three-dimensional cubic lattice. (author). 12 refs, 4 figs

Generating equilateral random polygons in confinement II

International Nuclear Information System (INIS)

Diao, Y; Ernst, C; Montemayor, A; Ziegler, U

2012-01-01

In this paper we continue an earlier study (Diao et al 2011 J. Phys. A: Math. Theor. 44 405202) on the generation algorithms of random equilateral polygons confined in a sphere. Here, the equilateral random polygons are rooted at the center of the confining sphere and the confining sphere behaves like an absorbing boundary. One way to generate such a random polygon is the accept/reject method in which an unconditioned equilateral random polygon rooted at origin is generated. The polygon is accepted if it is within the confining sphere, otherwise it is rejected and the process is repeated. The algorithm proposed in this paper offers an alternative to the accept/reject method, yielding a faster generation process when the confining sphere is small. In order to use this algorithm effectively, a large, reusable data set needs to be pre-computed only once. We derive the theoretical distribution of the given random polygon model and demonstrate, with strong numerical evidence, that our implementation of the algorithm follows this distribution. A run time analysis and a numerical error estimate are given at the end of the paper. (paper)

Some results on convergence rates for probabilities of moderate deviations for sums of random variables

Directory of Open Access Journals (Sweden)

Deli Li

1992-01-01

Full Text Available Let X, Xn, n≥1 be a sequence of iid real random variables, and Sn=∑k=1nXk, n≥1. Convergence rates of moderate deviations are derived, i.e., the rate of convergence to zero of certain tail probabilities of the partial sums are determined. For example, we obtain equivalent conditions for the convergence of series ∑n≥1(ψ2(n/nP(|Sn|≥nφ(n only under the assumptions convergence that EX=0 and EX2=1, where φ and ψ are taken from a broad class of functions. These results generalize and improve some recent results of Li (1991 and Gafurov (1982 and some previous work of Davis (1968. For b∈[0,1] and ϵ>0, letλϵ,b=∑n≥3((loglognb/nI(|Sn|≥(2+ϵnloglogn.The behaviour of Eλϵ,b as ϵ↓0 is also studied.

Does transfusion improve the outcome for HNSCC patients treated with radiotherapy? - Results from the randomized DAHANCA 5 and 7 trials

DEFF Research Database (Denmark)

Hoff, Camilla Molich; Lassen, Pernille; Eriksen, Jesper Grau

2011-01-01

of transfusion by the results from the randomized DAHANCA 5 trial, including 414 patients in the analysis. Aim of the current analysis was to gain additional power by adding patients from the continued subrandomization in the DAHANCA 7 trial, now including a total of almost 1200 patients. Material and methods...

Inadequacy of ethical conduct and reporting of stepped wedge cluster randomized trials: Results from a systematic review.

Science.gov (United States)

Taljaard, Monica; Hemming, Karla; Shah, Lena; Giraudeau, Bruno; Grimshaw, Jeremy M; Weijer, Charles

2017-08-01

Background/aims The use of the stepped wedge cluster randomized design is rapidly increasing. This design is commonly used to evaluate health policy and service delivery interventions. Stepped wedge cluster randomized trials have unique characteristics that complicate their ethical interpretation. The 2012 Ottawa Statement provides comprehensive guidance on the ethical design and conduct of cluster randomized trials, and the 2010 CONSORT extension for cluster randomized trials provides guidelines for reporting. Our aims were to assess the adequacy of the ethical conduct and reporting of stepped wedge trials to date, focusing on research ethics review and informed consent. Methods We conducted a systematic review of stepped wedge cluster randomized trials in health research published up to 2014 in English language journals. We extracted details of study intervention and data collection procedures, as well as reporting of research ethics review and informed consent. Two reviewers independently extracted data from each trial; discrepancies were resolved through discussion. We identified the presence of any research participants at the cluster level and the individual level. We assessed ethical conduct by tabulating reporting of research ethics review and informed consent against the presence of research participants. Results Of 32 identified stepped wedge trials, only 24 (75%) reported review by a research ethics committee, and only 16 (50%) reported informed consent from any research participants-yet, all trials included research participants at some level. In the subgroup of 20 trials with research participants at cluster level, only 4 (20%) reported informed consent from such participants; in 26 trials with individual-level research participants, only 15 (58%) reported their informed consent. Interventions (regardless of whether targeting cluster- or individual-level participants) were delivered at the group level in more than two-thirds of trials; nine trials (28

Unbiased All-Optical Random-Number Generator

Science.gov (United States)

Steinle, Tobias; Greiner, Johannes N.; Wrachtrup, Jörg; Giessen, Harald; Gerhardt, Ilja

2017-10-01

The generation of random bits is of enormous importance in modern information science. Cryptographic security is based on random numbers which require a physical process for their generation. This is commonly performed by hardware random-number generators. These often exhibit a number of problems, namely experimental bias, memory in the system, and other technical subtleties, which reduce the reliability in the entropy estimation. Further, the generated outcome has to be postprocessed to "iron out" such spurious effects. Here, we present a purely optical randomness generator, based on the bistable output of an optical parametric oscillator. Detector noise plays no role and postprocessing is reduced to a minimum. Upon entering the bistable regime, initially the resulting output phase depends on vacuum fluctuations. Later, the phase is rigidly locked and can be well determined versus a pulse train, which is derived from the pump laser. This delivers an ambiguity-free output, which is reliably detected and associated with a binary outcome. The resulting random bit stream resembles a perfect coin toss and passes all relevant randomness measures. The random nature of the generated binary outcome is furthermore confirmed by an analysis of resulting conditional entropies.

Parallel Monte Carlo Particle Transport and the Quality of Random Number Generators: How Good is Good Enough?

International Nuclear Information System (INIS)

Procassini, R J; Beck, B R

2004-01-01

It might be assumed that use of a ''high-quality'' random number generator (RNG), producing a sequence of ''pseudo random'' numbers with a ''long'' repetition period, is crucial for producing unbiased results in Monte Carlo particle transport simulations. While several theoretical and empirical tests have been devised to check the quality (randomness and period) of an RNG, for many applications it is not clear what level of RNG quality is required to produce unbiased results. This paper explores the issue of RNG quality in the context of parallel, Monte Carlo transport simulations in order to determine how ''good'' is ''good enough''. This study employs the MERCURY Monte Carlo code, which incorporates the CNPRNG library for the generation of pseudo-random numbers via linear congruential generator (LCG) algorithms. The paper outlines the usage of random numbers during parallel MERCURY simulations, and then describes the source and criticality transport simulations which comprise the empirical basis of this study. A series of calculations for each test problem in which the quality of the RNG (period of the LCG) is varied provides the empirical basis for determining the minimum repetition period which may be employed without producing a bias in the mean integrated results

Tolerance limits and tolerance intervals for ratios of normal random variables using a bootstrap calibration.

Science.gov (United States)

Flouri, Marilena; Zhai, Shuyan; Mathew, Thomas; Bebu, Ionut

2017-05-01

This paper addresses the problem of deriving one-sided tolerance limits and two-sided tolerance intervals for a ratio of two random variables that follow a bivariate normal distribution, or a lognormal/normal distribution. The methodology that is developed uses nonparametric tolerance limits based on a parametric bootstrap sample, coupled with a bootstrap calibration in order to improve accuracy. The methodology is also adopted for computing confidence limits for the median of the ratio random variable. Numerical results are reported to demonstrate the accuracy of the proposed approach. The methodology is illustrated using examples where ratio random variables are of interest: an example on the radioactivity count in reverse transcriptase assays and an example from the area of cost-effectiveness analysis in health economics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A distribution-free newsvendor model with balking penalty and random yield

Directory of Open Access Journals (Sweden)

Chongfeng Lan

2015-05-01

Full Text Available Purpose: The purpose of this paper is to extend the analysis of the distribution-free newsvendor problem in an environment of customer balking, which occurs when customers are reluctant to buy a product if its available inventory falls below a threshold level. Design/methodology/approach: We provide a new tradeoff tool as a replacement of the traditional one to weigh the holding cost and the goodwill costs segment: in addition to the shortage penalty, we also introduce the balking penalty. Furthermore, we extend our model to the case of random yield. Findings: A model is presented for determining both an optimal order quantity and a lower bound on the profit under the worst possible distribution of the demand. We also study the effects of shortage penalty and the balking penalty on the optimal order quantity, which have been largely bypassed in the existing distribution free single period models with balking. Numerical examples are presented to illustrate the result. Originality/value: The incorporation of balking penalty and random yield represents an important improvement in inventory policy performance for distribution-free newsvendor problem when customer balking occurs and the distributional form of demand is unknown.

Nurse-delivered counselling intervention for parental HIV disclosure: Results from a pilot randomized controlled trial in China

Science.gov (United States)

Simoni, Jane M.; Yang, Joyce P.; Shiu, Cheng-Shi; Chen, Wei-ti; Udell, Wadiya; Bao, Meijuan; Zhang, Lin; Lu, Hongzhou

2016-01-01

Objective The objective of this study was to design and conduct a preliminary evaluation of an intervention to assist parents in decision-making about disclosure of their HIV diagnosis to their children. Design This was a pilot randomized controlled trial (RCT) with blinded assessment. Participants were randomized to intervention or treatment-as-usual (TAU) arms. Setting The study occurred at an outpatient HIV primary care centre in Shanghai, China. Participants Participants were 20 HIV-positive outpatients with at least one child (13–25 years old) who was unaware of the parent’s HIV diagnosis. Intervention The nurse-delivered intervention involved three, hour-long, individual sessions over 4 weeks. Intervention content comprised family assessment, discussion of advantages and disadvantages of disclosure, psycho-education about cognitive, social and emotional abilities of children at different developmental stages, and disclosure planning and practicing via role-plays. Main outcome measure(s) Primary study outcomes for intervention versus TAU arms were self-reported disclosure distress, self-efficacy and behaviours along a continuum from no disclosure to full disclosure and open communication about HIV. Results In all cross-sectional (Wald tests) and longitudinal (general estimating equations) analyses, at both postintervention (4 weeks) and follow-up (13 weeks), effects were in the hypothesized directions. Despite the small sample size, most of these between-arm comparisons were statistically significant, with at least one result for each outcome indicating a ‘large’ effect size. Conclusion Our results suggest that nurses are able to deliver a counselling intervention in a clinic setting with the potential to alleviate parental distress around HIV disclosure to their children. Findings warrant future trials powered for efficacy. PMID:26049544

The treatment of disc herniation-induced sciatica with infliximab - One-year follow-up results of FIRST II, a randomized controlled trial

NARCIS (Netherlands)

Korhonen, Timo; Karppinen, Jaro; Paimela, Leena; Malmivaara, Antti; Lindgren, Karl-August; Bowman, Chris; Hammond, Anthony; Kirkham, Bruce; Jarvinen, Simo; Niinimaki, Jaakko; Veeger, Nic; Haapea, Marianne; Torkki, Markus; Tervonen, Osmo; Seitsalo, Seppo; Hurri, Heikki

2006-01-01

Study Design. A randomized controlled trial. Objectives. To evaluate the long-term efficacy of infliximab, a monoclonal antibody against tumor necrosis factor alpha (TNF-alpha), in patients with acute/subacute sciatica secondary to herniated disc. Summary of Background Data. The results of

The effects of radiation therapy on quality of life in women with breast cancer: Results of a randomized trial

International Nuclear Information System (INIS)

Whelan, T.; Levine, M.; Julian, J.; Skingley, P.; Kirkbride, P.; Clark, R.; Lipa, M.; Wilkinson, R.

1997-01-01

Purpose/Objective: The effects of radiation therapy on quality of life of women with breast cancer are not well known. The purpose of this study was to evaluate the effect of breast irradiation on quality of life including cosmetic outcome in the context of a randomized controlled trial. Methods: Between 1984 and 1989 a randomized trial was conducted in Ontario in which women with node-negative breast cancer who had undergone lumpectomy and axillary section were randomized either to postoperative radiation (4000 cGy in 16 fractions to the whole breast, followed by a boost of 1250 cGy in five fractions to the primary site) or no further treatment (J Natl Cancer Inst 1996; 88:1659). A modified version of the breast cancer chemotherapy questionnaire (J Clin Oncol 1988; 6:1798) containing 17 items was administered to women at baseline, one month and two months postrandomization. Each item was scored on a Likert scale from ''1'' All of the Time to ''7'' None of the Time. Patient assessments of breast pain and cosmetic outcome were also evaluated every three months for the first two years of the study. Results: Of 837 patients, 416 were randomly allocated to radiation therapy and 421 to no further treatment. The groups were comparable in terms of baseline characteristics. Factor analysis identified three different domains of the quality of life instrument: emotional/social, fatigue, and physical/inconvenience. There was a significant difference in the physical/inconvenience and fatigue domain scores between the radiation and control groups over time. The differences in scores between groups at two months post randomization were 0.97, p = 0.0001; 0.33, p=0.0001; and 0.03, p=0.62 for the physical/inconvenience, fatigue and emotional/social domains respectively. The percentage of patients who were troubled by breast pain differed between radiation and control groups up to one year (33.3% vs 19.9%, p = 0.001 at 6 months). Beyond one year, no difference was detected. The

Magnetic Excitations and Magnetic Ordering in Praseodymium

DEFF Research Database (Denmark)

Houmann, Jens Christian Gylden; Chapellier, M.; Mackintosh, A. R.

1975-01-01

The dispersion relations for magnetic excitons propagating on the hexagonal sites of double-hcp Pr provide clear evidence for a pronounced anisotropy in the exchange. The energy of the excitations decreases rapidly as the temperature is lowered, but becomes almost constant below about 7 K......, in agreement with a random-phase-approximation calculation. No evidence of magnetic ordering has been observed above 0.4 K, although the exchange is close to the critical value necessary for an antiferromagnetic state....

Study of the effect of magnetic ordering on order–disorder transitions in binary alloys

Energy Technology Data Exchange (ETDEWEB)

Jena, Ambika Prasad [Department of Condensed Matter and Materials Science, S.N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake City, Kolkata 700098 (India); Sanyal, Biplab [Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala (Sweden); Mookerjee, Abhijit, E-mail: abhijit@bose.res.in [Department of Condensed Matter and Materials Science, S.N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake City, Kolkata 700098 (India)

2014-06-01

We set up a mean-field approximation in a random Ising model characterized by two order parameters: the local sublattice magnetization and a mean-field occupation variable which act as an order parameter for the order–disorder transition. In the effective model Hamiltonian the two order-parameters are coupled. We solve the coupled equations arising from this to describe the total phase diagram. The exchange energies for FeCo alloys have then been accurately obtained from first-principles based on the technique of orbital peeling and a Monte Carlo analysis using a coupled Metropolis-Kawasaki updating has been carried out. Our results reasonably successfully agree with earlier experimental data. - Highlights: • In this paper we study the effect of magnetic ordering on order–disorder transitions in binary alloys. • It describes a system with two order parameters, magnetic and chemical ordering, which are coupled. • We set up a mean-field theory for initial understanding and then carry out Monte Carlo simulations. • One parameter follows Kawasaki-dynamics and the other Metropolis. • It is an interesting system for study and we apply it to FeCo with exchanges calculated from first principles techniques.

Efficacy of the epilepsy nurse: Results of a randomized controlled study.

Science.gov (United States)

Pfäfflin, Margarete; Schmitz, Bettina; May, Theodor W

2016-07-01

We investigated the efficacy of epilepsy nurses on satisfaction with counseling about epilepsy in a randomized, controlled, prospective trial. Patients with epilepsy treated by neurologists in outpatient clinics were consecutively enrolled and randomly allocated to either the epilepsy nurse (EN) group (n = 92) or the control group (n = 95). Patients in the EN group were advised according to their needs by epilepsy nurses. The control group received routine care without additional counseling. The EN group completed the questionnaires before the first consultation (T1) and 6 months later (T2); the control group completed the questionnaires twice with an interval of 6 months. Primary outcome measure was satisfaction of patients with information and support. Secondary outcome measures were satisfaction with patient-doctor relationship, organization of treatment, epilepsy knowledge, coping, and restrictions in daily life. Anxiety and depression (Hospital Anxiety and Depression Scale) and global Quality of Life (item from QOLIE-31) were also assessed. Statistical analysis included generalized estimating equation (GEE) and nonparametric tests. Satisfaction with information and support improved significantly in the EN group compared to the control group (GEE, interaction group × time, p = 0.001). In addition, Epilepsy Knowledge (p = 0.014) and Coping (subscale Information Seeking) (p = 0.023) improved. Increase in satisfaction with counseling was dependent on patients' needs for information and on the amount of received information (Jonckheere-Terpstra test, p < 0.001). No differences between the groups were observed on other epilepsy-specific scales. A reliable questionnaire for satisfaction with epilepsy care has been developed. Epilepsy nurses improve the satisfaction of patients with counseling and information about epilepsy and concomitant problems. Wiley Periodicals, Inc. © 2016 International League Against Epilepsy.

Tunnelling through a Gaussian random barrier

International Nuclear Information System (INIS)

Bezak, Viktor

2008-01-01

A thorough analysis of the tunnelling of electrons through a laterally inhomogeneous rectangular barrier is presented. The barrier height is defined as a statistically homogeneous Gaussian random function. In order to simplify calculations, we assume that the electron energy is low enough in comparison with the mean value of the barrier height. The randomness of the barrier height is defined vertically by a constant variance and horizontally by a finite correlation length. We present detailed calculations of the angular probability density for the tunnelled electrons (i.e. for the scattering forwards). The tunnelling manifests a remarkably diffusive character if the wavelength of the electrons is comparable with the correlation length of the barrier

Higher-Order Spectrum in Understanding Nonlinearity in EEG Rhythms

Directory of Open Access Journals (Sweden)

Cauchy Pradhan

2012-01-01

Full Text Available The fundamental nature of the brain's electrical activities recorded as electroencephalogram (EEG remains unknown. Linear stochastic models and spectral estimates are the most common methods for the analysis of EEG because of their robustness, simplicity of interpretation, and apparent association with rhythmic behavioral patterns in nature. In this paper, we extend the use of higher-order spectrum in order to indicate the hidden characteristics of EEG signals that simply do not arise from random processes. The higher-order spectrum is an extension Fourier spectrum that uses higher moments for spectral estimates. This essentially nullifies all Gaussian random effects, therefore, can reveal non-Gaussian and nonlinear characteristics in the complex patterns of EEG time series. The paper demonstrates the distinguishing features of bispectral analysis for chaotic systems, filtered noises, and normal background EEG activity. The bispectrum analysis detects nonlinear interactions; however, it does not quantify the coupling strength. The squared bicoherence in the nonredundant region has been estimated to demonstrate nonlinear coupling. The bicoherence values are minimal for white Gaussian noises (WGNs and filtered noises. Higher bicoherence values in chaotic time series and normal background EEG activities are indicative of nonlinear coupling in these systems. The paper shows utility of bispectral methods as an analytical tool in understanding neural process underlying human EEG patterns.

Large leptonic Dirac CP phase from broken democracy with random perturbations

Science.gov (United States)

Ge, Shao-Feng; Kusenko, Alexander; Yanagida, Tsutomu T.

2018-06-01

A large value of the leptonic Dirac CP phase can arise from broken democracy, where the mass matrices are democratic up to small random perturbations. Such perturbations are a natural consequence of broken residual S3 symmetries that dictate the democratic mass matrices at leading order. With random perturbations, the leptonic Dirac CP phase has a higher probability to attain a value around ± π / 2. Comparing with the anarchy model, broken democracy can benefit from residual S3 symmetries, and it can produce much better, realistic predictions for the mass hierarchy, mixing angles, and Dirac CP phase in both quark and lepton sectors. Our approach provides a general framework for a class of models in which a residual symmetry determines the general features at leading order, and where, in the absence of other fundamental principles, the symmetry breaking appears in the form of random perturbations.

Quantum Entanglement Growth under Random Unitary Dynamics

Directory of Open Access Journals (Sweden)

Adam Nahum

2017-07-01

Full Text Available Characterizing how entanglement grows with time in a many-body system, for example, after a quantum quench, is a key problem in nonequilibrium quantum physics. We study this problem for the case of random unitary dynamics, representing either Hamiltonian evolution with time-dependent noise or evolution by a random quantum circuit. Our results reveal a universal structure behind noisy entanglement growth, and also provide simple new heuristics for the “entanglement tsunami” in Hamiltonian systems without noise. In 1D, we show that noise causes the entanglement entropy across a cut to grow according to the celebrated Kardar-Parisi-Zhang (KPZ equation. The mean entanglement grows linearly in time, while fluctuations grow like (time^{1/3} and are spatially correlated over a distance ∝(time^{2/3}. We derive KPZ universal behavior in three complementary ways, by mapping random entanglement growth to (i a stochastic model of a growing surface, (ii a “minimal cut” picture, reminiscent of the Ryu-Takayanagi formula in holography, and (iii a hydrodynamic problem involving the dynamical spreading of operators. We demonstrate KPZ universality in 1D numerically using simulations of random unitary circuits. Importantly, the leading-order time dependence of the entropy is deterministic even in the presence of noise, allowing us to propose a simple coarse grained minimal cut picture for the entanglement growth of generic Hamiltonians, even without noise, in arbitrary dimensionality. We clarify the meaning of the “velocity” of entanglement growth in the 1D entanglement tsunami. We show that in higher dimensions, noisy entanglement evolution maps to the well-studied problem of pinning of a membrane or domain wall by disorder.

Quantum Entanglement Growth under Random Unitary Dynamics

Science.gov (United States)

Nahum, Adam; Ruhman, Jonathan; Vijay, Sagar; Haah, Jeongwan

2017-07-01

Characterizing how entanglement grows with time in a many-body system, for example, after a quantum quench, is a key problem in nonequilibrium quantum physics. We study this problem for the case of random unitary dynamics, representing either Hamiltonian evolution with time-dependent noise or evolution by a random quantum circuit. Our results reveal a universal structure behind noisy entanglement growth, and also provide simple new heuristics for the "entanglement tsunami" in Hamiltonian systems without noise. In 1D, we show that noise causes the entanglement entropy across a cut to grow according to the celebrated Kardar-Parisi-Zhang (KPZ) equation. The mean entanglement grows linearly in time, while fluctuations grow like (time )1/3 and are spatially correlated over a distance ∝(time )2/3. We derive KPZ universal behavior in three complementary ways, by mapping random entanglement growth to (i) a stochastic model of a growing surface, (ii) a "minimal cut" picture, reminiscent of the Ryu-Takayanagi formula in holography, and (iii) a hydrodynamic problem involving the dynamical spreading of operators. We demonstrate KPZ universality in 1D numerically using simulations of random unitary circuits. Importantly, the leading-order time dependence of the entropy is deterministic even in the presence of noise, allowing us to propose a simple coarse grained minimal cut picture for the entanglement growth of generic Hamiltonians, even without noise, in arbitrary dimensionality. We clarify the meaning of the "velocity" of entanglement growth in the 1D entanglement tsunami. We show that in higher dimensions, noisy entanglement evolution maps to the well-studied problem of pinning of a membrane or domain wall by disorder.

A lattice-model representation of continuous-time random walks

International Nuclear Information System (INIS)

Campos, Daniel; Mendez, Vicenc

2008-01-01

We report some ideas for constructing lattice models (LMs) as a discrete approach to the reaction-dispersal (RD) or reaction-random walks (RRW) models. The analysis of a rather general class of Markovian and non-Markovian processes, from the point of view of their wavefront solutions, let us show that in some regimes their macroscopic dynamics (front speed) turns out to be different from that by classical reaction-diffusion equations, which are often used as a mean-field approximation to the problem. So, the convenience of a more general framework as that given by the continuous-time random walks (CTRW) is claimed. Here we use LMs as a numerical approach in order to support that idea, while in previous works our discussion was restricted to analytical models. For the two specific cases studied here, we derive and analyze the mean-field expressions for our LMs. As a result, we are able to provide some links between the numerical and analytical approaches studied

A lattice-model representation of continuous-time random walks

Energy Technology Data Exchange (ETDEWEB)

Campos, Daniel [School of Mathematics, Department of Applied Mathematics, University of Manchester, Manchester M60 1QD (United Kingdom); Mendez, Vicenc [Grup de Fisica Estadistica, Departament de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra (Barcelona) (Spain)], E-mail: daniel.campos@uab.es, E-mail: vicenc.mendez@uab.es

2008-02-29

We report some ideas for constructing lattice models (LMs) as a discrete approach to the reaction-dispersal (RD) or reaction-random walks (RRW) models. The analysis of a rather general class of Markovian and non-Markovian processes, from the point of view of their wavefront solutions, let us show that in some regimes their macroscopic dynamics (front speed) turns out to be different from that by classical reaction-diffusion equations, which are often used as a mean-field approximation to the problem. So, the convenience of a more general framework as that given by the continuous-time random walks (CTRW) is claimed. Here we use LMs as a numerical approach in order to support that idea, while in previous works our discussion was restricted to analytical models. For the two specific cases studied here, we derive and analyze the mean-field expressions for our LMs. As a result, we are able to provide some links between the numerical and analytical approaches studied.

First-order inflation

International Nuclear Information System (INIS)

Kolb, E.W.

1991-01-01

In the original proposal, inflation occurred in the process of a strongly first-order phase transition. This model was soon demonstrated to be fatally flawed. Subsequent models for inflation involved phase transitions that were second-order, or perhaps weakly first-order; some even involved no phase transition at all. Recently the possibility of inflation during a strongly first-order phase transition has been reviewed. In this talk I will discuss some models for first-order inflation, and emphasize unique signatures that result if inflation is realized in a first-order transition. Before discussing first-order inflation, I will briefly review some of the history of inflation to demonstrate how first-order inflation differs from other models. (orig.)

Visibility-Based Hypothesis Testing Using Higher-Order Optical Interference

Science.gov (United States)

Jachura, Michał; Jarzyna, Marcin; Lipka, Michał; Wasilewski, Wojciech; Banaszek, Konrad

2018-03-01

Many quantum information protocols rely on optical interference to compare data sets with efficiency or security unattainable by classical means. Standard implementations exploit first-order coherence between signals whose preparation requires a shared phase reference. Here, we analyze and experimentally demonstrate the binary discrimination of visibility hypotheses based on higher-order interference for optical signals with a random relative phase. This provides a robust protocol implementation primitive when a phase lock is unavailable or impractical. With the primitive cost quantified by the total detected optical energy, optimal operation is typically reached in the few-photon regime.

Fourth order Douglas implicit scheme for solving three dimension reaction diffusion equation with non-linear source term

Science.gov (United States)

Hasnain, Shahid; Saqib, Muhammad; Mashat, Daoud Suleiman

2017-07-01

This research paper represents a numerical approximation to non-linear three dimension reaction diffusion equation with non-linear source term from population genetics. Since various initial and boundary value problems exist in three dimension reaction diffusion phenomena, which are studied numerically by different numerical methods, here we use finite difference schemes (Alternating Direction Implicit and Fourth Order Douglas Implicit) to approximate the solution. Accuracy is studied in term of L2, L∞ and relative error norms by random selected grids along time levels for comparison with analytical results. The test example demonstrates the accuracy, efficiency and versatility of the proposed schemes. Numerical results showed that Fourth Order Douglas Implicit scheme is very efficient and reliable for solving 3-D non-linear reaction diffusion equation.

Fourth order Douglas implicit scheme for solving three dimension reaction diffusion equation with non-linear source term

Directory of Open Access Journals (Sweden)

Shahid Hasnain

2017-07-01

Full Text Available This research paper represents a numerical approximation to non-linear three dimension reaction diffusion equation with non-linear source term from population genetics. Since various initial and boundary value problems exist in three dimension reaction diffusion phenomena, which are studied numerically by different numerical methods, here we use finite difference schemes (Alternating Direction Implicit and Fourth Order Douglas Implicit to approximate the solution. Accuracy is studied in term of L2, L∞ and relative error norms by random selected grids along time levels for comparison with analytical results. The test example demonstrates the accuracy, efficiency and versatility of the proposed schemes. Numerical results showed that Fourth Order Douglas Implicit scheme is very efficient and reliable for solving 3-D non-linear reaction diffusion equation.

Pedestrian Walking Behavior Revealed through a Random Walk Model

Directory of Open Access Journals (Sweden)

Hui Xiong

2012-01-01

Full Text Available This paper applies method of continuous-time random walks for pedestrian flow simulation. In the model, pedestrians can walk forward or backward and turn left or right if there is no block. Velocities of pedestrian flow moving forward or diffusing are dominated by coefficients. The waiting time preceding each jump is assumed to follow an exponential distribution. To solve the model, a second-order two-dimensional partial differential equation, a high-order compact scheme with the alternating direction implicit method, is employed. In the numerical experiments, the walking domain of the first one is two-dimensional with two entrances and one exit, and that of the second one is two-dimensional with one entrance and one exit. The flows in both scenarios are one way. Numerical results show that the model can be used for pedestrian flow simulation.