Skewed factor models using selection mechanisms

KAUST Repository

Kim, Hyoung-Moon

2015-12-21

Traditional factor models explicitly or implicitly assume that the factors follow a multivariate normal distribution; that is, only moments up to order two are involved. However, it may happen in real data problems that the first two moments cannot explain the factors. Based on this motivation, here we devise three new skewed factor models, the skew-normal, the skew-tt, and the generalized skew-normal factor models depending on a selection mechanism on the factors. The ECME algorithms are adopted to estimate related parameters for statistical inference. Monte Carlo simulations validate our new models and we demonstrate the need for skewed factor models using the classic open/closed book exam scores dataset.

Skewed factor models using selection mechanisms

KAUST Repository

Kim, Hyoung-Moon; Maadooliat, Mehdi; Arellano-Valle, Reinaldo B.; Genton, Marc G.

2015-01-01

Traditional factor models explicitly or implicitly assume that the factors follow a multivariate normal distribution; that is, only moments up to order two are involved. However, it may happen in real data problems that the first two moments cannot explain the factors. Based on this motivation, here we devise three new skewed factor models, the skew-normal, the skew-tt, and the generalized skew-normal factor models depending on a selection mechanism on the factors. The ECME algorithms are adopted to estimate related parameters for statistical inference. Monte Carlo simulations validate our new models and we demonstrate the need for skewed factor models using the classic open/closed book exam scores dataset.

On the Effects of Wind Turbine Wake Skew Caused by Wind Veer

Energy Technology Data Exchange (ETDEWEB)

Churchfield, Matthew J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sirnivas, Senu [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2018-01-12

Because of Coriolis forces caused by the Earth's rotation, the structure of the atmospheric boundary layer often contains wind-direction change with height, also known as wind-direction veer. Under low turbulence conditions, such as in stably stratified atmospheric conditions, this veer can be significant, even across the vertical extent of a wind turbine's rotor disk. The veer then causes the wind turbine wake to skew as it advects downstream. This wake skew has been observed both experimentally and numerically. In this work, we attempt to examine the wake skewing process in some detail, and quantify how differently a skewed wake versus a non skewed wake affects a downstream turbine. We do this by performing atmospheric large-eddy simulations to create turbulent inflow winds with and without veer. In the veer case, there is a roughly 8 degree wind direction change across the turbine rotor. We then perform subsequent large-eddy simulations using these inflow data with an actuator line rotor model to create wakes. The turbine modeled is a large, modern, offshore, multimegawatt turbine. We examine the unsteady wake data in detail and show that the skewed wake recovers faster than the non skewed wake. We also show that the wake deficit does not skew to the same degree that a passive tracer would if subject to veered inflow. Last, we use the wake data to place a hypothetical turbine 9 rotor diameters downstream by running aeroelastic simulations with the simulated wake data. We see differences in power and loads if this downstream turbine is subject to a skewed or non skewed wake. We feel that the differences observed between the skewed and nonskewed wake are important enough that the skewing effect should be included in engineering wake models.

Quantum skew divergence

Energy Technology Data Exchange (ETDEWEB)

Audenaert, Koenraad M. R., E-mail: koenraad.audenaert@rhul.ac.uk [Department of Mathematics, Royal Holloway University of London, Egham TW20 0EX, United Kingdom and Department of Physics and Astronomy, University of Ghent, S9, Krijgslaan 281, B-9000 Ghent (Belgium)

2014-11-15

In this paper, we study the quantum generalisation of the skew divergence, which is a dissimilarity measure between distributions introduced by Lee in the context of natural language processing. We provide an in-depth study of the quantum skew divergence, including its relation to other state distinguishability measures. Finally, we present a number of important applications: new continuity inequalities for the quantum Jensen-Shannon divergence and the Holevo information, and a new and short proof of Bravyi's Small Incremental Mixing conjecture.

Large-scale genomic 2D visualization reveals extensive CG-AT skew correlation in bird genomes

Directory of Open Access Journals (Sweden)

Deng Xuemei

2007-11-01

Full Text Available Abstract Background Bird genomes have very different compositional structure compared with other warm-blooded animals. The variation in the base skew rules in the vertebrate genomes remains puzzling, but it must relate somehow to large-scale genome evolution. Current research is inclined to relate base skew with mutations and their fixation. Here we wish to explore base skew correlations in bird genomes, to develop methods for displaying and quantifying such correlations at different scales, and to discuss possible explanations for the peculiarities of the bird genomes in skew correlation. Results We have developed a method called Base Skew Double Triangle (BSDT for exhibiting the genome-scale change of AT/CG skew as a two-dimensional square picture, showing base skews at many scales simultaneously in a single image. By this method we found that most chicken chromosomes have high AT/CG skew correlation (symmetry in 2D picture, except for some microchromosomes. No other organisms studied (18 species show such high skew correlations. This visualized high correlation was validated by three kinds of quantitative calculations with overlapping and non-overlapping windows, all indicating that chicken and birds in general have a special genome structure. Similar features were also found in some of the mammal genomes, but clearly much weaker than in chickens. We presume that the skew correlation feature evolved near the time that birds separated from other vertebrate lineages. When we eliminated the repeat sequences from the genomes, the AT and CG skews correlation increased for some mammal genomes, but were still clearly lower than in chickens. Conclusion Our results suggest that BSDT is an expressive visualization method for AT and CG skew and enabled the discovery of the very high skew correlation in bird genomes; this peculiarity is worth further study. Computational analysis indicated that this correlation might be a compositional characteristic

WFC3/UVIS image skew

Science.gov (United States)

Petro, Larry

2009-07-01

This proposal will provide an independent check of the skew in the ACS astrometric catalog of Omega Cen stars, using exposures taken in a 45-deg range of telescope roll. The roll sequence will also provide a test for orbital variation of skew and field angle dependent PSF variations. The astrometric catalog of Omega Cen, improved for a skew, will be used to derive the geometric distorion to all UVIS filters, which has preliminarily been determined from F606W images and an astrometric catalog of 47 Tuc.

On the Effects of Wind Turbine Wake Skew Caused by Wind Veer: Preprint

Energy Technology Data Exchange (ETDEWEB)

Churchfield, Matthew J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sirnivas, Senu [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2018-03-01

Because of Coriolis forces caused by the Earth's rotation, the structure of the atmospheric boundary layer often contains wind-direction change with height, also known as wind-direction veer. Under low turbulence conditions, such as in stably stratified atmospheric conditions, this veer can be significant, even across the vertical extent of a wind turbine's rotor disk. The veer then causes the wind turbine wake to skew as it advects downstream. This wake skew has been observed both experimentally and numerically. In this work, we attempt to examine the wake skewing process in some detail, and quantify how differently a skewed wake versus a non skewed wake affects a downstream turbine. We do this by performing atmospheric large-eddy simulations to create turbulent inflow winds with and without veer. In the veer case, there is a roughly 8 degree wind direction change across the turbine rotor. We then perform subsequent large-eddy simulations using these inflow data with an actuator line rotor model to create wakes. The turbine modeled is a large, modern, offshore, multimegawatt turbine. We examine the unsteady wake data in detail and show that the skewed wake recovers faster than the non skewed wake. We also show that the wake deficit does not skew to the same degree that a passive tracer would if subject to veered inflow. Last, we use the wake data to place a hypothetical turbine 9 rotor diameters downstream by running aeroelastic simulations with the simulated wake data. We see differences in power and loads if this downstream turbine is subject to a skewed or non skewed wake. We feel that the differences observed between the skewed and nonskewed wake are important enough that the skewing effect should be included in engineering wake models.

Skew harmonics suppression in electromagnets with application to the Advanced Light Source (ALS) storage ring corrector magnet design

International Nuclear Information System (INIS)

Schlueter, R.; Halbach, K.

1993-09-01

An analytical expression for prediction of skew harmonics in an iron core combined function regular/skew dipole magnet due to arbitrarily positioned electromagnet coils is developed. A structured approach is presented for the suppression of an arbitrary number of harmonic components to arbitrarily low values. Application of the analytical harmonic strength calculations coupled to the structured harmonic suppression approach is presented in the context of the design of the ALS storage ring corrector magnets, where quadrupole, sextupole, and octupole skew harmonics were reduced to less than 1.0% of the skew dipole at the beam aperture radius r = 3.0 cm

A Multi-Resolution Spatial Model for Large Datasets Based on the Skew-t Distribution

KAUST Repository

Tagle, Felipe

2017-12-06

Large, non-Gaussian spatial datasets pose a considerable modeling challenge as the dependence structure implied by the model needs to be captured at different scales, while retaining feasible inference. Skew-normal and skew-t distributions have only recently begun to appear in the spatial statistics literature, without much consideration, however, for the ability to capture dependence at multiple resolutions, and simultaneously achieve feasible inference for increasingly large data sets. This article presents the first multi-resolution spatial model inspired by the skew-t distribution, where a large-scale effect follows a multivariate normal distribution and the fine-scale effects follow a multivariate skew-normal distributions. The resulting marginal distribution for each region is skew-t, thereby allowing for greater flexibility in capturing skewness and heavy tails characterizing many environmental datasets. Likelihood-based inference is performed using a Monte Carlo EM algorithm. The model is applied as a stochastic generator of daily wind speeds over Saudi Arabia.

Skew-adjacency matrices of graphs

NARCIS (Netherlands)

Cavers, M.; Cioaba, S.M.; Fallat, S.; Gregory, D.A.; Haemers, W.H.; Kirkland, S.J.; McDonald, J.J.; Tsatsomeros, M.

2012-01-01

The spectra of the skew-adjacency matrices of a graph are considered as a possible way to distinguish adjacency cospectral graphs. This leads to the following topics: graphs whose skew-adjacency matrices are all cospectral; relations between the matchings polynomial of a graph and the characteristic

Skew cyclic codes over F_q+uF_q+vF_q+uvF_q

Directory of Open Access Journals (Sweden)

Ting Yao

2015-09-01

Full Text Available In this paper, we study skew cyclic codes over the ring $R=F_q+uF_q+vF_q+uvF_q$, where $u^{2}=u,v^{2}=v,uv=vu$, $q=p^{m}$ and $p$ is an odd prime. We investigate the structural properties of skew cyclic codes over $R$ through a decomposition theorem. Furthermore, we give a formula for the number of skew cyclic codes of length $n$ over $R.$

Skewed X-inactivation in cloned mice

International Nuclear Information System (INIS)

Senda, Sho; Wakayama, Teruhiko; Yamazaki, Yukiko; Ohgane, Jun; Hattori, Naka; Tanaka, Satoshi; Yanagimachi, Ryuzo; Shiota, Kunio

2004-01-01

In female mammals, dosage compensation for X-linked genes is accomplished by inactivation of one of two X chromosomes. The X-inactivation ratio (a percentage of the cells with inactivated maternal X chromosomes in the whole cells) is skewed as a consequence of various genetic mutations, and has been observed in a number of X-linked disorders. We previously reported that phenotypically normal full-term cloned mouse fetuses had loci with inappropriate DNA methylation. Thus, cloned mice are excellent models to study abnormal epigenetic events in mammalian development. In the present study, we analyzed X-inactivation ratios in adult female cloned mice (B6C3F1). Kidneys of eight naturally produced controls and 11 cloned mice were analyzed. Although variations in X-inactivation ratio among the mice were observed in both groups, the distributions were significantly different (Ansary-Bradley test, P < 0.01). In particular, 2 of 11 cloned mice showed skewed X-inactivation ratios (19.2% and 86.8%). Similarly, in intestine, 1 of 10 cloned mice had a skewed ratio (75.7%). Skewed X-inactivation was observed to various degrees in different tissues of different individuals, suggesting that skewed X-inactivation in cloned mice is the result of secondary cell selection in combination with stochastic distortion of primary choice. The present study is the first demonstration that skewed X-inactivation occurs in cloned animals. This finding is important for understanding both nuclear transfer technology and etiology of X-linked disorders

Skewed Binary Search Trees

DEFF Research Database (Denmark)

Brodal, Gerth Stølting; Moruz, Gabriel

2006-01-01

It is well-known that to minimize the number of comparisons a binary search tree should be perfectly balanced. Previous work has shown that a dominating factor over the running time for a search is the number of cache faults performed, and that an appropriate memory layout of a binary search tree...... can reduce the number of cache faults by several hundred percent. Motivated by the fact that during a search branching to the left or right at a node does not necessarily have the same cost, e.g. because of branch prediction schemes, we in this paper study the class of skewed binary search trees....... For all nodes in a skewed binary search tree the ratio between the size of the left subtree and the size of the tree is a fixed constant (a ratio of 1/2 gives perfect balanced trees). In this paper we present an experimental study of various memory layouts of static skewed binary search trees, where each...

Auto-Calibration and Fault Detection and Isolation of Skewed Redundant Accelerometers in Measurement While Drilling Systems.

Science.gov (United States)

Seyed Moosavi, Seyed Mohsen; Moaveni, Bijan; Moshiri, Behzad; Arvan, Mohammad Reza

2018-02-27

The present study designed skewed redundant accelerometers for a Measurement While Drilling (MWD) tool and executed auto-calibration, fault diagnosis and isolation of accelerometers in this tool. The optimal structure includes four accelerometers was selected and designed precisely in accordance with the physical shape of the existing MWD tool. A new four-accelerometer structure was designed, implemented and installed on the current system, replacing the conventional orthogonal structure. Auto-calibration operation of skewed redundant accelerometers and all combinations of three accelerometers have been done. Consequently, biases, scale factors, and misalignment factors of accelerometers have been successfully estimated. By defecting the sensors in the new optimal skewed redundant structure, the fault was detected using the proposed FDI method and the faulty sensor was diagnosed and isolated. The results indicate that the system can continue to operate with at least three correct sensors.

Characteristic functions of scale mixtures of multivariate skew-normal distributions

KAUST Repository

Kim, Hyoung-Moon

2011-08-01

We obtain the characteristic function of scale mixtures of skew-normal distributions both in the univariate and multivariate cases. The derivation uses the simple stochastic relationship between skew-normal distributions and scale mixtures of skew-normal distributions. In particular, we describe the characteristic function of skew-normal, skew-t, and other related distributions. © 2011 Elsevier Inc.

The structure of mode-locking regions of piecewise-linear continuous maps: II. Skew sawtooth maps

Science.gov (United States)

Simpson, D. J. W.

2018-05-01

In two-parameter bifurcation diagrams of piecewise-linear continuous maps on , mode-locking regions typically have points of zero width known as shrinking points. Near any shrinking point, but outside the associated mode-locking region, a significant proportion of parameter space can be usefully partitioned into a two-dimensional array of annular sectors. The purpose of this paper is to show that in these sectors the dynamics is well-approximated by a three-parameter family of skew sawtooth circle maps, where the relationship between the skew sawtooth maps and the N-dimensional map is fixed within each sector. The skew sawtooth maps are continuous, degree-one, and piecewise-linear, with two different slopes. They approximate the stable dynamics of the N-dimensional map with an error that goes to zero with the distance from the shrinking point. The results explain the complicated radial pattern of periodic, quasi-periodic, and chaotic dynamics that occurs near shrinking points.

Auto-Calibration and Fault Detection and Isolation of Skewed Redundant Accelerometers in Measurement While Drilling Systems

Directory of Open Access Journals (Sweden)

Seyed Mohsen Seyed Moosavi

2018-02-01

Full Text Available The present study designed skewed redundant accelerometers for a Measurement While Drilling (MWD tool and executed auto-calibration, fault diagnosis and isolation of accelerometers in this tool. The optimal structure includes four accelerometers was selected and designed precisely in accordance with the physical shape of the existing MWD tool. A new four-accelerometer structure was designed, implemented and installed on the current system, replacing the conventional orthogonal structure. Auto-calibration operation of skewed redundant accelerometers and all combinations of three accelerometers have been done. Consequently, biases, scale factors, and misalignment factors of accelerometers have been successfully estimated. By defecting the sensors in the new optimal skewed redundant structure, the fault was detected using the proposed FDI method and the faulty sensor was diagnosed and isolated. The results indicate that the system can continue to operate with at least three correct sensors.

Wave steering effects in anisotropic composite structures: Direct calculation of the energy skew angle through a finite element scheme.

Science.gov (United States)

Chronopoulos, D

2017-01-01

A systematic expression quantifying the wave energy skewing phenomenon as a function of the mechanical characteristics of a non-isotropic structure is derived in this study. A structure of arbitrary anisotropy, layering and geometric complexity is modelled through Finite Elements (FEs) coupled to a periodic structure wave scheme. A generic approach for efficiently computing the angular sensitivity of the wave slowness for each wave type, direction and frequency is presented. The approach does not involve any finite differentiation scheme and is therefore computationally efficient and not prone to the associated numerical errors. Copyright © 2016 Elsevier B.V. All rights reserved.

Multivariate extended skew-t distributions and related families

KAUST Repository

Arellano-Valle, Reinaldo B.

2010-12-01

A class of multivariate extended skew-t (EST) distributions is introduced and studied in detail, along with closely related families such as the subclass of extended skew-normal distributions. Besides mathematical tractability and modeling flexibility in terms of both skewness and heavier tails than the normal distribution, the most relevant properties of the EST distribution include closure under conditioning and ability to model lighter tails as well. The first part of the present paper examines probabilistic properties of the EST distribution, such as various stochastic representations, marginal and conditional distributions, linear transformations, moments and in particular Mardia’s measures of multivariate skewness and kurtosis. The second part of the paper studies statistical properties of the EST distribution, such as likelihood inference, behavior of the profile log-likelihood, the score vector and the Fisher information matrix. Especially, unlike the extended skew-normal distribution, the Fisher information matrix of the univariate EST distribution is shown to be non-singular when the skewness is set to zero. Finally, a numerical application of the conditional EST distribution is presented in the context of confidential data perturbation.

Multivariate extended skew-t distributions and related families

KAUST Repository

Arellano-Valle, Reinaldo B.; Genton, Marc G.

2010-01-01

A class of multivariate extended skew-t (EST) distributions is introduced and studied in detail, along with closely related families such as the subclass of extended skew-normal distributions. Besides mathematical tractability and modeling flexibility in terms of both skewness and heavier tails than the normal distribution, the most relevant properties of the EST distribution include closure under conditioning and ability to model lighter tails as well. The first part of the present paper examines probabilistic properties of the EST distribution, such as various stochastic representations, marginal and conditional distributions, linear transformations, moments and in particular Mardia’s measures of multivariate skewness and kurtosis. The second part of the paper studies statistical properties of the EST distribution, such as likelihood inference, behavior of the profile log-likelihood, the score vector and the Fisher information matrix. Especially, unlike the extended skew-normal distribution, the Fisher information matrix of the univariate EST distribution is shown to be non-singular when the skewness is set to zero. Finally, a numerical application of the conditional EST distribution is presented in the context of confidential data perturbation.

Isomorphic Operators and Functional Equations for the Skew-Circulant Algebra

Directory of Open Access Journals (Sweden)

Zhaolin Jiang

2014-01-01

Full Text Available The skew-circulant matrix has been used in solving ordinary differential equations. We prove that the set of skew-circulants with complex entries has an idempotent basis. On that basis, a skew-cyclic group of automorphisms and functional equations on the skew-circulant algebra is introduced. And different operators on linear vector space that are isomorphic to the algebra of n×n complex skew-circulant matrices are displayed in this paper.

Selection on skewed characters and the paradox of stasis.

Science.gov (United States)

Bonamour, Suzanne; Teplitsky, Céline; Charmantier, Anne; Crochet, Pierre-André; Chevin, Luis-Miguel

2017-11-01

Observed phenotypic responses to selection in the wild often differ from predictions based on measurements of selection and genetic variance. An overlooked hypothesis to explain this paradox of stasis is that a skewed phenotypic distribution affects natural selection and evolution. We show through mathematical modeling that, when a trait selected for an optimum phenotype has a skewed distribution, directional selection is detected even at evolutionary equilibrium, where it causes no change in the mean phenotype. When environmental effects are skewed, Lande and Arnold's (1983) directional gradient is in the direction opposite to the skew. In contrast, skewed breeding values can displace the mean phenotype from the optimum, causing directional selection in the direction of the skew. These effects can be partitioned out using alternative selection estimates based on average derivatives of individual relative fitness, or additive genetic covariances between relative fitness and trait (Robertson-Price identity). We assess the validity of these predictions using simulations of selection estimation under moderate sample sizes. Ecologically relevant traits may commonly have skewed distributions, as we here exemplify with avian laying date - repeatedly described as more evolutionarily stable than expected - so this skewness should be accounted for when investigating evolutionary dynamics in the wild. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

Parameterizing unconditional skewness in models for financial time series

DEFF Research Database (Denmark)

He, Changli; Silvennoinen, Annastiina; Teräsvirta, Timo

In this paper we consider the third-moment structure of a class of time series models. It is often argued that the marginal distribution of financial time series such as returns is skewed. Therefore it is of importance to know what properties a model should possess if it is to accommodate...

Objective Bayesian Analysis of Skew- t Distributions

KAUST Repository

BRANCO, MARCIA D'ELIA; GENTON, MARC G.; LISEO, BRUNERO

2012-01-01

We study the Jeffreys prior and its properties for the shape parameter of univariate skew-t distributions with linear and nonlinear Student's t skewing functions. In both cases, we show that the resulting priors for the shape parameter are symmetric

Flow induced by a skewed vortex cylinder

DEFF Research Database (Denmark)

Branlard, Emmanuel Simon Pierre

2017-01-01

The velocity field induced by a skewed vortex cylinder of longitudinal and tangential vorticity is derived in this chapter by direct integration of the Biot– Savart law. The derivation steps are provided in details. The results of Castles and Durham for the skewed semi-infinite cylinder....... The content of this chapter is based on the publication of the author entitled "Cylindrical vortex wake model: skewed cylinder, application to yawed or tilted rotors" [1]. Results from this chapter are applied: in Chap. 21 to model a wind turbine (or rotor) in yaw, in Chap. 22 to derive a new yaw...

Differential models of twin correlations in skew for body-mass index (BMI).

Science.gov (United States)

Tsang, Siny; Duncan, Glen E; Dinescu, Diana; Turkheimer, Eric

2018-01-01

Body Mass Index (BMI), like most human phenotypes, is substantially heritable. However, BMI is not normally distributed; the skew appears to be structural, and increases as a function of age. Moreover, twin correlations for BMI commonly violate the assumptions of the most common variety of the classical twin model, with the MZ twin correlation greater than twice the DZ correlation. This study aimed to decompose twin correlations for BMI using more general skew-t distributions. Same sex MZ and DZ twin pairs (N = 7,086) from the community-based Washington State Twin Registry were included. We used latent profile analysis (LPA) to decompose twin correlations for BMI into multiple mixture distributions. LPA was performed using the default normal mixture distribution and the skew-t mixture distribution. Similar analyses were performed for height as a comparison. Our analyses are then replicated in an independent dataset. A two-class solution under the skew-t mixture distribution fits the BMI distribution for both genders. The first class consists of a relatively normally distributed, highly heritable BMI with a mean in the normal range. The second class is a positively skewed BMI in the overweight and obese range, with lower twin correlations. In contrast, height is normally distributed, highly heritable, and is well-fit by a single latent class. Results in the replication dataset were highly similar. Our findings suggest that two distinct processes underlie the skew of the BMI distribution. The contrast between height and weight is in accord with subjective psychological experience: both are under obvious genetic influence, but BMI is also subject to behavioral control, whereas height is not.

A skewed distribution with asset pricing applications

NARCIS (Netherlands)

de Roon, Frans; Karehnke, P.

2017-01-01

Recent research has identified skewness and downside risk as one of the most important features of risk. We present a new distribution which makes modeling skewed risks no more difficult than normally distributed (symmetric) risks. Our distribution is a combination of the “downside” and “upside”

Characteristic functions of scale mixtures of multivariate skew-normal distributions

KAUST Repository

Kim, Hyoung-Moon; Genton, Marc G.

2011-01-01

We obtain the characteristic function of scale mixtures of skew-normal distributions both in the univariate and multivariate cases. The derivation uses the simple stochastic relationship between skew-normal distributions and scale mixtures of skew

Skewness of the standard model possible implications

International Nuclear Information System (INIS)

Nielsen, H.B.; Brene, N.

1989-09-01

In this paper we consider combinations of gauge algebra and set of rules for quantization of gauge charges. We show that the combination of the algebra of the standard model and the rule satisfied by the electric charges of the quarks and leptons has an exceptional high degree of a kind of asymmetry which we call skewness. Assuming that skewness has physical significance and adding two other rather plausible assumptions, we may conclude that space time must have a non simply connected topology on very small distances. Such topology would allow a kind of symmetry breakdown leading to a more skew combination of gauge algebra and set of quantization rules. (orig.)

Investigating the Investigative Task: Testing for Skewness--An Investigation of Different Test Statistics and Their Power to Detect Skewness

Science.gov (United States)

Tabor, Josh

2010-01-01

On the 2009 AP[c] Statistics Exam, students were asked to create a statistic to measure skewness in a distribution. This paper explores several of the most popular student responses and evaluates which statistic performs best when sampling from various skewed populations. (Contains 8 figures, 3 tables, and 4 footnotes.)

Objective Bayesian Analysis of Skew- t Distributions

KAUST Repository

BRANCO, MARCIA D'ELIA

2012-02-27

We study the Jeffreys prior and its properties for the shape parameter of univariate skew-t distributions with linear and nonlinear Student\\'s t skewing functions. In both cases, we show that the resulting priors for the shape parameter are symmetric around zero and proper. Moreover, we propose a Student\\'s t approximation of the Jeffreys prior that makes an objective Bayesian analysis easy to perform. We carry out a Monte Carlo simulation study that demonstrates an overall better behaviour of the maximum a posteriori estimator compared with the maximum likelihood estimator. We also compare the frequentist coverage of the credible intervals based on the Jeffreys prior and its approximation and show that they are similar. We further discuss location-scale models under scale mixtures of skew-normal distributions and show some conditions for the existence of the posterior distribution and its moments. Finally, we present three numerical examples to illustrate the implications of our results on inference for skew-t distributions. © 2012 Board of the Foundation of the Scandinavian Journal of Statistics.

Skew-signings of positive weighted digraphs

Directory of Open Access Journals (Sweden)

Kawtar Attas

2018-07-01

Full Text Available An arc-weighted digraph is a pair (D , ω where D is a digraph and ω is an arc-weight function that assigns to each arc u v of D a nonzero real number ω (u v . Given an arc-weighted digraph (D , ω with vertices v 1 , … , v n , the weighted adjacency matrix of (D , ω is defined as the n × n matrix A (D , ω = [ a i j ] where a i j = ω ( v i v j if v i v j is an arc of D , and 0 otherwise. Let (D , ω be a positive arc-weighted digraph and assume that D is loopless and symmetric. A skew-signing of (D , ω is an arc-weight function ω ′ such that ω ′ (u v = ± ω (u v and ω ′ (u v ω ′ (v u < 0 for every arc u v of D . In this paper, we give necessary and sufficient conditions under which the characteristic polynomial of A (D , ω ′ is the same for all skew-signings ω ′ of (D , ω . Our main theorem generalizes a result of Cavers et al. (2012 about skew-adjacency matrices of graphs. Keywords: Arc-weighted digraphs, Skew-signing of a digraph, Weighted adjacency matrix, Mathematics Subject Classification: 05C22, 05C31, 05C50

PRINCIPLE OF SKEW QUADRUPOLE MODULATION TO MEASURE BETATRON COUPLING

International Nuclear Information System (INIS)

LUO, Y.; PILAT, F.; ROSER, T.

2004-01-01

The measurement of the residual betatron coupling via skew quadrupole modulation is a new diagnostics technique that has been developed and tested at the Relativistic Heavy Ion Collider (RHIC) as a very promising method for the linear decoupling on the ramp. By modulating the strengths of different skew quadrupole families the two eigentunes are precisely measured with the phase lock loop system. The projections of the residual coupling coefficient onto the skew quadrupole coupling modulation directions are determined. The residual linear coupling could be corrected according to the measurement. An analytical solution for skew quadrupole modulation based on Hamiltonian perturbation approximation is given, and simulation code using smooth accelerator model is also developed. Some issues concerning the practical applications of this technique are discussed

Validation of an Acoustic Impedance Prediction Model for Skewed Resonators

Science.gov (United States)

Howerton, Brian M.; Parrott, Tony L.

2009-01-01

An impedance prediction model was validated experimentally to determine the composite impedance of a series of high-aspect ratio slot resonators incorporating channel skew and sharp bends. Such structures are useful for packaging acoustic liners into constrained spaces for turbofan noise control applications. A formulation of the Zwikker-Kosten Transmission Line (ZKTL) model, incorporating the Richards correction for rectangular channels, is used to calculate the composite normalized impedance of a series of six multi-slot resonator arrays with constant channel length. Experimentally, acoustic data was acquired in the NASA Langley Normal Incidence Tube over the frequency range of 500 to 3500 Hz at 120 and 140 dB OASPL. Normalized impedance was reduced using the Two-Microphone Method for the various combinations of channel skew and sharp 90o and 180o bends. Results show that the presence of skew and/or sharp bends does not significantly alter the impedance of a slot resonator as compared to a straight resonator of the same total channel length. ZKTL predicts the impedance of such resonators very well over the frequency range of interest. The model can be used to design arrays of slot resonators that can be packaged into complex geometries heretofore unsuitable for effective acoustic treatment.

A method for generating skewed random numbers using two overlapping uniform distributions

International Nuclear Information System (INIS)

Ermak, D.L.; Nasstrom, J.S.

1995-02-01

The objective of this work was to implement and evaluate a method for generating skewed random numbers using a combination of uniform random numbers. The method provides a simple and accurate way of generating skewed random numbers from the specified first three moments without an a priori specification of the probability density function. We describe the procedure for generating skewed random numbers from unifon-n random numbers, and show that it accurately produces random numbers with the desired first three moments over a range of skewness values. We also show that in the limit of zero skewness, the distribution of random numbers is an accurate approximation to the Gaussian probability density function. Future work win use this method to provide skewed random numbers for a Langevin equation model for diffusion in skewed turbulence

Continuity diaphragm for skewed continuous span precast prestressed concrete girder bridges.

Science.gov (United States)

2004-10-01

Continuity diaphragms used on skewed bents in prestressed girder bridges cause difficulties in detailing and : construction. Details for bridges with large diaphragm skew angles (>30) have not been a problem for LA DOTD. : However, as the skew angl...

Multivariate log-skew-elliptical distributions with applications to precipitation data

KAUST Repository

Marchenko, Yulia V.

2009-07-13

We introduce a family of multivariate log-skew-elliptical distributions, extending the list of multivariate distributions with positive support. We investigate their probabilistic properties such as stochastic representations, marginal and conditional distributions, and existence of moments, as well as inferential properties. We demonstrate, for example, that as for the log-t distribution, the positive moments of the log-skew-t distribution do not exist. Our emphasis is on two special cases, the log-skew-normal and log-skew-t distributions, which we use to analyze US national (univariate) and regional (multivariate) monthly precipitation data. © 2009 John Wiley & Sons, Ltd.

Multivariate log-skew-elliptical distributions with applications to precipitation data

KAUST Repository

Marchenko, Yulia V.; Genton, Marc G.

2009-01-01

We introduce a family of multivariate log-skew-elliptical distributions, extending the list of multivariate distributions with positive support. We investigate their probabilistic properties such as stochastic representations, marginal and conditional distributions, and existence of moments, as well as inferential properties. We demonstrate, for example, that as for the log-t distribution, the positive moments of the log-skew-t distribution do not exist. Our emphasis is on two special cases, the log-skew-normal and log-skew-t distributions, which we use to analyze US national (univariate) and regional (multivariate) monthly precipitation data. © 2009 John Wiley & Sons, Ltd.

Symmetries and structure of skewed and double distributions

International Nuclear Information System (INIS)

Radyushkin, A.V.

1998-01-01

Extending the concept of parton densities onto nonforward matrix elements b arO(0,z)vert b arp> of quark and gluon light-cone operators, one can use two types of nonperturbative functions: double distributions (DDs) f(x,α;t), F(x,y;t) and skewed (off and nonforward) parton distributions (SPDs) H(x,ξ;t), F ζ (X,t). The authors treat DDs as primary objects producing SPDs after integration. They emphasize the role of DDs in understanding interplay between (x) and ζ (ξ) dependences of SPDs. In particular, the use of DDs is crucial to secure the polynomiality condition: Nth moments of SPDs are Nth degree polynomials in the relevant skewedness parameter ζ or ξ. They propose simple ansaetze for DDs having correct spectral and symmetry properties and derive model expressions for SPDs satisfying all known constraints. Finally, they argue that for small skewedness, one can obtain SPDs from the usual parton densities by averaging the latter with an appropriate weight over the region [Xminusζ,X] (or [ x minus ξ, x + ξ])

Investors’ Risk Preference Characteristics and Conditional Skewness

Directory of Open Access Journals (Sweden)

Fenghua Wen

2014-01-01

Full Text Available Perspective on behavioral finance, we take a new look at the characteristics of investors’ risk preference, building the D-GARCH-M model, DR-GARCH-M model, and GARCHC-M model to investigate their changes with states of gain and loss and values of return together with other time-varying characteristics of investors’ risk preference. Based on a full description of risk preference characteristic, we develop a GARCHCS-M model to study its effect on the return skewness. The top ten market value stock composite indexes from Global Stock Exchange in 2012 are adopted to make the empirical analysis. The results show that investors are risk aversion when they gain and risk seeking when they lose, which effectively explains the inconsistent risk-return relationship. Moreover, the degree of risk aversion rises with the increasing gain and that of risk seeking improves with the increasing losses. Meanwhile, we find that investors’ inherent risk preference in most countries displays risk seeking, and their current risk preference is influenced by last period’s risk preference and disturbances. At last, investors’ risk preferences affect the conditional skewness; specifically, their risk aversion makes return skewness reduce, while risk seeking makes the skewness increase.

Modeling multivariate time series on manifolds with skew radial basis functions.

Science.gov (United States)

Jamshidi, Arta A; Kirby, Michael J

2011-01-01

We present an approach for constructing nonlinear empirical mappings from high-dimensional domains to multivariate ranges. We employ radial basis functions and skew radial basis functions for constructing a model using data that are potentially scattered or sparse. The algorithm progresses iteratively, adding a new function at each step to refine the model. The placement of the functions is driven by a statistical hypothesis test that accounts for correlation in the multivariate range variables. The test is applied on training and validation data and reveals nonstatistical or geometric structure when it fails. At each step, the added function is fit to data contained in a spatiotemporally defined local region to determine the parameters--in particular, the scale of the local model. The scale of the function is determined by the zero crossings of the autocorrelation function of the residuals. The model parameters and the number of basis functions are determined automatically from the given data, and there is no need to initialize any ad hoc parameters save for the selection of the skew radial basis functions. Compactly supported skew radial basis functions are employed to improve model accuracy, order, and convergence properties. The extension of the algorithm to higher-dimensional ranges produces reduced-order models by exploiting the existence of correlation in the range variable data. Structure is tested not just in a single time series but between all pairs of time series. We illustrate the new methodologies using several illustrative problems, including modeling data on manifolds and the prediction of chaotic time series.

Steel framing strategies for highly skewed bridges to reduce/eliminate distortion near skewed supports.

Science.gov (United States)

2014-05-01

Different problems in straight skewed steel I-girder bridges are often associated with the methods used for detailing the cross-frames. Use of theoretical terms to describe these detailing methods and absence of complete and simplified design approac...

Characteristic function-based semiparametric inference for skew-symmetric models

KAUST Repository

Potgieter, Cornelis J.

2012-12-26

Skew-symmetric models offer a very flexible class of distributions for modelling data. These distributions can also be viewed as selection models for the symmetric component of the specified skew-symmetric distribution. The estimation of the location and scale parameters corresponding to the symmetric component is considered here, with the symmetric component known. Emphasis is placed on using the empirical characteristic function to estimate these parameters. This is made possible by an invariance property of the skew-symmetric family of distributions, namely that even transformations of random variables that are skew-symmetric have a distribution only depending on the symmetric density. A distance metric between the real components of the empirical and true characteristic functions is minimized to obtain the estimators. The method is semiparametric, in that the symmetric component is specified, but the skewing function is assumed unknown. Furthermore, the methodology is extended to hypothesis testing. Two tests for a hypothesis of specific parameter values are considered, as well as a test for the hypothesis that the symmetric component has a specific parametric form. A resampling algorithm is described for practical implementation of these tests. The outcomes of various numerical experiments are presented. © 2012 Board of the Foundation of the Scandinavian Journal of Statistics.

Dip and anisotropy effects on flow using a vertically skewed model grid.

Science.gov (United States)

Hoaglund, John R; Pollard, David

2003-01-01

Darcy flow equations relating vertical and bedding-parallel flow to vertical and bedding-parallel gradient components are derived for a skewed Cartesian grid in a vertical plane, correcting for structural dip given the principal hydraulic conductivities in bedding-parallel and bedding-orthogonal directions. Incorrect-minus-correct flow error results are presented for ranges of structural dip (0 strike and dip, and a solver that can handle off-diagonal hydraulic conductivity terms.

Breeding system and reproductive skew in a highly polygynous ant population

DEFF Research Database (Denmark)

Haag-Liautard, C.; Pedersen, Jes Søe; Ovaskainen, O.

2008-01-01

of mature queens by mark-release-recapture in 29 nests and dissected a sub-sample of queens to assess their reproductive status. We also used microsatellites to estimate relatedness within and between all classes of nestmates (queens, their mates, worker brood, queen brood and male brood). Queen number...... Factors affecting relatedness among nest members in ant colonies with high queen number are still poorly understood. In order to identify the major determinants of nest kin structure, we conducted a detailed analysis of the breeding system of the ant Formica exsecta. We estimated the number...... was very high, with an arithmetic mean of 253 per nest. Most queens (90%) were reproductively active, consistent with the genetic analyses revealing that there was only a minimal reproductive skew among nestmate queens. Despite the high queen number and low reproductive skew, almost all classes...

Quantum Fisher and skew information for Unruh accelerated Dirac qubit

Energy Technology Data Exchange (ETDEWEB)

Banerjee, Subhashish; Alok, Ashutosh Kumar [Indian Institute of Technology Jodhpur, Jodhpur (India); Omkar, S. [Indian Institute of Science Education and Research, Thiruvananthapuram (India)

2016-08-15

We develop a Bloch vector representation of the Unruh channel for a Dirac field mode. This is used to provide a unified, analytical treatment of quantum Fisher and skew information for a qubit subjected to the Unruh channel, both in its pure form as well as in the presence of experimentally relevant external noise channels. The time evolution of Fisher and skew information is studied along with the impact of external environment parameters such as temperature and squeezing. The external noises are modelled by both purely dephasing phase damping and the squeezed generalised amplitude damping channels. An interesting interplay between the external reservoir temperature and squeezing on the Fisher and skew information is observed, in particular, for the action of the squeezed generalised amplitude damping channel. It is seen that for some regimes, squeezing can enhance the quantum information against the deteriorating influence of the ambient environment. Similar features are also observed for the analogous study of skew information, highlighting a similar origin of the Fisher and skew information. (orig.)

Quantum Fisher and skew information for Unruh accelerated Dirac qubit

International Nuclear Information System (INIS)

Banerjee, Subhashish; Alok, Ashutosh Kumar; Omkar, S.

2016-01-01

We develop a Bloch vector representation of the Unruh channel for a Dirac field mode. This is used to provide a unified, analytical treatment of quantum Fisher and skew information for a qubit subjected to the Unruh channel, both in its pure form as well as in the presence of experimentally relevant external noise channels. The time evolution of Fisher and skew information is studied along with the impact of external environment parameters such as temperature and squeezing. The external noises are modelled by both purely dephasing phase damping and the squeezed generalised amplitude damping channels. An interesting interplay between the external reservoir temperature and squeezing on the Fisher and skew information is observed, in particular, for the action of the squeezed generalised amplitude damping channel. It is seen that for some regimes, squeezing can enhance the quantum information against the deteriorating influence of the ambient environment. Similar features are also observed for the analogous study of skew information, highlighting a similar origin of the Fisher and skew information. (orig.)

Joint IQ Skew and Chromatic Dispersion Estimation for Coherent Optical Communication Receivers

DEFF Research Database (Denmark)

Medeiros Diniz, Júlio César; Porto da Silva, Edson; Piels, Molly

2016-01-01

A low-complexity scanning method for joint estimation of receiver IQ skew and chromatic dispersion is proposed. This method shows less than 1 ps skew error for a 1200-km 32-GBd DP-16QAM optical transmission experiment.......A low-complexity scanning method for joint estimation of receiver IQ skew and chromatic dispersion is proposed. This method shows less than 1 ps skew error for a 1200-km 32-GBd DP-16QAM optical transmission experiment....

Learning a Novel Pattern through Balanced and Skewed Input

Science.gov (United States)

McDonough, Kim; Trofimovich, Pavel

2013-01-01

This study compared the effectiveness of balanced and skewed input at facilitating the acquisition of the transitive construction in Esperanto, characterized by the accusative suffix "-n" and variable word order (SVO, OVS). Thai university students (N = 98) listened to 24 sentences under skewed (one noun with high token frequency) or…

Bayesian inference for two-part mixed-effects model using skew distributions, with application to longitudinal semicontinuous alcohol data.

Science.gov (United States)

Xing, Dongyuan; Huang, Yangxin; Chen, Henian; Zhu, Yiliang; Dagne, Getachew A; Baldwin, Julie

2017-08-01

Semicontinuous data featured with an excessive proportion of zeros and right-skewed continuous positive values arise frequently in practice. One example would be the substance abuse/dependence symptoms data for which a substantial proportion of subjects investigated may report zero. Two-part mixed-effects models have been developed to analyze repeated measures of semicontinuous data from longitudinal studies. In this paper, we propose a flexible two-part mixed-effects model with skew distributions for correlated semicontinuous alcohol data under the framework of a Bayesian approach. The proposed model specification consists of two mixed-effects models linked by the correlated random effects: (i) a model on the occurrence of positive values using a generalized logistic mixed-effects model (Part I); and (ii) a model on the intensity of positive values using a linear mixed-effects model where the model errors follow skew distributions including skew- t and skew-normal distributions (Part II). The proposed method is illustrated with an alcohol abuse/dependence symptoms data from a longitudinal observational study, and the analytic results are reported by comparing potential models under different random-effects structures. Simulation studies are conducted to assess the performance of the proposed models and method.

Likelihood Inference of Nonlinear Models Based on a Class of Flexible Skewed Distributions

Directory of Open Access Journals (Sweden)

Xuedong Chen

2014-01-01

Full Text Available This paper deals with the issue of the likelihood inference for nonlinear models with a flexible skew-t-normal (FSTN distribution, which is proposed within a general framework of flexible skew-symmetric (FSS distributions by combining with skew-t-normal (STN distribution. In comparison with the common skewed distributions such as skew normal (SN, and skew-t (ST as well as scale mixtures of skew normal (SMSN, the FSTN distribution can accommodate more flexibility and robustness in the presence of skewed, heavy-tailed, especially multimodal outcomes. However, for this distribution, a usual approach of maximum likelihood estimates based on EM algorithm becomes unavailable and an alternative way is to return to the original Newton-Raphson type method. In order to improve the estimation as well as the way for confidence estimation and hypothesis test for the parameters of interest, a modified Newton-Raphson iterative algorithm is presented in this paper, based on profile likelihood for nonlinear regression models with FSTN distribution, and, then, the confidence interval and hypothesis test are also developed. Furthermore, a real example and simulation are conducted to demonstrate the usefulness and the superiority of our approach.

Neoclassical versus Frontier Production Models ? Testing for the Skewness of Regression Residuals

DEFF Research Database (Denmark)

Kuosmanen, T; Fosgerau, Mogens

2009-01-01

The empirical literature on production and cost functions is divided into two strands. The neoclassical approach concentrates on model parameters, while the frontier approach decomposes the disturbance term to a symmetric noise term and a positively skewed inefficiency term. We propose a theoreti......The empirical literature on production and cost functions is divided into two strands. The neoclassical approach concentrates on model parameters, while the frontier approach decomposes the disturbance term to a symmetric noise term and a positively skewed inefficiency term. We propose...... a theoretical justification for the skewness of the inefficiency term, arguing that this skewness is the key testable hypothesis of the frontier approach. We propose to test the regression residuals for skewness in order to distinguish the two competing approaches. Our test builds directly upon the asymmetry...

Skew information in the XY model with staggered Dzyaloshinskii-Moriya interaction

Energy Technology Data Exchange (ETDEWEB)

Qiu, Liang, E-mail: lqiu@cumt.edu.cn [School of Physics, China University of Mining and Technology, Xuzhou, Jiangsu 221116 (China); Quan, Dongxiao [State Key Laboratory of Integrated Services Networks, Xidian University, Xi' an, Shaanxi 710071 (China); Pan, Fei; Liu, Zhi [School of Physics, China University of Mining and Technology, Xuzhou, Jiangsu 221116 (China)

2017-06-01

We study the performance of the lower bound of skew information in the vicinity of transition point for the anisotropic spin-1/2 XY chain with staggered Dzyaloshinskii-Moriya interaction by use of quantum renormalization-group method. For a fixed value of the Dzyaloshinskii-Moriya interaction, there are two saturated values for the lower bound of skew information corresponding to the spin-fluid and Néel phases, respectively. The scaling exponent of the lower bound of skew information closely relates to the correlation length of the model and the Dzyaloshinskii-Moriya interaction shifts the factorization point. Our results show that the lower bound of skew information can be a good candidate to detect the critical point of XY spin chain with staggered Dzyaloshinskii-Moriya interaction.

Random skew plane partitions with a piecewise periodic back wall

DEFF Research Database (Denmark)

Boutillier, Cedric; Mkrtchyan, Sevak; Reshetikhin, Nicolai

Random skew plane partitions of large size distributed according to an appropriately scaled Schur process develop limit shapes. In the present work we consider the limit of large random skew plane partitions where the inner boundary approaches a piecewise linear curve with non-lattice slopes. Muc...

Does Realized Skewness Predict the Cross-Section of Equity Returns?

DEFF Research Database (Denmark)

Amaya, Diego; Christoffersen, Peter; Jacobs, Kris

2015-01-01

We use intraday data to compute weekly realized moments for equity returns and study their time-series and cross-sectional properties. Buying stocks in the lowest realized skewness decile and selling stocks in the highest realized skewness decile generates an average return of 19 basis points...

The skew ray ambiguity in the analysis of videokeratoscopic data.

Science.gov (United States)

Iskander, D Robert; Davis, Brett A; Collins, Michael J

2007-05-01

Skew ray ambiguity is present in most videokeratoscopic measurements when azimuthal components of the corneal curvature are not taken into account. There have been some reported studies based on theoretical predictions and measured test surfaces suggesting that skew ray ambiguity is significant for highly deformed corneas or decentered corneal measurements. However, the effect of skew ray ambiguity in ray tracing through videokeratoscopic data has not been studied in depth. We have evaluated the significance of the skew ray ambiguity and its effect on the analyzed corneal optics. This has been achieved by devising a procedure in which we compared the corneal wavefront aberrations estimated from 3D ray tracing with those determined from 2D (meridional based) estimates of the refractive power. The latter was possible due to recently developed concept of refractive Zernike power polynomials which links the refractive power domain with that of the wavefront. Simulated corneal surfaces as well as data from a range of corneas (from two different Placido disk-based videokeratoscopes) were used to find the limit at which the difference in estimated corneal wavefronts (or the corresponding refractive powers) would have clinical significance (e.g., equivalent to 0.125 D or more). The inclusion/exclusion of the skew ray in the analyses showed some differences in the results. However, the proposed procedure showed clinically significant differences only for highly deformed corneas and only for large corneal diameters. For the overwhelming majority of surfaces, the skew ray ambiguity is not a clinically significant issue in the analysis of the videokeratoscopic data indicating that the meridional processing such as that encountered in calculation of the refractive power maps is adequate.

Analysis of Parasite and Other Skewed Counts

Science.gov (United States)

Alexander, Neal

2012-01-01

Objective To review methods for the statistical analysis of parasite and other skewed count data. Methods Statistical methods for skewed count data are described and compared, with reference to those used over a ten year period of Tropical Medicine and International Health. Two parasitological datasets are used for illustration. Results Ninety papers were identified, 89 with descriptive and 60 with inferential analysis. A lack of clarity is noted in identifying measures of location, in particular the Williams and geometric mean. The different measures are compared, emphasizing the legitimacy of the arithmetic mean for skewed data. In the published papers, the t test and related methods were often used on untransformed data, which is likely to be invalid. Several approaches to inferential analysis are described, emphasizing 1) non-parametric methods, while noting that they are not simply comparisons of medians, and 2) generalized linear modelling, in particular with the negative binomial distribution. Additional methods, such as the bootstrap, with potential for greater use are described. Conclusions Clarity is recommended when describing transformations and measures of location. It is suggested that non-parametric methods and generalized linear models are likely to be sufficient for most analyses. PMID:22943299

Uncovering the skewness news impact curve

Czech Academy of Sciences Publication Activity Database

Anatolyev, Stanislav; Petukhov, A.

2016-01-01

Roč. 14, č. 4 (2016), s. 746-771 ISSN 1479-8409 Institutional support: RVO:67985998 Keywords : conditional skewness * news impact curve * stock returns Subject RIV: AH - Economics Impact factor: 1.800, year: 2016

Shannon Entropy and Mutual Information for Multivariate Skew-Elliptical Distributions

KAUST Repository

Arellano-Valle, Reinaldo B.

2012-02-27

The entropy and mutual information index are important concepts developed by Shannon in the context of information theory. They have been widely studied in the case of the multivariate normal distribution. We first extend these tools to the full symmetric class of multivariate elliptical distributions and then to the more flexible families of multivariate skew-elliptical distributions. We study in detail the cases of the multivariate skew-normal and skew-t distributions. We implement our findings to the application of the optimal design of an ozone monitoring station network in Santiago de Chile. © 2012 Board of the Foundation of the Scandinavian Journal of Statistics.

Shannon Entropy and Mutual Information for Multivariate Skew-Elliptical Distributions

KAUST Repository

Arellano-Valle, Reinaldo B.; Contreras-Reyes, Javier E.; Genton, Marc G.

2012-01-01

The entropy and mutual information index are important concepts developed by Shannon in the context of information theory. They have been widely studied in the case of the multivariate normal distribution. We first extend these tools to the full symmetric class of multivariate elliptical distributions and then to the more flexible families of multivariate skew-elliptical distributions. We study in detail the cases of the multivariate skew-normal and skew-t distributions. We implement our findings to the application of the optimal design of an ozone monitoring station network in Santiago de Chile. © 2012 Board of the Foundation of the Scandinavian Journal of Statistics.

Uncovering the skewness news impact curve

Czech Academy of Sciences Publication Activity Database

Anatolyev, Stanislav; Petukhov, A.

2016-01-01

Roč. 14, č. 4 (2016), s. 746-771 ISSN 1479-8409 Institutional support: PRVOUK-P23 Keywords : conditional skewness * news impact curve * stock returns Subject RIV: AH - Economics Impact factor: 1.800, year: 2016

Effects of trophic skewing of species richness on ecosystem functioning in a diverse marine community.

Directory of Open Access Journals (Sweden)

Pamela L Reynolds

Full Text Available Widespread overharvesting of top consumers of the world's ecosystems has "skewed" food webs, in terms of biomass and species richness, towards a generally greater domination at lower trophic levels. This skewing is exacerbated in locations where exotic species are predominantly low-trophic level consumers such as benthic macrophytes, detritivores, and filter feeders. However, in some systems where numerous exotic predators have been added, sometimes purposefully as in many freshwater systems, food webs are skewed in the opposite direction toward consumer dominance. Little is known about how such modifications to food web topology, e.g., changes in the ratio of predator to prey species richness, affect ecosystem functioning. We experimentally measured the effects of trophic skew on production in an estuarine food web by manipulating ratios of species richness across three trophic levels in experimental mesocosms. After 24 days, increasing macroalgal richness promoted both plant biomass and grazer abundance, although the positive effect on plant biomass disappeared in the presence of grazers. The strongest trophic cascade on the experimentally stocked macroalgae emerged in communities with a greater ratio of prey to predator richness (bottom-rich food webs, while stronger cascades on the accumulation of naturally colonizing algae (primarily microalgae with some early successional macroalgae that recruited and grew in the mesocosms generally emerged in communities with greater predator to prey richness (the more top-rich food webs. These results suggest that trophic skewing of species richness and overall changes in food web topology can influence marine community structure and food web dynamics in complex ways, emphasizing the need for multitrophic approaches to understand the consequences of marine extinctions and invasions.

Inferring climate variability from skewed proxy records

Science.gov (United States)

Emile-Geay, J.; Tingley, M.

2013-12-01

Many paleoclimate analyses assume a linear relationship between the proxy and the target climate variable, and that both the climate quantity and the errors follow normal distributions. An ever-increasing number of proxy records, however, are better modeled using distributions that are heavy-tailed, skewed, or otherwise non-normal, on account of the proxies reflecting non-normally distributed climate variables, or having non-linear relationships with a normally distributed climate variable. The analysis of such proxies requires a different set of tools, and this work serves as a cautionary tale on the danger of making conclusions about the underlying climate from applications of classic statistical procedures to heavily skewed proxy records. Inspired by runoff proxies, we consider an idealized proxy characterized by a nonlinear, thresholded relationship with climate, and describe three approaches to using such a record to infer past climate: (i) applying standard methods commonly used in the paleoclimate literature, without considering the non-linearities inherent to the proxy record; (ii) applying a power transform prior to using these standard methods; (iii) constructing a Bayesian model to invert the mechanistic relationship between the climate and the proxy. We find that neglecting the skewness in the proxy leads to erroneous conclusions and often exaggerates changes in climate variability between different time intervals. In contrast, an explicit treatment of the skewness, using either power transforms or a Bayesian inversion of the mechanistic model for the proxy, yields significantly better estimates of past climate variations. We apply these insights in two paleoclimate settings: (1) a classical sedimentary record from Laguna Pallcacocha, Ecuador (Moy et al., 2002). Our results agree with the qualitative aspects of previous analyses of this record, but quantitative departures are evident and hold implications for how such records are interpreted, and

A note on generalized skew derivations on Lie ideals

Indian Academy of Sciences (India)

MOHAMMAD ASHRAF

2018-04-24

Apr 24, 2018 ... Abstract. Let R be a prime ring, Z(R) its center, C its extended centroid, L a Lie ideal of R, F a generalized skew derivation associated with a skew derivation d and automorphism α. Assume that there exist t ≥ 1 and m, n ≥ 0 fixed integers such that vu = umF(uv)tun for all u,v ∈ L. Then it is shown that either ...

Investigation of free vibration characteristics for skew multiphase magneto-electro-elastic plate

Science.gov (United States)

Kiran, M. C.; Kattimani, S.

2018-04-01

This article presents the investigation of skew multiphase magneto-electro-elastic (MMEE) plate to assess its free vibration characteristics. A finite element (FE) model is formulated considering the different couplings involved via coupled constitutive equations. The transformation matrices are derived to transform local degrees of freedom into the global degrees of freedom for the nodes lying on the skew edges. Effect of different volume fraction (Vf) on the free vibration behavior is explicitly studied. In addition, influence of width to thickness ratio, the aspect ratio, and the stacking arrangement on natural frequencies of skew multiphase MEE plate investigated. Particular attention has been paid to investigate the effect of skew angle on the non-dimensional Eigen frequencies of multiphase MEE plate with simply supported edges.

Skewed steel bridges, part ii : cross-frame and connection design to ensure brace effectiveness : technical summary.

Science.gov (United States)

2017-08-01

Skewed bridges in Kansas are often designed such that the cross-frames are carried parallel to the skew angle up to 40, while many other states place cross-frames perpendicular to the girder for skew angles greater than 20. Skewed-parallel cross-...

Skewed steel bridges, part ii : cross-frame and connection design to ensure brace effectiveness : final report.

Science.gov (United States)

2017-08-01

Skewed bridges in Kansas are often designed such that the cross-frames are carried parallel to the skew angle up to 40, while many other states place cross-frames perpendicular to the girder for skew angles greater than 20. Skewed-parallel cross-...

PARAMETRIC STUDY OF SKEW ANGLE ON BOX GIRDER BRIDGE DECK

OpenAIRE

Shrikant D. Bobade *, Dr. Valsson Varghese

2016-01-01

Box girder bridge deck, is the most common type of bridges in world and India, it consists of several Slab or girders. The span in the direction of the roadway and connected across their tops and bottoms by a thin continuous structural stab, the longitudinal box girders can be made of steel or concrete. The Simple supported single span concrete bridge deck is presented in present study. Skewed bridges are suitable in highway design when the geometry of straight bridges is not possible. The sk...

Handling Data Skew in MapReduce Cluster by Using Partition Tuning

Directory of Open Access Journals (Sweden)

Yufei Gao

2017-01-01

Full Text Available The healthcare industry has generated large amounts of data, and analyzing these has emerged as an important problem in recent years. The MapReduce programming model has been successfully used for big data analytics. However, data skew invariably occurs in big data analytics and seriously affects efficiency. To overcome the data skew problem in MapReduce, we have in the past proposed a data processing algorithm called Partition Tuning-based Skew Handling (PTSH. In comparison with the one-stage partitioning strategy used in the traditional MapReduce model, PTSH uses a two-stage strategy and the partition tuning method to disperse key-value pairs in virtual partitions and recombines each partition in case of data skew. The robustness and efficiency of the proposed algorithm were tested on a wide variety of simulated datasets and real healthcare datasets. The results showed that PTSH algorithm can handle data skew in MapReduce efficiently and improve the performance of MapReduce jobs in comparison with the native Hadoop, Closer, and locality-aware and fairness-aware key partitioning (LEEN. We also found that the time needed for rule extraction can be reduced significantly by adopting the PTSH algorithm, since it is more suitable for association rule mining (ARM on healthcare data.

Resonance multiphoton ionization and dissociation of dimethyl ether via the {\\skew1\\tilde{\\rm C}^{\\prime}}, {\\skew1\\tilde{\\rm C}} and \\tilde{\\rm B} states

Science.gov (United States)

Mejia-Ospino, E.; García, G.; Guerrero, A.; Alvarez, I.; Cisneros, C.

2005-01-01

The three-photon resonance four-photon ionization and dissociation spectra of dimethyl ether (DME) are presented in the wavelength range 450-550 nm at 1 nm intervals. The (3+1) REMPI spectra show three prominent bands corresponding to the \\tildeB \\leftarrow \\skew1\\tildeX, {\\skew1\\tildeC} \\leftarrow \\skew1\\tildeX and {\\skew1\\tildeC^{\\prime}} \\leftarrow \\skew1\\tildeX transitions with origins at 61 457 cm-1 (7.615 eV), 59 055 cm-1 (7.322 eV) and 58 010 cm-1 (7.194 eV), respectively. Several ionized species, CH3+, CHnO+ (n = 1-3) and CH3OCH3+, are observed in the region of wavelengths studied here. In order to compare the results, a shorter wavelength multiphoton dissociation and ionization of DME at 355 nm is also presented. At this wavelength, DME undergoes neutral dissociation to CH3 and CH3O and each fragment is then ionized by multiphoton absorption. The fragmentation at 355 nm is very intense and only small fragments such as CH3+, CHO+, CH2+, CH+ and C+ ions are observed. The measurement of photoelectron energy allows us to establish that the DME ionization potential is at least 9.55 ± 0.15 eV. The experiments were performed using a Nd:YAG-OPO (optical parametric oscillator) tunable laser system coupled to a time-of-flight mass spectrometer and a hemispherical electron energy analyser.

The Skew Risk Premium in the Equity Index Market

OpenAIRE

Roman Kozhan; Anthony Neuberger; Paul Schneider

2013-01-01

We develop a new method for measuring moment risk premiums. We find that the skew premium accounts for over 40% of the slope in the implied volatility curve in the S&P 500 market. Skew risk is tightly related to variance risk, in the sense that strategies designed to capture the one and hedge out exposure to the other earn an insignificant risk premium. This provides a new testable restriction for asset pricing models trying to capture, in particular, disaster risk premiums. We base our resul...

Simple skew category algebras associated with minimal partially defined dynamical systems

DEFF Research Database (Denmark)

Nystedt, Patrik; Öinert, Per Johan

2013-01-01

In this article, we continue our study of category dynamical systems, that is functors s from a category G to Topop, and their corresponding skew category algebras. Suppose that the spaces s(e), for e∈ob(G), are compact Hausdorff. We show that if (i) the skew category algebra is simple, then (ii) G...

Experimental study of the turbulent boundary layer in acceleration-skewed oscillatory flow

NARCIS (Netherlands)

van der A, D.A.; O' Donoghue, T.; Davies, A.G; Ribberink, Jan S.

2011-01-01

Experiments have been conducted in a large oscillatory flow tunnel to investigate the effects of acceleration skewness on oscillatory boundary layer flow over fixed beds. As well as enabling experimental investigation of the effects of acceleration skewness, the new experiments add substantially to

The effect of forward skewed rotor blades on aerodynamic and aeroacoustic performance of axial-flow fan

Science.gov (United States)

Wei, Jun; Zhong, Fangyuan

Based on comparative experiment, this paper deals with using tangentially skewed rotor blades in axial-flow fan. It is seen from the comparison of the overall performance of the fan with skewed bladed rotor and radial bladed rotor that the skewed blades operate more efficiently than the radial blades, especially at low volume flows. Meanwhile, decrease in pressure rise and flow rate of axial-flow fan with skewed rotor blades is found. The rotor-stator interaction noise and broadband noise of axial-flow fan are reduced with skewed rotor blades. Forward skewed blades tend to reduce the accumulation of the blade boundary layer in the tip region resulting from the effect of centrifugal forces. The turning of streamlines from the outer radius region into inner radius region in blade passages due to the radial component of blade forces of skewed blades is the main reason for the decrease in pressure rise and flow rate.

T helper cell 2 immune skewing in pregnancy/early life

DEFF Research Database (Denmark)

McFadden, J P; Thyssen, J P; Basketter, D A

2015-01-01

During the last 50 years there has been a significant increase in Western societies of atopic disease and associated allergy. The balance between functional subpopulations of T helper cells (Th) determines the quality of the immune response provoked by antigen. One such subpopulation - Th2 cells...... that in Westernized societies reduced exposure during early childhood to pathogenic microorganisms favours the development of atopic allergy. Pregnancy is normally associated with Th2 skewing, which persists for some months in the neonate before Th1/Th2 realignment occurs. In this review, we consider...... the immunophysiology of Th2 immune skewing during pregnancy. In particular, we explore the possibility that altered and increased patterns of exposure to certain chemicals have served to accentuate this normal Th2 skewing and therefore further promote the persistence of a Th2 bias in neonates. Furthermore, we propose...

Study and optimal correction of a systematic skew quadrupole field in the Tevatron

International Nuclear Information System (INIS)

Snopok, Pavel; Johnstone, Carol; Berz, Martin; Ovsyannikov, Dmitry A.; Ovsyannikov, Alexander D.

2006-01-01

Increasing demands for luminosity in existing and future colliders have made lattice design and error tolerance and correction critical to achieving performance goals. The current state of the Tevatron collider is an example, with a strong skew quadrupole error present in the operational lattice. This work studies the high-order performance of the Tevatron and the strong nonlinear behavior introduced when a significant skew quadrupole error is combined with conventional sextupole correction, a behavior still clearly evident after optimal tuning of available skew quadrupole circuits. An optimization study is performed using different skew quadrupole families, and, importantly, local and global correction of the linear skew terms in maps generated by the code COSY INFINITY [M. Berz, COSY INFINITY version 8.1 user's guide and reference manual, Department of Physics and Astronomy MSUHEP-20704, Michigan State University (2002). URL http://cosy.pa.msu.edu/cosymanu/index.html]. Two correction schemes with one family locally correcting each arc and eight independent correctors in the straight sections for global correction are proposed and shown to dramatically improve linearity and performance of the baseline Tevatron lattice

Natural frequencies and an atlas of mode shapes for generally-laminated, thick, skew, trapezoidal plates

OpenAIRE

Lovejoy, Andrew Elwyn

1994-01-01

Composite materials are increasingly finding use in structures, such as aircraft components, and thus, an accurate method of predicting response is required. Even laminated structures that are considered thin can be significantly affected by transverse shear effects, and as a result, transverse shear should not be neglected. The free vibration response of generally-laminated, thick, skew, trapezoidal plates is investigated as there appears to be a lack of information in this ar...

Generalized parton distribution for non zero skewness

International Nuclear Information System (INIS)

Kumar, Narinder; Dahiya, Harleen; Teryaev, Oleg

2012-01-01

In the theory of strong interactions the main open question is how the nucleon and other hadrons are built from quarks and gluons, the fundamental degrees of freedom in QCD. An essential tool to investigate hadron structure is the study of deep inelastic scattering processes, where individual quarks and gluons can be resolved. The parton densities extracted from such processes encode the distribution of longitudinal momentum and polarization carried by quarks, antiquarks and gluons within a fast moving hadron. They have provided much to shape the physical picture of hadron structure. In the recent years, it has become clear that appropriate exclusive scattering processes may provide such information encoded in the general parton distributions (GPDs). Here, we investigate the GPD for deep virtual compton scattering (DVCS) for the non zero skewness. The study has investigated the GPDs by expressing them in terms of overlaps of light front wave functions (LFWFs). The work represented a spin 1/2 system as a composite of spin 1/2 fermion and spin 1 boson with arbitrary masses

Generation of net sediment transport by velocity skewness in oscillatory sheet flow

Science.gov (United States)

Chen, Xin; Li, Yong; Chen, Genfa; Wang, Fujun; Tang, Xuelin

2018-01-01

This study utilizes a qualitative approach and a two-phase numerical model to investigate net sediment transport caused by velocity skewness beneath oscillatory sheet flow and current. The qualitative approach is derived based on the pseudo-laminar approximation of boundary layer velocity and exponential approximation of concentration. The two-phase model can obtain well the instantaneous erosion depth, sediment flux, boundary layer thickness, and sediment transport rate. It can especially illustrate the difference between positive and negative flow stages caused by velocity skewness, which is considerably important in determining the net boundary layer flow and sediment transport direction. The two-phase model also explains the effect of sediment diameter and phase-lag to sediment transport by comparing the instantaneous-type formulas to better illustrate velocity skewness effect. In previous studies about sheet flow transport in pure velocity-skewed flows, net sediment transport is only attributed to the phase-lag effect. In the present study with the qualitative approach and two-phase model, phase-lag effect is shown important but not sufficient for the net sediment transport beneath pure velocity-skewed flow and current, while the asymmetric wave boundary layer development between positive and negative flow stages also contributes to the sediment transport.

Few Skewed Results from IOTA Interferometer YSO Disk Survey

Science.gov (United States)

Monnier, J. D.; Millan-Gabet, R.; Berger, J.-P.; Pedretti, E.; Traub, W.; Schloerb, F. P.

2005-12-01

The 3-telescope IOTA interferometer is capable of measuring closure phases for dozens of Herbig Ae/Be stars in the near-infrared. The closure phase unambiguously identifies deviations from centro-symmetry (i.e., skew) in the brightness distribution, at the scale of 4 milliarcseconds (sub-AU physical scales) for our work. Indeed, hot dust emission from the inner circumstellar accretion disk is expected to be skewed for (generic) flared disks viewed at intermediate inclination angles, as has been observed for LkHa 101. Surprisingly, we find very little evidence for skewed disk emission in our IOTA3 sample, setting strong constraints on the geometry of the inner disk. In particular, we rule out the currently-popular model of a VERTICAL hot inner wall of dust at the sublimation radius. Instead, our data is more consistent with a curved inner wall that bends away from the midplane as might be expected from the pressure-dependence of dust sublimation or limited absorption of stellar luminosity in the disk midplane by gas.

Screening Immunomodulators To Skew the Antigen-Specific Autoimmune Response.

Science.gov (United States)

Northrup, Laura; Sullivan, Bradley P; Hartwell, Brittany L; Garza, Aaron; Berkland, Cory

2017-01-03

Current therapies to treat autoimmune diseases often result in side effects such as nonspecific immunosuppression. Therapies that can induce antigen-specific immune tolerance provide an opportunity to reverse autoimmunity and mitigate the risks associated with global immunosuppression. In an effort to induce antigen-specific immune tolerance, co-administration of immunomodulators with autoantigens has been investigated in an effort to reprogram autoimmunity. To date, identifying immunomodulators that may skew the antigen-specific immune response has been ad hoc at best. To address this need, we utilized splenocytes obtained from mice with experimental autoimmune encephalomyelitis (EAE) in order to determine if certain immunomodulators may induce markers of immune tolerance following antigen rechallenge. Of the immunomodulatory compounds investigated, only dexamethasone modified the antigen-specific immune response by skewing the cytokine response and decreasing T-cell populations at a concentration corresponding to a relevant in vivo dose. Thus, antigen-educated EAE splenocytes provide an ex vivo screen for investigating compounds capable of skewing the antigen-specific immune response, and this approach could be extrapolated to antigen-educated cells from other diseases or human tissues.

Skewed Normal Distribution Of Return Assets In Call European Option Pricing

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Evy Sulistianingsih

2011-12-01

Full Text Available Option is one of security derivates. In financial market, option is a contract that gives a right (notthe obligation for its owner to buy or sell a particular asset for a certain price at a certain time.Option can give a guarantee for a risk that can be faced in a market.This paper studies about theuse of Skewed Normal Distribution (SN in call europeanoption pricing. The SN provides aflexible framework that captures the skewness of log return. We obtain aclosed form solution forthe european call option pricing when log return follow the SN. Then, we will compare optionprices that is obtained by the SN and the Black-Scholes model with the option prices of market. Keywords: skewed normaldistribution, log return, options.

Asympotic efficiency of signed - rank symmetry tests under skew alternatives.

OpenAIRE

Alessandra Durio; Yakov Nikitin

2002-01-01

The efficiency of some known tests for symmetry such as the sign test, the Wilcoxon signed-rank test or more general linear signed rank tests was studied mainly under the classical alternatives of location. However it is interesting to compare the efficiencies of these tests under asymmetric alternatives like the so-called skew alternative proposed in Azzalini (1985). We find and compare local Bahadur efficiencies of linear signed-rank statistics for skew alternatives and discuss also the con...

Highly Efficient, Zero-Skew, Integrated Clock Distribution Networks Using Salphasic Principles

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PASCA, A.

2016-02-01

Full Text Available The design of highly efficient clock distributions for integrated circuits is an active topic of research as there will never be a single solution for all systems. For high performance digital or mixed-signal circuits, achieving zero-skew clock over large areas usually comes with high costs in power requirements and design complexity. The present paper shows an overview of a recently proposed technique for ICs - on-die salphasic clock distribution, introduced by the author for CMOS processes. Initially reported in literature for rack-systems, the present paper shows that further refinements are needed for the concept to be applicable on a silicon die. Based on the formation of a standing wave (intrinsically presenting extended in-phase regions with a voltage peak at the input (creating a no-load condition, it is shown that any IC implementation must use transmission lines loss compensation techniques to maintain the proper standing wave configuration. Furthermore, the paper shows theoretical solutions and describes practical on-die techniques for pseudo-spherical bidimensional surfaces, which, with the already reported orthogonal and pseudo-orthogonal structures, can be used to distribute with minimal power requirements a zero-skew clock signal, over large silicon areas.

Performance Analyses of IDEAL Algorithm on Highly Skewed Grid System

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Dongliang Sun

2014-03-01

Full Text Available IDEAL is an efficient segregated algorithm for the fluid flow and heat transfer problems. This algorithm has now been extended to the 3D nonorthogonal curvilinear coordinates. Highly skewed grids in the nonorthogonal curvilinear coordinates can decrease the convergence rate and deteriorate the calculating stability. In this study, the feasibility of the IDEAL algorithm on highly skewed grid system is analyzed by investigating the lid-driven flow in the inclined cavity. It can be concluded that the IDEAL algorithm is more robust and more efficient than the traditional SIMPLER algorithm, especially for the highly skewed and fine grid system. For example, at θ = 5° and grid number = 70 × 70 × 70, the convergence rate of the IDEAL algorithm is 6.3 times faster than that of the SIMPLER algorithm, and the IDEAL algorithm can converge almost at any time step multiple.

Using purine skews to predict genes in AT-rich poxviruses

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Upton Chris

2005-02-01

Full Text Available Abstract Background Clusters or runs of purines on the mRNA synonymous strand have been found in many different organisms including orthopoxviruses. The purine bias that is exhibited by these clusters can be observed using a purine skew and in the case of poxviruses, these skews can be used to help determine the coding strand of a particular segment of the genome. Combined with previous findings that minor ORFs have lower than average aspartate and glutamate composition and higher than average serine composition, purine content can be used to predict the likelihood of a poxvirus ORF being a "real gene". Results Using purine skews and a "quality" measure designed to incorporate previous findings about minor ORFs, we have found that in our training case (vaccinia virus strain Copenhagen, 59 of 65 minor (small and unlikely to be a real genes ORFs were correctly classified as being minor. Of the 201 major (large and likely to be real genes vaccinia ORFs, 192 were correctly classified as being major. Performing a similar analysis with the entomopoxvirus amsacta moorei (AMEV, it was found that 4 major ORFs were incorrectly classified as minor and 9 minor ORFs were incorrectly classified as major. The purine abundance observed for major ORFs in vaccinia virus was found to stem primarily from the first codon position with both the second and third codon positions containing roughly equal amounts of purines and pyrimidines. Conclusion Purine skews and a "quality" measure can be used to predict functional ORFs and purine skews in particular can be used to determine which of two overlapping ORFs is most likely to be the real gene if neither of the two ORFs has orthologs in other poxviruses.

Study on seismic behaviour of integral concrete bridges with different skew angles through fragility curves

Directory of Open Access Journals (Sweden)

Mahmoud Reza ُُShiravand

2017-12-01

Full Text Available Bridges are key elements in urban transportation system and should be designed to sustain earthquake induced damages to be utilized after earthquake. Extensive damages during last earthquakes highlighted the importance of seismic assessment and damage estimation of bridges. Skewness is one of the primary parameters effects on seismic behavior of bridges. Skew bridges are defined as bridges with skew angle piers and abutments. In these bridges, the piers have some degrees of skewness due to construction restrictions, such as those caused by crossing a waterway, railway line or road. This paper aims to investigate seismic behavior of skew concrete bridges using damage criteria and estimate probability of piers damage with fragility curves. To this end, three types of concrete bridges with two, three and four spans and varying skew angles of 00 ,100, 200 and 300 are modeled with finite element software. Seismic responses of bridge piers under 10 earthquake ground motion records are calculated using incremental dynamic analysis. Following, damage criteria proposed by Mackie and Stojadinovic are used to define damage limits of bridge piers in four damage states of slight, moderate, extensive and complete and bridge fragility curves are developed. The results show that increasing skew angles increases the probability of damage occurrence, particularly in extensive and complete damage states.

Skew-orthogonal polynomials, differential systems and random matrix theory

International Nuclear Information System (INIS)

Ghosh, S.

2007-01-01

We study skew-orthogonal polynomials with respect to the weight function exp[-2V (x)], with V (x) = Σ K=1 2d (u K /K)x K , u 2d > 0, d > 0. A finite subsequence of such skew-orthogonal polynomials arising in the study of Orthogonal and Symplectic ensembles of random matrices, satisfy a system of differential-difference-deformation equation. The vectors formed by such subsequence has the rank equal to the degree of the potential in the quaternion sense. These solutions satisfy certain compatibility condition and hence admit a simultaneous fundamental system of solutions. (author)

Skin friction measurements of systematically-varied roughness: Probing the role of roughness amplitude and skewness

Science.gov (United States)

Barros, Julio; Flack, Karen; Schultz, Michael

2017-11-01

Real-world engineering systems which feature either external or internal wall-bounded turbulent flow are routinely affected by surface roughness. This gives rise to performance degradation in the form of increased drag or head loss. However, at present there is no reliable means to predict these performance losses based upon the roughness topography alone. This work takes a systematic approach by generating random surface roughness in which the surface statistics are closely controlled. Skin friction and roughness function results will be presented for two groups of these rough surfaces. The first group is Gaussian (i.e. zero skewness) in which the root-mean-square roughness height (krms) is varied. The second group has a fixed krms, and the skewness is varied from approximately -1 to +1. The effect of the roughness amplitude and skewness on the skin friction will be discussed. Particular attention will be paid to the effect of these parameters on the roughness function in the transitionally-rough flow regime. For example, the role these parameters play in the monotonic or inflectional nature of the roughness function will be addressed. Future research into the details of the turbulence structure over these rough surfaces will also be outlined. Research funded by U.S. Office of Naval Research (ONR).

Uniqueness: skews bit occurrence frequencies in randomly generated fingerprint libraries.

Science.gov (United States)

Chen, Nelson G

2016-08-01

Requiring that randomly generated chemical fingerprint libraries have unique fingerprints such that no two fingerprints are identical causes a systematic skew in bit occurrence frequencies, the proportion at which specified bits are set. Observed frequencies (O) at which each bit is set within the resulting libraries systematically differ from frequencies at which bits are set at fingerprint generation (E). Observed frequencies systematically skew toward 0.5, with the effect being more pronounced as library size approaches the compound space, which is the total number of unique possible fingerprints given the number of bit positions each fingerprint contains. The effect is quantified for varying library sizes as a fraction of the overall compound space, and for changes in the specified frequency E. The cause and implications for this systematic skew are subsequently discussed. When generating random libraries of chemical fingerprints, the imposition of a uniqueness requirement should either be avoided or taken into account.

Risk Aversion and Skewness Preference: a comment

NARCIS (Netherlands)

G.T. Post (Thierry); P. van Vliet (Pim)

2003-01-01

textabstractEmpirically, co-skewness of asset returns seems to explain a substantial part of the cross-sectional variation of mean return not explained by beta. Thisfinding is typically interpreted in terms of a risk averse representativeinvestor with a cubic utility function. This comment questions

Generalized Skew Coefficients of Annual Peak Flows for Rural, Unregulated Streams in West Virginia

Science.gov (United States)

Atkins, John T.; Wiley, Jeffrey B.; Paybins, Katherine S.

2009-01-01

Generalized skew was determined from analysis of records from 147 streamflow-gaging stations in or near West Virginia. The analysis followed guidelines established by the Interagency Advisory Committee on Water Data described in Bulletin 17B, except that stations having 50 or more years of record were used instead of stations with the less restrictive recommendation of 25 or more years of record. The generalized-skew analysis included contouring, averaging, and regression of station skews. The best method was considered the one with the smallest mean square error (MSE). MSE is defined as the following quantity summed and divided by the number of peaks: the square of the difference of an individual logarithm (base 10) of peak flow less the mean of all individual logarithms of peak flow. Contouring of station skews was the best method for determining generalized skew for West Virginia, with a MSE of about 0.2174. This MSE is an improvement over the MSE of about 0.3025 for the national map presented in Bulletin 17B.

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 ...

Consistent paternity skew through ontogeny in Peron's tree frog (Litoria peronii.

Directory of Open Access Journals (Sweden)

Craig D H Sherman

Full Text Available BACKGROUND: A large number of studies in postcopulatory sexual selection use paternity success as a proxy for fertilization success. However, selective mortality during embryonic development can lead to skews in paternity in situations of polyandry and sperm competition. Thus, when assessment of paternity fails to incorporate mortality skews during early ontogeny, this may interfere with correct interpretation of results and subsequent evolutionary inference. In a previous series of in vitro sperm competition experiments with amphibians (Litoria peronii, we showed skewed paternity patterns towards males more genetically similar to the female. METHODOLOGY/PRINCIPAL FINDINGS: Here we use in vitro fertilizations and sperm competition trials to test if this pattern of paternity of fully developed tadpoles reflects patterns of paternity at fertilization and if paternity skews changes during embryonic development. We show that there is no selective mortality through ontogeny and that patterns of paternity of hatched tadpoles reflects success of competing males in sperm competition at fertilization. CONCLUSIONS/SIGNIFICANCE: While this study shows that previous inferences of fertilization success from paternity data are valid for this species, rigorous testing of these assumptions is required to ensure that differential embryonic mortality does not confound estimations of true fertilization success.

Invariant graphs of a family of non-uniformly expanding skew products over Markov maps

Science.gov (United States)

Walkden, C. P.; Withers, T.

2018-06-01

We consider a family of skew-products of the form where T is a continuous, expanding, locally eventually onto Markov map and is a family of homeomorphisms of . A function is said to be an invariant graph if is an invariant set for the skew-product; equivalently, u(T(x))  =  g x (u(x)). A well-studied problem is to consider the existence, regularity and dimension-theoretic properties of such functions, usually under strong contraction or expansion conditions (in terms of Lyapunov exponents or partial hyperbolicity) in the fibre direction. Here we consider such problems in a setting where the Lyapunov exponent in the fibre direction is zero on a set of periodic orbits but expands except on a neighbourhood of these periodic orbits. We prove that u either has the structure of a ‘quasi-graph’ (or ‘bony graph’) or is as smooth as the dynamics, and we give a criteria for this to happen.

PS-Modules over Ore Extensions and Skew Generalized Power Series Rings

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Refaat M. Salem

2015-01-01

Full Text Available A right R-module MR is called a PS-module if its socle, SocMR, is projective. We investigate PS-modules over Ore extension and skew generalized power series extension. Let R be an associative ring with identity, MR a unitary right R-module, O=Rx;α,δ Ore extension, MxO a right O-module, S,≤ a strictly ordered additive monoid, ω:S→EndR a monoid homomorphism, A=RS,≤,ω the skew generalized power series ring, and BA=MS,≤RS,≤, ω the skew generalized power series module. Then, under some certain conditions, we prove the following: (1 If MR is a right PS-module, then MxO is a right PS-module. (2 If MR is a right PS-module, then BA is a right PS-module.

Univariate and multivariate skewness and kurtosis for measuring nonnormality: Prevalence, influence and estimation.

Science.gov (United States)

Cain, Meghan K; Zhang, Zhiyong; Yuan, Ke-Hai

2017-10-01

Nonnormality of univariate data has been extensively examined previously (Blanca et al., Methodology: European Journal of Research Methods for the Behavioral and Social Sciences, 9(2), 78-84, 2013; Miceeri, Psychological Bulletin, 105(1), 156, 1989). However, less is known of the potential nonnormality of multivariate data although multivariate analysis is commonly used in psychological and educational research. Using univariate and multivariate skewness and kurtosis as measures of nonnormality, this study examined 1,567 univariate distriubtions and 254 multivariate distributions collected from authors of articles published in Psychological Science and the American Education Research Journal. We found that 74 % of univariate distributions and 68 % multivariate distributions deviated from normal distributions. In a simulation study using typical values of skewness and kurtosis that we collected, we found that the resulting type I error rates were 17 % in a t-test and 30 % in a factor analysis under some conditions. Hence, we argue that it is time to routinely report skewness and kurtosis along with other summary statistics such as means and variances. To facilitate future report of skewness and kurtosis, we provide a tutorial on how to compute univariate and multivariate skewness and kurtosis by SAS, SPSS, R and a newly developed Web application.

Yaw-modelling using a skewed vortex cylinder

DEFF Research Database (Denmark)

Branlard, Emmanuel Simon Pierre

2017-01-01

The cylindrical vortex wake model presented in Chap. 17 for the case of uniform inflow is extended in the current chapter to the case of yawed inflow. Generalities regarding yaw are presented in Sect. 6.1 and only the skewed cylindrical vortex model is presented in this chapter. The chapter starts...... with a literature review on the topic of yaw-models and vorticity-based methods. The description of the model follows. The novelty of the current model is that the assumption of infinite tip-speed ratio is relaxed. The bound vorticity is assumed to be identical to the case of uniform inflow but the vortex cylinder...... and the root vortex are skewed with respect to the normal of the rotor disk. Closed form formulae for the induced velocities are provided. They can only be evaluated analytically for a limited part of the domain. A numerical integration is required to obtain the velocity everywhere in the domain. The numerical...

The generalised Sylvester matrix equations over the generalised bisymmetric and skew-symmetric matrices

Science.gov (United States)

Dehghan, Mehdi; Hajarian, Masoud

2012-08-01

A matrix P is called a symmetric orthogonal if P = P T = P -1. A matrix X is said to be a generalised bisymmetric with respect to P if X = X T = PXP. It is obvious that any symmetric matrix is also a generalised bisymmetric matrix with respect to I (identity matrix). By extending the idea of the Jacobi and the Gauss-Seidel iterations, this article proposes two new iterative methods, respectively, for computing the generalised bisymmetric (containing symmetric solution as a special case) and skew-symmetric solutions of the generalised Sylvester matrix equation ? (including Sylvester and Lyapunov matrix equations as special cases) which is encountered in many systems and control applications. When the generalised Sylvester matrix equation has a unique generalised bisymmetric (skew-symmetric) solution, the first (second) iterative method converges to the generalised bisymmetric (skew-symmetric) solution of this matrix equation for any initial generalised bisymmetric (skew-symmetric) matrix. Finally, some numerical results are given to illustrate the effect of the theoretical results.

The Universal Patient Centredness Questionnaire: scaling approaches to reduce positive skew

Directory of Open Access Journals (Sweden)

Bjertnaes O

2016-11-01

Full Text Available Oyvind Bjertnaes, Hilde Hestad Iversen, Andrew M Garratt Unit for Patient-Reported Quality, Norwegian Institute of Public Health, Oslo, Norway Purpose: Surveys of patients’ experiences typically show results that are indicative of positive experiences. Unbalanced response scales have reduced positive skew for responses to items within the Universal Patient Centeredness Questionnaire (UPC-Q. The objective of this study was to compare the unbalanced response scale with another unbalanced approach to scaling to assess whether the positive skew might be further reduced. Patients and methods: The UPC-Q was included in a patient experience survey conducted at the ward level at six hospitals in Norway in 2015. The postal survey included two reminders to nonrespondents. For patients in the first month of inclusion, UPC-Q items had standard scaling: poor, fairly good, good, very good, and excellent. For patients in the second month, the scaling was more positive: poor, good, very good, exceptionally good, and excellent. The effect of scaling on UPC-Q scores was tested with independent samples t-tests and multilevel linear regression analysis, the latter controlling for the hierarchical structure of data and known predictors of patient-reported experiences. Results: The response rate was 54.6% (n=4,970. Significantly lower scores were found for all items of the more positively worded scale: UPC-Q total score difference was 7.9 (P<0.001, on a scale from 0 to 100 where 100 is the best possible score. Differences between the four items of the UPC-Q ranged from 7.1 (P<0.001 to 10.4 (P<0.001. Multivariate multilevel regression analysis confirmed the difference between the response groups, after controlling for other background variables; UPC-Q total score difference estimate was 8.3 (P<0.001. Conclusion: The more positively worded scaling significantly lowered the mean scores, potentially increasing the sensitivity of the UPC-Q to identify differences over

Analysis of domain wall dynamics based on skewness of magnetic Barkhausen noise for applied stress determination

Energy Technology Data Exchange (ETDEWEB)

Ding, Song [College of Electrical Engineering and Control Science, Nanjing Tech University, Nanjing, Jiangsu 211816 (China); School of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China); Tian, GuiYun, E-mail: tian280@hotmail.com [School of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China); School of Electrical and Electronic Engineering, Merz Court, University of Newcastle upon Tyne, Newcastle NE1 7RU (United Kingdom); Dobmann, Gerd; Wang, Ping [School of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu 210016 (China)

2017-01-01

Skewness of Magnetic Barkhausen Noise (MBN) signal is used as a new feature for applied stress determination. After experimental studies, skewness presents its ability for measuring applied tensile stress compared with conventional feature, meanwhile, a non-linear behavior of this new feature and an independence of the excitation conditions under compressive stress are found and discussed. Effective damping during domain wall motion influencing the asymmetric shape of the MBN statistical distribution function is discussed under compressive and tensile stress variation. Domain wall (DW) energy and distance between pinning edges of the DW are considered altering the characteristic relaxation time, which is the reason for the non-linear phenomenon of skewness. - Highlights: • The skewness of magnetic Barkhausen noise profile is proposed as a new feature for applied stress determination. • The skewness is sensitive to applied stress and independent to excitation frequency. • Domain wall energy and pinning distance influence the relaxation time of domain wall, which leads to a non-linear behavior of skewness under compressive stress.

Finding the Right Distribution for Highly Skewed Zero-inflated Clinical Data

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Resmi Gupta

2013-03-01

Full Text Available Discrete, highly skewed distributions with excess numbers of zeros often result in biased estimates and misleading inferences if the zeros are not properly addressed. A clinical example of children with electrophysiologic disorders in which many of the children are treated without surgery is provided. The purpose of the current study was to identify the optimal modeling strategy for highly skewed, zeroinflated data often observed in the clinical setting by: (a simulating skewed, zero-inflated count data; (b fitting simulated data with Poisson, Negative Binomial, Zero-Inflated Poisson (ZIP and Zero-inflated Negative Binomial (ZINB models; and, (c applying the aforementioned models to actual, highlyskewed, clinical data of children with an EP disorder. The ZIP model was observed to be the optimal model based on traditional fit statistics as well as estimates of bias, mean-squared error, and coverage.  

Micromagnetic recording model of writer geometry effects at skew

Science.gov (United States)

Plumer, M. L.; Bozeman, S.; van Ek, J.; Michel, R. P.

2006-04-01

The effects of the pole-tip geometry at the air-bearing surface on perpendicular recording at a skew angle are examined through modeling and spin-stand test data. Head fields generated by the finite element method were used to record transitions within our previously described micromagnetic recording model. Write-field contours for a variety of square, rectangular, and trapezoidal pole shapes were evaluated to determine the impact of geometry on field contours. Comparing results for recorded track width, transition width, and media signal to noise ratio at 0° and 15° skew demonstrate the benefits of trapezoidal and reduced aspect-ratio pole shapes. Consistency between these modeled results and test data is demonstrated.

Quantifying the cross-sectional relationship between online sentiment and the skewness of stock returns

Science.gov (United States)

Shen, Dehua; Liu, Lanbiao; Zhang, Yongjie

2018-01-01

The constantly increasing utilization of social media as the alternative information channel, e.g., Twitter, provides us a unique opportunity to investigate the dynamics of the financial market. In this paper, we employ the daily happiness sentiment extracted from Twitter as the proxy for the online sentiment dynamics and investigate its association with the skewness of stock returns of 26 international stock market index returns. The empirical results show that: (1) by dividing the daily happiness sentiment into quintiles from the least to the most happiness days, the skewness of the Most-happiness subgroup is significantly larger than that of the Least-happiness subgroup. Besides, there exist significant differences in any pair of subgroups; (2) in an event study methodology, we further show that the skewness around the highest happiness days is significantly larger than the skewness around the lowest happiness days.

Stock Markets Volatility Spillovers during Financial Crises : A DCC-MGARCH with Skew-t Approach

OpenAIRE

Bala, Dahiru A.; Takimoto, Taro

2016-01-01

We investigate stock markets volatility spillovers in selected emerging and major developed markets using multivariate GARCH (MGARCH) models [namely; DVECH, CCC-MGARCH, CCC-VARMA-(A)MGARCH, VAR-EGARCH, BEKK-(A)MGARCH, DCC-MGARCH (with Gaussian and t distributions) and DCC-with-skew-t density]. The paper analyses the impacts of recent global financial crisis (2007{2009) on stock market volatility and examines their dynamic interactions using several MGARCH model variants. Structural break dete...

Deterioration of the Skew Quadrupole Moment in Tevatron Dipoles Over Time

CERN Document Server

Syphers, Michael J

2005-01-01

During the 20 years since it was first commissioned, the Fermilab Tevatron has developed strong coupling between the two transverse degrees of freedom. A circuit of skew quadrupole magnets is used to correct for coupling and, though capable, its required strength has increased since 1983 by more than an order of magnitude. In more recent years changes to the Tevatron for colliding beams operation have altered the skew quadrupole corrector distribution and strong local coupling become evident, often encumbering routine operation during the present physics run. Detailed magnet measurements were performed on each individual magnet during construction, and in early 2003 it was realized that measurements could be performed on the magnets in situ which could determine coil movements within the iron yoke since the early 1980's. It was discovered that the superconducting coils had become vertically displaced relative to their yokes since their construction. The ensuing systematic skew quadrupole field introduced by t...

Normalization of High Dimensional Genomics Data Where the Distribution of the Altered Variables Is Skewed

Science.gov (United States)

Landfors, Mattias; Philip, Philge; Rydén, Patrik; Stenberg, Per

2011-01-01

Genome-wide analysis of gene expression or protein binding patterns using different array or sequencing based technologies is now routinely performed to compare different populations, such as treatment and reference groups. It is often necessary to normalize the data obtained to remove technical variation introduced in the course of conducting experimental work, but standard normalization techniques are not capable of eliminating technical bias in cases where the distribution of the truly altered variables is skewed, i.e. when a large fraction of the variables are either positively or negatively affected by the treatment. However, several experiments are likely to generate such skewed distributions, including ChIP-chip experiments for the study of chromatin, gene expression experiments for the study of apoptosis, and SNP-studies of copy number variation in normal and tumour tissues. A preliminary study using spike-in array data established that the capacity of an experiment to identify altered variables and generate unbiased estimates of the fold change decreases as the fraction of altered variables and the skewness increases. We propose the following work-flow for analyzing high-dimensional experiments with regions of altered variables: (1) Pre-process raw data using one of the standard normalization techniques. (2) Investigate if the distribution of the altered variables is skewed. (3) If the distribution is not believed to be skewed, no additional normalization is needed. Otherwise, re-normalize the data using a novel HMM-assisted normalization procedure. (4) Perform downstream analysis. Here, ChIP-chip data and simulated data were used to evaluate the performance of the work-flow. It was found that skewed distributions can be detected by using the novel DSE-test (Detection of Skewed Experiments). Furthermore, applying the HMM-assisted normalization to experiments where the distribution of the truly altered variables is skewed results in considerably higher

Speckles generated by skewed, short-coherence light beams

International Nuclear Information System (INIS)

Brogioli, D; Salerno, D; Ziano, R; Mantegazza, F; Croccolo, F

2011-01-01

When a coherent laser beam impinges on a random sample (e.g. a colloidal suspension), the scattered light exhibits characteristic speckles. If the temporal coherence of the light source is too short, then the speckles disappear, along with the possibility of performing homodyne or heterodyne scattering detection or photon correlation spectroscopy. Here we investigate the scattering of a so-called ‘skewed coherence beam’, i.e. a short-coherence beam modified such that the field is coherent within slabs that are skewed with respect to the wave fronts. We show that such a beam generates speckles and can be used for heterodyne scattering detection, despite its short temporal coherence. Moreover, we show that the heterodyne signal is not affected by multiple scattering. We suggest that the phenomenon presented here can be used as a means of carrying out heterodyne scattering measurement with any short-coherence radiation, including x-rays. (paper)

Market skewness risk and the cross section of stock returns

DEFF Research Database (Denmark)

Chang, B.Y.; Christoffersen, Peter; Jacobs, K.

2013-01-01

The cross section of stock returns has substantial exposure to risk captured by higher moments of market returns. We estimate these moments from daily Standard & Poor's 500 index option data. The resulting time series of factors are genuinely conditional and forward-looking. Stocks with high...... exposure to innovations in implied market skewness exhibit low returns on average. The results are robust to various permutations of the empirical setup. The market skewness risk premium is statistically and economically significant and cannot be explained by other common risk factors such as the market...... excess return or the size, book-to-market, momentum, and market volatility factors, or by firm characteristics....

Skewness of the cosmic microwave background temperature fluctuations due to the non-linear gravitational instability

International Nuclear Information System (INIS)

Munshi, D.; Souradeep, T.; Starobinsky, A.A.

1995-01-01

The skewness of the temperature fluctuations of the cosmic microwave background (CMB) produced by initially Gaussian adiabatic perturbations with the flat (Harrison-Zeldovich) spectrum, which arises due to non-linear corrections to a gravitational potential at the matter-dominated stage, is calculated quantitatively. For the standard CDM model, the effect appears to be smaller than expected previously and lies below the cosmic variance limit even for small angles. The sign of the skewness is opposite to that of the skewness of density perturbations. (author)

Time Skew Estimator for Dual-Polarization QAM Transmitters

DEFF Research Database (Denmark)

Medeiros Diniz, Júlio César; Da Ros, Francesco; Jones, Rasmus Thomas

2017-01-01

A simple method for joint estimation of transmitter’s in-phase/quadrature and inter-polarization time skew is proposed and experimentally demonstrated. The method is based on clock tone extraction of a photodetected signal and genetic algorithm. The maximum estimation error was 0.5 ps....

Regularized multivariate regression models with skew-t error distributions

KAUST Repository

Chen, Lianfu; Pourahmadi, Mohsen; Maadooliat, Mehdi

2014-01-01

We consider regularization of the parameters in multivariate linear regression models with the errors having a multivariate skew-t distribution. An iterative penalized likelihood procedure is proposed for constructing sparse estimators of both

Differential properties and attracting sets of a simplest skew product of interval maps

International Nuclear Information System (INIS)

Efremova, Lyudmila S

2010-01-01

For a skew product of interval maps with a closed set of periodic points, the dependence of the structure of its ω-limit sets on its differential properties is investigated. An example of a map in this class is constructed which has the maximal differentiability properties (within a certain subclass) with respect to the variable x, is C 1 -smooth in the y-variable and has one-dimensional ω-limit sets. Theorems are proved that give necessary conditions for one-dimensional ω-limit sets to exist. One of them is formulated in terms of the divergence of the series consisting of the values of a function of x; this function is the C 0 -norm of the deviation of the restrictions of the fibre maps to some nondegenerate closed interval from the identity on the same interval. Another theorem is formulated in terms of the properties of the partial derivative with respect to x of the fibre maps. A complete description is given of the ω-limit sets of certain class of C 1 -smooth skew products satisfying some natural conditions. Bibliography: 33 titles.

International portfolio diversification, skewness and the role of gold

OpenAIRE

LUCEY, BRIAN MICHAEL

2007-01-01

PUBLISHED The paper examines the optimal allocation of assets in well diversified equity based portfolio where the investor is concerned not only with mean and variance but also with the skewness of the returns.

Bayesian semiparametric mixture Tobit models with left censoring, skewness, and covariate measurement errors.

Science.gov (United States)

Dagne, Getachew A; Huang, Yangxin

2013-09-30

Common problems to many longitudinal HIV/AIDS, cancer, vaccine, and environmental exposure studies are the presence of a lower limit of quantification of an outcome with skewness and time-varying covariates with measurement errors. There has been relatively little work published simultaneously dealing with these features of longitudinal data. In particular, left-censored data falling below a limit of detection may sometimes have a proportion larger than expected under a usually assumed log-normal distribution. In such cases, alternative models, which can account for a high proportion of censored data, should be considered. In this article, we present an extension of the Tobit model that incorporates a mixture of true undetectable observations and those values from a skew-normal distribution for an outcome with possible left censoring and skewness, and covariates with substantial measurement error. To quantify the covariate process, we offer a flexible nonparametric mixed-effects model within the Tobit framework. A Bayesian modeling approach is used to assess the simultaneous impact of left censoring, skewness, and measurement error in covariates on inference. The proposed methods are illustrated using real data from an AIDS clinical study. . Copyright © 2013 John Wiley & Sons, Ltd.

Regularized multivariate regression models with skew-t error distributions

KAUST Repository

Chen, Lianfu

2014-06-01

We consider regularization of the parameters in multivariate linear regression models with the errors having a multivariate skew-t distribution. An iterative penalized likelihood procedure is proposed for constructing sparse estimators of both the regression coefficient and inverse scale matrices simultaneously. The sparsity is introduced through penalizing the negative log-likelihood by adding L1-penalties on the entries of the two matrices. Taking advantage of the hierarchical representation of skew-t distributions, and using the expectation conditional maximization (ECM) algorithm, we reduce the problem to penalized normal likelihood and develop a procedure to minimize the ensuing objective function. Using a simulation study the performance of the method is assessed, and the methodology is illustrated using a real data set with a 24-dimensional response vector. © 2014 Elsevier B.V.

Polynomial combinatorial algorithms for skew-bisubmodular function minimization

NARCIS (Netherlands)

S. Fujishige (Satoru); S.-I. Tanigawa (Shin-Ichi)

2017-01-01

textabstractHuber et al. (SIAM J Comput 43:1064–1084, 2014) introduced a concept of skew bisubmodularity, as a generalization of bisubmodularity, in their complexity dichotomy theorem for valued constraint satisfaction problems over the three-value domain, and Huber and Krokhin (SIAM J Discrete Math

Some case studies of skewed (and other ab-normal) data distributions arising in low-level environmental research

International Nuclear Information System (INIS)

Currie, L.A.

2001-01-01

Three general classes of skewed data distributions have been encountered in research on background radiation, chemical and radiochemical blanks, and low levels of 85 Kr and 14 C in the atmosphere and the cryosphere. The first class of skewed data can be considered to be theoretically, or fundamentally skewed. It is typified by the exponential distribution of inter-arrival times for nuclear counting events for a Poisson process. As part of a study of the nature of low-level (anti-coincidence) Geiger- Mueller counter background radiation, tests were performed on the Poisson distribution of counts, the uniform distribution of arrival times, and the exponential distribution of inter-arrival times. The real laboratory system, of course, failed the (inter-arrival time) test - for very interesting reasons, linked to the physics of the measurement process. The second, computationally skewed, class relates to skewness induced by non-linear transformations. It is illustrated by non-linear concentration estimates from inverse calibration, and bivariate blank corrections for low-level 14 C- 12 C aerosol data that led to highly asymmetric uncertainty intervals for the biomass carbon contribution to urban ''soot''. The third, environmentally skewed, data class relates to a universal problem for the detection of excursions above blank or baseline levels: namely, the widespread occurrence of ab-normal distributions of environmental and laboratory blanks. This is illustrated by the search for fundamental factors that lurk behind skewed frequency distributions of sulfur laboratory blanks and 85 Kr environmental baselines, and the application of robust statistical procedures for reliable detection decisions in the face of skewed isotopic carbon procedural blanks with few degrees of freedom. (orig.)

Some case studies of skewed (and other ab-normal) data distributions arising in low-level environmental research.

Science.gov (United States)

Currie, L A

2001-07-01

Three general classes of skewed data distributions have been encountered in research on background radiation, chemical and radiochemical blanks, and low levels of 85Kr and 14C in the atmosphere and the cryosphere. The first class of skewed data can be considered to be theoretically, or fundamentally skewed. It is typified by the exponential distribution of inter-arrival times for nuclear counting events for a Poisson process. As part of a study of the nature of low-level (anti-coincidence) Geiger-Muller counter background radiation, tests were performed on the Poisson distribution of counts, the uniform distribution of arrival times, and the exponential distribution of inter-arrival times. The real laboratory system, of course, failed the (inter-arrival time) test--for very interesting reasons, linked to the physics of the measurement process. The second, computationally skewed, class relates to skewness induced by non-linear transformations. It is illustrated by non-linear concentration estimates from inverse calibration, and bivariate blank corrections for low-level 14C-12C aerosol data that led to highly asymmetric uncertainty intervals for the biomass carbon contribution to urban "soot". The third, environmentally, skewed, data class relates to a universal problem for the detection of excursions above blank or baseline levels: namely, the widespread occurrence of ab-normal distributions of environmental and laboratory blanks. This is illustrated by the search for fundamental factors that lurk behind skewed frequency distributions of sulfur laboratory blanks and 85Kr environmental baselines, and the application of robust statistical procedures for reliable detection decisions in the face of skewed isotopic carbon procedural blanks with few degrees of freedom.

Elevated mortality among birds in Chernobyl as judged from skewed age and sex ratios.

Directory of Open Access Journals (Sweden)

Anders Pape Møller

Full Text Available Radiation has negative effects on survival of animals including humans, although the generality of this claim is poorly documented under low-dose field conditions. Because females may suffer disproportionately from the effects of radiation on survival due to differences in sex roles during reproduction, radiation-induced mortality may result in male-skewed adult sex ratios.We estimated the effects of low-dose radiation on adult survival rates in birds by determining age ratios of adults captured in mist nets during the breeding season in relation to background radiation levels around Chernobyl and in nearby uncontaminated control areas. Age ratios were skewed towards yearlings, especially in the most contaminated areas, implying that adult survival rates were reduced in contaminated areas, and that populations in such areas could only be maintained through immigration from nearby uncontaminated areas. Differential mortality in females resulted in a strongly male-skewed sex ratio in the most contaminated areas. In addition, males sang disproportionately commonly in the most contaminated areas where the sex ratio was male skewed presumably because males had difficulty finding and acquiring mates when females were rare. The results were not caused by permanent emigration by females from the most contaminated areas because none of the recaptured birds had changed breeding site, and the proportion of individuals with morphological abnormalities did not differ significantly between the sexes for areas with normal and higher levels of contamination.These findings are consistent with the hypothesis that the adult survival rate of female birds is particularly susceptible to the effects of low-dose radiation, resulting in male skewed sex ratios at high levels of radiation. Such skewed age ratios towards yearlings in contaminated areas are consistent with the hypothesis that an area exceeding 30,000 km(2 in Chernobyl's surroundings constitutes an

Kinematic correction for roller skewing

Science.gov (United States)

Savage, M.; Loewenthal, S. H.

1980-01-01

A theory of kinematic stabilization of rolling cylinders is developed for high-speed cylindrical roller bearings. This stabilization requires race and roller crowning to product changes in the rolling geometry as the roller shifts axially. These changes put a reverse skew in the rolling elements by changing the rolling taper. Twelve basic possible bearing modifications are identified in this paper. Four have single transverse convex curvature in the rollers while eight have rollers with compound transverse curvature composed of a central cylindrical band of constant radius surrounded by symmetric bands with both slope and transverse curvature.

Scale and shape mixtures of multivariate skew-normal distributions

KAUST Repository

Arellano-Valle, Reinaldo B.; Ferreira, Clé cio S.; Genton, Marc G.

2018-01-01

We introduce a broad and flexible class of multivariate distributions obtained by both scale and shape mixtures of multivariate skew-normal distributions. We present the probabilistic properties of this family of distributions in detail and lay down

Skewed matrilineal genetic composition in a small wild chimpanzee community.

Science.gov (United States)

Shimada, Makoto K; Hayakawa, Sachiko; Fujita, Shiho; Sugiyama, Yukimaru; Saitou, Naruya

2009-01-01

Maternal kinship is important in primate societies because it affects individual behaviour as well as the sustainability of populations. All members of the Bossou chimpanzee community are descended from 8 individuals (herein referred to as original adults) who were already adults or subadults when field observations were initiated in 1976 and whose genetic relationships were unknown. Sequencing of the control region on the maternally inherited mtDNA revealed that 4 (1 male and 3 females) of the 8 original adults shared an identical haplotype. We investigated the effects of the skewed distribution of mtDNA haplotypes on the following two outcomes. First, we demonstrated that the probability of mtDNA haplotype extinction would be increased under such a skewed composition in a small community. Second, the ratio of potential mating candidates to competitors is likely to decrease if chimpanzees become aware of maternal kinship and avoid incest. We estimated that the magnitude of the decrease in the ratio is 10 times greater in males than in females. Here we demonstrate a scenario in which this matrilineal skewness in a small community accelerates extinction of mtDNA haplotype, which will make it more difficult to find a suitable mate within the community. 2008 S. Karger AG, Basel.

Random skew plane partitions and the Pearcey process

DEFF Research Database (Denmark)

Reshetikhin, Nicolai; Okounkov, Andrei

2007-01-01

We study random skew 3D partitions weighted by q vol and, specifically, the q → 1 asymptotics of local correlations near various points of the limit shape. We obtain sine-kernel asymptotics for correlations in the bulk of the disordered region, Airy kernel asymptotics near a general point of the ...

Systems of Differential Equations with Skew-Symmetric, Orthogonal Matrices

Science.gov (United States)

Glaister, P.

2008-01-01

The solution of a system of linear, inhomogeneous differential equations is discussed. The particular class considered is where the coefficient matrix is skew-symmetric and orthogonal, and where the forcing terms are sinusoidal. More general matrices are also considered.

Option-Based Estimation of the Price of Co-Skewness and Co-Kurtosis Risk

DEFF Research Database (Denmark)

Christoffersen, Peter; Fournier, Mathieu; Fournier, Mathieu

-neutral second moments, and the price of co-kurtosis risk corresponds to the spread between the physical and the risk-neutral third moments. The option-based estimates of the prices of risk lead to reasonable values of the associated risk premia. An out-of-sample analysis of factor models with co-skewness and co......We show that the prices of risk for factors that are nonlinear in the market return are readily obtained using index option prices. We apply this insight to the price of co-skewness and co-kurtosis risk. The price of co-skewness risk corresponds to the spread between the physical and the risk......-kurtosis risk indicates that the new estimates of the price of risk improve the models performance. Models with higher-order market moments also robustly outperform standard competitors such as the CAPM and the Fama-French model....

Option-Based Estimation of the Price of Co-Skewness and Co-Kurtosis Risk

DEFF Research Database (Denmark)

Christoffersen, Peter; Fournier, Mathieu; Jacobs, Kris

-neutral second moments, and the price of co-kurtosis risk corresponds to the spread between the physical and the risk-neutral third moments. The option-based estimates of the prices of risk lead to reasonable values of the associated risk premia. An out-of-sample analysis of factor models with co-skewness and co......We show that the prices of risk for factors that are nonlinear in the market return are readily obtained using index option prices. We apply this insight to the price of co-skewness and co-kurtosis risk. The price of co-skewness risk corresponds to the spread between the physical and the risk......-kurtosis risk indicates that the new estimates of the price of risk improve the models' performance. Models with higher-order market moments also robustly outperform standard competitors such as the CAPM and the Fama-French model....

A Bayesian estimate of the concordance correlation coefficient with skewed data.

Science.gov (United States)

Feng, Dai; Baumgartner, Richard; Svetnik, Vladimir

2015-01-01

Concordance correlation coefficient (CCC) is one of the most popular scaled indices used to evaluate agreement. Most commonly, it is used under the assumption that data is normally distributed. This assumption, however, does not apply to skewed data sets. While methods for the estimation of the CCC of skewed data sets have been introduced and studied, the Bayesian approach and its comparison with the previous methods has been lacking. In this study, we propose a Bayesian method for the estimation of the CCC of skewed data sets and compare it with the best method previously investigated. The proposed method has certain advantages. It tends to outperform the best method studied before when the variation of the data is mainly from the random subject effect instead of error. Furthermore, it allows for greater flexibility in application by enabling incorporation of missing data, confounding covariates, and replications, which was not considered previously. The superiority of this new approach is demonstrated using simulation as well as real-life biomarker data sets used in an electroencephalography clinical study. The implementation of the Bayesian method is accessible through the Comprehensive R Archive Network. Copyright © 2015 John Wiley & Sons, Ltd.

Report from LHC MD 2171: Amplitude dependent closest tune approach from normal and skew octupoles

CERN Document Server

Maclean, Ewen Hamish; Persson, Tobias Hakan Bjorn; Carlier, Felix Simon; CERN. Geneva. ATS Department

2018-01-01

Simulation-based studies predict significant amplitude-dependent closest tune approach can be generated by skew octupole sources in conjunction with their normal octupolar counterparts. This has the potential to significantly influence Landau damping at small β∗, where skew octupole errors in the experimental IRs, together with b4 introduced by the Landau octupoles, is predicted to cause large distortion of the tune footprint. This MD aimed to perform a first exploration of these predictions with beam, by enhancing skew octupole sources in the IRs at injection and measuring amplitude detuning with free kicks in the plane approaching the coupling resonance.

Stall inception and warning in a single-stage transonic axial compressor with axial skewed slot casing treatment

International Nuclear Information System (INIS)

Lim, Byeung Jun; Kwon, Se Jin; Park, Tae Choon

2014-01-01

Characteristic changes in the stall inception in a single-stage transonic axial compressor with an axial skewed slot casing treatment were investigated experimentally. A rotating stall occurred intermittently in a compressor with an axial skewed slot, whereas spike-type rotating stalls occurred in the case of smooth casing. The axial skewed slot suppressed stall cell growth and increased the operating range. A mild surge, the frequency of which is the Helmholtz frequency of the compressor system, occurred with the rotating stall. The irregularity in the pressure signals at the slot bottom increased decreasing flow rate. An autocorrelation-based stall warning method was applied to the measured pressure signals. Results estimate and warn against the stall margin in a compressor with an axial skewed slot.

Skew chromaticity in large accelerators

International Nuclear Information System (INIS)

Peggs, S.; Dell, G.F.

1995-01-01

The 2-D ''skew chromaticity'' vector k is introduced when the standard on-momentum description of linear coupling is extended to include off-momentum particles. A lattice that is well decoupled on-momentum may be badly decoupled off-momentum, inside the natural momentum spread of the beam. There are two general areas of concern: (1) the free space in the tune plane is decreased; (2) collective phenomena may be destabilized. Two strong new criteria for head-tail stability in the presence of off-momentum coupling are derived, which are consistent with experimental and operational observations at the Tevatron, and with tracking data from RHIC

Skewed sex ratios in India: "physician, heal thyself".

Science.gov (United States)

Patel, Archana B; Badhoniya, Neetu; Mamtani, Manju; Kulkarni, Hemant

2013-06-01

Sex selection, a gender discrimination of the worst kind, is highly prevalent across all strata of Indian society. Physicians have a crucial role in this practice and implementation of the Indian Government's Pre-Natal Diagnostic Techniques Act in 1996 to prevent the misuse of ultrasound techniques for the purpose of prenatal sex determination. Little is known about family preferences, let alone preferences among families of physicians. We investigated the sex ratios in 946 nuclear families with 1,624 children, for which either one or both parents were physicians. The overall child sex ratio was more skewed than the national average of 914. The conditional sex ratios decreased with increasing number of previous female births, and a previous birth of a daughter in the family was associated with a 38 % reduced likelihood of a subsequent female birth. The heavily skewed sex ratios in the families of physicians are indicative of a deeply rooted social malady that could pose a critical challenge in correcting the sex ratios in India.

Asymmetric skew Bessel processes and their applications to finance

NARCIS (Netherlands)

Decamps, M.; Goovaerts, M.J.; Schoutens, W.

2006-01-01

In this paper, we extend the Harrison and Shepp's construction of the skew Brownian motion (1981) and we obtain a diffusion similar to the two-dimensional Bessel process with speed and scale densities discontinuous at one point. Natural generalizations to multi-dimensional and fractional order

Determinants of (–1,1-matrices of the skew-symmetric type: a cocyclic approach

Directory of Open Access Journals (Sweden)

Álvarez Víctor

2015-01-01

Full Text Available An n by n skew-symmetric type (-1; 1-matrix K =[ki;j ] has 1’s on the main diagonal and ±1’s elsewhere with ki;j =-kj;i . The largest possible determinant of such a matrix K is an interesting problem. The literature is extensive for n ≡ 0 mod 4 (skew-Hadamard matrices, but for n ≡ 2 mod 4 there are few results known for this question. In this paper we approach this problem constructing cocyclic matrices over the dihedral group of 2t elements, for t odd, which are equivalent to (-1; 1-matrices of skew type. Some explicit calculations have been done up to t =11. To our knowledge, the upper bounds on the maximal determinant in orders 18 and 22 have been improved.

Leverage and Deepening Business Cycle Skewness

DEFF Research Database (Denmark)

Jensen, Henrik; Petrella, Ivan; Ravn, Søren Hove

2017-01-01

We document that the U.S. economy has been characterized by an increasingly negative business cycle asymmetry over the last three decades. This finding can be explained by the concurrent increase in the financial leverage of households and firms. To support this view, we devise and estimate......, booms become progressively smoother and more prolonged than busts. We are therefore able to reconcile a more negatively skewed business cycle with the Great Moderation in cyclical volatility. Finally, in line with recent empirical evidence, financially-driven expansions lead to deeper contractions...

Torque ripple minimization in a doubly salient permanent magnet motors by skewing the rotor teeth

International Nuclear Information System (INIS)

Sheth, N.K.; Sekharbabu, A.R.C.; Rajagopal, K.R.

2006-01-01

This paper presents the effects of skewing the rotor teeth on the performance of an 8/6 doubly salient permanent magnet motor using a simple method, which utilizes the results obtained from the 2-D FE analysis. The optimum skewing angle is obtained as 12-15 o for the least ripple torque without much reduction in the back-emf

Geometric representation of the mean-variance-skewness portfolio frontier based upon the shortage function

OpenAIRE

Kerstens, Kristiaan; Mounier, Amine; Van de Woestyne, Ignace

2008-01-01

The literature suggests that investors prefer portfolios based on mean, variance and skewness rather than portfolios based on mean-variance (MV) criteria solely. Furthermore, a small variety of methods have been proposed to determine mean-variance-skewness (MVS) optimal portfolios. Recently, the shortage function has been introduced as a measure of efficiency, allowing to characterize MVS optimalportfolios using non-parametric mathematical programming tools. While tracing the MV portfolio fro...

Skewed X inactivation and survival: a 13-year follow-up study of elderly twins and singletons

DEFF Research Database (Denmark)

Mengel-From, Jonas; Thinggaard, Mikael; Christiansen, Lene

2012-01-01

In mammalian females, one of the two X chromosomes is inactivated in early embryonic life. Females are therefore mosaics for two cell populations, one with the maternal and one with the paternal X as the active X chromosome. A skewed X inactivation is a marked deviation from a 50:50 ratio...... mortality than the majority of women who had a more skewed DS (hazard ratio: 1.30; 95% CI: 1.04-1.64). The association between X inactivation and mortality was replicated in dizygotic twin pairs for which the co-twin with the lowest DS also had a statistically significant tendency to die first in the twin....... In populations of women past 55-60 years of age, an increased degree of skewing (DS) is found. Here the association between age-related skewing and mortality is analyzed in a 13-year follow-up study of 500 women from three cohorts (73-100 years of age at intake). Women with low DS had significantly higher...

A Skewed Student-t Value-at-Risk Approach for Long Memory Volatility Processes in Japanese Financial Markets

Directory of Open Access Journals (Sweden)

Seong¡-Min Yoon

2007-06-01

Full Text Available This paper investigates the relevance of skewed Student-t distributions in capturing long memory volatility properties in the daily return series of Japanese financial data (Nikkei 225 Index and JPY-USD exchange rate. For this purpose, we assess the performance of two long memory Value-at-Risk (VaR models (FIGARCH and FIAPARCH VaR model with three different distribution innovations: the normal, Student-t, and skewed Student-t distributions. From our results, we find that the skewed Student-t distribution model produces more accurate VaR estimations than normal and Student-t distribution models. Thus, accounting for skewness and excess kurtosis in the asset return distribution can provide suitable criteria for VaR model selection in the context of long memory volatility and enhance the performance of risk management in Japanese financial markets.

Entrepreneurship and Financial Incentives of Return, Risk, and Skew

DEFF Research Database (Denmark)

Berkhout, Peter; Hartog, Joop; Van Praag, Mirjam

2016-01-01

. The focus on earnings forgone may help to solve the lack of robust empirical support for the effect of financial incentives on the decision to become an entrepreneur. We find, consistent with standard theory, that a higher mean, lower variance, and higher skew in the relevant wage distribution reduce...

NPIP: A skew line needle configuration optimization system for HDR brachytherapy

International Nuclear Information System (INIS)

Siauw, Timmy; Cunha, Adam; Berenson, Dmitry; Atamtürk, Alper; Hsu, I-Chow; Goldberg, Ken; Pouliot, Jean

2012-01-01

Purpose: In this study, the authors introduce skew line needle configurations for high dose rate (HDR) brachytherapy and needle planning by integer program (NPIP), a computational method for generating these configurations. NPIP generates needle configurations that are specific to the anatomy of the patient, avoid critical structures near the penile bulb and other healthy structures, and avoid needle collisions inside the body. Methods: NPIP consisted of three major components: a method for generating a set of candidate needles, a needle selection component that chose a candidate needle subset to be inserted, and a dose planner for verifying that the final needle configuration could meet dose objectives. NPIP was used to compute needle configurations for prostate cancer data sets from patients previously treated at our clinic. NPIP took two user-parameters: a number of candidate needles, and needle coverage radius, δ. The candidate needle set consisted of 5000 needles, and a range of δ values was used to compute different needle configurations for each patient. Dose plans were computed for each needle configuration. The number of needles generated and dosimetry were analyzed and compared to the physician implant. Results: NPIP computed at least one needle configuration for every patient that met dose objectives, avoided healthy structures and needle collisions, and used as many or fewer needles than standard practice. These needle configurations corresponded to a narrow range of δ values, which could be used as default values if this system is used in practice. The average end-to-end runtime for this implementation of NPIP was 286 s, but there was a wide variation from case to case. Conclusions: The authors have shown that NPIP can automatically generate skew line needle configurations with the aforementioned properties, and that given the correct input parameters, NPIP can generate needle configurations which meet dose objectives and use as many or fewer

The Factor Structure in Equity Options

DEFF Research Database (Denmark)

Christoffersen, Peter; Fournier, Mathieu; Jacobs, Kris

2018-01-01

Equity options display a strong factor structure. The first principal components of the equity volatility levels, skews, and term structures explain a substantial fraction of the crosssectional variation. Furthermore, these principal components are highly correlated with the S&P 500 index option...... volatility, skew, and term structure, respectively. We develop an equity option valuation model that captures this factor structure. The model predicts that firms with higher market betas have higher implied volatilities, steeper moneyness slopes, and a term structure that covaries more with the market...

Some homological properties of skew PBW extensions arising in non-commutative algebraic geometry

Directory of Open Access Journals (Sweden)

Lezama Oswaldo

2017-06-01

Full Text Available In this short paper we study for the skew PBW (Poincar-Birkhoff-Witt extensions some homological properties arising in non-commutative algebraic geometry, namely, Auslander-Gorenstein regularity, Cohen-Macaulayness and strongly noetherianity. Skew PBW extensions include a considerable number of non-commutative rings of polynomial type such that classical PBW extensions, quantum polynomial rings, multiplicative analogue of the Weyl algebra, some Sklyanin algebras, operator algebras, diffusion algebras, quadratic algebras in 3 variables, among many others. Parametrization of the point modules of some examples is also presented.

Widely Linear Equalization for IQ Imbalance and Skew Compensation in Optical Coherent Receivers

DEFF Research Database (Denmark)

Porto da Silva, Edson; Zibar, Darko

2016-01-01

In this paper, an alternative approach to design linear equalization algorithms for optical coherent receivers is introduced. Using widely linear complex analysis, a general analytical model it is shown, where In-phase/quadrature (IQ) imbalances and IQ skew at the coherent receiver front-end are ......In this paper, an alternative approach to design linear equalization algorithms for optical coherent receivers is introduced. Using widely linear complex analysis, a general analytical model it is shown, where In-phase/quadrature (IQ) imbalances and IQ skew at the coherent receiver front...

Delivering Left-Skewed Portfolio Payoff Distributions in the Presence of Transaction Costs

Directory of Open Access Journals (Sweden)

Jacek B Krawczyk

2015-08-01

Full Text Available For pension-savers, a low payoff is a financial disaster. Such investors will most likely prefer left-skewed payoff distributions over right-skewed payoff distributions. We explore how such distributions can be delivered. Cautious-relaxed utility measures are cautious in ensuring that payoffs don’t fall much below a reference value, but relaxed about exceeding it. We find that the payoff distribution delivered by a cautious-relaxed utility measure has appealing features which payoff distributions delivered by traditional utility functions don’t. In particular, cautious-relaxed distributions can have the mass concentrated on the left, hence be left-skewed. However, cautious-relaxed strategies prescribe frequent portfolio adjustments which may be expensive if transaction costs are charged. In contrast, more traditional strategies can be time-invariant. Thus we investigate the impact of transaction costs on the appeal of cautious-relaxed strategies. We find that relatively high transaction fees are required for the cautious-relaxed strategy to lose its appeal. This paper contributes to the literature which compares utility measures by the payoff distributions they produce and finds that a cautious-relaxed utility measure will deliver payoffs that many investors will prefer.

Impact of radius and skew angle on areal density in heat assisted magnetic recording hard disk drives

Science.gov (United States)

Cordle, Michael; Rea, Chris; Jury, Jason; Rausch, Tim; Hardie, Cal; Gage, Edward; Victora, R. H.

2018-05-01

This study aims to investigate the impact that factors such as skew, radius, and transition curvature have on areal density capability in heat-assisted magnetic recording hard disk drives. We explore a "ballistic seek" approach for capturing in-situ scan line images of the magnetization footprint on the recording media, and extract parametric results of recording characteristics such as transition curvature. We take full advantage of the significantly improved cycle time to apply a statistical treatment to relatively large samples of experimental curvature data to evaluate measurement capability. Quantitative analysis of factors that impact transition curvature reveals an asymmetry in the curvature profile that is strongly correlated to skew angle. Another less obvious skew-related effect is an overall decrease in curvature as skew angle increases. Using conventional perpendicular magnetic recording as the reference case, we characterize areal density capability as a function of recording position.

Matrix orderings and their associated skew fields

International Nuclear Information System (INIS)

Mahdavi-Hezavehi, M.

1990-08-01

Matrix orderings on rings are investigated. It is shown that in the commutative case they are essentially positive cones. This is proved by reducing it to the field case; similarly one can show that on a skew field, matrix positive cones can be reduced to positive cones by using the Dieudonne determinant. Our main result shows that there is a natural bijection between the matrix positive cones on a ring R and the ordered epic R-fields. (author). 7 refs

The Factor Structure in Equity Options

DEFF Research Database (Denmark)

Christoffersen, Peter; Fournier, Mathieu; Jacobs, Kris

Equity options display a strong factor structure. The first principal components of the equity volatility levels, skews, and term structures explain a substantial fraction of the cross-sectional variation. Furthermore, these principal components are highly correlated with the S&P500 index option...... volatility, skew, and term structure respectively. We develop an equity option valuation model that captures this factor structure. The model predicts that firms with higher market betas have higher implied volatilities, steeper moneyness slopes, and a term structure that co-varies more with the market...

Quantitative analysis of replication-related mutation and selection pressures in bacterial chromosomes and plasmids using generalised GC skew index

Directory of Open Access Journals (Sweden)

Suzuki Haruo

2009-12-01

Full Text Available Abstract Background Due to their bi-directional replication machinery starting from a single finite origin, bacterial genomes show characteristic nucleotide compositional bias between the two replichores, which can be visualised through GC skew or (C-G/(C+G. Although this polarisation is used for computational prediction of replication origins in many bacterial genomes, the degree of GC skew visibility varies widely among different species, necessitating a quantitative measurement of GC skew strength in order to provide confidence measures for GC skew-based predictions of replication origins. Results Here we discuss a quantitative index for the measurement of GC skew strength, named the generalised GC skew index (gGCSI, which is applicable to genomes of any length, including bacterial chromosomes and plasmids. We demonstrate that gGCSI is independent of the window size and can thus be used to compare genomes with different sizes, such as bacterial chromosomes and plasmids. It can suggest the existence of different replication mechanisms in archaea and of rolling-circle replication in plasmids. Correlation of gGCSI values between plasmids and their corresponding host chromosomes suggests that within the same strain, these replicons have reproduced using the same replication machinery and thus exhibit similar strengths of replication strand skew. Conclusions gGCSI can be applied to genomes of any length and thus allows comparative study of replication-related mutation and selection pressures in genomes of different lengths such as bacterial chromosomes and plasmids. Using gGCSI, we showed that replication-related mutation or selection pressure is similar for replicons with similar machinery.

FLECHT low flooding rate skewed test series data report

International Nuclear Information System (INIS)

Rosal, E.R.; Conway, C.E.; Krepinevich, M.C.

1977-05-01

The FLECHT Low Flooding Rate Tests were conducted in an improved original FLECHT Test Facility to provide heat transfer coefficient and entrainment data at forced flooding rates of 1 in./sec. and with electrically heated rod bundles which had cosine and top skewed axial power profiles. The top-skewed axial power profile test series has now been successfully completed and is here reported. For these tests the rod bundle was enclosed in a low mass cylindrical housing which would minimize the wall housing effects encountered in the cosine test series. These tests examined the effects of initial clad temperature, variable stepped and continuously variable flooding rates, housing heat release, rod peak power, constant low flooding rates, coolant subcooling, hot and cold channel entrainment, and bundle stored and generated power. Data obtained in runs which met the test specifications are reported here, and include rod clad temperatures, turn around and quench times, heat transfer coefficients, inlet flooding rates, overall mass balances, differential pressures and calculated void fractions in the test section, thimble wall and steam temperatures, and exhaust steam and liquid carryover rates

Partially linear mixed-effects joint models for skewed and missing longitudinal competing risks outcomes.

Science.gov (United States)

Lu, Tao; Lu, Minggen; Wang, Min; Zhang, Jun; Dong, Guang-Hui; Xu, Yong

2017-12-18

Longitudinal competing risks data frequently arise in clinical studies. Skewness and missingness are commonly observed for these data in practice. However, most joint models do not account for these data features. In this article, we propose partially linear mixed-effects joint models to analyze skew longitudinal competing risks data with missingness. In particular, to account for skewness, we replace the commonly assumed symmetric distributions by asymmetric distribution for model errors. To deal with missingness, we employ an informative missing data model. The joint models that couple the partially linear mixed-effects model for the longitudinal process, the cause-specific proportional hazard model for competing risks process and missing data process are developed. To estimate the parameters in the joint models, we propose a fully Bayesian approach based on the joint likelihood. To illustrate the proposed model and method, we implement them to an AIDS clinical study. Some interesting findings are reported. We also conduct simulation studies to validate the proposed method.

The skewed weak lensing likelihood: why biases arise, despite data and theory being sound.

Science.gov (United States)

Sellentin, Elena; Heymans, Catherine; Harnois-Déraps, Joachim

2018-04-01

We derive the essentials of the skewed weak lensing likelihood via a simple Hierarchical Forward Model. Our likelihood passes four objective and cosmology-independent tests which a standard Gaussian likelihood fails. We demonstrate that sound weak lensing data are naturally biased low, since they are drawn from a skewed distribution. This occurs already in the framework of ΛCDM. Mathematically, the biases arise because noisy two-point functions follow skewed distributions. This form of bias is already known from CMB analyses, where the low multipoles have asymmetric error bars. Weak lensing is more strongly affected by this asymmetry as galaxies form a discrete set of shear tracer particles, in contrast to a smooth shear field. We demonstrate that the biases can be up to 30% of the standard deviation per data point, dependent on the properties of the weak lensing survey and the employed filter function. Our likelihood provides a versatile framework with which to address this bias in future weak lensing analyses.

Low reproductive skew despite high male-biased operational sex ratio in a glass frog with paternal care.

Science.gov (United States)

Mangold, Alexandra; Trenkwalder, Katharina; Ringler, Max; Hödl, Walter; Ringler, Eva

2015-09-03

Reproductive skew, the uneven distribution of reproductive success among individuals, is a common feature of many animal populations. Several scenarios have been proposed to favour either high or low levels of reproductive skew. Particularly a male-biased operational sex ratio and the asynchronous arrival of females is expected to cause high variation in reproductive success among males. Recently it has been suggested that the type of benefits provided by males (fixed vs. dilutable) could also strongly impact individual mating patterns, and thereby affecting reproductive skew. We tested this hypothesis in Hyalinobatrachium valerioi, a Neotropical glass frog with prolonged breeding and paternal care. We monitored and genetically sampled a natural population in southwestern Costa Rica during the breeding season in 2012 and performed parentage analysis of adult frogs and tadpoles to investigate individual mating frequencies, possible mating preferences, and estimate reproductive skew in males and females. We identified a polygamous mating system, where high proportions of males (69 %) and females (94 %) reproduced successfully. The variance in male mating success could largely be attributed to differences in time spent calling at the reproductive site, but not to body size or relatedness. Female H. valerioi were not choosy and mated indiscriminately with available males. Our findings support the hypothesis that dilutable male benefits - such as parental care - can favour female polyandry and maintain low levels of reproductive skew among males within a population, even in the presence of direct male-male competition and a highly male-biased operational sex ratio. We hypothesize that low male reproductive skew might be a general characteristic in prolonged breeders with paternal care.

The curious anomaly of skewed judgment distributions and systematic error in the wisdom of crowds.

Directory of Open Access Journals (Sweden)

Ulrik W Nash

Full Text Available Judgment distributions are often skewed and we know little about why. This paper explains the phenomenon of skewed judgment distributions by introducing the augmented quincunx (AQ model of sequential and probabilistic cue categorization by neurons of judges. In the process of developing inferences about true values, when neurons categorize cues better than chance, and when the particular true value is extreme compared to what is typical and anchored upon, then populations of judges form skewed judgment distributions with high probability. Moreover, the collective error made by these people can be inferred from how skewed their judgment distributions are, and in what direction they tilt. This implies not just that judgment distributions are shaped by cues, but that judgment distributions are cues themselves for the wisdom of crowds. The AQ model also predicts that judgment variance correlates positively with collective error, thereby challenging what is commonly believed about how diversity and collective intelligence relate. Data from 3053 judgment surveys about US macroeconomic variables obtained from the Federal Reserve Bank of Philadelphia and the Wall Street Journal provide strong support, and implications are discussed with reference to three central ideas on collective intelligence, these being Galton's conjecture on the distribution of judgments, Muth's rational expectations hypothesis, and Page's diversity prediction theorem.

A novel technique for estimation of skew in binary text document ...

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

Gatos et al (1997) have proposed a new skew detection method based on the information ..... different books, magazines and journals. ..... Duda R O, Hart P E 1973 Pattern classification and scene analysis (New York: Wiley-Interscience).

A variational analysis for large deflection of skew plates under ...

African Journals Online (AJOL)

In the present paper, the static behaviour of thin isotropic skew plates under uniformly distributed load is analyzed with the geometric nonlinearity of the model properly handled. A variational method based on total potential energy has been implemented through assumed displacement field. The computational work has ...

The Factor Structure in Equity Options

DEFF Research Database (Denmark)

Christoffersen, Peter; Fournier, Mathieu; Jacobs, Kris

Principal component analysis of equity options on Dow-Jones firms reveals a strong factor structure. The first principal component explains 77% of the variation in the equity volatility level, 77% of the variation in the equity option skew, and 60% of the implied volatility term structure across...... equities. Furthermore, the first principal component has a 92% correlation with S&P500 index option volatility, a 64% correlation with the index option skew, and a 80% correlation with the index option term structure. We develop an equity option valuation model that captures this factor structure...

Skew quad compensation for SPEAR minibeta optics

International Nuclear Information System (INIS)

Wille, K.

1984-06-01

With the new minibeta insertion for SPEAR the betatron coupling and the perturbations of beam optics caused by the solenoid field of the MARK III detector can't be compensated by the simple coils used so far. Therefore another scheme with four skew quads arranged in two families has been chosen. Even though this scheme doesn't compensate the effect of the solenoid on the beam completely, the residual emittance coupling is much less than 1% which should be sufficient under all running conditions. The major advantage of this concept is its simplicity

Does Realized Skewness Predict the Cross-Section of Equity Returns?

DEFF Research Database (Denmark)

Amaya, Diego; Christoffersen, Peter; Jacobs, Kris

We use intraday data to compute weekly realized variance, skewness, and kurtosis for equity returns and study the realized moments’ time-series and cross-sectional properties. We investigate if this week’'s realized moments are informative for the cross-section of next week'’s stock returns. We...

On the skew-symmetric character of the couple-stress tensor

OpenAIRE

Hadjesfandiari, Ali R.

2013-01-01

In this paper, the skew-symmetric character of the couple-stress tensor is established as the result of arguments from tensor analysis. Consequently, the couple-stress pseudo-tensor has a true vectorial character. The fundamental step in this development is that the isotropic couple-stress tensor cannot exist.

A Cable-Passive Damper System for Sway and Skew Motion Control of a Crane Spreader

Directory of Open Access Journals (Sweden)

La Duc Viet

2015-01-01

Full Text Available While the crane control problem is often approached by applying a certain active control command to some parts of the crane, this paper proposes a cable-passive damper system to reduce the vibration of a four-cable suspended crane spreader. The residual sway and skew motions of a crane spreader always produce the angle deflections between the crane cables and the crane spreader. The idea in this paper is to convert those deflections into energy dissipated by the viscous dampers, which connect the cables and the spreader. The proposed damper system is effective in reducing spreader sway and skew motions. Moreover, the optimal damping coefficient can be found analytically by minimizing the time integral of system energy. The numerical simulations show that the proposed passive system can assist the input shaping control of the trolley motion in reducing both sway and skew responses.

Forces in wingwalls from thermal expansion of skewed semi-integral bridges.

Science.gov (United States)

2010-11-01

Jointless bridges, such as semi-integral and integral bridges, have become more popular in recent years because of their simplicity in the construction and the elimination of high costs related to joint maintenance. Prior research has shown that skew...

The role of the SST-thermocline relationship in Indian Ocean Dipole skewness and its response to global warming

Science.gov (United States)

Ng, Benjamin; Cai, Wenju; Walsh, Kevin

2014-01-01

A positive Indian Ocean Dipole (IOD) tends to have stronger cold sea surface temperature anomalies (SSTAs) over the eastern Indian Ocean with greater impacts than warm SSTAs that occur during its negative phase. Two feedbacks have been suggested as the cause of positive IOD skewness, a positive Bjerknes feedback and a negative SST-cloud-radiation (SCR) feedback, but their relative importance is debated. Using inter-model statistics, we show that the most important process for IOD skewness is an asymmetry in the thermocline feedback, whereby SSTAs respond to thermocline depth anomalies more strongly during the positive phase than negative phase. This asymmetric thermocline feedback drives IOD skewness despite positive IODs receiving greater damping from the SCR feedback. In response to global warming, although the thermocline feedback strengthens, its asymmetry between positive and negative IODs weakens. This behaviour change explains the reduction in IOD skewness that many models display under global warming. PMID:25112717

Subordinate wasps are more aggressive in colonies with low reproductive skew

DEFF Research Database (Denmark)

Fanelli, D.; Boomsma, Jacobus Jan; Turillazzi, S.

2008-01-01

The small societies of primitively eusocial wasps have provided interesting testing grounds for reproductive skew theory because all individuals have similar reproductive potential, which is unusual in social insects but common in vertebrate societies. Aggression is a key parameter in testing the...

Guided ultrasonic wave beam skew in silicon wafers

Science.gov (United States)

Pizzolato, Marco; Masserey, Bernard; Robyr, Jean-Luc; Fromme, Paul

2018-04-01

In the photovoltaic industry, monocrystalline silicon wafers are employed for solar cells with high conversion efficiency. Micro-cracks induced by the cutting process in the thin wafers can lead to brittle wafer fracture. Guided ultrasonic waves would offer an efficient methodology for the in-process non-destructive testing of wafers to assess micro-crack density. The material anisotropy of the monocrystalline silicon leads to variations of the guided wave characteristics, depending on the propagation direction relative to the crystal orientation. Selective guided ultrasonic wave excitation was achieved using a contact piezoelectric transducer with custom-made wedges for the A0 and S0 Lamb wave modes and a transducer holder to achieve controlled contact pressure and orientation. The out-of-plane component of the guided wave propagation was measured using a non-contact laser interferometer. The phase slowness (velocity) of the two fundamental Lamb wave modes was measured experimentally for varying propagation directions relative to the crystal orientation and found to match theoretical predictions. Significant wave beam skew was observed experimentally, especially for the S0 mode, and investigated from 3D finite element simulations. Good agreement was found with the theoretical predictions based on nominal material properties of the silicon wafer. The important contribution of guided wave beam skewing effects for the non-destructive testing of silicon wafers was demonstrated.

Effect of Phase Response Curve Skew on Synchronization with and without Conduction Delays

Directory of Open Access Journals (Sweden)

Carmen eCanavier

2013-12-01

Full Text Available A central problem in cortical processing including sensory binding and attentional gating is how neurons can synchronize their responses with zero or near-zero time lag. For a spontaneously firing neuron, an input from another neuron can delay or advance the next spike by different amounts depending upon the timing of the input relative to the previous spike. This information constitutes the phase response curve (PRC. We present a simple graphical method for determining the effect of PRC shape on synchronization tendencies and illustrate it using type 1 PRCs, which consist entirely of advances (delays in response to excitation (inhibition. We obtained the following generic solutions for type 1 PRCs, which include the pulse coupled leaky integrate and fire model. For pairs with mutual excitation, exact synchrony can be stable for strong coupling because of the stabilizing effect of the causal limit region of the PRC in which an input triggers a spike immediately upon arrival. However, synchrony is unstable for short delays, because delayed inputs arrive during a refractory period and cannot trigger an immediate spike. Right skew destabilizes antiphase and enables modes with time lags that grow as the conduction delay is increased. Therefore, right skew favors near-synchrony at short conduction delays and a gradual transition between synchrony and antiphase for pairs coupled by mutual excitation. For pairs with mutual inhibition, zero time lag synchrony is stable for conduction delays ranging from zero to a substantial fraction of the period for pairs. However, for right skew there is a preferred antiphase mode at short delays. In contrast to mutual excitation, left skew destabilizes antiphase for mutual inhibition so that synchrony dominates at short delays as well. These pairwise synchronization tendencies constrain the synchronization properties of neurons embedded in larger networks.

Halo Pressure Profile through the Skew Cross-power Spectrum of the Sunyaev–Zel’dovich Effect and CMB Lensing in Planck

Energy Technology Data Exchange (ETDEWEB)

Timmons, Nicholas; Cooray, Asantha; Feng, Chang [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Keating, Brian [Department of Physics, University of California, San Diego, La Jolla, CA 92093 (United States)

2017-11-01

We measure the cosmic microwave background (CMB) skewness power spectrum in Planck , using frequency maps of the HFI instrument and the Sunyaev–Zel’dovich (SZ) component map. The two-to-one skewness power spectrum measures the cross-correlation between CMB lensing and the thermal SZ effect. We also directly measure the same cross-correlation using the Planck CMB lensing map and the SZ map and compare it to the cross-correlation derived from the skewness power spectrum. We model fit the SZ power spectrum and CMB lensing–SZ cross-power spectrum via the skewness power spectrum to constrain the gas pressure profile of dark matter halos. The gas pressure profile is compared to existing measurements in the literature including a direct estimate based on the stacking of SZ clusters in Planck .

Incorporating Skew into RMS Surface Roughness Probability Distribution

Science.gov (United States)

Stahl, Mark T.; Stahl, H. Philip.

2013-01-01

The standard treatment of RMS surface roughness data is the application of a Gaussian probability distribution. This handling of surface roughness ignores the skew present in the surface and overestimates the most probable RMS of the surface, the mode. Using experimental data we confirm the Gaussian distribution overestimates the mode and application of an asymmetric distribution provides a better fit. Implementing the proposed asymmetric distribution into the optical manufacturing process would reduce the polishing time required to meet surface roughness specifications.

On the Empirical Importance of the Conditional Skewness Assumption in Modelling the Relationship between Risk and Return

Science.gov (United States)

Pipień, M.

2008-09-01

We present the results of an application of Bayesian inference in testing the relation between risk and return on the financial instruments. On the basis of the Intertemporal Capital Asset Pricing Model, proposed by Merton we built a general sampling distribution suitable in analysing this relationship. The most important feature of our assumptions is that the skewness of the conditional distribution of returns is used as an alternative source of relation between risk and return. This general specification relates to Skewed Generalized Autoregressive Conditionally Heteroscedastic-in-Mean model. In order to make conditional distribution of financial returns skewed we considered the unified approach based on the inverse probability integral transformation. In particular, we applied hidden truncation mechanism, inverse scale factors, order statistics concept, Beta and Bernstein distribution transformations and also a constructive method. Based on the daily excess returns on the Warsaw Stock Exchange Index we checked the empirical importance of the conditional skewness assumption on the relation between risk and return on the Warsaw Stock Market. We present posterior probabilities of all competing specifications as well as the posterior analysis of the positive sign of the tested relationship.

The role of semantics, pre-emption and skew in linguistic distributions: the case of the un-construction.

Directory of Open Access Journals (Sweden)

Paul eIbbotson

2013-12-01

Full Text Available We use the Google Ngram database, a corpus of 5,195,769 digitized books containing ~4% of all books ever published, to test three ideas that are hypothesized to account for linguistic generalizations: verbal semantics, pre-emption and skew. Using 828,813 tokens of un-forms as a test case for these mechanisms, we found verbal semantics was a good predictor of the frequency of un-forms in the English language over the past 200 years – both in terms of how the frequency changed over time and their rank frequency. We did not find strong evidence for the direct competition of un-forms and their top pre-emptors, however the skew of the un-construction competitors was inversely correlated with the acceptability of the un-form. We suggest a cognitive explanation for this, namely, that the more the set of relevant pre-emptors is skewed then the more easily it is retrieved from memory. This suggests that it is not just the frequency of pre-emptive forms that must be taken into account when trying to explain usage patterns but their skew as well.

A Skew-t space-varying regression model for the spectral analysis of resting state brain activity.

Science.gov (United States)

Ismail, Salimah; Sun, Wenqi; Nathoo, Farouk S; Babul, Arif; Moiseev, Alexader; Beg, Mirza Faisal; Virji-Babul, Naznin

2013-08-01

It is known that in many neurological disorders such as Down syndrome, main brain rhythms shift their frequencies slightly, and characterizing the spatial distribution of these shifts is of interest. This article reports on the development of a Skew-t mixed model for the spatial analysis of resting state brain activity in healthy controls and individuals with Down syndrome. Time series of oscillatory brain activity are recorded using magnetoencephalography, and spectral summaries are examined at multiple sensor locations across the scalp. We focus on the mean frequency of the power spectral density, and use space-varying regression to examine associations with age, gender and Down syndrome across several scalp regions. Spatial smoothing priors are incorporated based on a multivariate Markov random field, and the markedly non-Gaussian nature of the spectral response variable is accommodated by the use of a Skew-t distribution. A range of models representing different assumptions on the association structure and response distribution are examined, and we conduct model selection using the deviance information criterion. (1) Our analysis suggests region-specific differences between healthy controls and individuals with Down syndrome, particularly in the left and right temporal regions, and produces smoothed maps indicating the scalp topography of the estimated differences.

Non-local correlations via Wigner-Yanase skew information in two SC-qubit having mutual interaction under phase decoherence

Science.gov (United States)

Mohamed, Abdel-Baset A.

2017-10-01

An analytical solution of the master equation that describes a superconducting cavity containing two coupled superconducting charge qubits is obtained. Quantum-mechanical correlations based on Wigner-Yanase skew information, as local quantum uncertainty and uncertainty-induced quantum non-locality, are compared to the concurrence under the effects of the phase decoherence. Local quantum uncertainty exhibits sudden changes during its time evolution and revival process. Sudden death and sudden birth occur only for entanglement, depending on the initial state of the two coupled charge qubits, while the correlations of skew information does not vanish. The quantum correlations of skew information are found to be sensitive to the dephasing rate, the photons number in the cavity, the interaction strength between the two qubits, and the qubit distribution angle of the initial state. With a proper initial state, the stationary correlation of the skew information has a non-zero stationary value for a long time interval under the phase decoherence, that it may be useful in quantum information and computation processes.

Skew Information for a Single Cooper Pair Box Interacting with a Single Cavity Field

International Nuclear Information System (INIS)

Metwally, N.; Al-Mannai, A.; Abdel-Aty, M.

2013-01-01

The dynamics of the skew information (SI) is investigated for a single Cooper Pair Box (CPB) interacting with a single cavity field. By suitably choosing the system parameters and precisely controlling the dynamics, novel connection is found between the SI and entanglement generation. It is shown that SI can be increased and reach its maximum value either by increasing the number of photons inside the cavity or considering the far off-resonant case. The number of oscillations of SI is increased by decreasing this ratio between the Josephson junction capacity and the gate capacity. This leads to significant improvement of the travelling time between the maximum and minimum values. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Influence of skew rays on the sensitivity and signal-to-noise ratio of a fiber-optic surface-plasmon-resonance sensor: a theoretical study

International Nuclear Information System (INIS)

Dwivedi, Yogendra S.; Sharma, Anuj K.; Gupta, Banshi D.

2007-01-01

We have theoretically analyzed the influence of skew rays on the performance of a fiber-optic sensor based on surface plasmon resonance. The performance of the sensor has been evaluated in terms of its sensitivity and signal-to-noise ratio (SNR). The theoretical model for skewness dependence includes the material dispersion in fiber cores and metal layers, simultaneous excitation of skew rays, and meridional rays in the fiber core along with all guided rays launching from a collimated light source. The effect of skew rays on the SNR and the sensitivity of the sensor with two different metals has been compared. The same comparison is carried out for the different values of design parameters such as numerical aperture, fiber core diameter, and the length of the surface-plasmon-resonance (SPR)active sensing region. This detailed analysis for the effect of skewness on the SNR and the sensitivity of the sensor leads us to achieve the best possible performance from a fiber-optic SPR sensor against the skewness in the optical fiber

Fast and Accurate Ground Truth Generation for Skew-Tolerance Evaluation of Page Segmentation Algorithms

Directory of Open Access Journals (Sweden)

Okun Oleg

2006-01-01

Full Text Available Many image segmentation algorithms are known, but often there is an inherent obstacle in the unbiased evaluation of segmentation quality: the absence or lack of a common objective representation for segmentation results. Such a representation, known as the ground truth, is a description of what one should obtain as the result of ideal segmentation, independently of the segmentation algorithm used. The creation of ground truth is a laborious process and therefore any degree of automation is always welcome. Document image analysis is one of the areas where ground truths are employed. In this paper, we describe an automated tool called GROTTO intended to generate ground truths for skewed document images, which can be used for the performance evaluation of page segmentation algorithms. Some of these algorithms are claimed to be insensitive to skew (tilt of text lines. However, this fact is usually supported only by a visual comparison of what one obtains and what one should obtain since ground truths are mostly available for upright images, that is, those without skew. As a result, the evaluation is both subjective; that is, prone to errors, and tedious. Our tool allows users to quickly and easily produce many sufficiently accurate ground truths that can be employed in practice and therefore it facilitates automatic performance evaluation. The main idea is to utilize the ground truths available for upright images and the concept of the representative square [9] in order to produce the ground truths for skewed images. The usefulness of our tool is demonstrated through a number of experiments with real-document images of complex layout.

Impaired imprinted X chromosome inactivation is responsible for the skewed sex ratio following in vitro fertilization

Science.gov (United States)

Tan, Kun; An, Lei; Miao, Kai; Ren, Likun; Hou, Zhuocheng; Tao, Li; Zhang, Zhenni; Wang, Xiaodong; Xia, Wei; Liu, Jinghao; Wang, Zhuqing; Xi, Guangyin; Gao, Shuai; Sui, Linlin; Zhu, De-Sheng; Wang, Shumin; Wu, Zhonghong; Bach, Ingolf; Chen, Dong-bao; Tian, Jianhui

2016-01-01

Dynamic epigenetic reprogramming occurs during normal embryonic development at the preimplantation stage. Erroneous epigenetic modifications due to environmental perturbations such as manipulation and culture of embryos during in vitro fertilization (IVF) are linked to various short- or long-term consequences. Among these, the skewed sex ratio, an indicator of reproductive hazards, was reported in bovine and porcine embryos and even human IVF newborns. However, since the first case of sex skewing reported in 1991, the underlying mechanisms remain unclear. We reported herein that sex ratio is skewed in mouse IVF offspring, and this was a result of female-biased peri-implantation developmental defects that were originated from impaired imprinted X chromosome inactivation (iXCI) through reduced ring finger protein 12 (Rnf12)/X-inactive specific transcript (Xist) expression. Compensation of impaired iXCI by overexpression of Rnf12 to up-regulate Xist significantly rescued female-biased developmental defects and corrected sex ratio in IVF offspring. Moreover, supplementation of an epigenetic modulator retinoic acid in embryo culture medium up-regulated Rnf12/Xist expression, improved iXCI, and successfully redeemed the skewed sex ratio to nearly 50% in mouse IVF offspring. Thus, our data show that iXCI is one of the major epigenetic barriers for the developmental competence of female embryos during preimplantation stage, and targeting erroneous epigenetic modifications may provide a potential approach for preventing IVF-associated complications. PMID:26951653

A probit- log- skew-normal mixture model for repeated measures data with excess zeros, with application to a cohort study of paediatric respiratory symptoms

Directory of Open Access Journals (Sweden)

Johnston Neil W

2010-06-01

Full Text Available Abstract Background A zero-inflated continuous outcome is characterized by occurrence of "excess" zeros that more than a single distribution can explain, with the positive observations forming a skewed distribution. Mixture models are employed for regression analysis of zero-inflated data. Moreover, for repeated measures zero-inflated data the clustering structure should also be modeled for an adequate analysis. Methods Diary of Asthma and Viral Infections Study (DAVIS was a one year (2004 cohort study conducted at McMaster University to monitor viral infection and respiratory symptoms in children aged 5-11 years with and without asthma. Respiratory symptoms were recorded daily using either an Internet or paper-based diary. Changes in symptoms were assessed by study staff and led to collection of nasal fluid specimens for virological testing. The study objectives included investigating the response of respiratory symptoms to respiratory viral infection in children with and without asthma over a one year period. Due to sparse data daily respiratory symptom scores were aggregated into weekly average scores. More than 70% of the weekly average scores were zero, with the positive scores forming a skewed distribution. We propose a random effects probit/log-skew-normal mixture model to analyze the DAVIS data. The model parameters were estimated using a maximum marginal likelihood approach. A simulation study was conducted to assess the performance of the proposed mixture model if the underlying distribution of the positive response is different from log-skew normal. Results Viral infection status was highly significant in both probit and log-skew normal model components respectively. The probability of being symptom free was much lower for the week a child was viral positive relative to the week she/he was viral negative. The severity of the symptoms was also greater for the week a child was viral positive. The probability of being symptom free was

Skewed Marriage Markets and Sex Ratios of Finnish People in their Twenties

Directory of Open Access Journals (Sweden)

Lassi Lainiala

2014-03-01

Full Text Available This article studies variation in regional sex ratios in Finland and outlines potential implications of the skewed sex ratios for family formation patterns. Difficulties in finding a suitable partner are typically mentioned as one of the most important reasons for remaining childless, and we explore if this reason is apparent structurally at the regional macro level. We found significant variation in sex ratios in age-groups 18–30 at the regional and sub-regional levels. Of the whole 20–29-year old population in Finland, almost 50 percent live in sub-region areas with a male surplus. As expected, a higher proportion of men compared to women appears to increase fertility of women in younger age groups. Contrary to expectations, high male-female ratios were not related to higher proportion of women living with a partner

Hölder properties of perturbed skew products and Fubini regained

International Nuclear Information System (INIS)

Ilyashenko, Yu; Negut, A

2012-01-01

In 2006, Gorodetski proved that central fibres of perturbed skew products are Hölder continuous with respect to the base point. In this paper, we give an explicit estimate of this Hölder exponent. Moreover, we extend Gorodetski's result from the case when the fibre maps are close to the identity to a much wider class of maps that satisfy the so-called modified dominated splitting condition. In many cases (for example, in the case of skew products over the solenoid or over linear Anosov diffeomorphisms of the torus), the Hölder exponent is close to 1. This allows one to overcome the so-called Fubini nightmare, in some sense. Namely, we prove that the union of central fibres that are strongly atypical from the point of view of ergodic theory, has Lebesgue measure zero despite the lack of absolute continuity of the holonomy map for the central foliation. This result is based on a new kind of ergodic theorem, which we call special. To prove our main result, we revisit the theory of Hirsch, Pugh and Shub, and estimate the contraction constant of the graph transform map. (paper)

Skew Projection of Echo-Detected EPR Spectra for Increased Sensitivity and Resolution

Science.gov (United States)

Bowman, Michael K.; Krzyaniak, Matthew D.; Cruce, Alex A.; Weber, Ralph T.

2013-01-01

The measurement of EPR spectra during pulsed EPR experiments is commonly accomplished by recording the integral of the electron spin echo as the applied magnetic field is stepped through the spectrum. This approach to echo-detected EPR spectral measurement (ED-EPR) limits sensitivity and spectral resolution and can cause gross distortions in the resulting spectra because some of the information present in the electron spin echo is discarded in such measurements. However, Fourier Transformation of echo shapes measured at a series of magnetic field values followed by skew projection onto either a magnetic field or resonance frequency axis can increase both spectral resolution and sensitivity without the need to trade one against the other. Examples of skew-projected spectra with single crystals, glasses and powders show resolution improvements as large as a factor of seven with sensitivity increases of as much as a factor of five. PMID:23644351

Overcoming the effects of differential skewness of test items in scale construction

Directory of Open Access Journals (Sweden)

Johann M. Schepers

2004-10-01

Full Text Available The principal objective of the study was to develop a procedure for overcoming the effects of differential skewness of test items in scale construction. It was shown that the degree of skewness of test items places an upper limit on the correlations between the items, regardless of the contents of the items. If the items are ordered in terms of skewness the resulting inter correlation matrix forms a simplex or a pseudo simplex. Factoring such a matrix results in a multiplicity of factors, most of which are artifacts. A procedure for overcoming this problem was demonstrated with items from the Locus of Control Inventory (Schepers, 1995. The analysis was based on a sample of 1662 first year university students. Opsomming Die hoofdoel van die studie was om ’n prosedure te ontwikkel om die gevolge van differensiële skeefheid van toetsitems, in skaalkonstruksie, teen te werk. Daar is getoon dat die graad van skeefheid van toetsitems ’n boonste grens plaas op die korrelasies tussen die items ongeag die inhoud daarvan. Indien die items gerangskik word volgens graad van skeefheid, sal die interkorrelasiematriks van die items ’n simpleks of pseudosimpleks vorm. Indien so ’n matriks aan faktorontleding onderwerp word, lei dit tot ’n veelheid van faktore waarvan die meerderheid artefakte is. ’n Prosedure om hierdie probleem te bowe te kom, is gedemonstreer met behulp van die items van die Lokus van Beheer-vraelys (Schepers, 1995. Die ontledings is op ’n steekproef van 1662 eerstejaaruniversiteitstudente gebaseer.

Enhancing tumor apparent diffusion coefficient histogram skewness stratifies the postoperative survival in recurrent glioblastoma multiforme patients undergoing salvage surgery.

Science.gov (United States)

Zolal, Amir; Juratli, Tareq A; Linn, Jennifer; Podlesek, Dino; Sitoci Ficici, Kerim Hakan; Kitzler, Hagen H; Schackert, Gabriele; Sobottka, Stephan B; Rieger, Bernhard; Krex, Dietmar

2016-05-01

Objective To determine the value of apparent diffusion coefficient (ADC) histogram parameters for the prediction of individual survival in patients undergoing surgery for recurrent glioblastoma (GBM) in a retrospective cohort study. Methods Thirty-one patients who underwent surgery for first recurrence of a known GBM between 2008 and 2012 were included. The following parameters were collected: age, sex, enhancing tumor size, mean ADC, median ADC, ADC skewness, ADC kurtosis and fifth percentile of the ADC histogram, initial progression free survival (PFS), extent of second resection and further adjuvant treatment. The association of these parameters with survival and PFS after second surgery was analyzed using log-rank test and Cox regression. Results Using log-rank test, ADC histogram skewness of the enhancing tumor was significantly associated with both survival (p = 0.001) and PFS after second surgery (p = 0.005). Further parameters associated with prolonged survival after second surgery were: gross total resection at second surgery (p = 0.026), tumor size (0.040) and third surgery (p = 0.003). In the multivariate Cox analysis, ADC histogram skewness was shown to be an independent prognostic factor for survival after second surgery. Conclusion ADC histogram skewness of the enhancing lesion, enhancing lesion size, third surgery, as well as gross total resection have been shown to be associated with survival following the second surgery. ADC histogram skewness was an independent prognostic factor for survival in the multivariate analysis.

Cavitation Simulation on Conventional and Highly-Skewed Propellers in the Behind Condition

DEFF Research Database (Denmark)

Shin, Keun Woo; Andersen, Poul; Mikkelsen, Robert Flemming

2011-01-01

The cavitating flows around conventional and highly-skewed propellers in the behind-hull condition are simulated by an in-house RANS solver, EllipSys (Sørensen 2003), with the cavitation model, based on the homogeneous equilibrium modeling (HEM) approach and a vapor transport equation. The valida...

Squaring the Circle: Geometric Skewness and Symmetry Breaking for Passive Scalar Transport in Ducts and Pipes.

Science.gov (United States)

Aminian, Manuchehr; Bernardi, Francesca; Camassa, Roberto; McLaughlin, Richard M

2015-10-09

We study the role geometry plays in the emergence of asymmetries in diffusing passive scalars advected by pressure-driven flows in ducts and pipes of different aspect ratios. We uncover nonintuitive, multi-time-scale behavior gauged by a new statistic, which we term "geometric skewness" S^{G}, which measures instantaneously forming asymmetries at short times due to flow geometry. This signature distinguishes elliptical pipes of any aspect ratio, for which S^{G}=0, from rectangular ducts whose S^{G} is generically nonzero, and, interestingly, shows that a special duct of aspect ratio ≈0.53335 behaves like a circular pipe as its geometric skewness vanishes. Using a combination of exact solutions, novel short-time asymptotics, and Monte Carlo simulations, we establish the relevant time scales for plateaus and extrema in the evolution of the skewness and kurtosis for our class of geometries. For ducts limiting to channel geometries, we present new exact, single-series formulas for the first four moments on slices used to benchmark Monte Carlo simulations.

MEASURING LOCAL GRADIENT AND SKEW QUADRUPOLE ERRORS IN RHIC IRS

International Nuclear Information System (INIS)

CARDONA, J.; PEGGS, S.; PILAT, R.; PTITSYN, V.

2004-01-01

The measurement of local linear errors at RHIC interaction regions using an ''action and phase'' analysis of difference orbits has already been presented [2]. This paper evaluates the accuracy of this technique using difference orbits that were taken when known gradient errors and skew quadrupole errors were intentionally introduced. It also presents action and phase analysis of simulated orbits when controlled errors are intentionally placed in a RHIC simulation model

Analysis of financial time series using multiscale entropy based on skewness and kurtosis

Science.gov (United States)

Xu, Meng; Shang, Pengjian

2018-01-01

There is a great interest in studying dynamic characteristics of the financial time series of the daily stock closing price in different regions. Multi-scale entropy (MSE) is effective, mainly in quantifying the complexity of time series on different time scales. This paper applies a new method for financial stability from the perspective of MSE based on skewness and kurtosis. To better understand the superior coarse-graining method for the different kinds of stock indexes, we take into account the developmental characteristics of the three continents of Asia, North America and European stock markets. We study the volatility of different financial time series in addition to analyze the similarities and differences of coarsening time series from the perspective of skewness and kurtosis. A kind of corresponding relationship between the entropy value of stock sequences and the degree of stability of financial markets, were observed. The three stocks which have particular characteristics in the eight piece of stock sequences were discussed, finding the fact that it matches the result of applying the MSE method to showing results on a graph. A comparative study is conducted to simulate over synthetic and real world data. Results show that the modified method is more effective to the change of dynamics and has more valuable information. The result is obtained at the same time, finding the results of skewness and kurtosis discrimination is obvious, but also more stable.

SKEWNESS IN STOCK RETURNS: EVIDENCE FROM THE BUCHAREST STOCK EXCHANGE DURING 2000 – 2011

Directory of Open Access Journals (Sweden)

IULIAN PANAIT

2012-05-01

Full Text Available Our paper investigates the symmetry in stock returns of the 30 most liquid companies traded on Bucharest Stock Exchange during 2000 – 2011 and also the most representative 5 market indices. Our daily data shows that skewness estimates are slightly negative for most indices and individual stocks, but only a few present values significantly different from the characteristics of a normal distribution. We compare our results with skewness estimates for 21 major and emerging stock market indices around the world and find that such results are similar to other low capitalization and trading volume markets. For all the Romanian and international assets studied, the Studentized-Range (St-R and Jarque-Bera (J-B tests reject the hypothesis of normal distribution of daily returns.

On nomenclature for, and the relative merits of, two formulations of skew distributions

KAUST Repository

Azzalini, Adelchi

2015-12-21

We examine some skew distributions used extensively within the model-based clustering literature in recent years, paying special attention to claims that have been made about their relative efficacy. Theoretical arguments are provided as well as real data examples.

On nomenclature for, and the relative merits of, two formulations of skew distributions

KAUST Repository

Azzalini, Adelchi; Browne, Ryan P.; Genton, Marc G.; McNicholas, Paul D.

2015-01-01

We examine some skew distributions used extensively within the model-based clustering literature in recent years, paying special attention to claims that have been made about their relative efficacy. Theoretical arguments are provided as well as real data examples.

Approximate median regression for complex survey data with skewed response.

Science.gov (United States)

Fraser, Raphael André; Lipsitz, Stuart R; Sinha, Debajyoti; Fitzmaurice, Garrett M; Pan, Yi

2016-12-01

The ready availability of public-use data from various large national complex surveys has immense potential for the assessment of population characteristics using regression models. Complex surveys can be used to identify risk factors for important diseases such as cancer. Existing statistical methods based on estimating equations and/or utilizing resampling methods are often not valid with survey data due to complex survey design features. That is, stratification, multistage sampling, and weighting. In this article, we accommodate these design features in the analysis of highly skewed response variables arising from large complex surveys. Specifically, we propose a double-transform-both-sides (DTBS)'based estimating equations approach to estimate the median regression parameters of the highly skewed response; the DTBS approach applies the same Box-Cox type transformation twice to both the outcome and regression function. The usual sandwich variance estimate can be used in our approach, whereas a resampling approach would be needed for a pseudo-likelihood based on minimizing absolute deviations (MAD). Furthermore, the approach is relatively robust to the true underlying distribution, and has much smaller mean square error than a MAD approach. The method is motivated by an analysis of laboratory data on urinary iodine (UI) concentration from the National Health and Nutrition Examination Survey. © 2016, The International Biometric Society.

Estimating the mean and standard deviation of environmental data with below detection limit observations: Considering highly skewed data and model misspecification.

Science.gov (United States)

Shoari, Niloofar; Dubé, Jean-Sébastien; Chenouri, Shoja'eddin

2015-11-01

In environmental studies, concentration measurements frequently fall below detection limits of measuring instruments, resulting in left-censored data. Some studies employ parametric methods such as the maximum likelihood estimator (MLE), robust regression on order statistic (rROS), and gamma regression on order statistic (GROS), while others suggest a non-parametric approach, the Kaplan-Meier method (KM). Using examples of real data from a soil characterization study in Montreal, we highlight the need for additional investigations that aim at unifying the existing literature. A number of studies have examined this issue; however, those considering data skewness and model misspecification are rare. These aspects are investigated in this paper through simulations. Among other findings, results show that for low skewed data, the performance of different statistical methods is comparable, regardless of the censoring percentage and sample size. For highly skewed data, the performance of the MLE method under lognormal and Weibull distributions is questionable; particularly, when the sample size is small or censoring percentage is high. In such conditions, MLE under gamma distribution, rROS, GROS, and KM are less sensitive to skewness. Related to model misspecification, MLE based on lognormal and Weibull distributions provides poor estimates when the true distribution of data is misspecified. However, the methods of rROS, GROS, and MLE under gamma distribution are generally robust to model misspecifications regardless of skewness, sample size, and censoring percentage. Since the characteristics of environmental data (e.g., type of distribution and skewness) are unknown a priori, we suggest using MLE based on gamma distribution, rROS and GROS. Copyright © 2015 Elsevier Ltd. All rights reserved.

An algorithm to construct the basic algebra of a skew group algebra

NARCIS (Netherlands)

Horobeţ, E.

2016-01-01

We give an algorithm for the computation of the basic algebra Morita equivalent to a skew group algebra of a path algebra by obtaining formulas for the number of vertices and arrows of the new quiver Qb. We apply this algorithm to compute the basic algebra corresponding to all simple quaternion

Crossover ensembles of random matrices and skew-orthogonal polynomials

International Nuclear Information System (INIS)

Kumar, Santosh; Pandey, Akhilesh

2011-01-01

Highlights: → We study crossover ensembles of Jacobi family of random matrices. → We consider correlations for orthogonal-unitary and symplectic-unitary crossovers. → We use the method of skew-orthogonal polynomials and quaternion determinants. → We prove universality of spectral correlations in crossover ensembles. → We discuss applications to quantum conductance and communication theory problems. - Abstract: In a recent paper (S. Kumar, A. Pandey, Phys. Rev. E, 79, 2009, p. 026211) we considered Jacobi family (including Laguerre and Gaussian cases) of random matrix ensembles and reported exact solutions of crossover problems involving time-reversal symmetry breaking. In the present paper we give details of the work. We start with Dyson's Brownian motion description of random matrix ensembles and obtain universal hierarchic relations among the unfolded correlation functions. For arbitrary dimensions we derive the joint probability density (jpd) of eigenvalues for all transitions leading to unitary ensembles as equilibrium ensembles. We focus on the orthogonal-unitary and symplectic-unitary crossovers and give generic expressions for jpd of eigenvalues, two-point kernels and n-level correlation functions. This involves generalization of the theory of skew-orthogonal polynomials to crossover ensembles. We also consider crossovers in the circular ensembles to show the generality of our method. In the large dimensionality limit, correlations in spectra with arbitrary initial density are shown to be universal when expressed in terms of a rescaled symmetry breaking parameter. Applications of our crossover results to communication theory and quantum conductance problems are also briefly discussed.

INVESTIGATION OF SEISMIC PERFORMANCE AND DESIGN OF TYPICAL CURVED AND SKEWED BRIDGES IN COLORADO

Science.gov (United States)

2018-01-15

This report summarizes the analytical studies on the seismic performance of typical Colorado concrete bridges, particularly those with curved and skewed configurations. A set of bridge models with different geometric configurations derived from a pro...

An extraction of the skewing factor from DESY-HERA data

International Nuclear Information System (INIS)

Favart, Laurent; Machado, Magno V.T.; Schoeffel, Laurent

2007-01-01

In this contribution we present recent investigation on the extraction of the skewing factor, defined as the ratio of the imaginary parts of the amplitudes ImA (gamma * p → gamma * p) / ImA (gamma * p → gamma p). This factor is extracted from the data using the recent DVCS and the inclusive inelastic cross section measurements at DESY-HERA. We compare the results to the theoretical predictions for NLO QCD and the color dipole approach. (author)

Comparative study of reproductive skew and pair-bond stability using genealogies from 80 small-scale human societies.

Science.gov (United States)

Ellsworth, Ryan M; Shenk, Mary K; Bailey, Drew H; Walker, Robert S

2016-05-01

Genealogies contain information on the prevalence of different sibling types that result from past reproductive behavior. Full sibling sets stem from stable monogamy, paternal half siblings primarily indicate male reproductive skew, and maternal half siblings reflect unstable pair bonds. Full and half sibling types are calculated for a total of 61,181 siblings from published genealogies for 80 small-scale societies, including foragers, horticulturalists, agriculturalists, and pastoralists from around the world. Most siblings are full (61%) followed by paternal half siblings (27%) and maternal half siblings (13%). Paternal half siblings are positively correlated with more polygynous marriages, higher at low latitudes, and slightly higher in nonforagers, Maternal half sibling fractions are slightly higher at low latitudes but do not vary with subsistence. Partible paternity societies in Amazonia have more paternal half siblings indicating higher male reproductive skew. Sibling counts from genealogies provide a convenient method to simultaneously investigate the reproductive skew and pair-bond stability dimensions of human mating systems cross-culturally. Am. J. Hum. Biol. 28:335-342, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

Skewed task conflicts in teams: What happens when a few members see more conflict than the rest?

Science.gov (United States)

Sinha, Ruchi; Janardhanan, Niranjan S; Greer, Lindred L; Conlon, Donald E; Edwards, Jeffery R

2016-07-01

Task conflict has been the subject of a long-standing debate in the literature-when does task conflict help or hurt team performance? We propose that this debate can be resolved by taking a more precise view of how task conflicts are perceived in teams. Specifically, we propose that in teams, when a few team members perceive a high level of task disagreement while a majority of others perceive low levels of task disagreement-that is, there is positively skewed task conflict, task conflict is most likely to live up to its purported benefits for team performance. In our first study of student teams engaged in a business decision game, we find support for the positive relationship between skewed task conflict and team performance. In our second field study of teams in a financial corporation, we find that the relationship between positively skewed task conflict and supervisor ratings of team performance is mediated by reflective communication within the team. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Widely Linear Blind Adaptive Equalization for Transmitter IQ-Imbalance/Skew Compensation in Multicarrier Systems

DEFF Research Database (Denmark)

Porto da Silva, Edson; Zibar, Darko

2016-01-01

Simple analytical widely linear complex-valued models for IQ-imbalance and IQ-skew effects in multicarrier transmitters are presented. To compensate for such effects, a 4×4 MIMO widely linear adaptive equalizer is proposed and experimentally validated....

Multi-objective mean-variance-skewness model for generation portfolio allocation in electricity markets

Energy Technology Data Exchange (ETDEWEB)

Pindoriya, N.M.; Singh, S.N. [Department of Electrical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016 (India); Singh, S.K. [Indian Institute of Management Lucknow, Lucknow 226013 (India)

2010-10-15

This paper proposes an approach for generation portfolio allocation based on mean-variance-skewness (MVS) model which is an extension of the classical mean-variance (MV) portfolio theory, to deal with assets whose return distribution is non-normal. The MVS model allocates portfolios optimally by considering the maximization of both the expected return and skewness of portfolio return while simultaneously minimizing the risk. Since, it is competing and conflicting non-smooth multi-objective optimization problem, this paper employed a multi-objective particle swarm optimization (MOPSO) based meta-heuristic technique to provide Pareto-optimal solution in a single simulation run. Using a case study of the PJM electricity market, the performance of the MVS portfolio theory based method and the classical MV method is compared. It has been found that the MVS portfolio theory based method can provide significantly better portfolios in the situation where non-normally distributed assets exist for trading. (author)

Multi-objective mean-variance-skewness model for generation portfolio allocation in electricity markets

International Nuclear Information System (INIS)

Pindoriya, N.M.; Singh, S.N.; Singh, S.K.

2010-01-01

This paper proposes an approach for generation portfolio allocation based on mean-variance-skewness (MVS) model which is an extension of the classical mean-variance (MV) portfolio theory, to deal with assets whose return distribution is non-normal. The MVS model allocates portfolios optimally by considering the maximization of both the expected return and skewness of portfolio return while simultaneously minimizing the risk. Since, it is competing and conflicting non-smooth multi-objective optimization problem, this paper employed a multi-objective particle swarm optimization (MOPSO) based meta-heuristic technique to provide Pareto-optimal solution in a single simulation run. Using a case study of the PJM electricity market, the performance of the MVS portfolio theory based method and the classical MV method is compared. It has been found that the MVS portfolio theory based method can provide significantly better portfolios in the situation where non-normally distributed assets exist for trading. (author)

Determining the role of skewed X-chromosome inactivation in developing muscle symptoms in carriers of Duchenne muscular dystrophy.

Science.gov (United States)

Viggiano, Emanuela; Ergoli, Manuela; Picillo, Esther; Politano, Luisa

2016-07-01

Duchenne and Becker dystrophinopathies (DMD and BMD) are X-linked recessive disorders caused by mutations in the dystrophin gene that lead to absent or reduced expression of dystrophin in both skeletal and heart muscles. DMD/BMD female carriers are usually asymptomatic, although about 8 % may exhibit muscle or cardiac symptoms. Several mechanisms leading to a reduced dystrophin have been hypothesized to explain the clinical manifestations and, in particular, the role of the skewed XCI is questioned. In this review, the mechanism of XCI and its involvement in the phenotype of BMD/DMD carriers with both a normal karyotype or with X;autosome translocations with breakpoints at Xp21 (locus of the DMD gene) will be analyzed. We have previously observed that DMD carriers with moderate/severe muscle involvement, exhibit a moderate or extremely skewed XCI, in particular if presenting with an early onset of symptoms, while DMD carriers with mild muscle involvement present a random XCI. Moreover, we found that among 87.1 % of the carriers with X;autosome translocations involving the locus Xp21 who developed signs and symptoms of dystrophinopathy such as proximal muscle weakness, difficulty to run, jump and climb stairs, 95.2 % had a skewed XCI pattern in lymphocytes. These data support the hypothesis that skewed XCI is involved in the onset of phenotype in DMD carriers, the X chromosome carrying the normal DMD gene being preferentially inactivated and leading to a moderate-severe muscle involvement.

Frequent Pairs in Data Streams: Exploiting Parallelism and Skew

DEFF Research Database (Denmark)

Campagna, Andrea; Kutzkow, Konstantin; Pagh, Rasmus

2011-01-01

We introduce the Pair Streaming Engine (PairSE) that detects frequent pairs in a data stream of transactions. Our algorithm finds the most frequent pairs with high probability, and gives tight bounds on their frequency. It is particularly space efficient for skewed distribution of pair supports...... items mining in data streams. We show how to efficiently scale these approaches to handle large transactions. We report experimental results showcasing precision and recall of our method. In particular, we find that often our method achieves excellent precision, returning identical upper and lower...... bounds on the supports of the most frequent pairs....

Approaches to characterise chromatographic column performance based on global parameters accounting for peak broadening and skewness.

Science.gov (United States)

Baeza-Baeza, J J; Pous-Torres, S; Torres-Lapasió, J R; García-Alvarez-Coque, M C

2010-04-02

Peak broadening and skewness are fundamental parameters in chromatography, since they affect the resolution capability of a chromatographic column. A common practice to characterise chromatographic columns is to estimate the efficiency and asymmetry factor for the peaks of one or more solutes eluted at selected experimental conditions. This has the drawback that the extra-column contributions to the peak variance and skewness make the peak shape parameters depend on the retention time. We propose and discuss here the use of several approaches that allow the estimation of global parameters (non-dependent on the retention time) to describe the column performance. The global parameters arise from different linear relationships that can be established between the peak variance, standard deviation, or half-widths with the retention time. Some of them describe exclusively the column contribution to the peak broadening, whereas others consider the extra-column effects also. The estimation of peak skewness was also possible for the approaches based on the half-widths. The proposed approaches were applied to the characterisation of different columns (Spherisorb, Zorbax SB, Zorbax Eclipse, Kromasil, Chromolith, X-Terra and Inertsil), using the chromatographic data obtained for several diuretics and basic drugs (beta-blockers). Copyright (c) 2010 Elsevier B.V. All rights reserved.

Application of volume-weighted skew-upwind differencing to thermal and fluid mixing in the cold leg and downcomer of a PWR

International Nuclear Information System (INIS)

Chen, F.F.; Miao, C.C.; Chen, B.C.J.; Domanus, H.M.; Lyczkowski, R.W.; Sha, W.T.

1983-01-01

Upwind differencing has been the most common numerical scheme used in computational fluid flow and heat transfer in past years. However, the numerical diffusion induced by the use of upwind differencing can be significant in problems involving thermal mixing. Thermal and fluid mixing in a pressurized water reactor during high pressurized coolant injection is a typical example where numerical diffusion is significant. An improved volume-weighted skew-upwind differencing is used here to reduce numerical diffusion without overshooting or undershooting which is the major defect of original skew-upwind differencing proposed by Raithby. The basic concept of volume-weighted skew-upwind differencing is shown. Computations were performed using COMMIX-1B, an extended version of the COMMIX-1A. The experiment analyzed here is test No. 1 of the SAI experiment

Baryon number fluctuations and the phase structure in the PNJL model

Energy Technology Data Exchange (ETDEWEB)

Shao, Guo-yun; Tang, Zhan-duo; Gao, Xue-yan; He, Wei-bo [Xi' an Jiaotong University, School of Science, Xi' an, Shaanxi (China)

2018-02-15

We investigate the kurtosis and skewness of net-baryon number fluctuations in the Polyakov loop extended Nambu-Jona-Lasinio (PNJL) model, and discuss the relations between fluctuation distributions and the phase structure of quark-gluon matter. The calculation shows that the traces of chiral and deconfinement transitions can be effectively reflected by the kurtosis and skewness of net-baryon number fluctuations not only in the critical region but also in the crossover region. The contour plot of baryon number kurtosis derived in the PNJL model can qualitatively explain the behavior of net-proton number kurtosis in the STAR beam energy scan experiments. Moreover, the three-dimensional presentations of the kurtosis and skewness in this study are helpful to understand the relations between baryon number fluctuations and QCD phase structure. (orig.)

Scale and shape mixtures of multivariate skew-normal distributions

KAUST Repository

Arellano-Valle, Reinaldo B.

2018-02-26

We introduce a broad and flexible class of multivariate distributions obtained by both scale and shape mixtures of multivariate skew-normal distributions. We present the probabilistic properties of this family of distributions in detail and lay down the theoretical foundations for subsequent inference with this model. In particular, we study linear transformations, marginal distributions, selection representations, stochastic representations and hierarchical representations. We also describe an EM-type algorithm for maximum likelihood estimation of the parameters of the model and demonstrate its implementation on a wind dataset. Our family of multivariate distributions unifies and extends many existing models of the literature that can be seen as submodels of our proposal.

Performance improvements of symmetry-breaking reflector structures in nonimaging devices

Science.gov (United States)

Winston, Roland

2004-01-13

A structure and method for providing a broken symmetry reflector structure for a solar concentrator device. The component of the optical direction vector along the symmetry axis is conserved for all rays propagated through a translationally symmetric optical device. This quantity, referred to as the translational skew invariant, is conserved in rotationally symmetric optical systems. Performance limits for translationally symmetric nonimaging optical devices are derived from the distributions of the translational skew invariant for the optical source and for the target to which flux is to be transferred. A numerically optimized non-tracking solar concentrator utilizing symmetry-breaking reflector structures can overcome the performance limits associated with translational symmetry.

Aerodynamic forces and galloping instability for a skewed elliptical cylinder in a flow at the critical Reynolds number

Energy Technology Data Exchange (ETDEWEB)

Ma, Wenyong [Wind Engineering Research Center, Shijiazhuang Tiedao University, Shijiazhuang, Hebei 050043 (China); Liu, Qingkuan; Liu, Xiaobing [The Key Laboratory for Health Monitoring and Control of Large Structures, Hebei province, 050043 (China); Du, Xiaoqing, E-mail: ma@stdu.edu.cn, E-mail: dxq@shu.edu.cn [Department of Civil Engineering, Shanghai University, Shanghai, 200072 (China)

2017-08-15

The mechanism of large-amplitude aeroelastic vibrations of cylindrical bodies in the critical Reynolds number range are still unclear. This study concerns the aerodynamic forces acting on elliptical cylinders and the induced galloping instability resulting from skew flows (i.e., the direction of the flow is angled 0°–45° with respect to the central axis of the cylinder) for Reynolds numbers in the range of 37–235 k. The effects of the critical Reynolds number and the skew angle on the aerodynamic forces and the galloping instability are investigated with pressure wind tunnel tests. In all of the cases investigated in the present study, a sharp decrease in the lift coefficient with increasing angle of attack and a reduction in the drag coefficient at the critical Reynolds number could be responsible for the galloping instability. Variations in the torque coefficient leads to a torsional aerodynamic instability at the critical Reynolds number. Furthermore, the skew flow cause a critical flow state at lower Reynolds numbers. One possible reason for this behavior is that the longer effective cross section allows the flow to reattach. (paper)

Forecasting stock market volatility: Do realized skewness and kurtosis help?

Science.gov (United States)

Mei, Dexiang; Liu, Jing; Ma, Feng; Chen, Wang

2017-09-01

In this study, we investigate the predictability of the realized skewness (RSK) and realized kurtosis (RKU) to stock market volatility, that has not been addressed in the existing studies. Out-of-sample results show that RSK, which can significantly improve forecast accuracy in mid- and long-term, is more powerful than RKU in forecasting volatility. Whereas these variables are useless in short-term forecasting. Furthermore, we employ the realized kernel (RK) for the robustness analysis and the conclusions are consistent with the RV measures. Our results are of great importance for portfolio allocation and financial risk management.

Skewed X-chromosome inactivation in female carriers of dyskeratosis congenita

Energy Technology Data Exchange (ETDEWEB)

Devriendt, K.; Matthijs, G.; Legius, E. [Univ. Hospital Gasthuisberg, Leuven (Belgium)] [and others

1997-03-01

In this study, we report on a family with X-linked dyskeratosis congenita (DC). Linkage analysis with markers in the factor VIII gene at Xq28 yielded a LOD score of 2 at a recombination of 0. Clinical manifestations of DC, such as skin lesions following the Blaschko lines, were present in two obligate carrier females. Highly skewed X inactivation was observed in white blood cells, cultured skin fibroblasts, and buccal mucosa from female carriers of DC in this family. This suggests a critical role for the DC gene in bone marrow-cell and fibroblast-cell proliferation. 23 refs., 4 figs., 1 tab.

Genotype and phenotype in Klinefelter syndrome - impact of androgen receptor polymorphism and skewed X inactivation

DEFF Research Database (Denmark)

Bojesen, A; Hertz, J M; Gravholt, C H

2011-01-01

The phenotypic variation of Klinefelter syndrome (KS) is wide and may by caused by various genetic and epigenetic effects. Skewed inactivation of the supra-numerical X chromosome and polymorphism in the androgen receptor (AR) have been suggested as plausible causes. We wanted to describe X...

Uniform persistence and upper Lyapunov exponents for monotone skew-product semiflows

International Nuclear Information System (INIS)

Novo, Sylvia; Obaya, Rafael; Sanz, Ana M

2013-01-01

Several results of uniform persistence above and below a minimal set of an abstract monotone skew-product semiflow are obtained. When the minimal set has a continuous separation the results are given in terms of the principal spectrum. In the case that the semiflow is generated by the solutions of a family of non-autonomous differential equations of ordinary, delay or parabolic type, the former results are strongly improved. A method of calculus of the upper Lyapunov exponent of the minimal set is also determined. (paper)

Partial coherence with application to the monotonicity problem of coherence involving skew information

Science.gov (United States)

Luo, Shunlong; Sun, Yuan

2017-08-01

Quantifications of coherence are intensively studied in the context of completely decoherent operations (i.e., von Neuamnn measurements, or equivalently, orthonormal bases) in recent years. Here we investigate partial coherence (i.e., coherence in the context of partially decoherent operations such as Lüders measurements). A bona fide measure of partial coherence is introduced. As an application, we address the monotonicity problem of K -coherence (a quantifier for coherence in terms of Wigner-Yanase skew information) [Girolami, Phys. Rev. Lett. 113, 170401 (2014), 10.1103/PhysRevLett.113.170401], which is introduced to realize a measure of coherence as axiomatized by Baumgratz, Cramer, and Plenio [Phys. Rev. Lett. 113, 140401 (2014), 10.1103/PhysRevLett.113.140401]. Since K -coherence fails to meet the necessary requirement of monotonicity under incoherent operations, it is desirable to remedy this monotonicity problem. We show that if we modify the original measure by taking skew information with respect to the spectral decomposition of an observable, rather than the observable itself, as a measure of coherence, then the problem disappears, and the resultant coherence measure satisfies the monotonicity. Some concrete examples are discussed and related open issues are indicated.

Bayesian linear regression with skew-symmetric error distributions with applications to survival analysis

KAUST Repository

Rubio, Francisco J.

2016-02-09

We study Bayesian linear regression models with skew-symmetric scale mixtures of normal error distributions. These kinds of models can be used to capture departures from the usual assumption of normality of the errors in terms of heavy tails and asymmetry. We propose a general noninformative prior structure for these regression models and show that the corresponding posterior distribution is proper under mild conditions. We extend these propriety results to cases where the response variables are censored. The latter scenario is of interest in the context of accelerated failure time models, which are relevant in survival analysis. We present a simulation study that demonstrates good frequentist properties of the posterior credible intervals associated with the proposed priors. This study also sheds some light on the trade-off between increased model flexibility and the risk of over-fitting. We illustrate the performance of the proposed models with real data. Although we focus on models with univariate response variables, we also present some extensions to the multivariate case in the Supporting Information.

Non-skew-symmetric classical r-matrices, algebraic Bethe ansatz, and Bardeen-Cooper-Schrieffer-type integrable systems

International Nuclear Information System (INIS)

Skrypnyk, T.

2009-01-01

We construct quantum integrable systems associated with non-skew-symmetric gl(2)-valued classical r-matrices. We find a new explicit multiparametric family of such the non-skew-symmetric classical r-matrices. We consider two classes of examples of the corresponding integrable systems, namely generalized Gaudin systems with and without an external magnetic field. In the case of arbitrary r-matrices diagonal in a standard gl(2)-basis, we calculate the spectrum of the corresponding quantum integrable systems using the algebraic Bethe ansatz. We apply these results to a construction of integrable fermionic models and obtain a wide class of integrable Bardeen-Cooper-Schrieffer (BCS)-type fermionic Hamiltonians containing the pairing and electrostatic interaction terms. We also consider special cases when the corresponding integrable Hamiltonians contain only pairing interaction term and are exact analogs of the 'reduced BCS Hamiltonian' of Richardson

Development and Validation of a New Blade Element Momentum Skewed-Wake Model within AeroDyn: Preprint

Energy Technology Data Exchange (ETDEWEB)

Ning, S. A.; Hayman, G.; Damiani, R.; Jonkman, J.

2014-12-01

Blade element momentum methods, though conceptually simple, are highly useful for analyzing wind turbines aerodynamics and are widely used in many design and analysis applications. A new version of AeroDyn is being developed to take advantage of new robust solution methodologies, conform to a new modularization framework for National Renewable Energy Laboratory's FAST, utilize advanced skewed-wake analysis methods, fix limitations with previous implementations, and to enable modeling of highly flexible and nonstraight blades. This paper reviews blade element momentum theory and several of the options available for analyzing skewed inflow. AeroDyn implementation details are described for the benefit of users and developers. These new options are compared to solutions from the previous version of AeroDyn and to experimental data. Finally, recommendations are given on how one might select from the various available solution approaches.

On the effect of intermittency of turbulence on the parabolic relation between skewness and kurtosis in magnetized plasmas

Energy Technology Data Exchange (ETDEWEB)

Guszejnov, Dávid; Lazányi, Nóra [Department of Nuclear Techniques, Budapest University of Technology and Economics, Association EURATOM, Műegyetem rkp. 9., H-1111 Budapest (Hungary); Bencze, Attila; Zoletnik, Sándor [MTA Wigner RCP, EURATOM Association, PO Box 49, H-1525 Budapest (Hungary)

2013-11-15

This paper is aimed to contribute to the scientific discussions that have been triggered by the experimental observation of a quadratic relation between the kurtosis and skewness of turbulent fluctuations present in fusion plasmas and other nonlinear physical systems. In this paper, we offer a general statistical model which attributes the observed K=aS{sup 2}+b relation to the varying intermittency of the experimental signals. The model is a two random variable model constructed to catch the essential intermittent feature of the real signal. One of the variables is the amplitude of the underlying intermittent event (e.g., turbulent structure) while the other is connected to the intermittency level of the system. This simple model can attribute physical meaning to the a and b coefficients, as they characterize the spatio-temporal statistics of intermittent events. By constructing a particle-conserving Gaussian model for the underlying coherent structures, the experimentally measured a and b coefficients could be adequately reproduced.

On the effect of intermittency of turbulence on the parabolic relation between skewness and kurtosis in magnetized plasmas

International Nuclear Information System (INIS)

Guszejnov, Dávid; Lazányi, Nóra; Bencze, Attila; Zoletnik, Sándor

2013-01-01

This paper is aimed to contribute to the scientific discussions that have been triggered by the experimental observation of a quadratic relation between the kurtosis and skewness of turbulent fluctuations present in fusion plasmas and other nonlinear physical systems. In this paper, we offer a general statistical model which attributes the observed K=aS 2 +b relation to the varying intermittency of the experimental signals. The model is a two random variable model constructed to catch the essential intermittent feature of the real signal. One of the variables is the amplitude of the underlying intermittent event (e.g., turbulent structure) while the other is connected to the intermittency level of the system. This simple model can attribute physical meaning to the a and b coefficients, as they characterize the spatio-temporal statistics of intermittent events. By constructing a particle-conserving Gaussian model for the underlying coherent structures, the experimentally measured a and b coefficients could be adequately reproduced

Surveying and optical tooling technologies combined to align a skewed beamline at the LAMPF accelerator

International Nuclear Information System (INIS)

Bauke, W.; Clark, D.A.; Trujillo, P.B.

1985-01-01

Optical Tooling evolved from traditional surveying, and both technologies are sometimes used interchangeably in large industrial installations, since the instruments and their specialized adapters and supports complement each other well. A unique marriage of both technologies was accomplished in a novel application at LAMPF, the Los Alamos Meson Physics Facility. LAMPF consists of a linear accelerator with multiple target systems, one of which had to be altered to accommodate a new beamline for a neutrino experiment. The new line was to be installed into a crowded beam tunnel and had to be skewed and tilted in compound angles to avoid existing equipment. In this paper we describe how Optical Tooling was used in conjunction with simple alignment and reference fixtures to set fiducials on the magnets and other mechanical components of the beamline, and how theodolites and sight levels were then adapted to align these components along the calculated skew planes. Design tolerances are compared with measured alignment results

Different male versus female breeding periodicity helps mitigate offspring sex ratio skews in sea turtles

Directory of Open Access Journals (Sweden)

Graeme Clive Hays

2014-09-01

Full Text Available The implications of climate change for global biodiversity may be profound with those species with little capacity for adaptation being thought to be particularly vulnerable to warming. A classic case of groups for concern are those animals exhibiting temperature-dependent sex-determination (TSD, such as sea turtles, where climate warming may produce single sex populations and hence extinction. We show that, globally, female biased hatchling sex ratios dominate sea turtle populations (exceeding 3:1 in >50% records, which, at-a-glance, reiterates concerns for extinction. However, we also demonstrate that more frequent breeding by males, empirically shown by satellite tracking 23 individuals and supported by a generalized bio-energetic life history model, generates more balanced operational sex ratios (OSRs. Hence, concerns of increasingly skewed hatchling sex ratios and reduced population viability are less acute than previously thought for sea turtles. In fact, in some scenarios skewed hatchling sex ratios in groups with TSD may be adaptive to ensure optimum OSRs.

Demographic origins of skewed operational and adult sex ratios: perturbation analyses of two-sex models.

Science.gov (United States)

Veran, Sophie; Beissinger, Steven R

2009-02-01

Skewed sex ratios - operational (OSR) and Adult (ASR) - arise from sexual differences in reproductive behaviours and adult survival rates due to the cost of reproduction. However, skewed sex-ratio at birth, sex-biased dispersal and immigration, and sexual differences in juvenile mortality may also contribute. We present a framework to decompose the roles of demographic traits on sex ratios using perturbation analyses of two-sex matrix population models. Metrics of sensitivity are derived from analyses of sensitivity, elasticity, life-table response experiments and life stage simulation analyses, and applied to the stable stage distribution instead of lambda. We use these approaches to examine causes of male-biased sex ratios in two populations of green-rumped parrotlets (Forpus passerinus) in Venezuela. Female local juvenile survival contributed the most to the unbalanced OSR and ASR due to a female-biased dispersal rate, suggesting sexual differences in philopatry can influence sex ratios more strongly than the cost of reproduction.

Stock markets volatility spillovers during financial crises: A DCC-MGARCH with skewed-t density approach

Directory of Open Access Journals (Sweden)

Dahiru A. Bala

2017-03-01

Full Text Available This paper investigates stock returns volatility spillovers in emerging and developed markets (DMs using multivariate-GARCH (MGARCH models and their variants. In addition, we analyse the impacts of global financial crisis (2007–2009 on stock market volatility interactions and modify the BEKK-MGARCH-type models by including financial crisis dummies to assess their impact on volatilities and spillovers. Major findings reveal that correlations among emerging markets (EMs are lower compared with correlations among DMs and increase during financial crises. Furthermore, we detect evidence of volatility spillovers and observe that own-volatility spillovers are higher than cross-volatility spillovers for EMs suggesting that shocks have not been substantially transmitted among EMs compared to DMs. We also find significant asymmetric behaviour in DMs while weak evidence is detected for EMs. Finally, the DCC-with-skewed-t density model provided improved diagnostics compared to other models partly due to its taking into account fat tails and skewed features often present in financial returns.

Measurement of the width and skewness of elliptic flow fluctuations in PbPb collisions at 5.02 TeV with CMS

CERN Document Server

Castle, James Robert

2017-01-01

Flow harmonic fluctuations are studied for PbPb collisions at $\\sqrt{s_{NN}} = 5.02~\\mathrm{TeV}$ using the CMS detector at the LHC. Flow harmonic probability distributions $p\\left(v_2\\right)$ are obtained by unfolding smearing effects from observed azimuthal anisotropy distributions using particles of $0.3 < p_{\\mathrm{T}} < 3.0~\\mathrm{GeV}/c$ and $\\lvert \\eta \\rvert < 1.0$. Cumulant flow harmonics are determined from the moments of $p\\left(v_2\\right)$ and used to estimate the standardized elliptic flow skewness. Hydrodynamic models predict this skewness to be negative with respect to the reaction plane. A statistically significant negative skewness is observed for all centrality bins as evidenced by a splitting between $v_2$ $\\{{4}\\}$, $v_2$ $\\{{6}\\}$, and $v_2$ $\\{{8}\\}$ cumulants. Elliptic power law distribution fits are made to $p\\left(v_2\\right)$ distributions to infer information on the nature of initial-state eccentricity distributions and found to provide a more accurate description of the ...

The Use of the Skew T, Log P Diagram in Analysis and Forecasting. Revision

Science.gov (United States)

1990-03-01

28 x 30 been added to further enhance the value of the inches. This version now includes the Apple - diagram. A detailed description of the Skew T, man...airocrau rqor we ovailable. The eauning lIkIaatte U the lop rate Is. at times. recorded as swot - adobaik wheun the mulm leave* a cloud Up and ener

Skew-t partially linear mixed-effects models for AIDS clinical studies.

Science.gov (United States)

Lu, Tao

2016-01-01

We propose partially linear mixed-effects models with asymmetry and missingness to investigate the relationship between two biomarkers in clinical studies. The proposed models take into account irregular time effects commonly observed in clinical studies under a semiparametric model framework. In addition, commonly assumed symmetric distributions for model errors are substituted by asymmetric distribution to account for skewness. Further, informative missing data mechanism is accounted for. A Bayesian approach is developed to perform parameter estimation simultaneously. The proposed model and method are applied to an AIDS dataset and comparisons with alternative models are performed.

Environmental Effects on Flutter Characteristics of Laminated Composite Rectangular and Skew Panels

Directory of Open Access Journals (Sweden)

T.V.R. Chowdary

1996-01-01

Full Text Available A finite element method is presented for predicting the flutter response of laminated composite panels subjected to moisture concentration and temperature. The analysis accounts for material properties at elevated temperature and moisture concentration. The analysis is based on the first-order approximation to the linear piston theory and laminated plate theory that includes shear deformation. Both rectangular and skew panels are considered. Stability boundaries at moisture concentrations and temperatures for various lamination schemes and boundary conditions are discussed.

Robust bivariate error detection in skewed data with application to historical radiosonde winds

KAUST Repository

Sun, Ying

2017-01-18

The global historical radiosonde archives date back to the 1920s and contain the only directly observed measurements of temperature, wind, and moisture in the upper atmosphere, but they contain many random errors. Most of the focus on cleaning these large datasets has been on temperatures, but winds are important inputs to climate models and in studies of wind climatology. The bivariate distribution of the wind vector does not have elliptical contours but is skewed and heavy-tailed, so we develop two methods for outlier detection based on the bivariate skew-t (BST) distribution, using either distance-based or contour-based approaches to flag observations as potential outliers. We develop a framework to robustly estimate the parameters of the BST and then show how the tuning parameter to get these estimates is chosen. In simulation, we compare our methods with one based on a bivariate normal distribution and a nonparametric approach based on the bagplot. We then apply all four methods to the winds observed for over 35,000 radiosonde launches at a single station and demonstrate differences in the number of observations flagged across eight pressure levels and through time. In this pilot study, the method based on the BST contours performs very well.

Robust bivariate error detection in skewed data with application to historical radiosonde winds

KAUST Repository

Sun, Ying; Hering, Amanda S.; Browning, Joshua M.

2017-01-01

The global historical radiosonde archives date back to the 1920s and contain the only directly observed measurements of temperature, wind, and moisture in the upper atmosphere, but they contain many random errors. Most of the focus on cleaning these large datasets has been on temperatures, but winds are important inputs to climate models and in studies of wind climatology. The bivariate distribution of the wind vector does not have elliptical contours but is skewed and heavy-tailed, so we develop two methods for outlier detection based on the bivariate skew-t (BST) distribution, using either distance-based or contour-based approaches to flag observations as potential outliers. We develop a framework to robustly estimate the parameters of the BST and then show how the tuning parameter to get these estimates is chosen. In simulation, we compare our methods with one based on a bivariate normal distribution and a nonparametric approach based on the bagplot. We then apply all four methods to the winds observed for over 35,000 radiosonde launches at a single station and demonstrate differences in the number of observations flagged across eight pressure levels and through time. In this pilot study, the method based on the BST contours performs very well.

Exponential rate of correlation decay for characters in a three-parameter class of toral skew endomorphisms

International Nuclear Information System (INIS)

Siboni, S.

1998-01-01

A detailed analysis of the correlation decay for characters in a three-parameter class of mappings of the 2-torus onto itself is presented. Being these mappings the natural extension of toral transformations previously considered with regard to a model of modulated diffusion, they show the structure of a skew product between the Bernoulli endomorphism B p (x) and a translation on T 1 . The family of characters for which correlation decay occurs is fully characterized for any choice of the parameters, and the decay is proved to be exponential, with a rate analytically computable. This improves a previous result by W. Parry, provides a lower bound to the spectral radius of a Perron-Frobenius operator introduced by the same author in his proof and answers positively to the conjecture that the poorest is the rational approximation of the coupling parameter of the map the fastest is the decay rate

Nilradicals of skew Hurwitz series of rings

Directory of Open Access Journals (Sweden)

Morteza Ahmadi

2015-05-01

Full Text Available ‎For a ring endomorphism α of a ring R, ‎Krempa called α a rigid endomorphism if aα(a=0 implies a = 0 for a in R. ‎A ring R is called rigid if there exists a rigid endomorphism of R. ‎In this paper‎, ‎we extend the α-rigid property of a ring R to the upper nilradical N_r(R of R. ‎For an endomorphism α and the upper nilradical N_r(R of a ring R, ‎we introduce the condition (*: ‎N_r(R is a α-ideal of R and aα(a in N_r(R implies a in N_r(R for a in R. ‎We study characterizations of a ring R with an endomorphism α satisfying the condition (*, ‎and we investigate their related properties‎. ‎The connections between the upper nilradical of R and the upper nilradical of the skew Hurwitz series ring (HR,α of R are also investigated‎.

Measurement of the Skewness of Elliptic Flow Fluctuations in PbPb Collisions at $\\sqrt{s_{NN}} = 5.02~\\mathrm{TeV}$

CERN Document Server

CMS Collaboration

2017-01-01

Event-by-event flow harmonics are studied for PbPb collisions at $\\sqrt{s_{NN}} = 5.02~\\mathrm{TeV}$ using the CMS detector at the LHC. Flow harmonic probability distributions $p\\left(v_2\\right)$ are obtained using particles of $0.3 \\leq p_{T} \\leq 3.0~\\mathrm{GeV}/c$ and $\\left|\\eta\\right| \\leq 1.0$ and are unfolded to remove smearing effects from observed azimuthal particle distributions. Cumulant flow harmonics are determined from the moments of $p\\left(v_2\\right)$ and used to estimate the standardized elliptic flow skewness in $5\\%$ wide centrality bins up to $60\\%$. Hydrodynamic models predict that flow fluctuations will lead to a non-Gaussian component in the flow distributions with a negative skew with respect to the reaction plane. A significant negative skewness is observed for all centrality bins as evidenced by a splitting between $v_2\\left\\{4\\right\\}$ and $v_2\\left\\{6\\right\\}$ cumulants. In addition, elliptic power law distribution fits are made to the $p\\left(v_2\\right)$ distributions to infer in...

Stability management of high speed axial flow compressor stage through axial extensions of bend skewed casing treatment

Directory of Open Access Journals (Sweden)

DilipkumarBhanudasji Alone

2016-09-01

Full Text Available This paper presents the experimental results to understand the performance of moderately loaded high speed single stage transonic axial flow compressor subjected to various configurations of axial extensions of bend skewed casing treatment with moderate porosity. The bend skewed casing treatment of 33% porosity was coupled with rectangular plenum chamber of depth equal to the slots depth. The five axial extensions of 20%, 40%, 60%, 80% and 100% were used for the experimental evaluations of compressor performance. The main objective was to identify the optimum extension of the casing treatment with reference to rotor leading edge which results in maximum stall margin improvements with minimum loss in the stage efficiency. At each axial extension the compressor performance is distinctive. The improvement in the stall margin was very significant at some axial extensions with 4%–5% penalty in the stage efficiency. The compressors stage shows recovery in terms of efficiency at lower axial extensions of 20% and 40% with increase in the peak stage efficiency. Measurements of flow parameters showed the typical behaviors at near stall flow conditions. Hot wire sensor was placed at the rotor upstream in the tip region to capture the oscillations in the inlet axial and tangential velocities at stall conditions. In the absence of casing treatment the compressor exhibit abrupt stall with very high oscillations in the inlet axial and tangential velocity of the flow. The extents of oscillations reduce with bend skewed casing treatment. Few measurements were also performed in the plenum chamber and salient results are presented in this paper.

Understanding the distinctively skewed and heavy tailed character of atmospheric and oceanic probability distributions

Energy Technology Data Exchange (ETDEWEB)

Sardeshmukh, Prashant D., E-mail: Prashant.D.Sardeshmukh@noaa.gov [CIRES, University of Colorado, Boulder, Colorado 80309 (United States); NOAA/Earth System Research Laboratory, Boulder, Colorado 80305 (United States); Penland, Cécile [NOAA/Earth System Research Laboratory, Boulder, Colorado 80305 (United States)

2015-03-15

The probability distributions of large-scale atmospheric and oceanic variables are generally skewed and heavy-tailed. We argue that their distinctive departures from Gaussianity arise fundamentally from the fact that in a quadratically nonlinear system with a quadratic invariant, the coupling coefficients between system components are not constant but depend linearly on the system state in a distinctive way. In particular, the skewness arises from a tendency of the system trajectory to linger near states of weak coupling. We show that the salient features of the observed non-Gaussianity can be captured in the simplest such nonlinear 2-component system. If the system is stochastically forced and linearly damped, with one component damped much more strongly than the other, then the strongly damped fast component becomes effectively decoupled from the weakly damped slow component, and its impact on the slow component can be approximated as a stochastic noise forcing plus an augmented nonlinear damping. In the limit of large time-scale separation, the nonlinear augmentation of the damping becomes small, and the noise forcing can be approximated as an additive noise plus a correlated additive and multiplicative noise (CAM noise) forcing. Much of the diversity of observed large-scale atmospheric and oceanic probability distributions can be interpreted in this minimal framework.

T-cell receptor Vβ skewing frequently occurs in refractory cytopenia of childhood and is associated with an expansion of effector cytotoxic T cells: a prospective study by EWOG-MDS

International Nuclear Information System (INIS)

Aalbers, A M; Heuvel-Eibrink, M M van den; Baumann, I; Beverloo, H B; Driessen, G J; Dworzak, M; Fischer, A; Göhring, G; Hasle, H; Locatelli, F; De Moerloose, B; Noellke, P; Schmugge, M; Stary, J; Yoshimi, A; Zecca, M; Zwaan, C M; Dongen, J J M van; Pieters, R; Niemeyer, C M; Velden, V H J van der; Langerak, A W

2014-01-01

Immunosuppressive therapy (IST), consisting of antithymocyte globulin and cyclosporine A, is effective in refractory cytopenia of childhood (RCC), suggesting that, similar to low-grade myelodysplastic syndromes in adult patients, T lymphocytes are involved in suppressing hematopoiesis in a subset of RCC patients. However, the potential role of a T-cell-mediated pathophysiology in RCC remains poorly explored. In a cohort of 92 RCC patients, we prospectively assessed the frequency of T-cell receptor (TCR) β-chain variable (Vβ) domain skewing in bone marrow and peripheral blood by heteroduplex PCR, and analyzed T-cell subsets in peripheral blood by flow cytometry. TCRVβ skewing was present in 40% of RCC patients. TCRVβ skewing did not correlate with bone marrow cellularity, karyotype, transfusion history, HLA-DR15 or the presence of a PNH clone. In 28 patients treated with IST, TCRVβ skewing was not clearly related with treatment response. However, TCRVβ skewing did correlate with a disturbed CD4 + /CD8 + T-cell ratio, a reduction in naive CD8 + T cells, an expansion of effector CD8 + T cells and an increase in activated CD8 + T cells (defined as HLA-DR + , CD57 + or CD56 + ). These data suggest that T lymphocytes contribute to RCC pathogenesis in a proportion of patients, and provide a rationale for treatment with IST in selected patients with RCC

Fuel cell plates with skewed process channels for uniform distribution of stack compression load

Science.gov (United States)

Granata, Jr., Samuel J.; Woodle, Boyd M.

1989-01-01

An electrochemical fuel cell includes an anode electrode, a cathode electrode, an electrolyte matrix sandwiched between electrodes, and a pair of plates above and below the electrodes. The plate above the electrodes has a lower surface with a first group of process gas flow channels formed thereon and the plate below the electrodes has an upper surface with a second group of process gas flow channels formed thereon. The channels of each group extend generally parallel to one another. The improvement comprises the process gas flow channels on the lower surface of the plate above the anode electrode and the process gas flow channels on the upper surface of the plate below the cathode electrode being skewed in opposite directions such that contact areas of the surfaces of the plates through the electrodes are formed in crisscross arrangements. Also, the plates have at least one groove in areas of the surfaces thereof where the channels are absent for holding process gas and increasing electrochemical activity of the fuel cell. The groove in each plate surface intersects with the process channels therein. Also, the opposite surfaces of a bipolar plate for a fuel cell contain first and second arrangements of process gas flow channels in the respective surfaces which are skewed the same amount in opposite directions relative to the longitudinal centerline of the plate.

Real quartic surfaces containing 16 skew lines

Directory of Open Access Journals (Sweden)

Isidro Nieto

2004-01-01

Full Text Available It is well known that there is an open three-dimensional subvariety Ms of the Grassmannian of lines in ℙ3 which parametrizes smooth irreducible complex surfaces of degree 4 which are Heisenberg invariant, and each quartic contains 32 lines but only 16 skew lines, being determined by its configuration of lines, are called a double 16. We consider here the problem of visualizing in a computer the real Heisenberg invariant quartic surface and the real double 16. We construct a family of points l∈Ms parametrized by a two-dimensional semialgebraic variety such that under a change of coordinates of l into its Plüecker, coordinates transform into the real coordinates for a line L in ℙ3, which is then used to construct a program in Maple 7. The program allows us to draw the quartic surface and the set of transversal lines to L. Additionally, we include a table of a group of examples. For each test example we specify a parameter, the viewing angle of the image, compilation time, and other visual properties of the real surface and its real double 16. We include at the end of the paper an example showing the surface containing the double 16.

Phenotypic analysis of prostate-infiltrating lymphocytes reveals TH17 and Treg skewing.

Science.gov (United States)

Sfanos, Karen Sandell; Bruno, Tullia C; Maris, Charles H; Xu, Lauren; Thoburn, Christopher J; DeMarzo, Angelo M; Meeker, Alan K; Isaacs, William B; Drake, Charles G

2008-06-01

Pathologic examination of prostate glands removed from patients with prostate cancer commonly reveals infiltrating CD4+ and CD8+ T cells. Little is known about the phenotype of these cells, despite accumulating evidence suggesting a potential role for chronic inflammation in the etiology of prostate cancer. We developed a technique that samples the majority of the peripheral prostate through serial needle aspirates. CD4+ prostate-infiltrating lymphocytes (PIL) were isolated using magnetic beads and analyzed for subset skewing using both flow cytometry and quantitative reverse transcription-PCR. The transcriptional profile of fluorescence-activated cell sorted prostate-infiltrating regulatory T cells (CD4+, CD25+, GITR+) was compared with naïve, peripheral blood T cells using microarray analysis. CD4+ PIL showed a paucity of TH2 (interleukin-4-secreting) cells, a surprising finding given the generally accepted association of these cells with chronic, smoldering inflammation. Instead, CD4+ PIL seemed to be skewed towards a regulatory Treg phenotype (FoxP3+) as well as towards the TH17 phenotype (interleukin-17+). We also found that a preponderance of TH17-mediated inflammation was associated with a lower pathologic Gleason score. These protein level data were reflected at the message level, as analyzed by quantitative reverse transcription-PCR. Microarray analysis of pooled prostate-infiltrating T(reg) revealed expected Treg-associated transcripts (FoxP3, CTLA-4, GITR, LAG-3) as well as a number of unique cell surface markers that may serve as additional Treg markers. Taken together, these data suggest that TH17 and/or Treg CD4+ T cells (rather than TH2 T cells) may be involved in the development or progression of prostate cancer.

Time skewing and amplitude nonlinearity mitigation by feedback equalization for 56 Gbps VCSEL-based PAM-4 links

Science.gov (United States)

You, Yue; Zhang, Wenjia; Sun, Lin; Du, Jiangbing; Liang, Chenyu; Yang, Fan; He, Zuyuan

2018-03-01

The vertical cavity surface emitting laser (VCSEL)-based multimode optical transceivers enabled by pulse amplitude modulation (PAM)-4 will be commercialized in near future to meet the 400-Gbps standard short reach optical interconnects. It is still challenging to achieve over 56/112-Gbps with the multilevel signaling as the multimode property of the device and link would introduce the nonlinear temporal response for the different levels. In this work, we scrutinize the distortions that relates to the multilevel feature of PAM-4 modulation, and propose an effective feedback equalization scheme for 56-Gbps VCSEL-based PAM-4 optical interconnects system to mitigate the distortions caused by eye timing-skew and nonlinear power-dependent noise. Level redistribution at Tx side is theoretically modeled and constructed to achieve equivalent symbol error ratios (SERs) of four levels and improved BER performance. The cause of the eye skewing and the mitigation approach are also simulated at 100-Gbps and experimentally investigated at 56-Gbps. The results indicate more than 2-dB power penalty improvement has been achieved by using such a distortion aware equalizer.

Fecal bacteria from treatment-naive Crohn's disease patients can skew helper T cell responses.

Science.gov (United States)

Ma, Fei; Zhang, Yi; Xing, Junjie; Song, Xiaoling; Huang, Ling; Weng, Hao; Wu, Xiangsong; Walker, Emma; Wang, Zhongchuan

2017-12-01

Many studies have demonstrated that the inflamed mucosa of Crohn's disease (CD) patients presented a disturbed gut commensal community, and the shift in microbial composition and species variety is associated with disease severity. To establish a link between changes in the intestinal bacterial composition and the alteration of inflammation, we obtained fecal bacteria from CD patients and non-CD controls. The bacteria were then used to stimulate the peripheral blood mononuclear cells (PBMCs) from one non-CD individual. We found that the frequency of IFN-γ- and IL-17-expressing CD4 T cells was significantly higher after stimulation with CD bacteria than with non-CD bacteria, while the frequency of IL-4- and IL-10-expressing CD4 T cells was significantly decreased after stimulation with CD bacteria. A similar trend was observed in the level of cytokine expression and transcription expression. However, this difference was not clear-cut, as overlapping regions were observed between the two groups. With longer stimulation using CD bacteria, the skewing toward Th1/Th17 responses were further increased. This increase depended on the presence of monocytes/macrophages. Interestingly, we also found that B cells presented an inhibitory effect in CD bacteria-mediated skewing toward Th1/Th17 cells and promoted IL-10 secretion in CD bacteria-stimulated PBMCs. Together, our results demonstrated that CD bacteria could promote Th1/Th17 inflammation in a host factor-independent fashion. Copyright © 2017 Elsevier Inc. All rights reserved.

Skew category algebras associated with partially defined dynamical systems

DEFF Research Database (Denmark)

Lundström, Patrik; Öinert, Per Johan

2012-01-01

We introduce partially defined dynamical systems defined on a topological space. To each such system we associate a functor s from a category G to Topop and show that it defines what we call a skew category algebra A ⋊σ G. We study the connection between topological freeness of s and, on the one...... hand, ideal properties of A ⋊σ G and, on the other hand, maximal commutativity of A in A ⋊σ G. In particular, we show that if G is a groupoid and for each e ∈ ob(G) the group of all morphisms e → e is countable and the topological space s(e) is Tychonoff and Baire. Then the following assertions...... are equivalent: (i) s is topologically free; (ii) A has the ideal intersection property, i.e. if I is a nonzero ideal of A ⋊σ G, then I ∩ A ≠ {0}; (iii) the ring A is a maximal abelian complex subalgebra of A ⋊σ G. Thereby, we generalize a result by Svensson, Silvestrov and de Jeu from the additive group...

Separation of variables in anisotropic models and non-skew-symmetric elliptic r-matrix

Science.gov (United States)

Skrypnyk, Taras

2017-05-01

We solve a problem of separation of variables for the classical integrable hamiltonian systems possessing Lax matrices satisfying linear Poisson brackets with the non-skew-symmetric, non-dynamical elliptic so(3)⊗ so(3)-valued classical r-matrix. Using the corresponding Lax matrices, we present a general form of the "separating functions" B( u) and A( u) that generate the coordinates and the momenta of separation for the associated models. We consider several examples and perform the separation of variables for the classical anisotropic Euler's top, Steklov-Lyapunov model of the motion of anisotropic rigid body in the liquid, two-spin generalized Gaudin model and "spin" generalization of Steklov-Lyapunov model.

Low paternity skew and the influence of maternal kin in an egalitarian, patrilocal primate.

Science.gov (United States)

Strier, Karen B; Chaves, Paulo B; Mendes, Sérgio L; Fagundes, Valéria; Di Fiore, Anthony

2011-11-22

Levels of reproductive skew vary in wild primates living in multimale groups depending on the degree to which high-ranking males monopolize access to females. Still, the factors affecting paternity in egalitarian societies remain unexplored. We combine unique behavioral, life history, and genetic data to evaluate the distribution of paternity in the northern muriqui (Brachyteles hypoxanthus), a species known for its affiliative, nonhierarchical relationships. We genotyped 67 individuals (22 infants born over a 3-y period, their 21 mothers, and all 24 possible sires) at 17 microsatellite marker loci and assigned paternity to all infants. None of the 13 fathers were close maternal relatives of females with which they sired infants, and the most successful male sired a much lower percentage of infants (18%) than reported for the most successful males in other species. Our findings of inbreeding avoidance and low male reproductive skew are consistent with the muriqui's observed social and sexual behavior, but the long delay (≥2.08 y) between the onset of male sexual behavior and the age at which males first sire young is unexpected. The allocation of paternity implicates individual male life histories and access to maternal kin as key factors influencing variation in paternal--and grandmaternal--fitness. The apparent importance of lifelong maternal investment in coresident sons resonates with other recent examinations of maternal influences on offspring reproduction. This importance also extends the implications of the "grandmother hypothesis" in human evolution to include the possible influence of mothers and other maternal kin on male reproductive success in patrilocal societies.

B Cells Promote Th1- Skewed NKT Cell Response by CD1d-TCR Interaction

OpenAIRE

Shin, Jung Hoon; Park, Se-Ho

2013-01-01

CD1d expressing dendritic cells (DCs) are good glyco-lipid antigen presenting cells for NKT cells. However, resting B cells are very weak stimulators for NKT cells. Although ?-galactosylceramide (?-GalCer) loaded B cells can activate NKT cells, it is not well defined whether B cells interfere NKT cell stimulating activity of DCs. Unexpectedly, we found in this study that B cells can promote Th1-skewed NKT cell response, which means a increased level of IFN-? by NKT cells, concomitant with a d...

Turbulent flow field structure of initially asymmetric jets

International Nuclear Information System (INIS)

Kim, Kyung Hoon; Kim, Bong Whan; Kim, Suk Woo

2000-01-01

The near field structure of round turbulent jets with initially asymmetric velocity distributions is investigated experimentally. Experiments are carried out using a constant temperature hot-wire anemomentry system to measure streamwise velocity in the jets. The measurements are undertaken across the jet at various streamwise stations in a range starting from the jet exit plane and up to a downstream location of twelve diameters. The experimental results include the distributions of mean and instantaneous velocities, vorticity field, turbulence intensity, and the Reynolds shear stresses. The asymmetry of the jet exit plane was obtained by using circular cross-section pipes with a bend upstream of the exit. Three pipes used here include a straight pipe, and 90 and 160 degree-bend pipes. Therefore, at the upstream of the pipe exit, secondary flow through the bend and mean streamwise velocity distribution could be controlled by changing the curvature of pipes. The jets into the atmosphere have two levels of initial velocity skewness in addition to an axisymmetric jet from a straight pipe. In case of the curved pipe, a six diameterlong straight pipe section follows the bend upstream of the exit. The Reynolds number based on the exit bulk velocity is 13,400. The results indicate that the near field structure is considerably modified by the skewness of an initial mean velocity distribution. As the skewness increases, the decay rate of mean velocity at the centerline also increases

Mutual tolerance or reproductive competition? Patterns of reproductive skew among male redfronted lemurs (Eulemur fulvus rufus)

OpenAIRE

Kappeler, Peter M.; Port, Markus

2008-01-01

The social organization of gregarious lemurs significantly deviates from predictions of the socioecological model, as they form small groups in which the number of males approximately equals the number of females. This study uses models of reproductive skew theory as a new approach to explain this unusual group composition, in particular the high number of males, in a representative of these lemurs, the redfronted lemur (Eulemur fulvus rufus). We tested two central predictions of “concession”...

Skewness of citation impact data and covariates of citation distributions: A large-scale empirical analysis based on Web of Science data

NARCIS (Netherlands)

Bornmann, L.; Leydesdorff, L.

Using percentile shares, one can visualize and analyze the skewness in bibliometric data across disciplines and over time. The resulting figures can be intuitively interpreted and are more suitable for detailed analysis of the effects of independent and control variables on distributions than

The Curious Anomaly of Skewed Judgment Distributions and Systematic Error in the Wisdom of Crowds

DEFF Research Database (Denmark)

Nash, Ulrik William

2014-01-01

about true values, when neurons categorize cues better than chance, and when the particular true value is extreme compared to what is typical and anchored upon, then populations of judges form skewed judgment distributions with high probability. Moreover, the collective error made by these people can...... positively with collective error, thereby challenging what is commonly believed about how diversity and collective intelligence relate. Data from 3053 judgment surveys about US macroeconomic variables obtained from the Federal Reserve Bank of Philadelphia and the Wall Street Journal provide strong support...

Statistics on cannabis users skew perceptions of cannabis use

Directory of Open Access Journals (Sweden)

Rachel Melissa Burns

2013-11-01

Full Text Available Collecting information about the prevalence of cannabis use is necessary but not sufficient for understanding the size, dynamics, and outcomes associated with cannabis markets. This paper uses two data sets describing cannabis consumption in the United States and Europe to highlight 1 differences in inferences about sub-populations based on the measure used to quantify cannabis-related activity; 2 how different measures of cannabis-related activity can be used to more accurately describe trends in cannabis usage over time; and 3 the correlation between frequency of use in the past month and average grams consumed per day. Key findings: Focusing on days of use instead of prevalence shows substantially greater increases in U.S. cannabis use in recent years; however, the recent increase is mostly among adults, not youth. Relatively more rapid growth in use days also occurred among the college-educated and Hispanic. Further, data from a survey conducted in several European countries show a strong positive correlation between frequency of use and quantity consumed per day of use, suggesting consumption is even more skewed toward the minority of heavy users than is suggested by days-of-use calculations.

Mapping Causes and Implications of India's Skewed Sex Ratio and Poverty problem using Fuzzy & Neutrosophic Relational Maps

OpenAIRE

Gaurav; Kumar, Megha; Bhutani, Kanika; Aggarwal, Swati

2016-01-01

Numerous studies by different researchers have confirmed that skewed sex ratio is a critical social problem in India. This enduring problem of gender imbalance is the collective result of factors like sex selective abortion, gender discrimination, son preference for the preservation of tribe, emergence of new technologies in medical field and many more factors. Another severe problem to be addressed in India is poverty. Many factors contribute to the perpetuation of poverty such as illiteracy...

Noise measurement from magnitude MRI using local estimates of variance and skewness

International Nuclear Information System (INIS)

Rajan, Jeny; Poot, Dirk; Juntu, Jaber; Sijbers, Jan

2010-01-01

In this note, we address the estimation of the noise level in magnitude magnetic resonance (MR) images in the absence of background data. Most of the methods proposed earlier exploit the Rayleigh distributed background region in MR images to estimate the noise level. These methods, however, cannot be used for images where no background information is available. In this note, we propose two different approaches for noise level estimation in the absence of the image background. The first method is based on the local estimation of the noise variance using maximum likelihood estimation and the second method is based on the local estimation of the skewness of the magnitude data distribution. Experimental results on synthetic and real MR image datasets show that the proposed estimators accurately estimate the noise level in a magnitude MR image, even without background data. (note)

Scattering analysis of periodic structures using finite-difference time-domain

CERN Document Server

ElMahgoub, Khaled; Elsherbeni, Atef Z

2012-01-01

Periodic structures are of great importance in electromagnetics due to their wide range of applications such as frequency selective surfaces (FSS), electromagnetic band gap (EBG) structures, periodic absorbers, meta-materials, and many others. The aim of this book is to develop efficient computational algorithms to analyze the scattering properties of various electromagnetic periodic structures using the finite-difference time-domain periodic boundary condition (FDTD/PBC) method. A new FDTD/PBC-based algorithm is introduced to analyze general skewed grid periodic structures while another algor

Effects of within-colony competition on body size asymmetries and reproductive skew in a social spider

DEFF Research Database (Denmark)

Grinsted, Lena; Bilde, Trine

2013-01-01

Reproductive partitioning is a key component of social organization in groups of cooperative organisms. In colonies of permanently social spiders of the genus Stegodyphus less than half of the females reproduce, while all females, including nonreproducers, perform suicidal allo-maternal care. Some...... not increase over the course of the experiment, suggesting that body size variation is shaped at an early stage. This might facilitate task specialization within colonies and ensure colony-level reproductive output by early allocation of reproductive roles. We suggest that reproductive skew in social spiders...

Th1-skewed tissue responses to a mycolyl glycolipid in mycobacteria-infected rhesus macaques

Energy Technology Data Exchange (ETDEWEB)

Morita, Daisuke; Miyamoto, Ayumi; Hattori, Yuki; Komori, Takaya [Laboratory of Cell Regulation, Institute for Virus Research, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507 (Japan); Nakamura, Takashi [Faculty of Pharmaceutical Sciences, Hokkaido University, Kita 12 Nishi 6, Kita-ku, Sapporo, Hokkaido 060-0812 (Japan); Igarashi, Tatsuhiko [Laboratory of Primate Model, Institute for Virus Research, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507 (Japan); Harashima, Hideyoshi [Faculty of Pharmaceutical Sciences, Hokkaido University, Kita 12 Nishi 6, Kita-ku, Sapporo, Hokkaido 060-0812 (Japan); Sugita, Masahiko [Laboratory of Cell Regulation, Institute for Virus Research, Kyoto University, 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507 (Japan)

2013-11-08

Highlights: •Glucose monomycolate (GMM) is a marker glycolipid for active tuberculosis. •Tissue responses to GMM involved up-regulation of Th1-attracting chemokines. •Th1-skewed local responses were mounted at the GMM-injected tissue. -- Abstract: Trehalose 6,6′-dimycolate (TDM) is a major glycolipid of the cell wall of mycobacteria with remarkable adjuvant functions. To avoid detection by the host innate immune system, invading mycobacteria down-regulate the expression of TDM by utilizing host-derived glucose as a competitive substrate for their mycolyltransferases; however, this enzymatic reaction results in the concomitant biosynthesis of glucose monomycolate (GMM) which is recognized by the acquired immune system. GMM-specific, CD1-restricted T cell responses have been detected in the peripheral blood of infected human subjects and monkeys as well as in secondary lymphoid organs of small animals, such as guinea pigs and human CD1-transgenic mice. Nevertheless, it remains to be determined how tissues respond at the site where GMM is produced. Here we found that rhesus macaques vaccinated with Mycobacterium bovis bacillus Calmette–Guerin mounted a chemokine response in GMM-challenged skin that was favorable for recruiting T helper (Th)1 T cells. Indeed, the expression of interferon-γ, but not Th2 or Th17 cytokines, was prominent in the GMM-injected tissue. The GMM-elicited tissue response was also associated with the expression of monocyte/macrophage-attracting CC chemokines, such as CCL2, CCL4 and CCL8. Furthermore, the skin response to GMM involved the up-regulated expression of granulysin and perforin. Given that GMM is produced primarily by pathogenic mycobacteria proliferating within the host, the Th1-skewed tissue response to GMM may function efficiently at the site of infection.

Th1-skewed tissue responses to a mycolyl glycolipid in mycobacteria-infected rhesus macaques

International Nuclear Information System (INIS)

Morita, Daisuke; Miyamoto, Ayumi; Hattori, Yuki; Komori, Takaya; Nakamura, Takashi; Igarashi, Tatsuhiko; Harashima, Hideyoshi; Sugita, Masahiko

2013-01-01

Highlights: •Glucose monomycolate (GMM) is a marker glycolipid for active tuberculosis. •Tissue responses to GMM involved up-regulation of Th1-attracting chemokines. •Th1-skewed local responses were mounted at the GMM-injected tissue. -- Abstract: Trehalose 6,6′-dimycolate (TDM) is a major glycolipid of the cell wall of mycobacteria with remarkable adjuvant functions. To avoid detection by the host innate immune system, invading mycobacteria down-regulate the expression of TDM by utilizing host-derived glucose as a competitive substrate for their mycolyltransferases; however, this enzymatic reaction results in the concomitant biosynthesis of glucose monomycolate (GMM) which is recognized by the acquired immune system. GMM-specific, CD1-restricted T cell responses have been detected in the peripheral blood of infected human subjects and monkeys as well as in secondary lymphoid organs of small animals, such as guinea pigs and human CD1-transgenic mice. Nevertheless, it remains to be determined how tissues respond at the site where GMM is produced. Here we found that rhesus macaques vaccinated with Mycobacterium bovis bacillus Calmette–Guerin mounted a chemokine response in GMM-challenged skin that was favorable for recruiting T helper (Th)1 T cells. Indeed, the expression of interferon-γ, but not Th2 or Th17 cytokines, was prominent in the GMM-injected tissue. The GMM-elicited tissue response was also associated with the expression of monocyte/macrophage-attracting CC chemokines, such as CCL2, CCL4 and CCL8. Furthermore, the skin response to GMM involved the up-regulated expression of granulysin and perforin. Given that GMM is produced primarily by pathogenic mycobacteria proliferating within the host, the Th1-skewed tissue response to GMM may function efficiently at the site of infection

Fitting the CDO correlation skew: a tractable structural jump-diffusion model

DEFF Research Database (Denmark)

Willemann, Søren

2007-01-01

We extend a well-known structural jump-diffusion model for credit risk to handle both correlations through diffusion of asset values and common jumps in asset value. Through a simplifying assumption on the default timing and efficient numerical techniques, we develop a semi-analytic framework...... allowing for instantaneous calibration to heterogeneous CDS curves and fast computation of CDO tranche spreads. We calibrate the model to CDX and iTraxx data from February 2007 and achieve a satisfactory fit. To price the senior tranches for both indices, we require a risk-neutral probability of a market...

Skewness and kurtosis analysis for non-Gaussian distributions

Science.gov (United States)

Celikoglu, Ahmet; Tirnakli, Ugur

2018-06-01

In this paper we address a number of pitfalls regarding the use of kurtosis as a measure of deviations from the Gaussian. We treat kurtosis in both its standard definition and that which arises in q-statistics, namely q-kurtosis. We have recently shown that the relation proposed by Cristelli et al. (2012) between skewness and kurtosis can only be verified for relatively small data sets, independently of the type of statistics chosen; however it fails for sufficiently large data sets, if the fourth moment of the distribution is finite. For infinite fourth moments, kurtosis is not defined as the size of the data set tends to infinity. For distributions with finite fourth moments, the size, N, of the data set for which the standard kurtosis saturates to a fixed value, depends on the deviation of the original distribution from the Gaussian. Nevertheless, using kurtosis as a criterion for deciding which distribution deviates further from the Gaussian can be misleading for small data sets, even for finite fourth moment distributions. Going over to q-statistics, we find that although the value of q-kurtosis is finite in the range of 0 < q < 3, this quantity is not useful for comparing different non-Gaussian distributed data sets, unless the appropriate q value, which truly characterizes the data set of interest, is chosen. Finally, we propose a method to determine the correct q value and thereby to compute the q-kurtosis of q-Gaussian distributed data sets.

Parentage analysis of Ansell’s mole-rat family groups indicates a high reproductive skew despite relatively relaxed ecological constraints on dispersal

Czech Academy of Sciences Publication Activity Database

Patzenhauerová, Hana; Šklíba, J.; Bryja, Josef; Šumbera, R.

2013-01-01

Roč. 22, č. 19 (2013), s. 4988-5000 ISSN 0962-1083 R&D Projects: GA AV ČR IAA601410802; GA ČR GAP506/10/0983 Institutional support: RVO:68081766 Keywords : African mole-rat * dispersal * eusociality * Fukomys * mating system * reproductive skew Subject RIV: EH - Ecology, Behaviour Impact factor: 5.840, year: 2013

A novel generalized normal distribution for human longevity and other negatively skewed data.

Science.gov (United States)

Robertson, Henry T; Allison, David B

2012-01-01

Negatively skewed data arise occasionally in statistical practice; perhaps the most familiar example is the distribution of human longevity. Although other generalizations of the normal distribution exist, we demonstrate a new alternative that apparently fits human longevity data better. We propose an alternative approach of a normal distribution whose scale parameter is conditioned on attained age. This approach is consistent with previous findings that longevity conditioned on survival to the modal age behaves like a normal distribution. We derive such a distribution and demonstrate its accuracy in modeling human longevity data from life tables. The new distribution is characterized by 1. An intuitively straightforward genesis; 2. Closed forms for the pdf, cdf, mode, quantile, and hazard functions; and 3. Accessibility to non-statisticians, based on its close relationship to the normal distribution.

Three-part joint modeling methods for complex functional data mixed with zero-and-one-inflated proportions and zero-inflated continuous outcomes with skewness.

Science.gov (United States)

Li, Haocheng; Staudenmayer, John; Wang, Tianying; Keadle, Sarah Kozey; Carroll, Raymond J

2018-02-20

We take a functional data approach to longitudinal studies with complex bivariate outcomes. This work is motivated by data from a physical activity study that measured 2 responses over time in 5-minute intervals. One response is the proportion of time active in each interval, a continuous proportions with excess zeros and ones. The other response, energy expenditure rate in the interval, is a continuous variable with excess zeros and skewness. This outcome is complex because there are 3 possible activity patterns in each interval (inactive, partially active, and completely active), and those patterns, which are observed, induce both nonrandom and random associations between the responses. More specifically, the inactive pattern requires a zero value in both the proportion for active behavior and the energy expenditure rate; a partially active pattern means that the proportion of activity is strictly between zero and one and that the energy expenditure rate is greater than zero and likely to be moderate, and the completely active pattern means that the proportion of activity is exactly one, and the energy expenditure rate is greater than zero and likely to be higher. To address these challenges, we propose a 3-part functional data joint modeling approach. The first part is a continuation-ratio model to reorder the ordinal valued 3 activity patterns. The second part models the proportions when they are in interval (0,1). The last component specifies the skewed continuous energy expenditure rate with Box-Cox transformations when they are greater than zero. In this 3-part model, the regression structures are specified as smooth curves measured at various time points with random effects that have a correlation structure. The smoothed random curves for each variable are summarized using a few important principal components, and the association of the 3 longitudinal components is modeled through the association of the principal component scores. The difficulties in

Implementation of the flow-modulated skew-upwind difference scheme in the COMMIX-1C code: A first assessment

International Nuclear Information System (INIS)

Bottoni, M.; Chien, T.H.; Dommanus, H.M.; Sha, W.T.; Shen, Y.; Laster, R.

1991-01-01

This paper explains in detail the implementation of the Flow-Modulated Skew-Upwind Difference (FMSUD) scheme in the momentum equation of the COMMIX-1C computer program, where the scheme has been used so far only in the energy equation. Because the three scalar components of the momentum equation are solved in different meshes, staggered with respect to the mesh used for the energy equation and displaced in the respective coordinate direction, implementation of the FMSUD scheme in the momentum equations is by far more demanding than the implementation of a single scalar equation in centered cells. For this reason, a new approach has been devised to treat the problem, from the mathematical viewpoint, in the maximum generality and for all flow conditions, taking into account automatically the direction of the velocity vector and thus choosing automatically the weighting factors to be associated to different cells in the skew-upwind discretization. The new mathematical approach is straightforward for the treatment of inner cells of the fluid-dynamic definition domain, but particular care must be paid to its implementation for boundary cells where the appropriate boundary conditions must be applied. The paper explains the test cases in which the implementation of the FMSUD method has been applied and discusses the quality of the numerical results against the correct solution, when the latter is known. 14 refs., 2 figs., 1 tab

Noise-Induced Synchronization among Sub-RF CMOS Analog Oscillators for Skew-Free Clock Distribution

Science.gov (United States)

Utagawa, Akira; Asai, Tetsuya; Hirose, Tetsuya; Amemiya, Yoshihito

We present on-chip oscillator arrays synchronized by random noises, aiming at skew-free clock distribution on synchronous digital systems. Nakao et al. recently reported that independent neural oscillators can be synchronized by applying temporal random impulses to the oscillators [1], [2]. We regard neural oscillators as independent clock sources on LSIs; i. e., clock sources are distributed on LSIs, and they are forced to synchronize through the use of random noises. We designed neuron-based clock generators operating at sub-RF region (CMOS implementation with 0.25-μm CMOS parameters. Through circuit simulations, we demonstrate that i) the clock generators are certainly synchronized by pseudo-random noises and ii) clock generators exhibited phase-locked oscillations even if they had small device mismatches.

Non-linear analysis of skew thin plate by finite difference method

International Nuclear Information System (INIS)

Kim, Chi Kyung; Hwang, Myung Hwan

2012-01-01

This paper deals with a discrete analysis capability for predicting the geometrically nonlinear behavior of skew thin plate subjected to uniform pressure. The differential equations are discretized by means of the finite difference method which are used to determine the deflections and the in-plane stress functions of plates and reduced to several sets of linear algebraic simultaneous equations. For the geometrically non-linear, large deflection behavior of the plate, the non-linear plate theory is used for the analysis. An iterative scheme is employed to solve these quasi-linear algebraic equations. Several problems are solved which illustrate the potential of the method for predicting the finite deflection and stress. For increasing lateral pressures, the maximum principal tensile stress occurs at the center of the plate and migrates toward the corners as the load increases. It was deemed important to describe the locations of the maximum principal tensile stress as it occurs. The load-deflection relations and the maximum bending and membrane stresses for each case are presented and discussed

Robustness of S1 statistic with Hodges-Lehmann for skewed distributions

Science.gov (United States)

Ahad, Nor Aishah; Yahaya, Sharipah Soaad Syed; Yin, Lee Ping

2016-10-01

Analysis of variance (ANOVA) is a common use parametric method to test the differences in means for more than two groups when the populations are normally distributed. ANOVA is highly inefficient under the influence of non- normal and heteroscedastic settings. When the assumptions are violated, researchers are looking for alternative such as Kruskal-Wallis under nonparametric or robust method. This study focused on flexible method, S1 statistic for comparing groups using median as the location estimator. S1 statistic was modified by substituting the median with Hodges-Lehmann and the default scale estimator with the variance of Hodges-Lehmann and MADn to produce two different test statistics for comparing groups. Bootstrap method was used for testing the hypotheses since the sampling distributions of these modified S1 statistics are unknown. The performance of the proposed statistic in terms of Type I error was measured and compared against the original S1 statistic, ANOVA and Kruskal-Wallis. The propose procedures show improvement compared to the original statistic especially under extremely skewed distribution.

Skewed riskscapes and gentrified inequities: environmental exposure disparities in Seattle, Washington.

Science.gov (United States)

Abel, Troy D; White, Jonah

2011-12-01

Few studies have considered the sociohistorical intersection of environmental injustice and gentrification; a gap addressed by this case study of Seattle, Washington. This study explored the advantages of integrating air toxic risk screening with gentrification research to enhance proximity and health equity analysis methodologies. It was hypothesized that Seattle's industrial air toxic exposure risk was unevenly dispersed, that gentrification stratified the city's neighborhoods, and that the inequities of both converged. Spatial characterizations of air toxic pollution risk exposures from 1990 to 2007 were combined with longitudinal cluster analysis of census block groups in Seattle, Washington, from 1990 to 2000. A cluster of air toxic exposure inequality and socioeconomic inequity converged in 1 area of south central Seattle. Minority and working class residents were more concentrated in the same neighborhoods near Seattle's worst industrial pollution risks. Not all pollution was distributed equally in a dynamic urban landscape. Using techniques to examine skewed riskscapes and socioeconomic urban geographies provided a foundation for future research on the connections among environmental health hazard sources, socially vulnerable neighborhoods, and health inequity.

Skew redundant MEMS IMU calibration using a Kalman filter

International Nuclear Information System (INIS)

Jafari, M; Sahebjameyan, M; Moshiri, B; Najafabadi, T A

2015-01-01

In this paper, a novel calibration procedure for skew redundant inertial measurement units (SRIMUs) based on micro-electro mechanical systems (MEMS) is proposed. A general model of the SRIMU measurements is derived which contains the effects of bias, scale factor error and misalignments. For more accuracy, the effect of lever arms of the accelerometers to the center of the table are modeled and compensated in the calibration procedure. Two separate Kalman filters (KFs) are proposed to perform the estimation of error parameters for gyroscopes and accelerometers. The predictive error minimization (PEM) stochastic modeling method is used to simultaneously model the effect of bias instability and random walk noise on the calibration Kalman filters to diminish the biased estimations. The proposed procedure is simulated numerically and has expected experimental results. The calibration maneuvers are applied using a two-axis angle turntable in a way that the persistency of excitation (PE) condition for parameter estimation is met. For this purpose, a trapezoidal calibration profile is utilized to excite different deterministic error parameters of the accelerometers and a pulse profile is used for the gyroscopes. Furthermore, to evaluate the performance of the proposed KF calibration method, a conventional least squares (LS) calibration procedure is derived for the SRIMUs and the simulation and experimental results compare the functionality of the two proposed methods with each other. (paper)

The Atacama Cosmology Telescope: A Measurement of the Thermal Sunyaev-Zel'dovich Effect Using the Skewness of the CMB Temperature Distribution

Science.gov (United States)

Wilson, Michael J.; Sherwin, Blake D.; Hill, J. Collin; Addison, Graeme; Battaglia, Nick; Bond, J. Richard; Das, Sudeep; Devlin, Mark J.; Dunkley, Joanna; Duenner, Rolando;

Flexible mixture modeling via the multivariate t distribution with the Box-Cox transformation: an alternative to the skew-t distribution.

Science.gov (United States)

Lo, Kenneth; Gottardo, Raphael

2012-01-01

Cluster analysis is the automated search for groups of homogeneous observations in a data set. A popular modeling approach for clustering is based on finite normal mixture models, which assume that each cluster is modeled as a multivariate normal distribution. However, the normality assumption that each component is symmetric is often unrealistic. Furthermore, normal mixture models are not robust against outliers; they often require extra components for modeling outliers and/or give a poor representation of the data. To address these issues, we propose a new class of distributions, multivariate t distributions with the Box-Cox transformation, for mixture modeling. This class of distributions generalizes the normal distribution with the more heavy-tailed t distribution, and introduces skewness via the Box-Cox transformation. As a result, this provides a unified framework to simultaneously handle outlier identification and data transformation, two interrelated issues. We describe an Expectation-Maximization algorithm for parameter estimation along with transformation selection. We demonstrate the proposed methodology with three real data sets and simulation studies. Compared with a wealth of approaches including the skew-t mixture model, the proposed t mixture model with the Box-Cox transformation performs favorably in terms of accuracy in the assignment of observations, robustness against model misspecification, and selection of the number of components.

Parallel tiled Nussinov RNA folding loop nest generated using both dependence graph transitive closure and loop skewing.

Science.gov (United States)

Palkowski, Marek; Bielecki, Wlodzimierz

2017-06-02

RNA secondary structure prediction is a compute intensive task that lies at the core of several search algorithms in bioinformatics. Fortunately, the RNA folding approaches, such as the Nussinov base pair maximization, involve mathematical operations over affine control loops whose iteration space can be represented by the polyhedral model. Polyhedral compilation techniques have proven to be a powerful tool for optimization of dense array codes. However, classical affine loop nest transformations used with these techniques do not optimize effectively codes of dynamic programming of RNA structure predictions. The purpose of this paper is to present a novel approach allowing for generation of a parallel tiled Nussinov RNA loop nest exposing significantly higher performance than that of known related code. This effect is achieved due to improving code locality and calculation parallelization. In order to improve code locality, we apply our previously published technique of automatic loop nest tiling to all the three loops of the Nussinov loop nest. This approach first forms original rectangular 3D tiles and then corrects them to establish their validity by means of applying the transitive closure of a dependence graph. To produce parallel code, we apply the loop skewing technique to a tiled Nussinov loop nest. The technique is implemented as a part of the publicly available polyhedral source-to-source TRACO compiler. Generated code was run on modern Intel multi-core processors and coprocessors. We present the speed-up factor of generated Nussinov RNA parallel code and demonstrate that it is considerably faster than related codes in which only the two outer loops of the Nussinov loop nest are tiled.

B Cells Promote Th1- Skewed NKT Cell Response by CD1d-TCR Interaction.

Science.gov (United States)

Shin, Jung Hoon; Park, Se-Ho

2013-10-01

CD1d expressing dendritic cells (DCs) are good glyco-lipid antigen presenting cells for NKT cells. However, resting B cells are very weak stimulators for NKT cells. Although α-galactosylceramide (α-GalCer) loaded B cells can activate NKT cells, it is not well defined whether B cells interfere NKT cell stimulating activity of DCs. Unexpectedly, we found in this study that B cells can promote Th1-skewed NKT cell response, which means a increased level of IFN-γ by NKT cells, concomitant with a decreased level of IL-4, in the circumstance of co-culture of DCs and B Cells. Remarkably, the response promoted by B cells was dependent on CD1d expression of B cells.

Assessing Potential Wind Energy Resources in Saudi Arabia with a Skew-t Distribution

KAUST Repository

Tagle, Felipe

2017-03-13

Facing increasing domestic energy consumption from population growth and industrialization, Saudi Arabia is aiming to reduce its reliance on fossil fuels and to broaden its energy mix by expanding investment in renewable energy sources, including wind energy. A preliminary task in the development of wind energy infrastructure is the assessment of wind energy potential, a key aspect of which is the characterization of its spatio-temporal behavior. In this study we examine the impact of internal climate variability on seasonal wind power density fluctuations using 30 simulations from the Large Ensemble Project (LENS) developed at the National Center for Atmospheric Research. Furthermore, a spatio-temporal model for daily wind speed is proposed with neighbor-based cross-temporal dependence, and a multivariate skew-t distribution to capture the spatial patterns of higher order moments. The model can be used to generate synthetic time series over the entire spatial domain that adequately reproduces the internal variability of the LENS dataset.

Assessing Potential Wind Energy Resources in Saudi Arabia with a Skew-t Distribution

KAUST Repository

Tagle, Felipe; Castruccio, Stefano; Crippa, Paola; Genton, Marc G.

2017-01-01

Facing increasing domestic energy consumption from population growth and industrialization, Saudi Arabia is aiming to reduce its reliance on fossil fuels and to broaden its energy mix by expanding investment in renewable energy sources, including wind energy. A preliminary task in the development of wind energy infrastructure is the assessment of wind energy potential, a key aspect of which is the characterization of its spatio-temporal behavior. In this study we examine the impact of internal climate variability on seasonal wind power density fluctuations using 30 simulations from the Large Ensemble Project (LENS) developed at the National Center for Atmospheric Research. Furthermore, a spatio-temporal model for daily wind speed is proposed with neighbor-based cross-temporal dependence, and a multivariate skew-t distribution to capture the spatial patterns of higher order moments. The model can be used to generate synthetic time series over the entire spatial domain that adequately reproduces the internal variability of the LENS dataset.

Comparison of the binary logistic and skewed logistic (Scobit) models of injury severity in motor vehicle collisions.

Science.gov (United States)

Tay, Richard

2016-03-01

The binary logistic model has been extensively used to analyze traffic collision and injury data where the outcome of interest has two categories. However, the assumption of a symmetric distribution may not be a desirable property in some cases, especially when there is a significant imbalance in the two categories of outcome. This study compares the standard binary logistic model with the skewed logistic model in two cases in which the symmetry assumption is violated in one but not the other case. The differences in the estimates, and thus the marginal effects obtained, are significant when the assumption of symmetry is violated. Copyright © 2015 Elsevier Ltd. All rights reserved.

Quantifying social asymmetric structures.

Science.gov (United States)

Solanas, Antonio; Salafranca, Lluís; Riba, Carles; Sierra, Vicenta; Leiva, David

2006-08-01

Many social phenomena involve a set of dyadic relations among agents whose actions may be dependent. Although individualistic approaches have frequently been applied to analyze social processes, these are not generally concerned with dyadic relations, nor do they deal with dependency. This article describes a mathematical procedure for analyzing dyadic interactions in a social system. The proposed method consists mainly of decomposing asymmetric data into their symmetric and skew-symmetric parts. A quantification of skew symmetry for a social system can be obtained by dividing the norm of the skew-symmetric matrix by the norm of the asymmetric matrix. This calculation makes available to researchers a quantity related to the amount of dyadic reciprocity. With regard to agents, the procedure enables researchers to identify those whose behavior is asymmetric with respect to all agents. It is also possible to derive symmetric measurements among agents and to use multivariate statistical techniques.

The subgroups in the special linear group over a skew field that contain the group of diagonal matrices

International Nuclear Information System (INIS)

Bui Xuan Hai.

1990-05-01

For an arbitrary skew field T we study the lattice of subgroups of the special linear group Γ=SL(n,T) that contain the subgroup Δ-SD(n,T) of diagonal matrices with Dieudonne's determinant equal to 1. We show that the description of these subgroups is standard in the following sense: For any subgroup H,Δ≤H≤Γ there exists a unique unital net such that Γ(σ) ≤H≤N(σ), where Γ(σ) is the net subgroup that corresponds to the net σ and N(σ) is the normalizer of Γ(σ) in Γ. (author). 11 refs

Mapping Causes and Implications of India’s Skewed Sex Ratio and Poverty problem using Fuzzy & Neutrosophic Relational Maps

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Gaurav

2016-08-01

Full Text Available Numerous studies by different researchers have confirmed that skewed sex ratio is a critical social problem in India. This enduring problem of gender imbalance is the collective result of factors like sex selective abortion, gender discrimination, son preference for the preservation of tribe, emergence of new technologies in medical field and many more factors. Another severe problem to be addressed in India is poverty. Many factors contribute to the perpetuation of poverty such as illiteracy, bad governance, under employment and various other reasons. Despite of India's accelerated growth rate, poverty in India is still prevalent.

Coalescent Processes with Skewed Offspring Distributions and Nonequilibrium Demography.

Science.gov (United States)

Matuszewski, Sebastian; Hildebrandt, Marcel E; Achaz, Guillaume; Jensen, Jeffrey D

2018-01-01

Nonequilibrium demography impacts coalescent genealogies leaving detectable, well-studied signatures of variation. However, similar genomic footprints are also expected under models of large reproductive skew, posing a serious problem when trying to make inference. Furthermore, current approaches consider only one of the two processes at a time, neglecting any genomic signal that could arise from their simultaneous effects, preventing the possibility of jointly inferring parameters relating to both offspring distribution and population history. Here, we develop an extended Moran model with exponential population growth, and demonstrate that the underlying ancestral process converges to a time-inhomogeneous psi-coalescent. However, by applying a nonlinear change of time scale-analogous to the Kingman coalescent-we find that the ancestral process can be rescaled to its time-homogeneous analog, allowing the process to be simulated quickly and efficiently. Furthermore, we derive analytical expressions for the expected site-frequency spectrum under the time-inhomogeneous psi-coalescent, and develop an approximate-likelihood framework for the joint estimation of the coalescent and growth parameters. By means of extensive simulation, we demonstrate that both can be estimated accurately from whole-genome data. In addition, not accounting for demography can lead to serious biases in the inferred coalescent model, with broad implications for genomic studies ranging from ecology to conservation biology. Finally, we use our method to analyze sequence data from Japanese sardine populations, and find evidence of high variation in individual reproductive success, but few signs of a recent demographic expansion. Copyright © 2018 by the Genetics Society of America.

Example of the Smooth Skew Product in the Plane with the One-dimensional Ramified Continuum as the Global Attractor*

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Efremova L.S.

2012-08-01

Full Text Available The example is constructed of the C1-smooth skew product of interval maps possessing the one-dimensional ramified continuum (containing no arcs homeomorphic to the circle with an infinite set of ramification points as the global attractor. L’exemple est construit à partir d’un produit biaisé lisse de classe C1 de transformations d’un intervalle, qui a un continuum unidimensionnel ramifié (ne contenant pas d’arcs homéomorphes à un cercle avec un ensemble infini de points de branchement comme attracteur global.

Sample size calculations based on a difference in medians for positively skewed outcomes in health care studies

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Aidan G. O’Keeffe

2017-12-01

Full Text Available Abstract Background In healthcare research, outcomes with skewed probability distributions are common. Sample size calculations for such outcomes are typically based on estimates on a transformed scale (e.g. log which may sometimes be difficult to obtain. In contrast, estimates of median and variance on the untransformed scale are generally easier to pre-specify. The aim of this paper is to describe how to calculate a sample size for a two group comparison of interest based on median and untransformed variance estimates for log-normal outcome data. Methods A log-normal distribution for outcome data is assumed and a sample size calculation approach for a two-sample t-test that compares log-transformed outcome data is demonstrated where the change of interest is specified as difference in median values on the untransformed scale. A simulation study is used to compare the method with a non-parametric alternative (Mann-Whitney U test in a variety of scenarios and the method is applied to a real example in neurosurgery. Results The method attained a nominal power value in simulation studies and was favourable in comparison to a Mann-Whitney U test and a two-sample t-test of untransformed outcomes. In addition, the method can be adjusted and used in some situations where the outcome distribution is not strictly log-normal. Conclusions We recommend the use of this sample size calculation approach for outcome data that are expected to be positively skewed and where a two group comparison on a log-transformed scale is planned. An advantage of this method over usual calculations based on estimates on the log-transformed scale is that it allows clinical efficacy to be specified as a difference in medians and requires a variance estimate on the untransformed scale. Such estimates are often easier to obtain and more interpretable than those for log-transformed outcomes.

Progressivity of Taxes, Skeweness of Income Distribution and Violations of the Progressive Principle in Income Tax Systems

Directory of Open Access Journals (Sweden)

Edyta Mazurek

2014-06-01

Full Text Available Kakwani and Lambert state the three axioms, which should be respected by an equitable tax system. They also proposed a measurement system to evaluate the violations of the axioms. One of the axioms, axiom 2, formulates the progression principle in income tax systems. Vernizzi and Pellegrino improved the alternative index to evaluate violations concerning the progressive command in a tax system. The main aim of this paper is to compare the two indexes in order to evaluate violations of progressive principle in income tax systém using the real data. We also check how the progressivity of taxes and skewness of income distribution affect the measurement of the progressive principle violation.

p-hacking by post hoc selection with multiple opportunities: Detectability by skewness test?: Comment on Simonsohn, Nelson, and Simmons (2014).

Science.gov (United States)

Ulrich, Rolf; Miller, Jeff

2015-12-01

Simonsohn, Nelson, and Simmons (2014) have suggested a novel test to detect p-hacking in research, that is, when researchers report excessive rates of "significant effects" that are truly false positives. Although this test is very useful for identifying true effects in some cases, it fails to identify false positives in several situations when researchers conduct multiple statistical tests (e.g., reporting the most significant result). In these cases, p-curves are right-skewed, thereby mimicking the existence of real effects even if no effect is actually present. (c) 2015 APA, all rights reserved).

Bed slope effects on turbulent wave boundary layers: 2. Comparison with skewness, asymmetry, and other effects

DEFF Research Database (Denmark)

Fuhrman, David R.; Fredsøe, Jørgen; Sumer, B. Mutlu

2009-01-01

currents or undertow). The effects from each of the four components are isolated and quantified using a standard set of bed shear stress quantities, allowing their easy comparison. For conditions representing large shallow-water waves on steep slopes, the results suggest that converging-diverging effects......A numerical model solving incompressible Reynolds-averaged Navier-Stokes equations, combined with a two-equation k-omega model for turbulence closure, is used to systematically compare the relative strength of bed shear stress quantities and boundary layer streaming under wave motions from four...... from beach slope may make a significant onshore bed load contribution. Generally, however, the results suggest wave skewness (in addition to conventional steady streaming) as the most important onshore contribution outside the surf zone. Streaming induced within the wave boundary layer is also...

Skew scattering dominated anomalous Hall effect in Cox(MgO)100-x granular thin films

KAUST Repository

Zhang, Qiang

2017-07-31

We investigated the mechanism(s) of the anomalous Hall effect (AHE) in magnetic granular materials by fabricating 100-nm-thick thin films of Co_x(MgO)_100-x with a Co volume fraction of 34≤x≤100 using co-sputtering at room temperature. We measured the temperature dependence of longitudinal resistivity (ρ_xx) and anomalous Hall resistivity (ρ_AHE) from 5 K to 300 K in all samples. We found that when x decreases from 100 to 34, the values of ρ_xx and ρ_AHE respectively increased by about four and three orders in magnitude. By linearly fitting the data, obtained at 5 K, of anomalous Hall coefficient (R_s) and of ρ_xx to log(R_s)~γlog(ρ_xx), we found that our results perfectly fell on a straight line with a slope of γ= 0.97±0.02. This fitting value of γ in R_s∝ρ_xx^γ clearly suggests that skew scattering dominated the AHE in this granular system. To explore the effect of the scattering on the AHE, we performed the same measurements on annealed samples. We found that although both ρ_xx and ρ_AHE significantly reduced after annealing, the correlation between them was almost the same, which was confirmed by the fitted value, γ=0.99±0.03. These data strongly suggest that the AHE originates from the skew scattering in Co-MgO granular thin films no matter how strong the scatterings of electrons by the interfaces and defects is. This observation may be of importance to the development of spintronic devices based on MgO.

A novel hierarchy of differential—integral equations and their generalized bi-Hamiltonian structures

International Nuclear Information System (INIS)

Zhai Yun-Yun; Geng Xian-Guo; He Guo-Liang

2014-01-01

With the aid of the zero-curvature equation, a novel integrable hierarchy of nonlinear evolution equations associated with a 3 × 3 matrix spectral problem is proposed. By using the trace identity, the bi-Hamiltonian structures of the hierarchy are established with two skew-symmetric operators. Based on two linear spectral problems, we obtain the infinite many conservation laws of the first member in the hierarchy

Skewed X-chromosome inactivation plays a crucial role in the onset of symptoms in carriers of Becker muscular dystrophy.

Science.gov (United States)

Viggiano, Emanuela; Picillo, Esther; Ergoli, Manuela; Cirillo, Alessandra; Del Gaudio, Stefania; Politano, Luisa

2017-04-01

Becker muscular dystrophy (BMD) is an X-linked recessive disorder affecting approximately 1: 18.000 male births. Female carriers are usually asymptomatic, although 2.5-18% may present muscle or heart symptoms. In the present study, the role of the X chromosome inactivation (XCI) on the onset of symptoms in BMD carriers was analysed and compared with the pattern observed in Duchenne muscular dystrophy (DMD) carriers. XCI was determined on the lymphocytes of 36 BMD carriers (both symptomatic and not symptomatic) from 11 families requiring genetic advice at the Cardiomyology and Medical Genetics of the Second University of Naples, using the AR methylation-based assay. Carriers were subdivided into two groups, according to age above or below 50 years. Seven females from the same families known as noncarriers were used as controls. A Student's t-test for nonpaired data was performed to evaluate the differences observed in the XCI values between asymptomatic and symptomatic carriers, and carriers aged above or below 50 years. A Pearson correlation test was used to evaluate the inheritance of the XCI pattern in 19 mother-daughter pairs. The results showed that symptomatic BMD carriers had a skewed XCI with a preferential inactivation of the X chromosome carrying the normal allele, whereas the asymptomatic carriers and controls showed a random XCI. No concordance concerning the XCI pattern was observed between mothers and related daughters. The data obtained in the present study suggest that the onset of symptoms in BMD carriers is related to a skewed XCI, as observed in DMD carriers. Furthermore, they showed no concordance in the XCI pattern inheritance. Copyright © 2017 John Wiley & Sons, Ltd.

A robust and efficient finite volume scheme for the discretization of diffusive flux on extremely skewed meshes in complex geometries

Science.gov (United States)

Traoré, Philippe; Ahipo, Yves Marcel; Louste, Christophe

2009-08-01

In this paper an improved finite volume scheme to discretize diffusive flux on a non-orthogonal mesh is proposed. This approach, based on an iterative technique initially suggested by Khosla [P.K. Khosla, S.G. Rubin, A diagonally dominant second-order accurate implicit scheme, Computers and Fluids 2 (1974) 207-209] and known as deferred correction, has been intensively utilized by Muzaferija [S. Muzaferija, Adaptative finite volume method for flow prediction using unstructured meshes and multigrid approach, Ph.D. Thesis, Imperial College, 1994] and later Fergizer and Peric [J.H. Fergizer, M. Peric, Computational Methods for Fluid Dynamics, Springer, 2002] to deal with the non-orthogonality of the control volumes. Using a more suitable decomposition of the normal gradient, our scheme gives accurate solutions in geometries where the basic idea of Muzaferija fails. First the performances of both schemes are compared for a Poisson problem solved in quadrangular domains where control volumes are increasingly skewed in order to test their robustness and efficiency. It is shown that convergence properties and the accuracy order of the solution are not degraded even on extremely skewed mesh. Next, the very stable behavior of the method is successfully demonstrated on a randomly distorted grid as well as on an anisotropically distorted one. Finally we compare the solution obtained for quadrilateral control volumes to the ones obtained with a finite element code and with an unstructured version of our finite volume code for triangular control volumes. No differences can be observed between the different solutions, which demonstrates the effectiveness of our approach.

A Timing Estimation Method Based-on Skewness Analysis in Vehicular Wireless Networks.

Science.gov (United States)

Cui, Xuerong; Li, Juan; Wu, Chunlei; Liu, Jian-Hang

2015-11-13

Vehicle positioning technology has drawn more and more attention in vehicular wireless networks to reduce transportation time and traffic accidents. Nowadays, global navigation satellite systems (GNSS) are widely used in land vehicle positioning, but most of them are lack precision and reliability in situations where their signals are blocked. Positioning systems base-on short range wireless communication are another effective way that can be used in vehicle positioning or vehicle ranging. IEEE 802.11p is a new real-time short range wireless communication standard for vehicles, so a new method is proposed to estimate the time delay or ranges between vehicles based on the IEEE 802.11p standard which includes three main steps: cross-correlation between the received signal and the short preamble, summing up the correlated results in groups, and finding the maximum peak using a dynamic threshold based on the skewness analysis. With the range between each vehicle or road-side infrastructure, the position of neighboring vehicles can be estimated correctly. Simulation results were presented in the International Telecommunications Union (ITU) vehicular multipath channel, which show that the proposed method provides better precision than some well-known timing estimation techniques, especially in low signal to noise ratio (SNR) environments.

A Timing Estimation Method Based-on Skewness Analysis in Vehicular Wireless Networks

Directory of Open Access Journals (Sweden)

Xuerong Cui

2015-11-01

Full Text Available Vehicle positioning technology has drawn more and more attention in vehicular wireless networks to reduce transportation time and traffic accidents. Nowadays, global navigation satellite systems (GNSS are widely used in land vehicle positioning, but most of them are lack precision and reliability in situations where their signals are blocked. Positioning systems base-on short range wireless communication are another effective way that can be used in vehicle positioning or vehicle ranging. IEEE 802.11p is a new real-time short range wireless communication standard for vehicles, so a new method is proposed to estimate the time delay or ranges between vehicles based on the IEEE 802.11p standard which includes three main steps: cross-correlation between the received signal and the short preamble, summing up the correlated results in groups, and finding the maximum peak using a dynamic threshold based on the skewness analysis. With the range between each vehicle or road-side infrastructure, the position of neighboring vehicles can be estimated correctly. Simulation results were presented in the International Telecommunications Union (ITU vehicular multipath channel, which show that the proposed method provides better precision than some well-known timing estimation techniques, especially in low signal to noise ratio (SNR environments.

Goals and organisational structure of the movement for global mental health.

Science.gov (United States)

Minas, Harry; Wright, Alexandra; Kakuma, Ritsuko

2014-01-01

The Movement for Global Mental Health (MGMH), established in 2008, is in a period of transition, as is the field of global mental health. The transfer of Secretariat functions from the Centre for International Mental Health to the Public Health Foundation of India was a suitable time to reflect on the goals of MGMH and on the form of organisational structure that would best serve the organisation in its efforts to achieve its goals. An online survey was sent to the 4,000 registered members of MGMH seeking the views of the membership on both the goals of MGMH and on the preferred form of organisational structure. There was near unanimous (95%) agreement with the MGMH goals as stated at the time of the survey. The current form of organisation of MGMH, a loose network of individuals and organisations registered through the MGMH website, was the least preferred (29.9%) form of organisation for the future of MGMH. More than two thirds (70.1%) of respondents would prefer a formal legal structure, with 60% of this group favouring a Charitable Organisation structure and 40% preferring an international Association structure. The response rate (7%) was too small and too skewed (predominantly academics and health professionals from high income countries) to allow any clear conclusions to be drawn from the survey. However, both the fact that responses were too few and skewed and the preferences expressed by respondents raise issues for careful consideration by the current MGMH Secretariat. The global mental health field and MGMH are in a time of transition. The move to the new secretariat is an opportunity for systematic consideration of the organisational structure and governance arrangements that will best serve the goals of MGMH.

The male handicap: male-biased mortality explains skewed sex ratios in brown trout embryos.

Science.gov (United States)

Morán, P; Labbé, L; Garcia de Leaniz, C

2016-12-01

Juvenile sex ratios are often assumed to be equal for many species with genetic sex determination, but this has rarely been tested in fish embryos due to their small size and absence of sex-specific markers. We artificially crossed three populations of brown trout and used a recently developed genetic marker for sexing the offspring of both pure and hybrid crosses. Sex ratios (SR = proportion of males) varied widely one month after hatching ranging from 0.15 to 0.90 (mean = 0.39 ± 0.03). Families with high survival tended to produce balanced or male-biased sex ratios, but SR was significantly female-biased when survival was low, suggesting that males sustain higher mortality during development. No difference in SR was found between pure and hybrid families, but the existence of sire × dam interactions suggests that genetic incompatibility may play a role in determining sex ratios. Our findings have implications for animal breeding and conservation because skewed sex ratios will tend to reduce effective population size and bias selection estimates. © 2016 The Authors.

Poisson structure of the equations of ideal multispecies fluid electrodynamics

International Nuclear Information System (INIS)

Spencer, R.G.

1984-01-01

The equations of the two- (or multi-) fluid model of plasma physics are recast in Hamiltonian form, following general methods of symplectic geometry. The dynamical variables are the fields of physical interest, but are noncanonical, so that the Poisson bracket in the theory is not the standard one. However, it is a skew-symmetric bilinear form which, from the method of derivation, automatically satisfies the Jacobi identity; therefore, this noncanonical structure has all the essential properties of a canonical Poisson bracket

Experimental and Simulation-Based Investigation of Polycentric Motion of an Inherent Compliant Pneumatic Bending Actuator with Skewed Rotary Elastic Chambers

Directory of Open Access Journals (Sweden)

André Wilkening

2017-01-01

Full Text Available To offer a functionality that could not be found in traditional rigid robots, compliant actuators are in development worldwide for a variety of applications and especially for human–robot interaction. Pneumatic bending actuators are a special kind of such actuators. Due to the absence of fixed mechanical axes and their soft behavior, these actuators generally possess a polycentric motion ability. This can be very useful to provide an implicit self-alignment to human joint axes in exoskeleton-like rehabilitation devices. As a possible realization, a novel bending actuator (BA was developed using patented pneumatic skewed rotary elastic chambers (sREC. To analyze the actuator self-alignment properties, knowledge about the motion of this bending actuator type, the so-called skewed rotary elastic chambers bending actuator (sRECBA, is of high interest and this paper presents experimental and simulation-based kinematic investigations. First, to describe actuator motion, the finite helical axes (FHA of basic actuator elements are determined using a three-dimensional (3D camera system. Afterwards, a simplified two-dimensional (2D kinematic simulation model based on a four-bar linkage was developed and the motion was compared to the experimental data by calculating the instantaneous center of rotation (ICR. The equivalent kinematic model of the sRECBA was realized using a series of four-bar linkages and the resulting ICR was analyzed in simulation. Finally, the FHA of the sRECBA were determined and analyzed for three different specific motions. The results show that the actuator’s FHA adapt to different motions performed and it can be assumed that implicit self-alignment to the polycentric motion of the human joint axis will be provided.

Torque Ripple Reduction of a Novel Modular Arc-Linear Flux-Switching Permanent-Magnet Motor with Rotor Step Skewing

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Xiangdong Liu

2016-05-01

Full Text Available A novel modular arc-linear flux-switching permanent-magnet motor (MAL-FSPM used for scanning system instead of reduction gearboxes and kinematic mechanisms is proposed and researched in this paper by the finite element method (FEM. The MAL-FSPM combines characteristics of flux-switching permanent-magnet motor and linear motor and can realize the direct driving and limited angular movement. Structure and operation principle of the MAL-FSPM are analyzed. Cogging torque model of the MAL-FSPM is established. The characteristics of cogging torque and torque ripple are investigated for: (1 distance (dend between left end of rotor and left end of stator is more than two rotor tooth pitch (τp; and (2 dend is less than two rotor tooth pitch. Cogging torque is an important component of torque ripple and the period ratio of the cogging torque to the back electromotive force (EMF equals one for the MAL-FSPM before optimization. In order to reduce the torque ripple as much as possible and affect the back EMF as little as possible, influence of period ratio of cogging torque to back EMF on rotor step skewing is investigated. Rotor tooth width and stator slot open width are optimized to increase the period ratio of cogging torque to back EMF. After the optimization, torque ripple is decreased by 79.8% for dend > τp and torque ripple is decreased by 49.7% for dend < τp. Finally, 3D FEM model is established to verify the 2D results.

An improved method to characterise the modulation of small-scale turbulent by large-scale structures

Science.gov (United States)

Agostini, Lionel; Leschziner, Michael; Gaitonde, Datta

2015-11-01

A key aspect of turbulent boundary layer dynamics is ``modulation,'' which refers to degree to which the intensity of coherent large-scale structures (LS) cause an amplification or attenuation of the intensity of the small-scale structures (SS) through large-scale-linkage. In order to identify the variation of the amplitude of the SS motion, the envelope of the fluctuations needs to be determined. Mathis et al. (2009) proposed to define this latter by low-pass filtering the modulus of the analytic signal built from the Hilbert transform of SS. The validity of this definition, as a basis for quantifying the modulated SS signal, is re-examined on the basis of DNS data for a channel flow. The analysis shows that the modulus of the analytic signal is very sensitive to the skewness of its PDF, which is dependent, in turn, on the sign of the LS fluctuation and thus of whether these fluctuations are associated with sweeps or ejections. The conclusion is that generating an envelope by use of a low-pass filtering step leads to an important loss of information associated with the effects of the local skewness of the PDF of the SS on the modulation process. An improved Hilbert-transform-based method is proposed to characterize the modulation of SS turbulence by LS structures

Systems of conservation laws with third-order Hamiltonian structures

Science.gov (United States)

Ferapontov, Evgeny V.; Pavlov, Maxim V.; Vitolo, Raffaele F.

2018-02-01

We investigate n-component systems of conservation laws that possess third-order Hamiltonian structures of differential-geometric type. The classification of such systems is reduced to the projective classification of linear congruences of lines in P^{n+2} satisfying additional geometric constraints. Algebraically, the problem can be reformulated as follows: for a vector space W of dimension n+2 , classify n-tuples of skew-symmetric 2-forms A^{α } \\in Λ ^2(W) such that φ _{β γ }A^{β }\\wedge A^{γ }=0, for some non-degenerate symmetric φ.

A unique dermal dendritic cell subset that skews the immune response toward Th2.

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Ryuichi Murakami

Full Text Available Dendritic cell (DC subsets in the skin and draining lymph nodes (LNs are likely to elicit distinct immune response types. In skin and skin-draining LNs, a dermal DC subset expressing macrophage galactose-type C-type lectin 2 (MGL2/CD301b was found distinct from migratory Langerhans cells (LCs or CD103(+ dermal DCs (dDCs. Lower expression levels of Th1-promoting and/or cross-presentation-related molecules were suggested by the transcriptome analysis and verified by the quantitative real-time PCR analysis in MGL2(+ dDCs than in CD103(+ dDCs. Transfer of MGL2(+ dDCs but not CD103(+ dDCs from FITC-sensitized mice induced a Th2-type immune response in vivo in a model of contact hypersensitivity. Targeting MGL2(+ dDCs with a rat monoclonal antibody against MGL2 efficiently induced a humoral immune response with Th2-type properties, as determined by the antibody subclass. We propose that the properties of MGL2(+ dDCs, are complementary to those of CD103(+ dDCs and skew the immune response toward a Th2-type response.

Effect of length to thickness ratio on free vibration analysis of thick fiber reinforced plastic skew cross-ply laminate with circular cutout

Science.gov (United States)

Srividya, K.; Reddy, Ch. Kishore; Sumanth, Ch. Mohan; Krishnaiah, P. Gopala; Kishan, V. Mallikharjuna

2018-04-01

The present investigation deals with the free vibration analysis of a thick four-layered symmetric cross-ply skew laminated composite plate with a circular cutout. Three dimensional finite element models (FEM) which use the elasticity theory for the determination of stiffness matrices are modeled in ANSYS software to evaluate first five natural frequencies of the laminate. The variations of the first five natural frequencies with respect to length to thickness ratio (S) for different diameter to length ratios (d/l) are presented. It is observed that, the natural frequencies decreases with increase of thickness ratio(S).

An improved model of induction motors for diagnosis purposes - Slot skewing effect and air-gap eccentricity faults

Energy Technology Data Exchange (ETDEWEB)

Ghoggal, A.; Zouzou, S.E.; Sahraoui, M. [Laboratoire de genie electrique de Biskra, Departement d' electrotechnique, Universite Mohamed Khider, BP 145, Biskra (Algeria); Razik, H. [Groupe de Recherche en Electrotechnique et Electronique de Nancy, Universite Henri Poincare, Faculte des Sciences et Techniques, BP 239, F-54506 Vandoeuvre-les-Nancy (France); Khezzar, A. [Laboratoire d' Electrotechnique de Constantine, Universite Mentouri, Constantine (Algeria)

2009-05-15

This paper describes an improved method for the modeling of axial and radial eccentricities in induction motors (IM). The model is based on an extension of the modified winding function approach (MWFA) which allows for all harmonics of the magnetomotive force (MMF) to be taken into account. It is shown that a plane view of IM gets easily the motor inductances and reduces considerably the calculation process. The described technique includes accurately the slot skewing effect and leads to pure analytical expressions of the inductances in case of radial eccentricity. In order to model the static, dynamic or mixed axial eccentricity, three suitable alternatives are explained. Unlike the previous proposals, the discussed alternatives take into account all the harmonics of the inverse of air-gap function without any development in Fourier series. Simulation results as well as experimental verifications prove the usefulness and the effectiveness of the proposed model. (author)

An improved model of induction motors for diagnosis purposes - Slot skewing effect and air-gap eccentricity faults

International Nuclear Information System (INIS)

Ghoggal, A.; Zouzou, S.E.; Razik, H.; Sahraoui, M.; Khezzar, A.

2009-01-01

This paper describes an improved method for the modeling of axial and radial eccentricities in induction motors (IM). The model is based on an extension of the modified winding function approach (MWFA) which allows for all harmonics of the magnetomotive force (MMF) to be taken into account. It is shown that a plane view of IM gets easily the motor inductances and reduces considerably the calculation process. The described technique includes accurately the slot skewing effect and leads to pure analytical expressions of the inductances in case of radial eccentricity. In order to model the static, dynamic or mixed axial eccentricity, three suitable alternatives are explained. Unlike the previous proposals, the discussed alternatives take into account all the harmonics of the inverse of air-gap function without any development in Fourier series. Simulation results as well as experimental verifications prove the usefulness and the effectiveness of the proposed model.

Strong reproductive skew among males in the multiply mated swordtail Xiphophorus multilineatus (Teleostei).

Science.gov (United States)

Luo, J; Sanetra, M; Schartl, M; Meyer, A

2005-01-01

Male swordtails in the genus Xiphophorus display a conspicuous ventral elongation of the caudal fin, the sword, which arose through sexual selection due to female preference. Females mate regularly and are able to store sperm for at least 6 months. If multiple mating is frequent, this would raise the intriguing question about the role of female choice and male-male competition in shaping the mating system of these fishes. Size-dependent alternate mating strategies occur in Xiphophorus; one such strategy is courtship with a sigmoid display by large dominant males, while the other is gonopodial thrusting, in which small subordinate males sneak copulations. Using microsatellite markers, we observed a frequency of multiple paternity in wild-caught Xiphophorus multilineatus in 28% of families analyzed, but the actual frequency of multiple mating suggested by the correction factor PrDM was 33%. The number of fathers contributing genetically to the brood ranged from one to three. Compared to other species in the family Poeciliidae, both frequency and degree of multiple paternity were low. Paternity was found to be highly skewed, with one male on average contributing more than 70% to the offspring. Hence in this Xiphophorus mating system, typically one male dominates and sneaker males do not appear to be particularly effective. Postcopulatory mechanisms, however, such as sperm competition, are also indicated by our data, using sex-linked phenotypes among the offspring.

Physical consequences of the interpretation of the skew part of gμν in Einstein's nonsymmetric unified field theory

International Nuclear Information System (INIS)

Voros, J.

1995-01-01

The electromagnetic interaction in the Einstein-Infeld-Hoffmann (EIH) equations of motion for charged particles in Einstein's unified field theory (EUFT) is found to be automatically precluded by the conventional identification of the skew part of the fundamental tensor with the Faraday tensor. It is shown that an alternative identification, suggested by observations of Einstein, Bergmann and Papapetrou, would lead to the expected electromagnetic interaction, were it not for the intervention of an infelicitous (radiation) gauge. Therefore, an EIH analysis of EUFT is inconclusive as a test of the physical viability of the theory, and it follows that EUFT cannot be considered necessarily unphysical on the basis of such an analysis. It is concluded that, historically, Einstein's unified field theory was rejected for the wrong reason. 26 refs

Viruses-to-mobile genetic elements skew in the deep Atlantis II brine pool sediments

KAUST Repository

Adel, Mustafa

2016-09-06

The central rift of the Red Sea has 25 brine pools with different physical and geochemical characteristics. Atlantis II (ATIID), Discovery Deeps (DD) and Chain Deep (CD) are characterized by high salinity, temperature and metal content. Several studies reported microbial communities in these brine pools, but few studies addressed the brine pool sediments. Therefore, sediment cores were collected from ATIID, DD, CD brine pools and an adjacent brine-influenced site. Sixteen different lithologic sediment sections were subjected to shotgun DNA pyrosequencing to generate 1.47 billion base pairs (1.47 × 109 bp). We generated sediment-specific reads and attempted to annotate all reads. We report the phylogenetic and biochemical uniqueness of the deepest ATIID sulfur-rich brine pool sediments. In contrary to all other sediment sections, bacteria dominate the deepest ATIID sulfur-rich brine pool sediments. This decrease in virus-to-bacteria ratio in selected sections and depth coincided with an overrepresentation of mobile genetic elements. Skewing in the composition of viruses-to-mobile genetic elements may uniquely contribute to the distinct microbial consortium in sediments in proximity to hydrothermally active vents of the Red Sea and possibly in their surroundings, through differential horizontal gene transfer.

Measurement of the Width and Skewness of Elliptic Flow Fluctuations in PbPb Collisions at 5.02 TeV with CMS

Science.gov (United States)

Castle, James R.; CMS Collaboration

2017-11-01

Flow harmonic fluctuations are studied for PbPb collisions at √{sNN} = 5.02 TeV using the CMS detector at the LHC. Flow harmonic probability distributions p(v2) are obtained by unfolding smearing effects from observed azimuthal anisotropy distributions using particles of 0.3 statistically significant negative skewness is observed for all centrality bins as evidenced by a splitting between v2 {4}, v2 {6}, and v2 {8} cumulants. Elliptic power law distribution fits are made to p(v2) distributions to infer information on the nature of initial-state eccentricity distributions and found to provide a more accurate description of the fluctuations than a Bessel-Gaussian parametrization.

Skewed distribution of circulating activated natural killer T (NKT) cells in patients with common variable immunodeficiency disorders (CVID).

Science.gov (United States)

Carvalho, Karina I; Melo, Karina M; Bruno, Fernanda R; Snyder-Cappione, Jennifer E; Nixon, Douglas F; Costa-Carvalho, Beatriz T; Kallas, Esper G

2010-09-09

Common variable immunodeficiency disorder (CVID) is the commonest cause of primary antibody failure in adults and children, and characterized clinically by recurrent bacterial infections and autoimmune manifestations. Several innate immune defects have been described in CVID, but no study has yet investigated the frequency, phenotype or function of the key regulatory cell population, natural killer T (NKT) cells. We measured the frequencies and subsets of NKT cells in patients with CVID and compared these to healthy controls. Our results show a skewing of NKT cell subsets, with CD4+ NKT cells at higher frequencies, and CD8+ NKT cells at lower frequencies. However, these cells were highly activated and expression CD161. The NKT cells had a higher expression of CCR5 and concomitantly expression of CCR5+CD69+CXCR6 suggesting a compensation of the remaining population of NKT cells for rapid effector action.

Vegetation structure and small-scale pattern in Miombo Woodland, Marondera, Zimbabwe

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B. M. Campbell

1995-10-01

Full Text Available The aim ol this paper is to describe woodland structure and small-scale patterning of woody plants at a miombo site, and to relate these to past disturbance and soil properties. Brachystegia spiciformis Benth. and Julbemardia globiflora (Benth. Troupin were the most frequent woody plants at the five hectare site, with size-class distributions which were markedly skewed towards the smaller size classes. The vegetation structure at the site and the increase in basal area over the past thirty years point to considerable disturbance prior to the present protected status. Six woodland subtypes were identified, grouped into two structural types: open and closed woodland. The distribution of woodland subtypes related closely to certain soil properties. It was hypothesized that the distribution of open and closed woodland is stable and a positive feedback mechanism by which this occurs is postulated.

Heavy metal mediated innate immune responses of the Indian green frog, Euphlyctis hexadactylus (Anura: Ranidae): Cellular profiles and associated Th1 skewed cytokine response

International Nuclear Information System (INIS)

Jayawardena, Uthpala A.; Ratnasooriya, Wanigasekara D.; Wickramasinghe, Deepthi D.; Udagama, Preethi V.

2016-01-01

Immune cell and cytokine profiles in relation to metal exposure though much studied in mammals has not been adequately investigated in amphibians, due mainly to lack of suitable reagents for cytokine profiling in non-model species. However, interspecies cross reactivity of cytokines permitted us to assay levels of IFNγ, TNFα, IL6 and IL10in a common anuran, the Indian green frog (Euphlyctis hexadactylus), exposed to heavy metals (Cd, Cr, Cu, Zn and Pb, at ~ 5 ppm each) under field and laboratory settings in Sri Lanka. Enumeration of immune cells in blood and melanomacrophages in the liver, assay of serum and hepatic cytokines, and Th1/Th2 cytokine polarisation were investigated. Immune cell counts indicated overall immunosuppression with decreasing total WBC and splenocyte counts while neutrophil/lymphocyte ratio increased with metal exposure, indicating metal mediated stress. Serum IL6 levels of metal exposed frogs reported the highest (~ 9360 pg/mL) of all cytokines tested. Significantly elevated IFNγ production (P < 0.05) was evident in heavy metal exposed frogs. Th1/Th2 cytokine ratio in both serum and liver tissue homogenates was Th1 skewed due to significantly higher production of pro-inflammatory cytokines, IFNγ in serum and TNFα in the liver (P < 0.01).Metal mediated aggregations of melanomacrophages in the liver were positively and significantly (P < 0.05) correlated with the hepatic expression of TNFα, IL6 and IL10 activity. Overall, Th1 skewed response may well be due to oxidative stress mediated nuclear factor κ-light chain enhancer of activated B cells (NFκB) which enhances the transcription of pro-inflammatory cytokines. Xenobiotic stress has recently imposed an unprecedented level of threat to wildlife, particularly to sensitive species such as amphibians. Therefore, understanding the interactions between physiological stress and related immune responses is fundamental to conserve these environmental sentinels in the face of emerging eco

Heavy metal mediated innate immune responses of the Indian green frog, Euphlyctis hexadactylus (Anura: Ranidae): Cellular profiles and associated Th1 skewed cytokine response

Energy Technology Data Exchange (ETDEWEB)

Jayawardena, Uthpala A.; Ratnasooriya, Wanigasekara D.; Wickramasinghe, Deepthi D.; Udagama, Preethi V., E-mail: dappvr@yahoo.com

2016-10-01

Immune cell and cytokine profiles in relation to metal exposure though much studied in mammals has not been adequately investigated in amphibians, due mainly to lack of suitable reagents for cytokine profiling in non-model species. However, interspecies cross reactivity of cytokines permitted us to assay levels of IFNγ, TNFα, IL6 and IL10in a common anuran, the Indian green frog (Euphlyctis hexadactylus), exposed to heavy metals (Cd, Cr, Cu, Zn and Pb, at ~ 5 ppm each) under field and laboratory settings in Sri Lanka. Enumeration of immune cells in blood and melanomacrophages in the liver, assay of serum and hepatic cytokines, and Th1/Th2 cytokine polarisation were investigated. Immune cell counts indicated overall immunosuppression with decreasing total WBC and splenocyte counts while neutrophil/lymphocyte ratio increased with metal exposure, indicating metal mediated stress. Serum IL6 levels of metal exposed frogs reported the highest (~ 9360 pg/mL) of all cytokines tested. Significantly elevated IFNγ production (P < 0.05) was evident in heavy metal exposed frogs. Th1/Th2 cytokine ratio in both serum and liver tissue homogenates was Th1 skewed due to significantly higher production of pro-inflammatory cytokines, IFNγ in serum and TNFα in the liver (P < 0.01).Metal mediated aggregations of melanomacrophages in the liver were positively and significantly (P < 0.05) correlated with the hepatic expression of TNFα, IL6 and IL10 activity. Overall, Th1 skewed response may well be due to oxidative stress mediated nuclear factor κ-light chain enhancer of activated B cells (NFκB) which enhances the transcription of pro-inflammatory cytokines. Xenobiotic stress has recently imposed an unprecedented level of threat to wildlife, particularly to sensitive species such as amphibians. Therefore, understanding the interactions between physiological stress and related immune responses is fundamental to conserve these environmental sentinels in the face of emerging eco

Hemiptera Mitochondrial Control Region: New Sights into the Structural Organization, Phylogenetic Utility, and Roles of Tandem Repetitions of the Noncoding Segment

Directory of Open Access Journals (Sweden)

Kui Li

2018-04-01

Full Text Available As a major noncoding fragment, the control region (CR of mtDNA is responsible for the initiation of mitogenome transcription and replication. Several structural features of CR sequences have been reported in many insects. However, comprehensive analyses on the structural organization and phylogenetic utility, as well as the role of tandem replications (TRs on length variation, high A+T content, and shift of base skew of CR sequences are poorly investigated in hemipteran insects. In this study, we conducted a series of comparative analyses, using 116 samples covering all 11 infraorders of the five currently recognized monophyletic groups in the Hemiptera. Several structural elements (mononucleotide stretches containing conserved sequence blocks (CSBs, TRs, and GA-rich region were identified in the mitochondrial control region in hemipteran insects, without showing a consistent location. The presence and absence of certain specific structural elements in CR sequences show the various structural organizations of that segment among the five monophyletic groups, which indicates the diversification of the control region’s structural organization in Hemiptera. Among the many groups within Hemiptera, eight monophyletic groups and three consistent phylogenetic trees were recovered, using CSBs datasets by maximum likelihood and Bayesian methods, which suggests the possible utility of CR sequences for phylogenetic reconstruction in certain groups of Hemiptera. Statistical analyses showed that TRs may contribute to the length variation, high AT content, and the shift of base skewing of CR sequences toward high AT content in the Hemiptera. Our findings enrich the knowledge of structural organization, phylogenetic utility, and roles of tandem replication of hemipteran CR, and provide a possible framework for mitochondrial control region analyses in hemimetabolous insects.

Lactobacilli activate human dendritic cells that skew T cells toward T helper 1 polarization.

Science.gov (United States)

Mohamadzadeh, Mansour; Olson, Scott; Kalina, Warren V; Ruthel, Gordon; Demmin, Gretchen L; Warfield, Kelly L; Bavari, Sina; Klaenhammer, Todd R

2005-02-22

Professional antigen-presenting dendritic cells (DCs) are critical in regulating T cell immune responses at both systemic and mucosal sites. Many Lactobacillus species are normal members of the human gut microflora and most are regarded as safe when administered as probiotics. Because DCs can naturally or therapeutically encounter lactobacilli, we investigated the effects of several well defined strains, representing three species of Lactobacillus on human myeloid DCs (MDCs) and found that they modulated the phenotype and functions of human MDCs. Lactobacillus-exposed MDCs up-regulated HLA-DR, CD83, CD40, CD80, and CD86 and secreted high levels of IL-12 and IL-18, but not IL-10. IL-12 was sustained in MDCs exposed to all three Lactobacillus species in the presence of LPS from Escherichia coli, whereas LPS-induced IL-10 was greatly inhibited. MDCs activated with lactobacilli clearly skewed CD4(+) and CD8(+) T cells to T helper 1 and Tc1 polarization, as evidenced by secretion of IFN-gamma, but not IL-4 or IL-13. These results emphasize a potentially important role for lactobacilli in modulating immunological functions of DCs and suggest that certain strains could be particularly advantageous as vaccine adjuvants, by promoting DCs to regulate T cell responses toward T helper 1 and Tc1 pathways.

Measuring structural similarity in large online networks.

Science.gov (United States)

Shi, Yongren; Macy, Michael

2016-09-01

Structural similarity based on bipartite graphs can be used to detect meaningful communities, but the networks have been tiny compared to massive online networks. Scalability is important in applications involving tens of millions of individuals with highly skewed degree distributions. Simulation analysis holding underlying similarity constant shows that two widely used measures - Jaccard index and cosine similarity - are biased by the distribution of out-degree in web-scale networks. However, an alternative measure, the Standardized Co-incident Ratio (SCR), is unbiased. We apply SCR to members of Congress, musical artists, and professional sports teams to show how massive co-following on Twitter can be used to map meaningful affiliations among cultural entities, even in the absence of direct connections to one another. Our results show how structural similarity can be used to map cultural alignments and demonstrate the potential usefulness of social media data in the study of culture, politics, and organizations across the social and behavioral sciences. Copyright © 2016 Elsevier Inc. All rights reserved.

Skewness and flatness factors of the longitudinal velocity derivative in wall-bounded flows

Science.gov (United States)

Djenidi, Lyazid; Antonia, Robert A.; Talluru, Murali K.; Abe, Hiroyuki

2017-06-01

Hot-wire measurements are carried out in turbulent boundary layers over smooth and rough walls in order the assess the behavior of the skewness (S ) and flatness (F ) factors of the longitudinal velocity derivative as y , the distance from the wall, increases. The measurements are complemented by direct numerical simulations of a smooth wall turbulent channel flow. It is observed that, as the distance to the wall increases, S and F vary significantly before approaching a constant in the outer layer of the boundary layer. Further, S and F exhibit a nontrivial dependence on the Taylor microscale Reynolds number (Reλ). For example, in the region below about 0.2 δ (δ is the boundary layer thickness) where Reλ varies significantly, S and F strongly vary with Reλ and can be multivalued at a given Reλ. In the outer region, between 0.3 δ and 0.6 δ , S , F , and Reλ remain approximately constant. The channel flow direct numerical simulation data for S and F exhibit a similar behavior. These results point to the ambiguity that can arise when assessing the Reλ dependence of S and F in wall shear flows. In particular, the multivaluedness of S and F can lead to erroneous conclusions if y /δ is known only poorly, as is the case for the atmospheric shear layer (ASL). If the laboratory turbulent boundary layer is considered an adequate surrogate to the neutral ASL, then the behavior of S and F in the ASL is expected to be similar to that reported here.

Coalgebraic structure of genetic inheritance.

Science.gov (United States)

Tian, Jianjun; Li, Bai-Lian

2004-09-01

Although in the broadly defined genetic algebra, multiplication suggests a forward direction of from parents to progeny, when looking from the reverse direction, it also suggests to us a new algebraic structure-coalge- braic structure, which we call genetic coalgebras. It is not the dual coalgebraic structure and can be used in the construction of phylogenetic trees. Math- ematically, to construct phylogenetic trees means we need to solve equations x([n]) = a, or x([n]) = b. It is generally impossible to solve these equations inalgebras. However, we can solve them in coalgebras in the sense of tracing back for their ancestors. A thorough exploration of coalgebraic structure in genetics is apparently necessary. Here, we develop a theoretical framework of the coalgebraic structure of genetics. From biological viewpoint, we defined various fundamental concepts and examined their elementary properties that contain genetic significance. Mathematically, by genetic coalgebra, we mean any coalgebra that occurs in genetics. They are generally noncoassociative and without counit; and in the case of non-sex-linked inheritance, they are cocommutative. Each coalgebra with genetic realization has a baric property. We have also discussed the methods to construct new genetic coalgebras, including cocommutative duplication, the tensor product, linear combinations and the skew linear map, which allow us to describe complex genetic traits. We also put forward certain theorems that state the relationship between gametic coalgebra and gametic algebra. By Brower's theorem in topology, we prove the existence of equilibrium state for the in-evolution operator.

Definição do tamanho amostral usando simulação Monte Carlo para o teste de normalidade baseado em assimetria e curtose. II.: abordagem multivariada Sample size definition using Monte Carlo simulation for the normality test based on skewness and kurtosis. II.: multivariate approach

Directory of Open Access Journals (Sweden)

Andréa Cristiane dos Santos

2003-02-01

Full Text Available Realizou-se este trabalho com o objetivo de determinar um tamanho amostral ótimo para as estatísticas univariadas de assimetria e curtose (z1 e z2 que, neste caso, foram adaptadas para o caso multivariado, e as estatísticas multivariadas de assimetria e curtose (k1 e k2 com base em simulação. Foram geradas diferentes funções densidade probabilidade multivariadas via método de Monte Carlo para avaliar a taxa de erro tipo I e o poder do teste para os valores nominais de 5% e 1%. Foram avaliadas as situações com p=2, 3, 4 e 5 variáveis, com diferentes estruturas de correlação. Para o caso multivariado, as diferentes estruturas de correlação não afetaram o poder e a taxa de erro tipo I dos testes; a estatística k2 é adequada para uso a partir de n> 50 para valores nominais de significância de 5% ou 1%; a estatística k2 é assintoticamente adequada para os testes de desvios de curtose para n> 100, independentemente dos valores nominais da significância. Pode-se concluir que as estatísticas de assimetria, em geral, são mais poderosas do que as de curtose, mas os testes da hipótese nula de normalidade multivariada devem considerar tanto os testes de desvios de assimetria como os de curtose conjuntamente, como sugerido no caso univariado.This work aimed to determine optimum sample size for the univariate skewness and kurtosis statistics (z1 and z2 adapted to multivariate situation and for the multivariate skewness and kurtosis statistics (k1 and k2 statistics based on simulation. Different probability density functions, univariate and multivariate, were generated by Monte Carlo simulation method to evaluate the type I error rates and the power of the tests. The simulations were done adopting the nominal significance level of 5% and 1%. Situations with p=2, 3, 4 and 5 variables with different correlation structures were evaluated in the case of multivariate distributions. The results showed that k1 statistics is adequate for n> 50

Social structure predicts genital morphology in African mole-rats.

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Marianne L Seney

2009-10-01

Full Text Available African mole-rats (Bathyergidae, Rodentia exhibit a wide range of social structures, from solitary to eusocial. We previously found a lack of sex differences in the external genitalia and morphology of the perineal muscles associated with the phallus in the eusocial naked mole-rat. This was quite surprising, as the external genitalia and perineal muscles are sexually dimorphic in all other mammals examined. We hypothesized that the lack of sex differences in naked mole-rats might be related to their unusual social structure.We compared the genitalia and perineal muscles in three African mole-rat species: the naked mole-rat, the solitary silvery mole-rat, and the Damaraland mole-rat, a species considered to be eusocial, but with less reproductive skew than naked mole-rats. Our findings support a relationship between social structure, mating system, and sexual differentiation. Naked mole-rats lack sex differences in genitalia and perineal morphology, silvery mole-rats exhibit sex differences, and Damaraland mole-rats are intermediate.The lack of sex differences in naked mole-rats is not an attribute of all African mole-rats, but appears to have evolved in relation to their unusual social structure and reproductive biology.

Social structure predicts genital morphology in African mole-rats.

Science.gov (United States)

Seney, Marianne L; Kelly, Diane A; Goldman, Bruce D; Sumbera, Radim; Forger, Nancy G

2009-10-15

African mole-rats (Bathyergidae, Rodentia) exhibit a wide range of social structures, from solitary to eusocial. We previously found a lack of sex differences in the external genitalia and morphology of the perineal muscles associated with the phallus in the eusocial naked mole-rat. This was quite surprising, as the external genitalia and perineal muscles are sexually dimorphic in all other mammals examined. We hypothesized that the lack of sex differences in naked mole-rats might be related to their unusual social structure. We compared the genitalia and perineal muscles in three African mole-rat species: the naked mole-rat, the solitary silvery mole-rat, and the Damaraland mole-rat, a species considered to be eusocial, but with less reproductive skew than naked mole-rats. Our findings support a relationship between social structure, mating system, and sexual differentiation. Naked mole-rats lack sex differences in genitalia and perineal morphology, silvery mole-rats exhibit sex differences, and Damaraland mole-rats are intermediate. The lack of sex differences in naked mole-rats is not an attribute of all African mole-rats, but appears to have evolved in relation to their unusual social structure and reproductive biology.

Social structure and space use of Amur tigers (Panthera tigris altaica) in Southern Russian Far East based on GPS telemetry data.

Science.gov (United States)

Hernandez-Blanco, Jose A; Naidenko, Sergei V; Chistopolova, Maria D; Lukarevskiy, Victor S; Kostyrya, Alexey; Rybin, Alexandr; Sorokin, Pavel A; Litvinov, Mikhail N; Kotlyar, Andrey K; Miquelle, Dale G; Rozhnov, Viatcheslav V

2015-07-01

To better understand the spatial structure of Amur tigers (Panthera tigris altaica) at the southern edge of their range we fitted 14 tigers (6♀♀ and 8♂♂) with 15 GPS-Argos collars between 2008 and 2011 in 2 study sites: the Ussuriskii Reserve of southern Sikhote-Alin and the Land of the Leopard National Park in southwest Primorye, Russian Far East. Fixed kernel estimates of male home ranges were larger than those of female home ranges (P tiger populations and other areas of the Russian Far East, the sex ratio in our 2 study areas was highly skewed towards males. We believe this skewed sex ratio resulted in the dissolution of territoriality of males due to an inability to defend individual females, with males resorting to scramble competition for mates. Continued monitoring of these sites to determine whether shifts in the sex ratio might result in a return to male territoriality would provide confirmation of our tentative hypothesis. © 2015 International Society of Zoological Sciences, Institute of Zoology/Chinese Academy of Sciences and Wiley Publishing Asia Pty Ltd.

Premalignant lesions skew spleen cell responses to immune modulation by adipocytes.

Science.gov (United States)

Vielma, Silvana A; Klein, Richard L; Levingston, Corinne A; Young, M Rita I

2013-05-01

Obesity can promote a chronic inflammatory state and is associated with an increased risk for cancer. Since adipocytes can produce mediators that can regulate conventional immune cells, this study sought to determine if the presence of premalignant oral lesions would skew how immune cells respond to adipocyte-derived mediators to create an environment that may be more favorable for their progression toward cancer. While media conditioned by adipocytes stimulated normal spleen cell production of the T helper (Th) type-1 cytokines interleukin (IL)-2, interferon-γ (IFN-γ), IL-12 and granulocyte-monocyte colony-stimulating factor (GM CSF), media from premalignant lesion cells either blocked or had no added affect on the adipocyte-stimulated Th1 cytokine production. In contrast, media conditioned by premalignant lesion cells exacerbated adipocyte-stimulated spleen cell production of the Th2 cytokines IL-10 and IL-13, although it did not further enhance the adipocyte-stimulated spleen cell production of IL-4 and TGF-β. The premalignant lesion environment also heightened the adipocyte-stimulated spleen cell production of the inflammatory mediators IL 1α, IL-1β, IL-6 and IL-9, although it did not further increase the adipocyte-stimulated production of tumor necrosis factor-α (TNF-α). IL 17 production was unaffected by the adipocyte-derived mediators, but was synergistically triggered by adding media from premalignant lesion cells. These stimulatory effects on spleen cell production of Th2 and inflammatory mediators were not induced in the absence of media conditioned by adipocytes. In contrast, media conditioned by adipocytes did not stimulate production of predominantly monocyte-derived chemokine C-X-C motif ligand (CXCL)9, chemokine C-C motif ligand (CCL)3 or CCL4, although it stimulated production of CCL2 and the predominantly T cell-derived chemokine CCL5, which was the only chemokine whose production was further increased by media from premalignant lesions

Next generation sequencing reveals skewing of the T and B cell receptor repertoires in patients with Wiskott Aldrich syndrome

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Amy E O'Connell

2014-07-01

Full Text Available The Wiskott Aldrich syndrome (WAS is due to mutations of the WAS gene encoding for the cytoskeletal WAS protein (WASp, leading to abnormal downstream signaling from the T cell and B cell antigen receptors (TCR, BCR. We hypothesized that the impaired signaling through the TCR and BCR in WAS would subsequently lead to aberrations in the immune repertoire of WAS patients. Using next generation sequencing, the T cell receptor beta (TRB and B cell immunoglobulin heavy chain (IGH repertoires of 8 patients with WAS and 6 controls were sequenced. Clonal expansions were identified within memory CD4+ cells, as well as in total, naïve and memory CD8+ cells from WAS patients. In the B cell compartment, WAS patient IGH repertoires were also clonally expanded and showed skewed usage of IGHV and IGHJ genes, and increased usage of IGHG constant genes, compared with controls. To our knowledge, this is the first study that demonstrates significant abnormalities of the immune repertoire in WAS patients using next generation sequencing.

Cadmium modulates hematopoietic stem and progenitor cells and skews toward myelopoiesis in mice

International Nuclear Information System (INIS)

Zhang, Yandong; Yu, Xinchun; Sun, Shuhui; Li, Qian; Xie, Yunli; Li, Qiang; Zhao, Yifan; Pei, Jianfeng; Zhang, Wenmin; Xue, Peng; Zhou, Zhijun; Zhang, Yubin

2016-01-01

The heavy metal cadmium (Cd) is known to modulate immunity and cause osteoporosis. However, how Cd influences on hematopoiesis remain largely unknown. Herein, we show that wild-type C57BL/6 (B6) mice exposed to Cd for 3 months had expanded bone marrow (BM) populations of long-term hematopoietic stem cells (LT-HSCs), common myeloid progenitors (CMPs) and granulocyte-macrophage progenitors (GMPs), while having reduced populations of multipotent progenitors (MPPs) and common lymphoid progenitors (CLPs). A competitive mixed BM transplantation assay indicates that BM from Cd-treated mice had impaired LT-HSC ability to differentiate into mature cells. In accordance with increased myeloid progenitors and decreased lymphoid progenitors, the BM and spleens of Cd-treated mice had more monocytes and/or neutrophils and fewer B cells and T cells. Cd impaired the ability of the non-hematopoietic system to support LT-HSCs, in that lethally irradiated Cd-treated recipients transplanted with normal BM cells had reduced LT-HSCs after the hematopoietic system was fully reconstituted. This is consistent with reduced osteoblasts, a known critical component for HSC niche, observed in Cd-treated mice. Conversely, lethally irradiated control recipients transplanted with BM cells from Cd-treated mice had normal LT-HSC reconstitution. Furthermore, both control mice and Cd-treated mice that received Alendronate, a clinical drug used for treating osteoporosis, had BM increases of LT-HSCs. Thus, the results suggest Cd increase of LT-HSCs is due to effects on HSCs and not on osteoblasts, although, Cd causes osteoblast reduction and impaired niche function for maintaining HSCs. Furthermore, Cd skews HSCs toward myelopoiesis. - Highlights: • Cd increases the number of LT-HSCs but impairs their development. • Cd-treated hosts have compromised ability to support LT-HSCs. • Cd promotes myelopoiesis at the expense of lymphopoiesis at the MPP level.

Cadmium modulates hematopoietic stem and progenitor cells and skews toward myelopoiesis in mice

Energy Technology Data Exchange (ETDEWEB)

Zhang, Yandong; Yu, Xinchun [School of Public Health and Key Laboratory of Public Health, MOE, Fudan University, Shanghai 200032 (China); Sun, Shuhui [Key Laboratory of Medical Molecular Virology, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032 (China); Li, Qian [School of Public Health and Key Laboratory of Public Health, MOE, Fudan University, Shanghai 200032 (China); Xie, Yunli [Insititute of Brain Sciences, Fudan University, Shanghai 200032 (China); Li, Qiang [Putuo District Center for Disease Control and Prevention, Shanghai 200062 (China); Zhao, Yifan; Pei, Jianfeng; Zhang, Wenmin; Xue, Peng; Zhou, Zhijun [School of Public Health and Key Laboratory of Public Health, MOE, Fudan University, Shanghai 200032 (China); Zhang, Yubin, E-mail: yz001@fudan.edu.cn [School of Public Health and Key Laboratory of Public Health, MOE, Fudan University, Shanghai 200032 (China)

2016-12-15

The heavy metal cadmium (Cd) is known to modulate immunity and cause osteoporosis. However, how Cd influences on hematopoiesis remain largely unknown. Herein, we show that wild-type C57BL/6 (B6) mice exposed to Cd for 3 months had expanded bone marrow (BM) populations of long-term hematopoietic stem cells (LT-HSCs), common myeloid progenitors (CMPs) and granulocyte-macrophage progenitors (GMPs), while having reduced populations of multipotent progenitors (MPPs) and common lymphoid progenitors (CLPs). A competitive mixed BM transplantation assay indicates that BM from Cd-treated mice had impaired LT-HSC ability to differentiate into mature cells. In accordance with increased myeloid progenitors and decreased lymphoid progenitors, the BM and spleens of Cd-treated mice had more monocytes and/or neutrophils and fewer B cells and T cells. Cd impaired the ability of the non-hematopoietic system to support LT-HSCs, in that lethally irradiated Cd-treated recipients transplanted with normal BM cells had reduced LT-HSCs after the hematopoietic system was fully reconstituted. This is consistent with reduced osteoblasts, a known critical component for HSC niche, observed in Cd-treated mice. Conversely, lethally irradiated control recipients transplanted with BM cells from Cd-treated mice had normal LT-HSC reconstitution. Furthermore, both control mice and Cd-treated mice that received Alendronate, a clinical drug used for treating osteoporosis, had BM increases of LT-HSCs. Thus, the results suggest Cd increase of LT-HSCs is due to effects on HSCs and not on osteoblasts, although, Cd causes osteoblast reduction and impaired niche function for maintaining HSCs. Furthermore, Cd skews HSCs toward myelopoiesis. - Highlights: • Cd increases the number of LT-HSCs but impairs their development. • Cd-treated hosts have compromised ability to support LT-HSCs. • Cd promotes myelopoiesis at the expense of lymphopoiesis at the MPP level.

Skewed Helper T-Cell Responses to IL-12 Family Cytokines Produced by Antigen-Presenting Cells and the Genetic Background in Behcet’s Disease

Directory of Open Access Journals (Sweden)

Jun Shimizu

2013-01-01

Full Text Available Behcet’s disease (BD is a multisystemic inflammatory disease and is characterized by recurrent attacks on eyes, brain, skin, and gut. There is evidence that skewed T-cell responses contributed to its pathophysiology in patients with BD. Recently, we found that Th17 cells, a new helper T (Th cell subset, were increased in patients with BD, and both Th type 1 (Th1 and Th17 cell differentiation signaling pathways were overactivated. Several researches revealed that genetic polymorphisms in Th1/Th17 cell differentiation signaling pathways were associated with the onset of BD. Here, we summarize current findings on the Th cell subsets, their contribution to the pathogenesis of BD and the genetic backgrounds, especially in view of IL-12 family cytokine production and pattern recognition receptors of macrophages/monocytes.

Experimental studies of the seismic response of structures incorporating base-isolation systems

International Nuclear Information System (INIS)

Kelly, J.M.; Aiken, I.D.

1991-01-01

This paper reviews some of the achievements of the Earthquake Engineering Research Center (EERC) at the University of California at Berkeley in the last few years. Component tests on single isolators are described. Tests on plain and high-damping natural-rubber bearings, lead-rubber bearings, sliding bearings, and bearings incorporating uplift resistance mechanisms have been performed. High-shear strain tests on large (up to full scale) elastomeric bearings have been conducted to determine the stability characteristics and limit states of the isolators. Performance evaluation studies using the earthquake simulator to test large-scale model isolated structures have been carried out for a variety of isolation systems and structures. Uplift studies of slender base-isolated buildings and investigation of the behavior of base-isolated skew bridge decks have been studied. This paper aims to highlight those areas where progress has been made. (orig./HP)

Spin Hall Effect in Doped Semiconductor Structures

Science.gov (United States)

Tse, Wang-Kong; Das Sarma, Sankar

2006-03-01

We present a microscopic theory of the extrinsic spin Hall effect based on the diagrammatic perturbation theory. Side-jump (SJ) and skew-scattering (SS) contributions are explicitly taken into account to calculate the spin Hall conductivity, and we show their effects scale as σxy^SJ/σxy^SS ˜(/τ)/ɛF, where τ being the transport relaxation time. Motivated by recent experimental work we apply our theory to n-doped and p-doped 3D and 2D GaAs structures, obtaining analytical formulas for the SJ and SS contributions. Moreover, the ratio of the spin Hall conductivity to longitudinal conductivity is found as σs/σc˜10-3-10-4, in reasonable agreement with the recent experimental results of Kato et al. [Science 306, 1910 (2004)] in n-doped 3D GaAs system.

Prediction of the moments in advection-diffusion lattice Boltzmann method. I. Truncation dispersion, skewness, and kurtosis

Science.gov (United States)

Ginzburg, Irina

2017-01-01

The effect of the heterogeneity in the soil structure or the nonuniformity of the velocity field on the modeled resident time distribution (RTD) and breakthrough curves is quantified by their moments. While the first moment provides the effective velocity, the second moment is related to the longitudinal dispersion coefficient (kT) in the developed Taylor regime; the third and fourth moments are characterized by their normalized values skewness (Sk) and kurtosis (Ku), respectively. The purpose of this investigation is to examine the role of the truncation corrections of the numerical scheme in kT, Sk, and Ku because of their interference with the second moment, in the form of the numerical dispersion, and in the higher-order moments, by their definition. Our symbolic procedure is based on the recently proposed extended method of moments (EMM). Originally, the EMM restores any-order physical moments of the RTD or averaged distributions assuming that the solute concentration obeys the advection-diffusion equation in multidimensional steady-state velocity field, in streamwise-periodic heterogeneous structure. In our work, the EMM is generalized to the fourth-order-accurate apparent mass-conservation equation in two- and three-dimensional duct flows. The method looks for the solution of the transport equation as the product of a long harmonic wave and a spatially periodic oscillating component; the moments of the given numerical scheme are derived from a chain of the steady-state fourth-order equations at a single cell. This mathematical technique is exemplified for the truncation terms of the two-relaxation-time lattice Boltzmann scheme, using plug and parabolic flow in straight channel and cylindrical capillary with the d2Q9 and d3Q15 discrete velocity sets as simple but illustrative examples. The derived symbolic dependencies can be readily extended for advection by another, Newtonian or non-Newtonian, flow profile in any-shape open-tabular conduits. It is

Determination of the diffusivity, dispersion, skewness and kurtosis in heterogeneous porous flow. Part I: Analytical solutions with the extended method of moments.

Science.gov (United States)

Ginzburg, Irina; Vikhansky, Alexander

2018-05-01

The extended method of moments (EMM) is elaborated in recursive algorithmic form for the prediction of the effective diffusivity, the Taylor dispersion dyadic and the associated longitudinal high-order coefficients in mean-concentration profiles and residence-time distributions. The method applies in any streamwise-periodic stationary d-dimensional velocity field resolved in the piecewise continuous heterogeneous porosity field. It is demonstrated that EMM reduces to the method of moments and the volume-averaging formulation in microscopic velocity field and homogeneous soil, respectively. The EMM simultaneously constructs two systems of moments, the spatial and the temporal, without resorting to solving of the high-order upscaled PDE. At the same time, the EMM is supported with the reconstruction of distribution from its moments, allowing to visualize the deviation from the classical ADE solution. The EMM can be handled by any linear advection-diffusion solver with explicit mass-source and diffusive-flux jump condition on the solid boundary and permeable interface. The prediction of the first four moments is decisive in the optimization of the dispersion, asymmetry, peakedness and heavy-tails of the solute distributions, through an adequate design of the composite materials, wetlands, chemical devices or oil recovery. The symbolic solutions for dispersion, skewness and kurtosis are constructed in basic configurations: diffusion process and Darcy flow through two porous blocks in "series", straight and radial Poiseuille flow, porous flow governed by the Stokes-Brinkman-Darcy channel equation and a fracture surrounded by penetrable diffusive matrix or embedded in porous flow. We examine the moments dependency upon porosity contrast, aspect ratio, Péclet and Darcy numbers, but also for their response on the effective Brinkman viscosity applied in flow modeling. Two numerical Lattice Boltzmann algorithms, a direct solver of the microscopic ADE in heterogeneous

Coassimetria e cocurtose na análise dos preços das ações no mercado financeiro nacional CO-SKEWNESS AND CO-KURTOSIS IN THE ANALYSIS OF STOCK PRICING AT IBOVESPA

Directory of Open Access Journals (Sweden)

Eduardo Botti Abbade

2010-12-01

, the influence of co-skewness in correlation with the proxy IBOV stocks, the influence of co-kurtosis in correlation with the proxy IBOV stocks, the influence of co-skewness and co-kurtosis in the correlation between the proxy IBOV and stocks, its performance compared with the CAPM and the increase of the accuracy. Is was developed literature research and study of time series of the stocks that constitutes the Ibovespa index on 30 May 2008, analyzed with the use of multiple regressions with the variables to systematic volatility, the systematic skewness and systematic kurtosis. As a result it was observed conclusively that co-skewness and co-kurtosis do not improve the performance of the model of pricing of assets.

Evaluating the performance of skewed prestressed concrete bridge after strengthening

Science.gov (United States)

Naser, Ali Fadhil; Zonglin, Wang

2013-06-01

The objectives of this paper are to explain the application of repairing and strengthening methods on the damaged members of the bridge structure, to analyze the static and dynamic structural response under static and dynamic loads after strengthening, and to evaluate the structural performance after application of strengthening method. The repairing and strengthening methods which are used in this study include treatment of the cracks, thickening the web of box girder along the bridge length and adding internal pre-stressing tendons in the thickening web, and construct reinforced concrete cross beams (diaphragms) between two box girders. The results of theoretical analysis of static and dynamic structural responses after strengthening show that the tensile stresses are decreased and become less than the allowable limit values in the codes. The values of vertical deflection are decreased after strengthening. The values of natural frequencies after strengthening are increased, indicating that the strengthening method is effective to reduce the vibration of the bridge structure. Therefore, the strengthening methods are effective to improve the bearing capacity and elastic working state of the bridge structure and to increase the service life of the bridge structure.

Niacin and olive oil promote skewing to the M2 phenotype in bone marrow-derived macrophages of mice with metabolic syndrome.

Science.gov (United States)

Montserrat-de la Paz, Sergio; Naranjo, Maria C; Lopez, Sergio; Abia, Rocio; Muriana, Francisco J G; Bermudez, Beatriz

2016-05-18

Metabolic syndrome (MetS) is associated with obesity, dyslipemia, type 2 diabetes and chronic low-grade inflammation. The aim of this study was to determine the role of high-fat low-cholesterol diets (HFLCDs) rich in SFAs (HFLCD-SFAs), MUFAs (HFLCD-MUFAs) or MUFAs plus omega-3 long-chain PUFAs (HFLCD-PUFAs) on polarisation and inflammatory potential in bone marrow-derived macrophages (BMDMs) from niacin (NA)-treated Lep(ob/ob)LDLR(-/-) mice. Animals fed with HFLCD-SFAs had increased weight and serum triglycerides, and their BMDMs accumulated triglycerides over the animals fed with HFLCD-MUFAs or -PUFAs. Furthermore, BMDMs from animals fed with HFLCD-SFAs were polarised towards the M1 phenotype with functional competence to produce pro-inflammatory cytokines, whereas BMDMs from animals fed with HFLCD-MUFAs or -PUFAs were skewed to the anti-inflammatory M2 phenotype. These findings open opportunities for developing novel nutritional strategies with olive oil as the most important dietary source of MUFAs (notably oleic acid) to prevent development and progression of metabolic complications in the NA-treated MetS.

A Two-Sided Market Model of Optimal Price Structure for Instant Messenger

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Jun Xu

2013-01-01

Full Text Available Instant messenger (IM is one of the most popular Internet applications all over the world. This paper examines the pricing problem of IM based on two-sided market model. IM serves as a two-sided platform, which gets both Internet users and advertisers on board. This paper concludes that IM operator adopts a heavily skewed price structure that favors IM users both under monopolistic case and under horizontal differentiated duopolistic case. When advertising revenue is large enough relatively to marginal cost for serving IM users, IM users can enjoy free service provided by IM operators. The competitive equilibrium of duopolistic case is not necessarily symmetric when advertisers choose singlehoming. Even in the symmetric equilibrium platform would rather deter all advertisers.

Construction of 3D Arrays of Cylindrically Hierarchical Structures with ZnO Nanorods Hydrothermally Synthesized on Optical Fiber Cores

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Weixuan Jing

2014-01-01

Full Text Available With ZnO nanorods hydrothermally synthesized on manually assembled arrays of optical fiber cores, 3D arrays of ZnO nanorod-based cylindrically hierarchical structures with nominal pitch 250 μm or 375 μm were constructed. Based on micrographs of scanning electron microscopy and image processing operators of MATLAB software, the 3D arrays of cylindrically hierarchical structures were quantitatively characterized. The values of the actual diameters, the actual pitches, and the parallelism errors suggest that the process capability of the manual assembling is sufficient and the quality of the 3D arrays of cylindrically hierarchical structures is acceptable. The values of the characteristic parameters such as roughness, skewness, kurtosis, correlation length, and power spectrum density show that the surface morphologies of the cylindrically hierarchical structures not only were affected significantly by Zn2+ concentration of the growth solution but also were anisotropic due to different curvature radii of the optical fiber core at side and front view.

Effects of baryons on the statistical properties of large scale structure of the Universe

International Nuclear Information System (INIS)

Guillet, T.

2010-01-01

Observations of weak gravitational lensing will provide strong constraints on the cosmic expansion history and the growth rate of large scale structure, yielding clues to the properties and nature of dark energy. Their interpretation is impacted by baryonic physics, which are expected to modify the total matter distribution at small scales. My work has focused on determining and modeling the impact of baryons on the statistics of the large scale matter distribution in the Universe. Using numerical simulations, I have extracted the effect of baryons on the power spectrum, variance and skewness of the total density field as predicted by these simulations. I have shown that a model based on the halo model construction, featuring a concentrated central component to account for cool condensed baryons, is able to reproduce accurately, and down to very small scales, the measured amplifications of both the variance and skewness of the density field. Because of well-known issues with baryons in current cosmological simulations, I have extended the central component model to rely on as many observation-based ingredients as possible. As an application, I have studied the effect of baryons on the predictions of the upcoming Euclid weak lensing survey. During the course of this work, I have also worked at developing and extending the RAMSES code, in particular by developing a parallel self-gravity solver, which offers significant performance gains, in particular for the simulation of some astrophysical setups such as isolated galaxy or cluster simulations. (author) [fr

Simulation of chloride transport based description soil structure

International Nuclear Information System (INIS)

Mahmood-ul-Hassan, M.; Akhtar, M.S.; Gill, S.M.; Nabi, G.

2003-01-01

There is a need of environmental implications of rapid appearance of surface by applying chemical at depths below the vadose zone (tile line or shallow groundwater) for developing better insight into solute flow mechanism through the arable lands. Transport of chloride, a representative non-adsorbing solute, through a moderately structured silty clay loam soil (Gujranwala series, Typic Ustochrepts) and an un-structured sandy loam soil (Nabipur series, Typic Camborthid) was characterized and two existing models viz. convection dispersion equation (CDE) and preferential flow models were tested. The flux average of solute concentration in the outflow as a function of cumulative drainage was fitted to the models. The CDE fitted, relatively, better in the non-structured soil than in the moderately structured soil. Dispersivity value determined by CDE was very high for the structured soil which is physically not possible. The preferential flow model fitted well in the Gujranwala soil, but not in the Nabipur soil. The breakthrough characteristics i.e. drainage to peak concentration (Dp), symmetry coefficient (SC), skewness, and kurtosis were compared. Chloride breakthrough was earlier than expected based on piston flow. It indicated preferential flow in both the soils, yet, immediate appearance of the tracer in the Gujranwala soil demonstrated even larger magnitude of the preferential flow. Breakthrough curves' parameters indicated a large amount of the solute movement through the preferred pathways by passing the soil matrix in the Gujranwala soil. The study suggests that some soil structure parameters (size/shape and degree of aggregation) should be incorporated in the solute transport models.(author)

A deformation of Sasakian structure in the presence of torsion and supergravity solutions

International Nuclear Information System (INIS)

Houri, Tsuyoshi; Takeuchi, Hiroshi; Yasui, Yukinori

2013-01-01

A deformation of Sasakian structure in the presence of totally skew-symmetric torsion is discussed on odd-dimensional manifolds whose metric cones are Kähler with torsion. It is shown that such a geometry inherits similar properties to those of Sasakian geometry. As their example, we present an explicit expression of local metrics. It is also demonstrated that our example of the metrics admits the existence of hidden symmetry described by non-trivial odd-rank generalized closed conformal Killing–Yano tensors. Furthermore, using these metrics as an ansatz, we construct exact solutions in five-dimensional minimal gauged/ungauged supergravity and 11-dimensional supergravity. Finally, the global structures of the solutions are discussed. We obtain regular metrics on compact manifolds in five dimensions, which give natural generalizations of Sasaki–Einstein manifolds Y p,q and L a,b,c . We also briefly discuss regular metrics on non-compact manifolds in 11 dimensions. (paper)

INCREASING RETURNS TO SCALE, DYNAMICS OF INDUSTRIAL STRUCTURE AND SIZE DISTRIBUTION OF FIRMS

Institute of Scientific and Technical Information of China (English)

Ying FAN; Menghui LI; Zengru DI

2006-01-01

A multi-agent model is presented to discuss the market dynamics and the size distribution of firms.The model emphasizes the effects of increasing returns to scale and gives the description of the born and death of adaptive producers. The evolution of market structure and its behavior under the technological shocks are investigated. Its dynamical results are in good agreement with some empirical "stylized facts" of industrial evolution. With the diversity of demand and adaptive growth strategies of firms, the firm size in the generalized model obeys the power-law distribution. Three factors mainly determine the competitive dynamics and the skewed size distributions of firms: 1. Self-reinforcing mechanism; 2. Adaptive firm growing strategies; 3. Demand diversity or widespread heterogeneity in the technological capabilities of firms.

Evolutionary dynamics of incubation periods.

Science.gov (United States)

Ottino-Loffler, Bertrand; Scott, Jacob G; Strogatz, Steven H

2017-12-21

The incubation period for typhoid, polio, measles, leukemia and many other diseases follows a right-skewed, approximately lognormal distribution. Although this pattern was discovered more than sixty years ago, it remains an open question to explain its ubiquity. Here, we propose an explanation based on evolutionary dynamics on graphs. For simple models of a mutant or pathogen invading a network-structured population of healthy cells, we show that skewed distributions of incubation periods emerge for a wide range of assumptions about invader fitness, competition dynamics, and network structure. The skewness stems from stochastic mechanisms associated with two classic problems in probability theory: the coupon collector and the random walk. Unlike previous explanations that rely crucially on heterogeneity, our results hold even for homogeneous populations. Thus, we predict that two equally healthy individuals subjected to equal doses of equally pathogenic agents may, by chance alone, show remarkably different time courses of disease.

Treatment to sustain a Th17-type phenotype to prevent skewing toward Treg and to limit premalignant lesion progression to cancer.

Science.gov (United States)

Young, M Rita I; Levingston, Corinne A; Johnson, Sara D

2016-05-15

While immune suppression is a hallmark of head and neck squamous cell carcinoma (HSNCC), the immunological impact of premalignant oral lesions, which often precedes development of HNSCC, is unknown. The present study assessed the changes in splenic and draining lymph node CD4(+) cell populations and their production of select cytokines that occur in mice with carcinogen-induced premalignant oral lesions and the changes that occur as lesions progress to oral cancer. These studies found skewing toward Th1 and Th17-type phenotypes in the spleen and lymph nodes of mice with premalignant oral lesions and a shift to Treg as lesions progress to cancer. Since the role of Th17 cells in the progression from premalignant lesions to cancer is not clear, studies determined the immunological and clinical effect of treating mice bearing premalignant oral lesions with a TGF-β type 1 receptor inhibitor plus IL-23 as an approach to sustain the Th17 phenotype. These studies showed that the treatment approach not only sustained the Th17 phenotype, but also increased distal spleen cell and regional lymph node cell production of other stimulatory/inflammatory mediators and slowed premalignant lesion progression to cancer. © 2016 UICC.

Learning about the internal structure of categories through classification and feature inference.

Science.gov (United States)

Jee, Benjamin D; Wiley, Jennifer

2014-01-01

Previous research on category learning has found that classification tasks produce representations that are skewed toward diagnostic feature dimensions, whereas feature inference tasks lead to richer representations of within-category structure. Yet, prior studies often measure category knowledge through tasks that involve identifying only the typical features of a category. This neglects an important aspect of a category's internal structure: how typical and atypical features are distributed within a category. The present experiments tested the hypothesis that inference learning results in richer knowledge of internal category structure than classification learning. We introduced several new measures to probe learners' representations of within-category structure. Experiment 1 found that participants in the inference condition learned and used a wider range of feature dimensions than classification learners. Classification learners, however, were more sensitive to the presence of atypical features within categories. Experiment 2 provided converging evidence that classification learners were more likely to incorporate atypical features into their representations. Inference learners were less likely to encode atypical category features, even in a "partial inference" condition that focused learners' attention on the feature dimensions relevant to classification. Overall, these results are contrary to the hypothesis that inference learning produces superior knowledge of within-category structure. Although inference learning promoted representations that included a broad range of category-typical features, classification learning promoted greater sensitivity to the distribution of typical and atypical features within categories.

A phase-contrast X-ray imaging system--with a 60x30 mm field of view--based on a skew-symmetric two-crystal X-ray interferometer

Energy Technology Data Exchange (ETDEWEB)

Yoneyama, Akio E-mail: a-yoneya@rd.hitachi.co.jp; Takeda, Tohoru; Tsuchiya, Yoshinori; Wu Jin; Lwin, T.-T.; Koizumi, Aritaka; Hyodo, Kazuyuki; Itai, Yuji

2004-05-01

A phase-contrast X-ray imaging system - with a 60x30 mm field of view - for biomedical observations was developed. To extend the observation field of view, the system is fitted with a skew-symmetric two-crystal X-ray interferometer. To attain the required sub-nanoradian mechanical stability between the crystal blocks for precise operation, the interferometer was mounted on two extremely rigid positioning tables (one with a sleeve bearings) and was controlled by a feedback positioning system using phase-lock interferometry. The imaging system produced a 60x30 mm interference pattern with 60% visibility using 17.7 keV monochromatic synchrotron X-rays at the Photon Factory. It was then used to perform radiographic observation (i.e., phase mapping) of rat liver vessels. These results indicate that this imaging system can be used to perform observations of large and in vivo biological samples.

A phase-contrast X-ray imaging system--with a 60x30 mm field of view--based on a skew-symmetric two-crystal X-ray interferometer

International Nuclear Information System (INIS)

Yoneyama, Akio; Takeda, Tohoru; Tsuchiya, Yoshinori; Wu Jin; Lwin, T.-T.; Koizumi, Aritaka; Hyodo, Kazuyuki; Itai, Yuji

2004-01-01

A phase-contrast X-ray imaging system - with a 60x30 mm field of view - for biomedical observations was developed. To extend the observation field of view, the system is fitted with a skew-symmetric two-crystal X-ray interferometer. To attain the required sub-nanoradian mechanical stability between the crystal blocks for precise operation, the interferometer was mounted on two extremely rigid positioning tables (one with a sleeve bearings) and was controlled by a feedback positioning system using phase-lock interferometry. The imaging system produced a 60x30 mm interference pattern with 60% visibility using 17.7 keV monochromatic synchrotron X-rays at the Photon Factory. It was then used to perform radiographic observation (i.e., phase mapping) of rat liver vessels. These results indicate that this imaging system can be used to perform observations of large and in vivo biological samples

A phase-contrast X-ray imaging system—with a 60×30 mm field of view—based on a skew-symmetric two-crystal X-ray interferometer

Science.gov (United States)

Yoneyama, Akio; Takeda, Tohoru; Tsuchiya, Yoshinori; Wu, Jin; Thet-Thet-Lwin; Koizumi, Aritaka; Hyodo, Kazuyuki; Itai, Yuji

2004-05-01

A phase-contrast X-ray imaging system—with a 60×30 mm field of view—for biomedical observations was developed. To extend the observation field of view, the system is fitted with a skew-symmetric two-crystal X-ray interferometer. To attain the required sub-nanoradian mechanical stability between the crystal blocks for precise operation, the interferometer was mounted on two extremely rigid positioning tables (one with a sleeve bearings) and was controlled by a feedback positioning system using phase-lock interferometry. The imaging system produced a 60×30 mm interference pattern with 60% visibility using 17.7 keV monochromatic synchrotron X-rays at the Photon Factory. It was then used to perform radiographic observation (i.e., phase mapping) of rat liver vessels. These results indicate that this imaging system can be used to perform observations of large and in vivo biological samples.

Multilevel covariance regression with correlated random effects in the mean and variance structure.

Science.gov (United States)

Quintero, Adrian; Lesaffre, Emmanuel

2017-09-01

Multivariate regression methods generally assume a constant covariance matrix for the observations. In case a heteroscedastic model is needed, the parametric and nonparametric covariance regression approaches can be restrictive in the literature. We propose a multilevel regression model for the mean and covariance structure, including random intercepts in both components and allowing for correlation between them. The implied conditional covariance function can be different across clusters as a result of the random effect in the variance structure. In addition, allowing for correlation between the random intercepts in the mean and covariance makes the model convenient for skewedly distributed responses. Furthermore, it permits us to analyse directly the relation between the mean response level and the variability in each cluster. Parameter estimation is carried out via Gibbs sampling. We compare the performance of our model to other covariance modelling approaches in a simulation study. Finally, the proposed model is applied to the RN4CAST dataset to identify the variables that impact burnout of nurses in Belgium. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Single HIV-1 Cluster and a Skewed Immune Homeostasis Drive the Early Spread of HIV among Resting CD4+ Cell Subsets within One Month Post-Infection

Science.gov (United States)

Avettand-Fenoël, Véronique; Nembot, Georges; Mélard, Adeline; Blanc, Catherine; Lascoux-Combe, Caroline; Slama, Laurence; Allegre, Thierry; Allavena, Clotilde; Yazdanpanah, Yazdan; Duvivier, Claudine; Katlama, Christine; Goujard, Cécile; Seksik, Bao Chau Phung; Leplatois, Anne; Molina, Jean-Michel; Meyer, Laurence; Autran, Brigitte; Rouzioux, Christine

2013-01-01

Optimizing therapeutic strategies for an HIV cure requires better understanding the characteristics of early HIV-1 spread among resting CD4+ cells within the first month of primary HIV-1 infection (PHI). We studied the immune distribution, diversity, and inducibility of total HIV-DNA among the following cell subsets: monocytes, peripheral blood activated and resting CD4 T cells, long-lived (naive [TN] and central-memory [TCM]) and short-lived (transitional-memory [TTM] and effector-memory cells [TEM]) resting CD4+T cells from 12 acutely-infected individuals recruited at a median 36 days from infection. Cells were sorted for total HIV-DNA quantification, phylogenetic analysis and inducibility, all studied in relation to activation status and cell signaling. One month post-infection, a single CCR5-restricted viral cluster was massively distributed in all resting CD4+ subsets from 88% subjects, while one subject showed a slight diversity. High levels of total HIV-DNA were measured among TN (median 3.4 log copies/million cells), although 10-fold less (p = 0.0005) than in equally infected TCM (4.5), TTM (4.7) and TEM (4.6) cells. CD3−CD4+ monocytes harbored a low viral burden (median 2.3 log copies/million cells), unlike equally infected resting and activated CD4+ T cells (4.5 log copies/million cells). The skewed repartition of resting CD4 subsets influenced their contribution to the pool of resting infected CD4+T cells, two thirds of which consisted of short-lived TTM and TEM subsets, whereas long-lived TN and TCM subsets contributed the balance. Each resting CD4 subset produced HIV in vitro after stimulation with anti-CD3/anti-CD28+IL-2 with kinetics and magnitude varying according to subset differentiation, while IL-7 preferentially induced virus production from long-lived resting TN cells. In conclusion, within a month of infection, a clonal HIV-1 cluster is massively distributed among resting CD4 T-cell subsets with a flexible inducibility, suggesting that

A single HIV-1 cluster and a skewed immune homeostasis drive the early spread of HIV among resting CD4+ cell subsets within one month post-infection.

Directory of Open Access Journals (Sweden)

Charline Bacchus

Full Text Available Optimizing therapeutic strategies for an HIV cure requires better understanding the characteristics of early HIV-1 spread among resting CD4+ cells within the first month of primary HIV-1 infection (PHI. We studied the immune distribution, diversity, and inducibility of total HIV-DNA among the following cell subsets: monocytes, peripheral blood activated and resting CD4 T cells, long-lived (naive [TN] and central-memory [TCM] and short-lived (transitional-memory [TTM] and effector-memory cells [TEM] resting CD4+T cells from 12 acutely-infected individuals recruited at a median 36 days from infection. Cells were sorted for total HIV-DNA quantification, phylogenetic analysis and inducibility, all studied in relation to activation status and cell signaling. One month post-infection, a single CCR5-restricted viral cluster was massively distributed in all resting CD4+ subsets from 88% subjects, while one subject showed a slight diversity. High levels of total HIV-DNA were measured among TN (median 3.4 log copies/million cells, although 10-fold less (p = 0.0005 than in equally infected TCM (4.5, TTM (4.7 and TEM (4.6 cells. CD3-CD4+ monocytes harbored a low viral burden (median 2.3 log copies/million cells, unlike equally infected resting and activated CD4+ T cells (4.5 log copies/million cells. The skewed repartition of resting CD4 subsets influenced their contribution to the pool of resting infected CD4+T cells, two thirds of which consisted of short-lived TTM and TEM subsets, whereas long-lived TN and TCM subsets contributed the balance. Each resting CD4 subset produced HIV in vitro after stimulation with anti-CD3/anti-CD28+IL-2 with kinetics and magnitude varying according to subset differentiation, while IL-7 preferentially induced virus production from long-lived resting TN cells. In conclusion, within a month of infection, a clonal HIV-1 cluster is massively distributed among resting CD4 T-cell subsets with a flexible inducibility

Charge structure of K-p interactions

International Nuclear Information System (INIS)

Goettgens, R.; Ransone, G.; Sixel, P.

1981-01-01

The charge transfer distribution, its average, dispersion and skewness are studied in K - p interactions at 110 GeV/c and lower energies. The ratio of dispersion squared to rapidity plateau height is found to be energy independent as suggested by the neutral cluster models. The short range charge correlations in rapidity are observed at all energies; at 110 GeV/c there is also evidence for a long range component. (author)

Structural changes in cross-border liabilities: A multidimensional approach

Science.gov (United States)

Araújo, Tanya; Spelta, Alessandro

2014-01-01

We study the international interbank market through a geometric analysis of empirical data. The geometric analysis of the time series of cross-country liabilities shows that the systematic information of the interbank international market is contained in a space of small dimension. Geometric spaces of financial relations across countries are developed, for which the space volume, multivariate skewness and multivariate kurtosis are computed. The behavior of these coefficients reveals an important modification acting in the financial linkages since 1997 and allows us to relate the shape of the geometric space that emerges in recent years to the globally turbulent period that has characterized financial systems since the late 1990s. Here we show that, besides a persistent decrease in the volume of the geometric space since 1997, the observation of a generalized increase in the values of the multivariate skewness and kurtosis sheds some light on the behavior of cross-border interdependencies during periods of financial crises. This was found to occur in such a systematic fashion, that these coefficients may be used as a proxy for systemic risk.

The Taming of the Skew: Facts On Canada’s Energy Trade

Directory of Open Access Journals (Sweden)

Trevor Tombe

2014-03-01

Full Text Available Public perception of Canada’s energy trade is skewed towards Alberta’s oilsands and pipeline projects; a look at the facts reveals a more complex picture. Over the last decade, growth in Canada’s energy trade has been nothing short of historic. Energy exports have become so significant that the revenue is now equivalent to nearly $9,000 for every Canadian household. And it is only projected to grow much, much larger. While Western Canada leads the industry, every region — including Ontario, Quebec and Atlantic Canada — plays a key role. Today, nearly every province is a net energy exporter. The energy sector also adds much to Canada’s economy, with valueadded and productivity higher than nearly every other sector. When it comes to labour compensation, oil and gas extraction is the highest-paying sector in the country, at more than three times the average hourly earnings in the Canadian economy generally, and nearly 50 per cent higher than manufacturing. It is vital that policy debates rely on accurate information; unfortunately, this is not always the case. The often heated rhetoric neglects important aspects of Canada’s energy trade. For example, the type of energy that Canada trades has undergone a dramatic transformation. Ten years ago, natural gas was the largest energy export but today accounts for less than one-tenth of the total. Meanwhile, crude oil exports have more than quadrupled. Even more surprising to many Canadians, and perhaps even policy-makers, is how much energy Canada imports. Even Alberta, with its vast energy reserves, imports a considerable amount of energy. Alberta’s energy imports have grown faster than any other province and will soon exceed Ontario’s, a province more than three times larger with very little of its own oil production. Trade in energy is also intimately tied with Canada’s foreign investment policies. The majority of Canada’s energy trade is in the form of related-party transactions

The Hopf algebra structure of the character rings of classical groups

International Nuclear Information System (INIS)

Fauser, Bertfried; Jarvis, Peter D; King, Ronald C

2013-01-01

The character ring Char-GL of covariant irreducible tensor representations of the general linear group admits a Hopf algebra structure isomorphic to the Hopf algebra Symm-Λ of symmetric functions. Here we study the character rings Char-O and Char-Sp of the orthogonal and symplectic subgroups of the general linear group within the same framework of symmetric functions. We show that Char-O and Char-Sp also admit natural Hopf algebra structures that are isomorphic to that of Char-GL, and hence to Symm-Λ. The isomorphisms are determined explicitly, along with the specification of standard bases for Char-O and Char-Sp analogous to those used for Symm-Λ. A major structural change arising from the adoption of these bases is the introduction of new orthogonal and symplectic Schur–Hall scalar products. Significantly, the adjoint with respect to multiplication no longer coincides, as it does in the Char-GL case, with a Foulkes derivative or skew operation. The adjoint and Foulkes derivative now require separate definitions, and their properties are explored here in the orthogonal and symplectic cases. Moreover, the Hopf algebras Char-O and Char-Sp are not self-dual. The dual Hopf algebras Char-O * and Char-Sp are identified. Finally, the Hopf algebra of the universal rational character ring Char-GLrat of mixed irreducible tensor representations of the general linear group is introduced and its structure maps identified. (paper)

Nicotine can skew the characterization of the macrophage type-1 (MΦ1) phenotype differentiated with granulocyte-macrophage colony-stimulating factor to the MΦ2 phenotype

International Nuclear Information System (INIS)

Yanagita, Manabu; Kobayashi, Ryohei; Murakami, Shinya

2009-01-01

Macrophages (MΦs) exhibit functional heterogeneity and plasticity in the local microenvironment. Recently, it was reported that MΦs can be divided into proinflammatory MΦs (MΦ1) and anti-inflammatory MΦs (MΦ2) based on their polarized functional properties. Here, we report that nicotine, the major ingredient of cigarette smoke, can modulate the characteristics of MΦ1. Granulocyte-macrophage colony-stimulating factor-driven MΦ1 with nicotine (Ni-MΦ1) showed the phenotypic characteristics of MΦ2. Like MΦ2, Ni-MΦ1 exhibited antigen-uptake activities. Ni-MΦ1 suppressed IL-12, but maintained IL-10 and produced high amounts of MCP-1 upon lipopolysaccharide stimulation compared with MΦ1. Moreover, we observed strong proliferative responses of T cells to lipopolysaccharide-stimulated MΦ1, whereas Ni-MΦ1 reduced T cell proliferation and inhibited IFN-γ production by T cells. These results suggest that nicotine can change the functional characteristics of MΦ and skew the MΦ1 phenotype to MΦ2. We propose that nicotine is a potent regulator that modulates immune responses in microenvironments.

Population Structure of Montastraea cavernosa on Shallow versus Mesophotic Reefs in Bermuda

Science.gov (United States)

Goodbody-Gringley, Gretchen; Marchini, Chiara; Chequer, Alex D.; Goffredo, Stefano

2015-01-01

Mesophotic coral reef ecosystems remain largely unexplored with only limited information available on taxonomic composition, abundance and distribution. Yet, mesophotic reefs may serve as potential refugia for shallow-water species and thus understanding biodiversity, ecology and connectivity of deep reef communities is integral for resource management and conservation. The Caribbean coral, Montastraea cavernosa, is considered a depth generalist and is commonly found at mesophotic depths. We surveyed abundance and size-frequency of M. cavernosa populations at six shallow (10m) and six upper mesophotic (45m) sites in Bermuda and found population structure was depth dependent. The mean surface area of colonies at mesophotic sites was significantly smaller than at shallow sites, suggesting that growth rates and maximum colony surface area are limited on mesophotic reefs. Colony density was significantly higher at mesophotic sites, however, resulting in equal contributions to overall percent cover. Size-frequency distributions between shallow and mesophotic sites were also significantly different with populations at mesophotic reefs skewed towards smaller individuals. Overall, the results of this study provide valuable baseline data on population structure, which indicate that the mesophotic reefs of Bermuda support an established population of M. cavernosa. PMID:26544963

Skewed Epigenetics: An Alternative Therapeutic Option for Diabetes Complications

Directory of Open Access Journals (Sweden)

Gabriele Togliatto

2015-01-01

Full Text Available Vascular complications are major causes of morbidity and mortality in type 2 diabetes patients. Mitochondrial reactive oxygen species (ROS generation and a lack of efficient antioxidant machinery, a result of hyperglycaemia, mainly contribute to this problem. Although advances in therapy have significantly reduced both morbidity and mortality in diabetic individuals, diabetes-associated vascular complications are still one of the most challenging health problems worldwide. New healing options are urgently needed as current therapeutics are failing to improve long-term outcomes. Particular effort has recently been devoted to understanding the functional relationship between chromatin structure regulation and the persistent change in gene expression which is driven by hyperglycaemia and which accounts for long-lasting diabetic complications. A detailed investigation into epigenetic chromatin modifications in type 2 diabetes is underway. This will be particularly useful in the design of mechanism-based therapeutics which interfere with long-lasting activating epigenetics and improve patient outcomes. We herein provide an overview of the most relevant mechanisms that account for hyperglycaemia-induced changes in chromatin structure; the most relevant mechanism is called “metabolic memory.”

Quaternionic Kaehler and hyperkaehler manifolds with torsion and twistor spaces

International Nuclear Information System (INIS)

Ivanov, Stefan; Minchev, Ivan

2001-12-01

The target space of a (4,0) supersymmetric two-dimensional sigma model with Wess-Zumino term has a connection with totally skew-symmetric torsion and holonomy contained in Sp(n)Sp(l) (resp. Sp(n)), QKT (resp. HKT)-spaces. We study the geometry of QKT, HKT manifold and their twistor spaces. We show that the Swann bundle of a QKT manifold admits a HKT structure with special symmetry if and only if the twistor space of the QKT manifold admits an almost hermitian structure with totally skew-symmetric Nijenhuis tensor, thus connecting two structures arising from quantum field theories and supersymmetric sigma models with Wess- Zumino term. We discovered that a HKT manifold has always co-closed Lee form. Applying this property to compact HKT manifold we get information about the plurigenera. (author)

Crystal structure of the enzyme-product complex reveals sugar ring distortion during catalysis by family 63 inverting α-glycosidase.

Science.gov (United States)

Miyazaki, Takatsugu; Nishikawa, Atsushi; Tonozuka, Takashi

2016-12-01

Glycoside hydrolases are divided into two groups, known as inverting and retaining enzymes, based on their hydrolytic mechanisms. Glycoside hydrolase family 63 (GH63) is composed of inverting α-glycosidases, which act mainly on α-glucosides. We previously found that Escherichia coli GH63 enzyme, YgjK, can hydrolyze 2-O-α-d-glucosyl-d-galactose. Two constructed glycosynthase mutants, D324N and E727A, which catalyze the transfer of a β-glucosyl fluoride donor to galactose, lactose, and melibiose. Here, we determined the crystal structures of D324N and E727A soaked with a mixture of glucose and lactose at 1.8- and 2.1-Å resolutions, respectively. Because glucose and lactose molecules are found at the active sites in both structures, it is possible that these structures mimic the enzyme-product complex of YgjK. A glucose molecule found at subsite -1 in both structures adopts an unusual 1 S 3 skew-boat conformation. Comparison between these structures and the previously determined enzyme-substrate complex structure reveals that the glucose pyranose ring might be distorted immediately after nucleophilic attack by a water molecule. These structures represent the first enzyme-product complex for the GH63 family, as well as the structurally-related glycosidases, and it may provide insight into the catalytic mechanism of these enzymes. Copyright © 2016 Elsevier Inc. All rights reserved.

True Polar Wander and Hotspot Fixity: A Paleomagnetic Investigation of the Skewness of Magnetic Anomaly 12r (32 Ma B.P.) on the Pacific Plate

Science.gov (United States)

Gordon, R. G.; Horner-Johnson, B. C.

2010-12-01

Prior studies have shown that Pacific hotspots and Indo-Atlantic hotspots have moved in approximate unison relative to the spin axis since 65 Ma B.P. [Morgan, 1981; Gordon and Cape, 1981; Gordon, 1982] and since 56 Ma B.P. [Petronotis et al., 1994], which is most simply interpreted as true polar wander. In contrast, Pacific hotspots and Indo-Atlantic hotspots give conflicting results for 72 Ma B.P. and for 81 Ma B.P., which may indicate motion between Pacific hotspots and Indo-Atlantic hotspots [Tarduno and Cottrell, 1997; Petronotis et al., 1999; Tarduno et al., 2003]. Thus it is important to estimate Pacific plate apparent polar wander (APW) for more time intervals. From such estimates the APW of Pacific hotspots can be inferred and compared with that of Indo-Atlantic hotspots [e.g., Besse and Courtillot 2002]. Here we present a study of the skewness of anomaly 12r between the Galapagos and Clipperton and between the Clipperton and Clarion fracture zones. We chose this region for several reasons: First, numerical experiments, like those conducted by Acton and Gordon [1991], indicate that magnetic profiles between the Galapagos and Clarion fracture zones should contain the most information about the Pacific plate paleomagnetic pole for chron C12r (32 Ma B.P.). Second, in these two spreading rate corridors, spreading half rates range from 72 to 86 mm/a and therefore have negligible anomalous skewness, given that they exceed ≈50 mm/a [Roest et al., 1992; Dyment et al. 1994]. Third, vector aeromagnetic profiles are available for analysis. One of the challenges to interpreting magnetic anomalies in low latitudes where the anomalies strike nearly north-south is the very low amplitude of the signal relative to the noise, the latter of which can be especially intense near the present magnetic equator due to the amplification of diurnal variation by the equatorial electrojet. Previously we showed that vector aeromagnetic profiles record low-latitude Pacific plate

Bayesian models for cost-effectiveness analysis in the presence of structural zero costs.

Science.gov (United States)

Baio, Gianluca

2014-05-20

Bayesian modelling for cost-effectiveness data has received much attention in both the health economics and the statistical literature, in recent years. Cost-effectiveness data are characterised by a relatively complex structure of relationships linking a suitable measure of clinical benefit (e.g. quality-adjusted life years) and the associated costs. Simplifying assumptions, such as (bivariate) normality of the underlying distributions, are usually not granted, particularly for the cost variable, which is characterised by markedly skewed distributions. In addition, individual-level data sets are often characterised by the presence of structural zeros in the cost variable. Hurdle models can be used to account for the presence of excess zeros in a distribution and have been applied in the context of cost data. We extend their application to cost-effectiveness data, defining a full Bayesian specification, which consists of a model for the individual probability of null costs, a marginal model for the costs and a conditional model for the measure of effectiveness (given the observed costs). We presented the model using a working example to describe its main features. © 2013 The Authors. Statistics in Medicine published by John Wiley & Sons, Ltd.

Optimal wavelength scale diffraction gratings for light trapping in solar cells

International Nuclear Information System (INIS)

Chong, Teck Kong; Wilson, Jonathan; Mokkapati, Sudha; Catchpole, Kylie R

2012-01-01

Dielectric gratings are a promising method of achieving light trapping for thin crystalline silicon solar cells. In this paper, we systematically examine the potential performance of thin silicon solar cells with either silicon (Si) or titanium dioxide (TiO 2 ) gratings using numerical simulations. The square pyramid structure with silicon nitride coating provides the best light trapping among all the symmetric structures investigated, with 89% of the expected short circuit current density of the Lambertian case. For structures where the grating is at the rear of the cell, we show that the light trapping provided by the square pyramid and the checkerboard structure is almost identical. Introducing asymmetry into the grating structures can further improve their light trapping properties. An optimized Si skewed pyramid grating on the front surface of the solar cell results in a maximum short circuit current density, J sc , of 33.4 mA cm −2 , which is 91% of the J sc expected from an ideal Lambertian scatterer. An optimized Si skewed pyramid grating on the rear performs as well as a rear Lambertian scatterer and an optimized TiO 2 grating on the rear results in 84% of the J sc expected from an optimized Si grating. The results show that submicron symmetric and skewed pyramids of Si or TiO 2 are a highly effective way of achieving light trapping in thin film solar cells. TiO 2 structures would have the additional advantage of not increasing recombination within the cell. (paper)

Comparison of linear, skewed-linear, and proportional hazard models for the analysis of lambing interval in Ripollesa ewes.

Science.gov (United States)

Casellas, J; Bach, R

2012-06-01

Lambing interval is a relevant reproductive indicator for sheep populations under continuous mating systems, although there is a shortage of selection programs accounting for this trait in the sheep industry. Both the historical assumption of small genetic background and its unorthodox distribution pattern have limited its implementation as a breeding objective. In this manuscript, statistical performances of 3 alternative parametrizations [i.e., symmetric Gaussian mixed linear (GML) model, skew-Gaussian mixed linear (SGML) model, and piecewise Weibull proportional hazard (PWPH) model] have been compared to elucidate the preferred methodology to handle lambing interval data. More specifically, flock-by-flock analyses were performed on 31,986 lambing interval records (257.3 ± 0.2 d) from 6 purebred Ripollesa flocks. Model performances were compared in terms of deviance information criterion (DIC) and Bayes factor (BF). For all flocks, PWPH models were clearly preferred; they generated a reduction of 1,900 or more DIC units and provided BF estimates larger than 100 (i.e., PWPH models against linear models). These differences were reduced when comparing PWPH models with different number of change points for the baseline hazard function. In 4 flocks, only 2 change points were required to minimize the DIC, whereas 4 and 6 change points were needed for the 2 remaining flocks. These differences demonstrated a remarkable degree of heterogeneity across sheep flocks that must be properly accounted for in genetic evaluation models to avoid statistical biases and suboptimal genetic trends. Within this context, all 6 Ripollesa flocks revealed substantial genetic background for lambing interval with heritabilities ranging between 0.13 and 0.19. This study provides the first evidence of the suitability of PWPH models for lambing interval analysis, clearly discarding previous parametrizations focused on mixed linear models.

Manycore processing of repeated range queries over massive moving objects observations

DEFF Research Database (Denmark)

Lettich, Francesco; Orlando, Salvatore; Silvestri, Claudio

2014-01-01

decomposition and allows to tackle effectively a broad range of spatial object distributions, even those very skewed. Also, to deal with the architectural peculiarities and limitations of the GPUs, we adopt non-trivial GPU data structures that avoid the need of locked memory accesses and favour coalesced memory...... accesses, thus enhancing the overall memory throughput. To the best of our knowledge this is the first work that exploits GPUs to efficiently solve repeated range queries over massive sets of continuously moving objects, characterized by highly skewed spatial distributions. In comparison with state...

The LMNA mutation p.Arg321Ter associated with dilated cardiomyopathy leads to reduced expression and a skewed ratio of lamin A and lamin C proteins

Energy Technology Data Exchange (ETDEWEB)

Al-Saaidi, Rasha [Research Unit for Molecular Medicine, Aarhus University and Aarhus University Hospital, Aarhus (Denmark); Rasmussen, Torsten B. [Department of Cardiology, Aarhus University Hospital, Aarhus (Denmark); Palmfeldt, Johan [Research Unit for Molecular Medicine, Aarhus University and Aarhus University Hospital, Aarhus (Denmark); Nissen, Peter H. [Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus (Denmark); Beqqali, Abdelaziz [Heart Failure Research Center, Academic Medical Center, Amsterdam (Netherlands); Hansen, Jakob [Department of Forensic Medicine, Bioanalytical Unit, University of Aarhus (Denmark); Pinto, Yigal M. [Heart Failure Research Center, Academic Medical Center, Amsterdam (Netherlands); Boesen, Thomas [Department of Molecular Biology and Genetics, University of Aarhus (Denmark); Mogensen, Jens [Department of Cardiology, Odense University Hospital, Odense (Denmark); Bross, Peter, E-mail: peter.bross@ki.au.dk [Research Unit for Molecular Medicine, Aarhus University and Aarhus University Hospital, Aarhus (Denmark)

2013-11-15

heterozygosity for the nonsense mutation causes NMD degradation of the mutant transcripts blocking expression of the truncated mutant protein and an additional trans effect on lamin A protein levels expressed from the wild type allele. We discuss the possibility that skewing of the lamin A to lamin C ratio may contribute to ensuing processes that destabilize cardiomyocytes and trigger cardiomyopathy - Highlights: • We study disease mechanisms in DCM patients carrying PTC mutations in the LMNA gene. • The mutant transcript is degraded by the nonsense mediated mRNA decay system. • Skewed lamin A to lamin C protein ratio expressed from the wild type allele. • We suggest a combined pathomechanism: haploinsuffiency plus lamin A/C imbalance.

Non-Gaussianity and cross-scale coupling in interplanetary magnetic field turbulence during a rope-rope magnetic reconnection event

Science.gov (United States)

Miranda, Rodrigo A.; Schelin, Adriane B.; Chian, Abraham C.-L.; Ferreira, José L.

2018-03-01

In a recent paper (Chian et al., 2016) it was shown that magnetic reconnection at the interface region between two magnetic flux ropes is responsible for the genesis of interplanetary intermittent turbulence. The normalized third-order moment (skewness) and the normalized fourth-order moment (kurtosis) display a quadratic relation with a parabolic shape that is commonly observed in observational data from turbulence in fluids and plasmas, and is linked to non-Gaussian fluctuations due to coherent structures. In this paper we perform a detailed study of the relation between the skewness and the kurtosis of the modulus of the magnetic field |B| during a triple interplanetary magnetic flux rope event. In addition, we investigate the skewness-kurtosis relation of two-point differences of |B| for the same event. The parabolic relation displays scale dependence and is found to be enhanced during magnetic reconnection, rendering support for the generation of non-Gaussian coherent structures via rope-rope magnetic reconnection. Our results also indicate that a direct coupling between the scales of magnetic flux ropes and the scales within the inertial subrange occurs in the solar wind.

Challenges for extension service to render efficient post-transformer ...

African Journals Online (AJOL)

LPhidza

A case study approach was applied and data was collected using a semi structured questionnaire and ... skewed family farming structure with about 50 000 large commercial family farmers and approximately 240 000 ..... help from government was important to sustain their businesses from one generation to the other.

Use of Quadratic Time-Frequency Representations to Analyze Cetacean Mammal Sounds

National Research Council Canada - National Science Library

Papandreou-Suppappola, Antonia

2001-01-01

.... Analysis of the group delay structure of the mammalian vocal communication signals was matched to the appropriate quadratic time-frequency class for proper signal processing with minimal skewing of the results...

Highly skewed T-cell receptor V-beta chain repertoire in the bone marrow is associated with response to immunosuppressive drug therapy in children with very severe aplastic anemia

Energy Technology Data Exchange (ETDEWEB)

Schuster, F R; Hubner, B [Clinic of Pediatric Oncology, Hematology and Clinical Immunology, Center for Child and Adolescent Health, Medical Faculty, Heinrich Heine University, Düsseldorf (Germany); Führer, M [Department of Pediatric Oncology and Hematology, Dr von Haunersches Children' s Hospital, University of Munich, Munich (Germany); Eckermann, O; Gombert, M [Clinic of Pediatric Oncology, Hematology and Clinical Immunology, Center for Child and Adolescent Health, Medical Faculty, Heinrich Heine University, Düsseldorf (Germany); Dornmair, K [Department for Clinical Neuroimmunology, University of Munich, Munich (Germany); Binder, V; Reuther, S; Krell, P [Clinic of Pediatric Oncology, Hematology and Clinical Immunology, Center for Child and Adolescent Health, Medical Faculty, Heinrich Heine University, Düsseldorf (Germany); Keller, T [Acomed, statistical analysis GmbH, Leipzig (Germany); Borkhardt, A [Clinic of Pediatric Oncology, Hematology and Clinical Immunology, Center for Child and Adolescent Health, Medical Faculty, Heinrich Heine University, Düsseldorf (Germany)

2011-03-01

One of the major obstacles of immunosuppressive therapy (IST) in children with severe aplastic anemia (SAA) comes from the often months-long unpredictability of bone-marrow (BM) recovery. In this prospective study in children with newly diagnosed very severe AA (n=10), who were enrolled in the therapy study SAA-BFM 94, we found a dramatically reduced diversity of both CD4+ and CD8+ BM cells, as scored by comprehensive V-beta chain T-cell receptor (TCR) analysis. Strongly skewed TCR V-beta pattern was highly predictive for good or at least partial treatment response (n=6, CD8+ complexity scoring median 35.5, range 24–73). In contrast, IST in patients with rather moderate reduction of TCR V-beta diversity (n=4, CD8+ complexity scoring median 109.5, range 82–124) always failed (P=0.0095). If confirmed in a larger series of patients, TCR V-beta repertoire in BM may help to assign children with SAA up-front either to IST or to allogeneic stem-cell transplantation.

Highly skewed T-cell receptor V-beta chain repertoire in the bone marrow is associated with response to immunosuppressive drug therapy in children with very severe aplastic anemia

International Nuclear Information System (INIS)

Schuster, F R; Hubner, B; Führer, M; Eckermann, O; Gombert, M; Dornmair, K; Binder, V; Reuther, S; Krell, P; Keller, T; Borkhardt, A

2011-01-01

One of the major obstacles of immunosuppressive therapy (IST) in children with severe aplastic anemia (SAA) comes from the often months-long unpredictability of bone-marrow (BM) recovery. In this prospective study in children with newly diagnosed very severe AA (n=10), who were enrolled in the therapy study SAA-BFM 94, we found a dramatically reduced diversity of both CD4+ and CD8+ BM cells, as scored by comprehensive V-beta chain T-cell receptor (TCR) analysis. Strongly skewed TCR V-beta pattern was highly predictive for good or at least partial treatment response (n=6, CD8+ complexity scoring median 35.5, range 24–73). In contrast, IST in patients with rather moderate reduction of TCR V-beta diversity (n=4, CD8+ complexity scoring median 109.5, range 82–124) always failed (P=0.0095). If confirmed in a larger series of patients, TCR V-beta repertoire in BM may help to assign children with SAA up-front either to IST or to allogeneic stem-cell transplantation

Skewed sex ratios and criminal victimization in India.

Science.gov (United States)

South, Scott J; Trent, Katherine; Bose, Sunita

2014-06-01

Although substantial research has explored the causes of India's excessively masculine population sex ratio, few studies have examined the consequences of this surplus of males. We merge individual-level data from the 2004-2005 India Human Development Survey with data from the 2001 India population census to examine the association between the district-level male-to-female sex ratio at ages 15 to 39 and self-reports of victimization by theft, breaking and entering, and assault. Multilevel logistic regression analyses reveal positive and statistically significant albeit substantively modest effects of the district-level sex ratio on all three victimization risks. We also find that higher male-to-female sex ratios are associated with the perception that young unmarried women in the local community are frequently harassed. Household-level indicators of family structure, socioeconomic status, and caste, as well as areal indicators of women's empowerment and collective efficacy, also emerge as significant predictors of self-reported criminal victimization and the perceived harassment of young women. The implications of these findings for India's growing sex ratio imbalance are discussed.

Skewed Sex Ratios and Criminal Victimization in India

Science.gov (United States)

South, Scott J.; Trent, Katherine; Bose, Sunita

2014-01-01

Although substantial research has explored the causes of India’s excessively masculine population sex ratio, few studies have examined the consequences of this surplus of males. We merge individual-level data from the 2004–2005 India Human Development Survey with data from the 2001 India population census to examine the association between the district-level male-to-female sex ratio at ages 15 to 39 and self-reports of victimization by theft, breaking and entering, and assault. Multilevel logistic regression analyses reveal positive and statistically significant albeit substantively modest effects of the district-level sex ratio on all three victimization risks. We also find that higher male-to-female sex ratios are associated with the perception that young unmarried women in the local community are frequently harassed. Household-level indicators of family structure, socioeconomic status, and caste, as well as areal indicators of women’s empowerment and collective efficacy, also emerge as significant predictors of self-reported criminal victimization and the perceived harassment of young women. The implications of these findings for India’s growing sex ratio imbalance are discussed. PMID:24682921

Long-term behavior of integral abutment bridges.

Science.gov (United States)

2011-01-01

Integral abutment (IA) construction has become the preferred method over conventional construction for use with typical : highway bridges. However, the use of these structures is limited due to state mandated length and skew limitations. To : expand ...

Dynamics of suspended sediment concentration, flow discharge and sediment particle size interdependency to identify sediment source

Science.gov (United States)

Sadeghi, Seyed Hamidreza; Singh, Vijay P.

2017-11-01

Spatiotemporal behavior of sediment yield is a key for proper watershed management. This study analyzed statistical characteristics and trends of suspended sediment concentration (SCS), flow discharge (FD) and sediment particle sizes using data from 24 gage stations scattered throughout the United States. Analysis showed significant time- and location-specific differences of these variables. The median values of SSC, FD and percentage of particle sizes smaller than 63 μm (P63) for all 24 gage stations were found to be 510.236 mg l-1 (right skewed), 45.406 m3 s-1 (left skewed) and 78.648% (right skewed), respectively. Most of the stations exhibited significant trends (P practices which may call for local or regional planning based on natural (i.e., precipitation amount, type and erosivity, watershed area, and soil erodibility) and human-affected (i.e., land use and hydraulic structures and water resources management) factors governing the study variables.

Improvement of detection of stress corrosion cracks with ultrasonic phased array probes

International Nuclear Information System (INIS)

Wustenberg, H.; Mohrle, W.; Wegner, W.; Schenk, G.; Erhard, A.

1986-01-01

Probes with linear arrays can be used for the detection of stress corrosion cracks especially if the variability of the sound field is used to change the skewing angle of angle beam probes. The phased array concept can be used to produce a variable skewing angle or a variable angle of incidence depending on the orientation of the linear array on the wedge. This helps to adapt the direction of the ultrasonic beam to probable crack orientations. It has been demonstrated with artificial reflectors as well as with corrosion cracks, that the detection of misoriented cracks can be improved by this approach. The experiences gained during the investigations are encouraging the application of phased array probes for stress corrosion phenomena close to the heat effected zone of welds. Probes with variable skewing angles may find some interesting applications on welds in tubular structures e.g., at off shore constructions and on some difficult geometries within the primary circuit of nuclear power plants

Nicotine can skew the characterization of the macrophage type-1 (M{Phi}1) phenotype differentiated with granulocyte-macrophage colony-stimulating factor to the M{Phi}2 phenotype

Energy Technology Data Exchange (ETDEWEB)

Yanagita, Manabu; Kobayashi, Ryohei [Department of Periodontology, Division of Oral Biology and Disease Control, Osaka University Graduate School of Dentistry, Osaka 565-0871 (Japan); Murakami, Shinya, E-mail: ipshinya@dent.osaka-u.ac.jp [Department of Periodontology, Division of Oral Biology and Disease Control, Osaka University Graduate School of Dentistry, Osaka 565-0871 (Japan)

2009-10-09

Macrophages (M{Phi}s) exhibit functional heterogeneity and plasticity in the local microenvironment. Recently, it was reported that M{Phi}s can be divided into proinflammatory M{Phi}s (M{Phi}1) and anti-inflammatory M{Phi}s (M{Phi}2) based on their polarized functional properties. Here, we report that nicotine, the major ingredient of cigarette smoke, can modulate the characteristics of M{Phi}1. Granulocyte-macrophage colony-stimulating factor-driven M{Phi}1 with nicotine (Ni-M{Phi}1) showed the phenotypic characteristics of M{Phi}2. Like M{Phi}2, Ni-M{Phi}1 exhibited antigen-uptake activities. Ni-M{Phi}1 suppressed IL-12, but maintained IL-10 and produced high amounts of MCP-1 upon lipopolysaccharide stimulation compared with M{Phi}1. Moreover, we observed strong proliferative responses of T cells to lipopolysaccharide-stimulated M{Phi}1, whereas Ni-M{Phi}1 reduced T cell proliferation and inhibited IFN-{gamma} production by T cells. These results suggest that nicotine can change the functional characteristics of M{Phi} and skew the M{Phi}1 phenotype to M{Phi}2. We propose that nicotine is a potent regulator that modulates immune responses in microenvironments.

The structure of a three-dimensional boundary layer subjected to streamwise-varying spanwise-homogeneous pressure gradient

International Nuclear Information System (INIS)

Bentaleb, Y.; Leschziner, M.A.

2013-01-01

Highlights: • We study a spatially-evolving three-dimensional boundary layer. • We impose a streamwise-varying spanwise-homogeneous pressure gradient. • A collateral flow is formed close to the wall, and this is investigated alongside the skewed upper part of the boundary layer. • A wide range of flow-physical properties have been studied. -- Abstract: A spatially-evolving three-dimensional boundary layer, subjected to a streamwise-varying spanwise-homogeneous pressure gradient, equivalent to a body force, is investigated by way of direct numerical simulation. The pressure gradient, prescribed to change its sign half-way along the boundary layer, provokes strong skewing of the velocity vector, with a layer of nearly collateral flow forming close to the wall up to the position of maximum spanwise velocity. A wide range of flow-physical properties have been studied, with particular emphasis on the near-wall layer, including second-moments, major budget contributions and wall-normal two-point correlations of velocity fluctuations and their angles, relative to wall-shear fluctuations. The results illustrate the complexity caused by skewing, including a damping in turbulent mixing and a significant lag between strains and stresses. The study has been undertaken in the context of efforts to develop and test novel hybrid LES–RANS schemes for non-equilibrium near-wall flows, with an emphasis on three-dimensional near-wall straining. Fundamental flow-physical issues aside, the data derived should be of particular relevance to a priori studies of second-moment RANS closure and the development and validation of RANS-type near-wall approximations implemented in LES schemes for high-Reynolds-number complex flows

Estimating flood magnitude and frequency at gaged and ungaged sites on streams in Alaska and conterminous basins in Canada, based on data through water year 2012

Science.gov (United States)

Curran, Janet H.; Barth, Nancy A.; Veilleux, Andrea G.; Ourso, Robert T.

2016-03-16

Estimates of the magnitude and frequency of floods are needed across Alaska for engineering design of transportation and water-conveyance structures, flood-insurance studies, flood-plain management, and other water-resource purposes. This report updates methods for estimating flood magnitude and frequency in Alaska and conterminous basins in Canada. Annual peak-flow data through water year 2012 were compiled from 387 streamgages on unregulated streams with at least 10 years of record. Flood-frequency estimates were computed for each streamgage using the Expected Moments Algorithm to fit a Pearson Type III distribution to the logarithms of annual peak flows. A multiple Grubbs-Beck test was used to identify potentially influential low floods in the time series of peak flows for censoring in the flood frequency analysis.For two new regional skew areas, flood-frequency estimates using station skew were computed for stations with at least 25 years of record for use in a Bayesian least-squares regression analysis to determine a regional skew value. The consideration of basin characteristics as explanatory variables for regional skew resulted in improvements in precision too small to warrant the additional model complexity, and a constant model was adopted. Regional Skew Area 1 in eastern-central Alaska had a regional skew of 0.54 and an average variance of prediction of 0.45, corresponding to an effective record length of 22 years. Regional Skew Area 2, encompassing coastal areas bordering the Gulf of Alaska, had a regional skew of 0.18 and an average variance of prediction of 0.12, corresponding to an effective record length of 59 years. Station flood-frequency estimates for study sites in regional skew areas were then recomputed using a weighted skew incorporating the station skew and regional skew. In a new regional skew exclusion area outside the regional skew areas, the density of long-record streamgages was too sparse for regional analysis and station skew was used

Nutritional skewing of conceptus sex in sheep: effects of a maternal diet enriched in rumen-protected polyunsaturated fatty acids (PUFA

Directory of Open Access Journals (Sweden)

Williams Jim E

2008-06-01

Full Text Available Abstract Background Evolutionary theory suggests that in polygynous mammalian species females in better body condition should produce more sons than daughters. Few controlled studies have however tested this hypothesis and controversy exists as to whether body condition score or maternal diet is in fact the determining factor of offspring sex. Here, we examined whether maternal diet, specifically increased n-6 polyunsaturated fatty acid (PUFA intake, of ewes with a constant body condition score around the time of conception influenced sex ratio. Methods Ewes (n = 44 maintained in similar body condition throughout the study were assigned either a control (C diet or one (F enriched in rumen-protected PUFA, but otherwise essentially equivalent, from four weeks prior to breeding until d13 post-estrus. On d13, conceptuses were recovered, measured, cultured to assess their capacity for interferon-tau (IFNT production and their sex determined. The experiment was repeated with all ewes being fed the F diet to remove any effects of parity order on sex ratio. Maternal body condition score (BCS, plasma hormone and metabolite concentrations were also assessed throughout the study and related to diet. Results In total 129 conceptuses were recovered. Ewes on the F diet produced significantly more male than female conceptuses (proportion male = 0.69; deviation from expected ratio of 0.5, P 0.1, but positively correlated with maternal body condition score (P Conclusion These results provide evidence that maternal diet, in the form of increased amounts of rumen-protected PUFA fed around conception, rather than maternal body condition, can skew the sex ratio towards males. These observations may have implications to the livestock industry and animal management policies when offspring of one sex may be preferred over the other.

Hunting or habitat? Drivers of waterbird abundance and community structure in agricultural wetlands of southern India.

Science.gov (United States)

Ramachandran, Ramesh; Kumar, Ajith; Gopi Sundar, Kolla S; Bhalla, Ravinder Singh

2017-09-01

The relative impacts of hunting and habitat on waterbird community were studied in agricultural wetlands of southern India. We surveyed wetlands to document waterbird community, and interviewed hunters to document hunting intensity, targeted species, and the motivations for hunting. Our results show that hunting leads to drastic declines in waterbird diversity and numbers, and skew the community towards smaller species. Hunting intensity, water spread, and vegetation cover were the three most important determinants of waterbird abundance and community structure. Species richness, density of piscivorous species, and medium-sized species (31-65 cm) were most affected by hunting. Out of 53 species recorded, 47 were hunted, with a preference for larger birds. Although illegal, hunting has increased in recent years and is driven by market demand. This challenges the widely held belief that waterbird hunting in India is a low intensity, subsistence activity, and undermines the importance of agricultural wetlands in waterbird conservation.

Structural, magnetic and transport properties of Co2FeAl Heusler films with varying thickness

International Nuclear Information System (INIS)

Wang, Xiaotian; Li, Yueqing; Du, Yin; Dai, Xuefang; Liu, Guodong; Liu, Enke; Liu, Zhongyuan; Wang, Wenhong; Wu, Guangheng

2014-01-01

We report on a systematic study of the structural, magnetic properties and the anomalous Hall effect, in the Heusler alloy Co 2 FeAl (CFA) epitaxial films on MgO (001), as a function of film thickness. It was found that the epitaxial CFA films show a highly ordered B2 structure with an in-plane uniaxial magnetic anisotropy. The electrical transport properties reveal that the lattice and magnon scattering contributions to the longitudinal resistivity. Independent on the thickness of films, the anomalous Hall resistivity of CFA films is found to be dominated by skew scattering only. Moreover, the anomalous Hall resistivity shows weakly temperature dependent behavior, and its absolute value increases as the thickness decreases. We attribute this temperature insensitivity in the anomalous Hall resistivity to the weak temperature dependent of tunneling spin-polarization in the CFA films, while the thickness dependence behavior is likely due to the increasing significance of interface or free surface electronic states. - Highlights: ●Highly ordered CFA films with various thicknesses were prepared on MgO substrates. ●The magnon scattering contributions to the longitudinal resistivity in the CFA films. ●The anomalous Hall resistivity of the CFA films shows weakly temperature dependent. ●The CFA films show weak temperature dependent of tunneling spin-polarization

Reproductive sharing among queens in the ant Formica fusca

OpenAIRE

Minttumaaria Hannonen; Liselotte Sundstro¨m

2003-01-01

Reproductive sharing among cobreeders, in which reproductive shares may vary from equal contribution (low reproductive skew) to reproductive dominance by one individual (high reproductive skew), is a fundamental feature of animal societies. Recent theoretical work, the reproductive skew models, has focused on factors affecting the degree to which reproduction is skewed within a society. We used the parameters provided by skew models as a guideline to study determinants of reproductive sharing...

The impact of mating systems and dispersal on fine-scale genetic structure at maternally, paternally and biparentally inherited markers.

Science.gov (United States)

Shaw, Robyn E; Banks, Sam C; Peakall, Rod

2018-01-01

For decades, studies have focused on how dispersal and mating systems influence genetic structure across populations or social groups. However, we still lack a thorough understanding of how these processes and their interaction shape spatial genetic patterns over a finer scale (tens-hundreds of metres). Using uniparentally inherited markers may help answer these questions, yet their potential has not been fully explored. Here, we use individual-level simulations to investigate the effects of dispersal and mating system on fine-scale genetic structure at autosomal, mitochondrial and Y chromosome markers. Using genetic spatial autocorrelation analysis, we found that dispersal was the major driver of fine-scale genetic structure across maternally, paternally and biparentally inherited markers. However, when dispersal was restricted (mean distance = 100 m), variation in mating behaviour created strong differences in the comparative level of structure detected at maternally and paternally inherited markers. Promiscuity reduced spatial genetic structure at Y chromosome loci (relative to monogamy), whereas structure increased under polygyny. In contrast, mitochondrial and autosomal markers were robust to differences in the specific mating system, although genetic structure increased across all markers when reproductive success was skewed towards fewer individuals. Comparing males and females at Y chromosome vs. mitochondrial markers, respectively, revealed that some mating systems can generate similar patterns to those expected under sex-biased dispersal. This demonstrates the need for caution when inferring ecological and behavioural processes from genetic results. Comparing patterns between the sexes, across a range of marker types, may help us tease apart the processes shaping fine-scale genetic structure. © 2017 John Wiley & Sons Ltd.

Analysis of a genetically structured variance heterogeneity model using the Box-Cox transformation.

Science.gov (United States)

Yang, Ye; Christensen, Ole F; Sorensen, Daniel

2011-02-01

Over recent years, statistical support for the presence of genetic factors operating at the level of the environmental variance has come from fitting a genetically structured heterogeneous variance model to field or experimental data in various species. Misleading results may arise due to skewness of the marginal distribution of the data. To investigate how the scale of measurement affects inferences, the genetically structured heterogeneous variance model is extended to accommodate the family of Box-Cox transformations. Litter size data in rabbits and pigs that had previously been analysed in the untransformed scale were reanalysed in a scale equal to the mode of the marginal posterior distribution of the Box-Cox parameter. In the rabbit data, the statistical evidence for a genetic component at the level of the environmental variance is considerably weaker than that resulting from an analysis in the original metric. In the pig data, the statistical evidence is stronger, but the coefficient of correlation between additive genetic effects affecting mean and variance changes sign, compared to the results in the untransformed scale. The study confirms that inferences on variances can be strongly affected by the presence of asymmetry in the distribution of data. We recommend that to avoid one important source of spurious inferences, future work seeking support for a genetic component acting on environmental variation using a parametric approach based on normality assumptions confirms that these are met.

Reformulation of the Children's Eating Attitudes Test (ChEAT): factor structure and scoring method in a non-clinical population.

Science.gov (United States)

Anton, S D; Han, H; Newton, R L; Martin, C K; York-Crowe, E; Stewart, T M; Williamson, D A

2006-12-01

The primary aims of this study were to empirically test the factor structure of the Children's Eating Attitudes Test (ChEAT) through both exploratory and confirmatory factor analyses and to interpret the factor structure of the ChEAT within the context of a new scoring method. The ChEAT was administered to 728 children in the 2nd through 6th grades (from five schools) at two different time points. Exactly half the students were male and half were female. To the best of our knowledge, this is the first study to empirically test the merits of an alternative 6-point scoring system as compared to the traditionally used 4-point scoring system. With the new scoring procedure, the skewness for all factor scores decreased, which resulted in increased variance in the item scores, as well as the total ChEAT score. Since the internal consistency of two factors in a recently proposed model was not acceptable (ChEAT reported by previous investigations. Intercorrelations among the factors suggested three higher order constructs. These findings indicate that the ChEAT subscales may be sufficiently stable to allow use in non-clinical samples of children.

Structural, magnetic and transport properties of Co{sub 2}FeAl Heusler films with varying thickness

Energy Technology Data Exchange (ETDEWEB)

Wang, Xiaotian [School of Material Sciences and Engineering, Hebei University Technology, Tianjin 300130 (China); Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Li, Yueqing [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); State Key Laboratory of Metastable Material Sciences and Technology, Yanshan University, Qinhuangdao 066004 (China); Du, Yin [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Dai, Xuefang; Liu, Guodong [School of Material Sciences and Engineering, Hebei University Technology, Tianjin 300130 (China); Liu, Enke [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Liu, Zhongyuan [State Key Laboratory of Metastable Material Sciences and Technology, Yanshan University, Qinhuangdao 066004 (China); Wang, Wenhong, E-mail: wenhong.wang@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wu, Guangheng [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2014-08-01

We report on a systematic study of the structural, magnetic properties and the anomalous Hall effect, in the Heusler alloy Co{sub 2}FeAl (CFA) epitaxial films on MgO (001), as a function of film thickness. It was found that the epitaxial CFA films show a highly ordered B2 structure with an in-plane uniaxial magnetic anisotropy. The electrical transport properties reveal that the lattice and magnon scattering contributions to the longitudinal resistivity. Independent on the thickness of films, the anomalous Hall resistivity of CFA films is found to be dominated by skew scattering only. Moreover, the anomalous Hall resistivity shows weakly temperature dependent behavior, and its absolute value increases as the thickness decreases. We attribute this temperature insensitivity in the anomalous Hall resistivity to the weak temperature dependent of tunneling spin-polarization in the CFA films, while the thickness dependence behavior is likely due to the increasing significance of interface or free surface electronic states. - Highlights: ●Highly ordered CFA films with various thicknesses were prepared on MgO substrates. ●The magnon scattering contributions to the longitudinal resistivity in the CFA films. ●The anomalous Hall resistivity of the CFA films shows weakly temperature dependent. ●The CFA films show weak temperature dependent of tunneling spin-polarization.

A comparison of methods to handle skew distributed cost variables in the analysis of the resource consumption in schizophrenia treatment.

Science.gov (United States)

Kilian, Reinhold; Matschinger, Herbert; Löeffler, Walter; Roick, Christiane; Angermeyer, Matthias C

2002-03-01

Transformation of the dependent cost variable is often used to solve the problems of heteroscedasticity and skewness in linear ordinary least square regression of health service cost data. However, transformation may cause difficulties in the interpretation of regression coefficients and the retransformation of predicted values. The study compares the advantages and disadvantages of different methods to estimate regression based cost functions using data on the annual costs of schizophrenia treatment. Annual costs of psychiatric service use and clinical and socio-demographic characteristics of the patients were assessed for a sample of 254 patients with a diagnosis of schizophrenia (ICD-10 F 20.0) living in Leipzig. The clinical characteristics of the participants were assessed by means of the BPRS 4.0, the GAF, and the CAN for service needs. Quality of life was measured by WHOQOL-BREF. A linear OLS regression model with non-parametric standard errors, a log-transformed OLS model and a generalized linear model with a log-link and a gamma distribution were used to estimate service costs. For the estimation of robust non-parametric standard errors, the variance estimator by White and a bootstrap estimator based on 2000 replications were employed. Models were evaluated by the comparison of the R2 and the root mean squared error (RMSE). RMSE of the log-transformed OLS model was computed with three different methods of bias-correction. The 95% confidence intervals for the differences between the RMSE were computed by means of bootstrapping. A split-sample-cross-validation procedure was used to forecast the costs for the one half of the sample on the basis of a regression equation computed for the other half of the sample. All three methods showed significant positive influences of psychiatric symptoms and met psychiatric service needs on service costs. Only the log- transformed OLS model showed a significant negative impact of age, and only the GLM shows a significant

Morphology and structural studies of WO_3 films deposited on SrTiO_3 by pulsed laser deposition

International Nuclear Information System (INIS)

Kalhori, Hossein; Porter, Stephen B.; Esmaeily, Amir Sajjad; Coey, Michael; Ranjbar, Mehdi; Salamati, Hadi

2016-01-01

Highlights: • Highly oriented WO_3 stoichiometric films were determined using pulsed laser deposition method. • Effective parameters on thin films including temperature, oxygen partial pressure and laser energy fluency was studied. • A phase transition was observed in WO_3 films at 700 °C from monoclinic to tetragonal. - Abstract: WO_3 films have been grown by pulsed laser deposition on SrTiO_3 (001) substrates. The effects of substrate temperature, oxygen partial pressure and energy fluence of the laser beam on the physical properties of the films were studied. Reflection high-energy electron diffraction (RHEED) patterns during and after growth were used to determine the surface structure and morphology. The chemical composition and crystalline phases were obtained by XPS and XRD respectively. AFM results showed that the roughness and skewness of the films depend on the substrate temperature during deposition. Optimal conditions were determined for the growth of the highly oriented films.

Magnetic focusing in triangular electron billiards

DEFF Research Database (Denmark)

Bøggild, Peter; Kristensen, A.; Lindelof, Poul Erik

1999-01-01

The classical ballistic magnetotransport in triangular electron billiards fabricated in a high mobility GaAs heterostructure has been studied at 4.2 K. The sample geometry may be viewed as a double-slit structure with a skewed injection angle. We observe a striking cancellation of the magnetic...... focusing spectrum compared to the case of a perpendicular injection angle. From numerical and analytical analysis, we confirm that the quenching is a fundamental geometrical effect, and identify two mechanisms responsible for the anomaly. The focusing spectrum of the considered skewed geometry...... is remarkably sensitive to the angular distribution of injected electrons as well as the overall injection angle. [S0163-1829(99)06619-9]....

Inferring network structure in non-normal and mixed discrete-continuous genomic data.

Science.gov (United States)

Bhadra, Anindya; Rao, Arvind; Baladandayuthapani, Veerabhadran

2018-03-01

Inferring dependence structure through undirected graphs is crucial for uncovering the major modes of multivariate interaction among high-dimensional genomic markers that are potentially associated with cancer. Traditionally, conditional independence has been studied using sparse Gaussian graphical models for continuous data and sparse Ising models for discrete data. However, there are two clear situations when these approaches are inadequate. The first occurs when the data are continuous but display non-normal marginal behavior such as heavy tails or skewness, rendering an assumption of normality inappropriate. The second occurs when a part of the data is ordinal or discrete (e.g., presence or absence of a mutation) and the other part is continuous (e.g., expression levels of genes or proteins). In this case, the existing Bayesian approaches typically employ a latent variable framework for the discrete part that precludes inferring conditional independence among the data that are actually observed. The current article overcomes these two challenges in a unified framework using Gaussian scale mixtures. Our framework is able to handle continuous data that are not normal and data that are of mixed continuous and discrete nature, while still being able to infer a sparse conditional sign independence structure among the observed data. Extensive performance comparison in simulations with alternative techniques and an analysis of a real cancer genomics data set demonstrate the effectiveness of the proposed approach. © 2017, The International Biometric Society.

Cogging Torque Reduction in Brushless DC Motors Using Slot-Opening Shift

Directory of Open Access Journals (Sweden)

SAIED, S. A.

2009-02-01

Full Text Available In this paper, two new methods for the stator skew are introduced. In contrary with the conventional stator skew, this paper is concentrate on the slot-opening skew. The simula-tion result by finite element shows a considerable reduction in the cogging torque of the motors, the new methods are applied to. Moreover the simulations justify that the back-EMF shape remains trapezoidal for various skew angles in contrary with that in the conventional skew, this fact makes the method highly applicable in BLDC motors.

The distribution of cigarette prices under different tax structures: findings from the International Tobacco Control Policy Evaluation (ITC) Project.

Science.gov (United States)

Shang, Ce; Chaloupka, Frank J; Zahra, Nahleen; Fong, Geoffrey T

2014-03-01

The distribution of cigarette prices has rarely been studied and compared under different tax structures. Descriptive evidence on price distributions by countries can shed light on opportunities for tax avoidance and brand switching under different tobacco tax structures, which could impact the effectiveness of increased taxation in reducing smoking. This paper aims to describe the distribution of cigarette prices by countries and to compare these distributions based on the tobacco tax structure in these countries. We employed data for 16 countries taken from the International Tobacco Control Policy Evaluation Project to construct survey-derived cigarette prices for each country. Self-reported prices were weighted by cigarette consumption and described using a comprehensive set of statistics. We then compared these statistics for cigarette prices under different tax structures. In particular, countries of similar income levels and countries that impose similar total excise taxes using different tax structures were paired and compared in mean and variance using a two-sample comparison test. Our investigation illustrates that, compared with specific uniform taxation, other tax structures, such as ad valorem uniform taxation, mixed (a tax system using ad valorem and specific taxes) uniform taxation, and tiered tax structures of specific, ad valorem and mixed taxation tend to have price distributions with greater variability. Countries that rely heavily on ad valorem and tiered taxes also tend to have greater price variability around the median. Among mixed taxation systems, countries that rely more heavily on the ad valorem component tend to have greater price variability than countries that rely more heavily on the specific component. In countries with tiered tax systems, cigarette prices are skewed more towards lower prices than are prices under uniform tax systems. The analyses presented here demonstrate that more opportunities exist for tax avoidance and brand

The distribution of cigarette prices under different tax structures: findings from the International Tobacco Control Policy Evaluation (ITC) Project

Science.gov (United States)

Shang, Ce; Chaloupka, Frank J; Zahra, Nahleen; Fong, Geoffrey T

2013-01-01

Background The distribution of cigarette prices has rarely been studied and compared under different tax structures. Descriptive evidence on price distributions by countries can shed light on opportunities for tax avoidance and brand switching under different tobacco tax structures, which could impact the effectiveness of increased taxation in reducing smoking. Objective This paper aims to describe the distribution of cigarette prices by countries and to compare these distributions based on the tobacco tax structure in these countries. Methods We employed data for 16 countries taken from the International Tobacco Control Policy Evaluation Project to construct survey-derived cigarette prices for each country. Self-reported prices were weighted by cigarette consumption and described using a comprehensive set of statistics. We then compared these statistics for cigarette prices under different tax structures. In particular, countries of similar income levels and countries that impose similar total excise taxes using different tax structures were paired and compared in mean and variance using a two-sample comparison test. Findings Our investigation illustrates that, compared with specific uniform taxation, other tax structures, such as ad valorem uniform taxation, mixed (a tax system using ad valorem and specific taxes) uniform taxation, and tiered tax structures of specific, ad valorem and mixed taxation tend to have price distributions with greater variability. Countries that rely heavily on ad valorem and tiered taxes also tend to have greater price variability around the median. Among mixed taxation systems, countries that rely more heavily on the ad valorem component tend to have greater price variability than countries that rely more heavily on the specific component. In countries with tiered tax systems, cigarette prices are skewed more towards lower prices than are prices under uniform tax systems. The analyses presented here demonstrate that more opportunities

75 FR 76505 - Self-Regulatory Organizations; Notice of Filing and Immediate Effectiveness of a Proposed Rule...

Science.gov (United States)

2010-12-08

..., 2010) (Concept Release on Equity Market Structure, ``Concept Release''). See also Mary L. Schapiro... believes that the inclusion of partial trading days \\7\\ may serve to improperly skew the operative... system which NASDAQ operates or controls, and it is designed to promote just and equitable principles of...

Morphology and structural studies of WO{sub 3} films deposited on SrTiO{sub 3} by pulsed laser deposition

Energy Technology Data Exchange (ETDEWEB)

Kalhori, Hossein, E-mail: h.kalhori@ph.iut.ac.ir [School of Physics and CRANN, Trinity College, Dublin 2 (Ireland); Department of Physics, Isfahan University of Technology, Isfahan 84156-8311 (Iran, Islamic Republic of); Porter, Stephen B.; Esmaeily, Amir Sajjad; Coey, Michael [School of Physics and CRANN, Trinity College, Dublin 2 (Ireland); Ranjbar, Mehdi; Salamati, Hadi [Department of Physics, Isfahan University of Technology, Isfahan 84156-8311 (Iran, Islamic Republic of)

2016-12-30

Highlights: • Highly oriented WO{sub 3} stoichiometric films were determined using pulsed laser deposition method. • Effective parameters on thin films including temperature, oxygen partial pressure and laser energy fluency was studied. • A phase transition was observed in WO{sub 3} films at 700 °C from monoclinic to tetragonal. - Abstract: WO{sub 3} films have been grown by pulsed laser deposition on SrTiO{sub 3} (001) substrates. The effects of substrate temperature, oxygen partial pressure and energy fluence of the laser beam on the physical properties of the films were studied. Reflection high-energy electron diffraction (RHEED) patterns during and after growth were used to determine the surface structure and morphology. The chemical composition and crystalline phases were obtained by XPS and XRD respectively. AFM results showed that the roughness and skewness of the films depend on the substrate temperature during deposition. Optimal conditions were determined for the growth of the highly oriented films.

Low Risk Anomalies?

DEFF Research Database (Denmark)

Schneider, Paul; Wagner, Christian; Zechner, Josef

This paper shows theoretically and empirically that beta- and volatility-based low risk anomalies are driven by return skewness. The empirical patterns concisely match the predictions of our model that endogenizes the role of skewness for stock returns through default risk. With increasing downside...... risk, the standard capital asset pricing model (CAPM) increasingly overestimates expected equity returns relative to firms' true (skew-adjusted) market risk. Empirically, the profitability of betting against beta/volatility increases with firms' downside risk, and the risk-adjusted return differential...... of betting against beta/volatility among low skew firms compared to high skew firms is economically large. Our results suggest that the returns to betting against beta or volatility do not necessarily pose asset pricing puzzles but rather that such strategies collect premia that compensate for skew risk...

Global network structure of dominance hierarchy of ant workers.

Science.gov (United States)

Shimoji, Hiroyuki; Abe, Masato S; Tsuji, Kazuki; Masuda, Naoki

2014-10-06

Dominance hierarchy among animals is widespread in various species and believed to serve to regulate resource allocation within an animal group. Unlike small groups, however, detection and quantification of linear hierarchy in large groups of animals are a difficult task. Here, we analyse aggression-based dominance hierarchies formed by worker ants in Diacamma sp. as large directed networks. We show that the observed dominance networks are perfect or approximate directed acyclic graphs, which are consistent with perfect linear hierarchy. The observed networks are also sparse and random but significantly different from networks generated through thinning of the perfect linear tournament (i.e. all individuals are linearly ranked and dominance relationship exists between every pair of individuals). These results pertain to global structure of the networks, which contrasts with the previous studies inspecting frequencies of different types of triads. In addition, the distribution of the out-degree (i.e. number of workers that the focal worker attacks), not in-degree (i.e. number of workers that attack the focal worker), of each observed network is right-skewed. Those having excessively large out-degrees are located near the top, but not the top, of the hierarchy. We also discuss evolutionary implications of the discovered properties of dominance networks. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Multilateral organizations and global inequality: A focus on IMF ...

African Journals Online (AJOL)

The paper examines issues relating to multilateral organizations, taking a particular look at the three multilateral organizations viz IMF, World Bank and WTO. It establishes that institutional and structural variables in the multilateral organizations are skewed in favour of the developed countries and this tends to entrench their ...

X-Ray Topography of the Subsurface Crystal Layers in the Skew Asymmetric Reflection Geometry

Directory of Open Access Journals (Sweden)

Swiątek Z.

2016-12-01

Full Text Available The technique of X ray topography with the asymmetric reflection geometry of X-ray diffraction presented in this paper as useful tool for structural characterization of materials, particularly, epitaxial thin films and semiconductor multi-layered crystal systems used for the optoelectronic devices. New possibilities of this technique for a layer-by-layer visualization of structural changes in the subsurface crystal layers are demonstrated for semiconductors after various types of surface treatment, such as chemical etching, laser irradiation and ion implantation.

Tailoring the laser pulse shape to improve the quality of the self-injected electron beam in laser wakefield acceleration

International Nuclear Information System (INIS)

Upadhyay, Ajay K.; Samant, Sushil A.; Krishnagopal, S.

2013-01-01

In laser wakefield acceleration, tailoring the shape of the laser pulse is one way of influencing the laser-plasma interaction and, therefore, of improving the quality of the self-injected electron beam in the bubble regime. Using three-dimensional particle-in-cell simulations, the evolution dynamics of the laser pulse and the quality of the self-injected beam, for a Gaussian pulse, a positive skew pulse (i.e., one with sharp rise and slow fall), and a negative skew pulse (i.e., one with a slow rise and sharp fall) are studied. It is observed that with a negative skew laser pulse there is a substantial improvement in the emittance (by around a factor of two), and a modest improvement in the energy-spread, compared to Gaussian as well as positive skew pulses. However, the injected charge is less in the negative skew pulse compared to the other two. It is also found that there is an optimal propagation distance that gives the best beam quality; beyond this distance, though the energy increases, the beam quality deteriorates, but this deterioration is least for the negative skew pulse. Thus, the negative skew pulse gives an improvement in terms of beam quality (emittance and energy spread) over what one can get with a Gaussian or positive skew pulse. In part, this is because of the lesser injected charge, and the strong suppression of continuous injection for the negative skew pulse.

Gene organization inside replication domains in mammalian genomes

Science.gov (United States)

Zaghloul, Lamia; Baker, Antoine; Audit, Benjamin; Arneodo, Alain

2012-11-01

We investigate the large-scale organization of human genes with respect to "master" replication origins that were previously identified as bordering nucleotide compositional skew domains. We separate genes in two categories depending on their CpG enrichment at the promoter which can be considered as a marker of germline DNA methylation. Using expression data in mouse, we confirm that CpG-rich genes are highly expressed in germline whereas CpG-poor genes are in a silent state. We further show that, whether tissue-specific or broadly expressed (housekeeping genes), the CpG-rich genes are over-represented close to the replication skew domain borders suggesting some coordination of replication and transcription. We also reveal that the transcription of the longest CpG-rich genes is co-oriented with replication fork progression so that the promoter of these transcriptionally active genes be located into the accessible open chromatin environment surrounding the master replication origins that border the replication skew domains. The observation of a similar gene organization in the mouse genome confirms the interplay of replication, transcription and chromatin structure as the cornerstone of mammalian genome architecture.

"We're the Mature People": A Study of Masculine Subjectivity and Its Relationship to Key Stage Four Religious Studies

Science.gov (United States)

Farrell, Francis

2015-01-01

Critical theory and research has shown that subjects carry gendered meanings. Numbers opting for Religious Studies (RS) have remained skewed towards girls. Drawing from post-structuralism and masculinities theory, this article critically analyses data from interviews with a group of key stage four boys who had opted for Religious Studies in…

The application of single-tree selection compared to diameter-limit cutting in an upland oak-hickory forest on the Cumberland Plateau in Jackson County, Alabama

Science.gov (United States)

Callie Jo Schweitzer; Greg Janzen

2012-01-01

Cumberland Plateau region upland oak forests have undergone a myriad of disturbances (including periods of few and minor disturbances). Traditional timber harvesting practices such as diameter-limit cutting have negatively altered species composition and skewed stand structure, especially on medium-quality sites. We assessed the ability of single-tree selection to...

Origins and Geochemistry of Oolitic Dolomite of the Feixianguan Formation from the Yudongzi Outcrop, Northwest Sichuan Basin, China

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Liya Zhang

2017-07-01

Full Text Available The topic of dolomite formation has long presented a challenge to researchers. In this study, the origin of widely occurring oolitic dolomites from the Yudongzi outcrop in the lower Triassic Feixianguan formation in northwest Sichuan, China, was investigated through petrographic observations, and mineralogical and geochemical analysis. Analytical methods used include cathodoluminescence, X-ray diffraction, stable isotopes, and electronic microprobe characterization. The dolomites were categorized into three major genetic types according to their textural and structural characteristics, which reflect their various origins. The first genetic type of these dolomites, seepage reflux dolomitization, occurs in marly to microcrystalline dolomite during the penecontemporaneous stage, and displays negatively skewed δ18Ο (−2.83‰ Pee Dee Belemnite (PDB, positively skewed δ13C (2.71‰ PDB, a low degree of order (0.48, and 87Sr/86Sr ratios of 0.707509–0.707634, indicating involvement of a Mg-rich brine fluid in an open evaporative environment. The second type, shallow burial dolomitization, is the most significant genetic type of dolomite reservoir in this area. This process produced dominantly silty to fine crystalline dolomite in a platform-margin oolitic beach facies with negatively skewed δ18Ο (−3.26‰ PDB, positively skewed δ13C (1.88‰ PDB, a high degree of order (0.70, and 87Sr/86Sr ratios of 0.707318–0.707661, which are related to seawater-derived fluids in a shallow burial environment. The third type is moderate to deep burial dolomitization, and is the main process responsible for zoned dolomite and dolomite with cloudy cores and clear rims (CCCR dolomite, which have the most strongly negatively skewed δ18Ο (−7.32‰ PDB, positively skewed δ13C (3.02‰ PDB, and 87Sr/86Sr ratios of 0.707217–0.707855, representing diagenetic alteration and fluid flow in a closed environment. These findings indicate that dolomite was likely

Inactive Gingipains from P. gingivalis Selectively Skews T Cells toward a Th17 Phenotype in an IL-6 Dependent Manner

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Jan Potempa

2017-04-01

, this study revealed a previously undisclosed role of gingipain activity in the process of Th17 differentiation reliant on blocking signaling through IL-6. Since inactivation of gingipains accelerates the skewing of T cells toward Th17 cells, which are detrimental in periodontitis, IL-6 signaling may serve as an attractive target for treatment of the disease.

Yeast-expressed recombinant As16 protects mice against Ascaris suum infection through induction of a Th2-skewed immune response.

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Junfei Wei

2017-07-01

Full Text Available Ascariasis remains the most common helminth infection in humans. As an alternative or complementary approach to global deworming, a pan-anthelminthic vaccine is under development targeting Ascaris, hookworm, and Trichuris infections. As16 and As14 have previously been described as two genetically related proteins from Ascaris suum that induced protective immunity in mice when formulated with cholera toxin B subunit (CTB as an adjuvant, but the exact protective mechanism was not well understood.As16 and As14 were highly expressed as soluble recombinant proteins (rAs16 and rAs14 in Pichia pastoris. The yeast-expressed rAs16 was highly recognized by immune sera from mice infected with A. suum eggs and elicited 99.6% protection against A. suum re-infection. Mice immunized with rAs16 formulated with ISA720 displayed significant larva reduction (36.7% and stunted larval development against A. suum eggs challenge. The protective immunity was associated with a predominant Th2-type response characterized by high titers of serological IgG1 (IgG1/IgG2a > 2000 and high levels of IL-4 and IL-5 produced by restimulated splenocytes. A similar level of protection was observed in mice immunized with rAs16 formulated with alum (Alhydrogel, known to induce mainly a Th2-type immune response, whereas mice immunized with rAs16 formulated with MPLA or AddaVax, both known to induce a Th1-type biased response, were not significantly protected against A. suum infection. The rAs14 protein was not recognized by A. suum infected mouse sera and mice immunized with rAs14 formulated with ISA720 did not show significant protection against challenge infection, possibly due to the protein's inaccessibility to the host immune system or a Th1-type response was induced which would counter a protective Th2-type response.Yeast-expressed rAs16 formulated with ISA720 or alum induced significant protection in mice against A. suum egg challenge that associates with a Th2-skewed immune

Inactive Gingipains from P. gingivalis Selectively Skews T Cells toward a Th17 Phenotype in an IL-6 Dependent Manner.

Science.gov (United States)

Glowczyk, Izabela; Wong, Alicia; Potempa, Barbara; Babyak, Olena; Lech, Maciej; Lamont, Richard J; Potempa, Jan; Koziel, Joanna

2017-01-01

revealed a previously undisclosed role of gingipain activity in the process of Th17 differentiation reliant on blocking signaling through IL-6. Since inactivation of gingipains accelerates the skewing of T cells toward Th17 cells, which are detrimental in periodontitis, IL-6 signaling may serve as an attractive target for treatment of the disease.

Image statistics and the perception of surface gloss and lightness.

Science.gov (United States)

Kim, Juno; Anderson, Barton L

2010-07-01

Despite previous data demonstrating the critical importance of 3D surface geometry in the perception of gloss and lightness, I. Motoyoshi, S. Nishida, L. Sharan, and E. H. Adelson (2007) recently proposed that a simple image statistic--histogram or sub-band skew--is computed by the visual system to infer the gloss and albedo of surfaces. One key source of evidence used to support this claim was an experiment in which adaptation to skewed image statistics resulted in opponent aftereffects in observers' judgments of gloss and lightness. We report a series of adaptation experiments that were designed to assess the cause of these aftereffects. We replicated their original aftereffects in gloss but found no consistent aftereffect in lightness. We report that adaptation to zero-skew adaptors produced similar aftereffects as positively skewed adaptors, and that negatively skewed adaptors induced no reliable aftereffects. We further find that the adaptation effect observed with positively skewed adaptors is not robust to changes in mean luminance that diminish the intensity of the luminance extrema. Finally, we show that adaptation to positive skew reduces (rather than increases) the apparent lightness of light pigmentation on non-uniform albedo surfaces. These results challenge the view that the adaptation results reported by Motoyoshi et al. (2007) provide evidence that skew is explicitly computed by the visual system.

Skewed Sociolinguistic Awareness of a Native Non-standard Dialect: Evidence from the Cypriot Greek Writing of Greek Cypriot Students

Directory of Open Access Journals (Sweden)

Ioli Ayiomamitou

2017-11-01

Cypriot students have a skewed sociolinguistic awareness of variation within their first dialect and a distorted impression of their own everyday language. We argue that the portrayal of CG in its basilectal form was performed intentionally by students in an effort to distance themselves from a socially constructed identity of a rural, uneducated, and stigmatized non-standard-dialect speaker. The study is of international relevance as it deals with sociolinguistic issues that pertain to all bidialectal speakers.

Mismatch oligonucleotides in human and yeast: guidelines for probe design on tiling microarrays

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Jee Justin

2008-12-01

Full Text Available Abstract Background Mismatched oligonucleotides are widely used on microarrays to differentiate specific from nonspecific hybridization. While many experiments rely on such oligos, the hybridization behavior of various degrees of mismatch (MM structure has not been extensively studied. Here, we present the results of two large-scale microarray experiments on S. cerevisiae and H. sapiens genomic DNA, to explore MM oligonucleotide behavior with real sample mixtures under tiling-array conditions. Results We examined all possible nucleotide substitutions at the central position of 36-nucleotide probes, and found that nonspecific binding by MM oligos depends upon the individual nucleotide substitutions they incorporate: C→A, C→G and T→A (yielding purine-purine mispairs are most disruptive, whereas A→X were least disruptive. We also quantify a marked GC skew effect: substitutions raising probe GC content exhibit higher intensity (and vice versa. This skew is small in highly-expressed regions (± 0.5% of total intensity range and large (± 2% or more elsewhere. Multiple mismatches per oligo are largely additive in effect: each MM added in a distributed fashion causes an additional 21% intensity drop relative to PM, three-fold more disruptive than adding adjacent mispairs (7% drop per MM. Conclusion We investigate several parameters for oligonucleotide design, including the effects of each central nucleotide substitution on array signal intensity and of multiple MM per oligo. To avoid GC skew, individual substitutions should not alter probe GC content. RNA sample mixture complexity may increase the amount of nonspecific hybridization, magnify GC skew and boost the intensity of MM oligos at all levels.

The CD8 and CD4 T-cell response against Kaposi's sarcoma-associated herpesvirus is skewed towards early and late lytic antigens.

Directory of Open Access Journals (Sweden)

Rebecca C Robey

Full Text Available Kaposi's sarcoma-associated herpesvirus (KSHV is causally related to Kaposi's sarcoma (KS, the most common malignancy in untreated individuals with HIV/AIDS. The adaptive T-cell immune response against KSHV has not been fully characterized. To achieve a better understanding of the antigenic repertoire of the CD8 and CD4 T-cell responses against KSHV, we constructed a library of lentiviral expression vectors each coding for one of 31 individual KSHV open reading frames (ORFs. We used these to transduce monocyte-derived dendritic cells (moDCs isolated from 14 KSHV-seropositive (12 HIV-positive and 7 KSHV-seronegative (4 HIV-positive individuals. moDCs were transduced with up to 3 KSHV ORFs simultaneously (ORFs grouped according to their expression during the viral life cycle. Transduced moDCs naturally process the KSHV genes and present the resulting antigens in the context of MHC class I and II. Transduced moDCs were cultured with purified autologous T cells and the CD8 and CD4 T-cell proliferative responses to each KSHV ORF (or group was assessed using a CFSE dye-based assay. Two pools of early lytic KSHV genes ([ORF8/ORF49/ORF61] and [ORF59/ORF65/K4.1] were frequently-recognized targets of both CD8 and CD4 T cells from KSHV seropositive individuals. One pool of late lytic KSHV genes ([ORF28/ORF36/ORF37] was a frequently-recognized CD8 target and another pool of late genes ([ORF33/K1/K8.1] was a frequently-recognized CD4 target. We report that both the CD8 and CD4 T-cell responses against KSHV are skewed towards genes expressed in the early and late phases of the viral lytic cycle, and identify some previously unknown targets of these responses. This knowledge will be important to future immunological investigations into KSHV and may eventually lead to the development of better immunotherapies for KSHV-related diseases.

75 FR 27249 - Standards of Performance for New Stationary Sources and Emissions Guidelines for Existing Sources...

Science.gov (United States)

2010-05-14

... distributions typically have a skewness of zero, we concluded that those datasets with a skewness less than 0.5 were normally distributed, while those with a skewness of 0.5 or greater were lognormally distributed... sources (used to determine the MACT floor for existing sources) and had a higher standard deviation...

A lattice Boltzmann simulation of coalescence-induced droplet jumping on superhydrophobic surfaces with randomly distributed structures

Science.gov (United States)

Zhang, Li-Zhi; Yuan, Wu-Zhi

2018-04-01

The motion of coalescence-induced condensate droplets on superhydrophobic surface (SHS) has attracted increasing attention in energy-related applications. Previous researches were focused on regularly rough surfaces. Here a new approach, a mesoscale lattice Boltzmann method (LBM), is proposed and used to model the dynamic behavior of coalescence-induced droplet jumping on SHS with randomly distributed rough structures. A Fast Fourier Transformation (FFT) method is used to generate non-Gaussian randomly distributed rough surfaces with the skewness (Sk), kurtosis (K) and root mean square (Rq) obtained from real surfaces. Three typical spreading states of coalesced droplets are observed through LBM modeling on various rough surfaces, which are found to significantly influence the jumping ability of coalesced droplet. The coalesced droplets spreading in Cassie state or in composite state will jump off the rough surfaces, while the ones spreading in Wenzel state would eventually remain on the rough surfaces. It is demonstrated that the rough surfaces with smaller Sks, larger Rqs and a K at 3.0 are beneficial to coalescence-induced droplet jumping. The new approach gives more detailed insights into the design of SHS.

Wave-induced coherent turbulence structures and sediment resuspension in the nearshore of a prototype-scale sandy barrier beach

Science.gov (United States)

Kassem, Hachem; Thompson, Charlotte E. L.; Amos, Carl L.; Townend, Ian H.

2015-10-01

The suspension of sediments by oscillatory flows is a complex case of fluid-particle interaction. The aim of this study is to provide insight into the spatial (time) and scale (frequency) relationships between wave-generated boundary layer turbulence and event-driven sediment transport beneath irregular shoaling and breaking waves in the nearshore of a prototype sandy barrier beach, using data collected through the Barrier Dynamics Experiment II (BARDEX II). Statistical, quadrant and spectral analyses reveal the anisotropic and intermittent nature of Reynolds' stresses (momentum exchange) in the wave boundary layer, in all three orthogonal planes of motion. The fractional contribution of coherent turbulence structures appears to be dictated by the structural form of eddies beneath plunging and spilling breakers, which in turn define the net sediment mobilisation towards or away from the barrier, and hence ensuing erosion and accretion trends. A standing transverse wave is also observed in the flume, contributing to the substantial skewness of spanwise turbulence. Observed low frequency suspensions are closely linked to the mean flow (wave) properties. Wavelet analysis reveals that the entrainment and maintenance of sediment in suspension through a cluster of bursting sequence is associated with the passage of intermittent slowly-evolving large structures, which can modulate the frequency of smaller motions. Outside the boundary layer, small scale, higher frequency turbulence drives the suspension. The extent to which these spatially varied perturbation clusters persist is associated with suspension events in the high frequency scales, decaying as the turbulent motion ceases to supply momentum, with an observed hysteresis effect.

Structural analysis of polarizing indels: an emerging consensus on the root of the tree of life

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Bourne Philip E

2009-08-01

Full Text Available Abstract Background The root of the tree of life has been a holy grail ever since Darwin first used the tree as a metaphor for evolution. New methods seek to narrow down the location of the root by excluding it from branches of the tree of life. This is done by finding traits that must be derived, and excluding the root from the taxa those traits cover. However the two most comprehensive attempts at this strategy, performed by Cavalier-Smith and Lake et al., have excluded each other's rootings. Results The indel polarizations of Lake et al. rely on high quality alignments between paralogs that diverged before the last universal common ancestor (LUCA. Therefore, sequence alignment artifacts may skew their conclusions. We have reviewed their data using protein structure information where available. Several of the conclusions are quite different when viewed in the light of structure which is conserved over longer evolutionary time scales than sequence. We argue there is no polarization that excludes the root from all Gram-negatives, and that polarizations robustly exclude the root from the Archaea. Conclusion We conclude that there is no contradiction between the polarization datasets. The combination of these datasets excludes the root from every possible position except near the Chloroflexi. Reviewers This article was reviewed by Greg Fournier (nominated by J. Peter Gogarten, Purificación López-García, and Eugene Koonin.

Structural and molecular dynamics studies of a C1-oxidizing lytic polysaccharide monooxygenase from Heterobasidion irregulare reveal amino acids important for substrate recognition

Energy Technology Data Exchange (ETDEWEB)

Liu, Bing [Department of Molecular Sciences, Swedish University of Agricultural Sciences, Uppsala Sweden; Kognole, Abhishek A. [Department of Chemical and Materials Engineering, University of Kentucky, Lexington KY USA; Wu, Miao [Department of Molecular Sciences, Swedish University of Agricultural Sciences, Uppsala Sweden; Westereng, Bjørge [Department of Chemistry, Biotechnology, and Food Science, Norwegian University of Life Sciences, Ås Norway; Crowley, Michael F. [Biosciences Center, National Renewable Energy Laboratory, Golden CO USA; Kim, Seonah [Biosciences Center, National Renewable Energy Laboratory, Golden CO USA; Dimarogona, Maria [Department of Molecular Sciences, Swedish University of Agricultural Sciences, Uppsala Sweden; Department of Chemical Engineering, University of Patras, Greece; Payne, Christina M. [Department of Chemical and Materials Engineering, University of Kentucky, Lexington KY USA; Directorate of Engineering, Division of Chemical, Bioengineering, Environmental, and Transport Systems, National Science Foundation, Alexandria VA USA; Sandgren, Mats [Department of Molecular Sciences, Swedish University of Agricultural Sciences, Uppsala Sweden

2018-04-24

Lytic polysaccharide monooxygenases (LPMOs) are a group of recently discovered enzymes that play important roles in the decomposition of recalcitrant polysaccharides. Here, we report the biochemical, structural, and computational characterization of an LPMO from the white-rot fungus Heterobasidion irregulare (HiLPMO9B). This enzyme oxidizes cellulose at the C1 carbon of glycosidic linkages. The crystal structure of HiLPMO9B was determined at 2.1 A resolution using X-ray crystallography. Unlike the majority of the currently available C1-specific LPMO structures, the HiLPMO9B structure contains an extended L2 loop, connecting ..beta..-strands ..beta..2 and ..beta..3 of the ..beta..-sandwich structure. Molecular dynamics (MD) simulations suggest roles for both aromatic and acidic residues in the substrate binding of HiLPMO9B, with the main contribution from the residues located on the extended region of the L2 loop (Tyr20) and the LC loop (Asp205, Tyr207, and Glu210). Asp205 and Glu210 were found to be involved in the hydrogen bonding with the hydroxyl group of the C6 carbon of glucose moieties directly or via a water molecule. Two different binding orientations were observed over the course of the MD simulations. In each orientation, the active-site copper of this LPMO preferentially skewed toward the pyranose C1 of the glycosidic linkage over the targeted glycosidic bond. This study provides additional insight into cellulose binding by C1-specific LPMOs, giving a molecular-level picture of active site substrate interactions.

The Effect of Kagan's Cooperative Structures on Speaking Skill of Iranian EFL Learners

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Hassan Soleimani

2018-03-01

Full Text Available Speaking is an important skill in language learning and EFL learners sometimes face difficulties when they want to speak. This study attempted to measure the effect of Kagan’s cooperative structures on speaking skill of Iranian EFL learners. The participants were selected from EFL learners studying at Ideal Language Institute. The Cambridge English Language Assessment was administered in order to select homogenous participants. Forty eight adult female EFL learners were selected as intermediate learners based on their results of the language proficiency test. They were divided into two groups, 24 as the control group and 24 as the experimental group. A pre-test was administered to both groups at the beginning of the experiment then, the students participated in 90 minute classes two times a week for eight sessions. At the end of the experiment, a post-test was assigned to both groups to determine whether the Kagan’s cooperative structures had positively affected the students’ speaking skills. The normality of data was tested through Skewness, Kurtosis, and K-S. To make sure the participants were homogenous, the parametric statistical technique of independent -samples t-test was calculated between the pre-tests of both groups and they were homogenous. Independent-samples t-test between the posttests of the experimental group and the control group was calculated and it showed that the participants of the experimental group outperformed the subjects of the control group. Moreover, paired-samples ttest between the pre-test and post-test of the experimental group was calculated and it was shown that the experimental participants progressed from the pre-test to the post-test. The study revealed that: (1 Kagan’s cooperative structures had a positive effect on the students’ speaking skills, (2 the experimental group obtained higher scores in the post-test than in the pre-test, making the difference between the pre-test and post-test scores

Are Clusters Races? A Discussion of the Rhetorical Appropriation of Rosenberg et al.'s “Genetic Structure of Human Populations”

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Melissa Wills

2017-01-01

Full Text Available Noah Rosenberg et al.'s 2002 article “Genetic Structure of Human Populations” reported that multivariate genomic analysis of a large cell line panel yielded reproducible groupings (clusters suggestive of individuals' geographical origins. The paper has been repeatedly cited as evidence that traditional notions of race have a biological basis, a claim its authors do not make. Critics of this misinterpretation have often suggested that it follows from interpreters' personal biases skewing the reception of an objective piece of scientific writing. I contend, however, that the article itself to some degree facilitates this misrepresentation. I analyze in detail several verbal and visual features of the original article that may predispose aspects of its racial interpretation; and, tracing the arguments of one philosopher and one popular science writer, I show how these features are absorbed, transformed into arguments for a biological basis of race, and re-attributed to the original. The essay demonstrates how even slight ambiguities can enable the misappropriation of scientific writing, unintentionally undermining the authors' stated circumspection on the relationship between cluster and race.

Global Distribution of Businesses Marketing Stem Cell-Based Interventions.

Science.gov (United States)

Berger, Israel; Ahmad, Amina; Bansal, Akhil; Kapoor, Tanvir; Sipp, Douglas; Rasko, John E J

2016-08-04

A structured search reveals that online marketing of stem-cell-based interventions is skewed toward developed economies including the United States, Ireland, Australia, and Germany. Websites made broad, imprecise therapeutic claims and frequently failed to detail procedures. Widespread marketing poses challenges to regulators, bioethicists, and those seeking realistic hope from therapies. Copyright © 2016 Elsevier Inc. All rights reserved.

Globalisation of Researcher Mobility within the UK Higher Education: Explaining the Presence of Overseas Academics in the UK Academia

Science.gov (United States)

Khattab, Nabil; Fenton, Steve

2016-01-01

In this paper, we argue that the power structure that lies within the UK elite universities dictates a division of labour through which the inflows of overseas academics into the UK academic labour markets are skewed towards these elite academic institutions where they are employed primarily in research-only posts. These posts, are less valued and…

Disease: H00994 [KEGG MEDICUS

Lifescience Database Archive (English)

Full Text Available me. The incidence of skewing is shown to be age dependent but in general, skewing does not have any biologic... consequence. However, in cases of individuals with nonlethal mutated allele, degree of skewing...ed X inactivation is defined as a pattern where the cells show a preferential inactivation of one X chromoso

Forces in wingwalls from thermal expansion of skewed semi-integral bridges : executive summary report.

Science.gov (United States)

2010-11-01

Bridges that utilize expansion joints have an overall higher maintenance cost due to leakage at the expansion joint leading to deterioration of the joint, as well as structural components beneath the joint including the superstructure and substructur...

Low Risk Anomalies?

DEFF Research Database (Denmark)

Schneider, Paul; Wagner, Christian; Zechner, Josef

. Empirically, we find that option-implied ex-ante skewness is strongly related to ex-post residual coskewness and alphas. Beta- and volatility-based low risk anomalies are largely driven by a single principal component, which is in turn largely explained by skewness. Controlling for skewness renders the alphas......This paper shows that stocks' CAPM alphas are negatively related to CAPM betas if investors demand compensation for negative skewness. Thus, high (low) beta stocks appear to underperform (outperform). This apparent anomaly merely reflects compensation for residual coskewness ignored by the CAPM...... of betting-against-beta and -volatility insignificant....

Geometric mean IELT and premature ejaculation: appropriate statistics to avoid overestimation of treatment efficacy.

Science.gov (United States)

Waldinger, Marcel D; Zwinderman, Aeilko H; Olivier, Berend; Schweitzer, Dave H

2008-02-01

The intravaginal ejaculation latency time (IELT) behaves in a skewed manner and needs the appropriate statistics for correct interpretation of treatment results. To explain the rightful use of geometrical mean IELT values and the fold increase of the geometric mean IELT because of the positively skewed IELT distribution. Linking theoretical arguments to the outcome of several selective serotonin reuptake inhibitor and modern antidepressant study results. Geometric mean IELT and fold increase of geometrical mean IELT. Log-transforming each separate IELT measurement of each individual man is the basis for the calculation of the geometric mean IELT. A drug-induced positively skewed IELT distribution necessitates the calculation of the geometric mean IELTs at baseline and during drug treatment. In a positively skewed IELT distribution, the use of the "arithmetic" mean IELT risks an overestimation of the drug-induced ejaculation delay as the mean IELT is always higher than the geometric mean IELT. Strong ejaculation-delaying drugs give rise to a strong positively skewed IELT distribution, whereas weak ejaculation-delaying drugs give rise to (much) less skewed IELT distributions. Ejaculation delay is expressed in fold increase of the geometric mean IELT. Drug-induced ejaculatory performance discloses a positively skewed IELT distribution, requiring the use of the geometric mean IELT and the fold increase of the geometric mean IELT.

Stochastic Skew in Currency Options

OpenAIRE

Peter Carr; Liuren Wu

2004-01-01

We document the behavior of over-the-counter currency option prices across moneyness, maturity, and calendar time on two of the most actively traded currency pairs over the past eight years. We find that the risk-neutral distribution of currency returns is relatively symmetric on average. However, on any given date, the conditional currency return distribution can show strong asymmetry. This asymmetry varies greatly over time and often switch directions. We design and estimate a class of mode...

Sediment Analysis Using a Structured Programming Approach

Directory of Open Access Journals (Sweden)

Daniela Arias-Madrid

2012-12-01

Full Text Available This paper presents an algorithm designed for the analysis of a sedimentary sample of unconsolidated material and seeks to identify very quickly the main features that occur in a sediment and thus classify them fast and efficiently. For this purpose, it requires that the weight of each particle size to be entered in the program and using the method of Moments, which is based on four equations representing the mean, standard deviation, skewness and kurtosis, is found the attributes of the sample in few seconds. With the program these calculations are performed in an effective and more accurately way, obtaining also the explanations of the results of the features such as grain size, sorting, symmetry and origin, which helps to improve the study of sediments and in general the study of sedimentary rocks.

Instantaneous fluctuation velocity and skewness distributions upstream of transition onset

International Nuclear Information System (INIS)

Hernon, D.; Walsh, E.J.; McEligot, D.M.

2007-01-01

The development of streamwise orientated disturbances through the boundary layer thickness prior to transition onset for zero-pressure gradient boundary layer flow under the influence %Tu = 4.2 is presented. The analysis concentrates on the development of the maximum positive and negative of the fluctuation velocity in order to gain further insight into the transition process. The average location of the peak negative fluctuation velocity over a range of Reynolds numbers was measured in the upper portion of the boundary layer at y/δ ∼ 0.6, whereas the location of the peak positive value was measured at y/δ ∼ 0.3. The disturbance magnitude of the negative fluctuation velocity increased beyond that of the positive as transition onset approached. The distribution and disturbance magnitude of the maximum positive and negative fluctuation velocities indicate that the initiation of transition may occur on the low-speed components of the flow that are lifted up to the upper region of the boundary layer. This is in qualitative agreement with recent direct numerical simulations on the breakdown of the flow on the lifted low-speed streaks near the boundary layer edge. The results presented in this investigation also demonstrate the increased physical insight gained by examining the distributions of the maximum positive and negative of the streamwise fluctuation velocity component associated with the low- and high-speed streaks, compared to time-averaged values, in determining what structures cause the breakdown to turbulence

Steel framing strategies for highly skewed bridges to reduce/eliminate distortion near skewed supports : [summary].

Science.gov (United States)

2014-05-01

In the past, bridges were aligned normal to crossing roads or obstacles in order to simplify bridge construction. However, the continuing expansion of the interstate system has challenged engineers to provide more horizontal clearance, reduce right-o...

Experimental investigation on wake galloping appeared in tandem cables of cable-stayed bridges subjected to wind in skewed direction; Normal narabini dimple tsuki heiretsu cable ni senpu ga sayoshita baai no wake galloping tokusei ni tsuite

Energy Technology Data Exchange (ETDEWEB)

Yoneda, M.; Miyachi, S.; Edamoto, K.; Mochizuki, H.; Setouchi, H. [Kawada Industries Inc., Tokyo (Japan)

1996-03-20

Concerning the smooth surface and dimpled surface cables, experiments were conducted to investigate relationship between their wake galloping characteristics and aerostatic force characteristics they demonstrate when exposed to wind blowing in a skewed direction. The wind tunnel used for the experiment was a closed type measuring wind tunnel, 2.0m wide, 2.5m high, and 15.0m long. In the wind tunnel, two cables were arranged with the distance between the cable centers three times as large as the cable diameter D, and with relative vertical difference of 0.25-0.50D, and spring-supported experiments for evaluating wake galloping characteristics and aerostatic force coefficient determining experiments were carried out. It was deemed as the result that turbulence exerts influence on the wake galloping characteristics of the dimpled surface cable more than on those of the smooth surface cable, that on a real bridge the effect of turbulence may be expected in case of exposure to natural wind of turbulence with intensity higher than 5-7%, and that therefore application of some damping by dampers will adequately damp wake galloping even in case of the 0.37D vertical difference. 12 refs., 23 figs.

Multi-site TBT binding skews the inhibition of oligomycin on the mitochondrial Mg-ATPase in Mytilus galloprovincialis.

Science.gov (United States)

Nesci, Salvatore; Ventrella, Vittoria; Trombetti, Fabiana; Pirini, Maurizio; Pagliarani, Alessandra

2011-07-01

Tributyltin (TBT), a persistent lipophilic contaminant found especially in the aquatic environment, is known to be toxic to mitochondria with the F(1)F(0)-ATPase as main target. Recently our research group pointed out that in mussel digestive gland mitochondria TBT, apart from decreasing the catalytic efficiency of Mg-ATPase activity, at concentrations ≥1.0 μM in the ATPase reaction medium lessens the enzyme inhibition promoted by the specific inhibitor oligomycin. The present work aims at casting light on the mechanisms involved in the TBT-driven enzyme desensitization to inhibitors, a poorly explored field. The mitochondrial Mg-ATPase desensitization is shown to be confined to inhibitors of transmembrane domain F(0), namely oligomycin and N,N'-dicyclohexylcarbodiimide (DCCD). Accordingly, quercetin, which binds to catalytic portion F(1), maintains its inhibitory efficiency in the presence of TBT. Among the possible mechanisms involved in the Mg-ATPase desensitization to oligomycin by ≥1.0 μM TBT concentrations, a structural detachment of the two F(1) and F(0) domains does not occur according to experimental data. On the other hand TBT covalently binds to thiol groups on the enzyme structure, which are apparently only available at TBT concentrations approaching 20 μM. TBT is able to interact with multiple sites on the enzyme structure by bonds of different nature. While electrostatic interactions with F(0) proton channel are likely to be responsible for the ATPase activity inhibition, possible changes in the redox state of thiol groups on the protein structure due to TBT binding may promote structural changes in the enzyme structure leading to the observed F(1)F(0)-ATPase oligomycin sensitivity loss. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

Log-gamma linear-mixed effects models for multiple outcomes with application to a longitudinal glaucoma study

Science.gov (United States)

Zhang, Peng; Luo, Dandan; Li, Pengfei; Sharpsten, Lucie; Medeiros, Felipe A.

2015-01-01

Glaucoma is a progressive disease due to damage in the optic nerve with associated functional losses. Although the relationship between structural and functional progression in glaucoma is well established, there is disagreement on how this association evolves over time. In addressing this issue, we propose a new class of non-Gaussian linear-mixed models to estimate the correlations among subject-specific effects in multivariate longitudinal studies with a skewed distribution of random effects, to be used in a study of glaucoma. This class provides an efficient estimation of subject-specific effects by modeling the skewed random effects through the log-gamma distribution. It also provides more reliable estimates of the correlations between the random effects. To validate the log-gamma assumption against the usual normality assumption of the random effects, we propose a lack-of-fit test using the profile likelihood function of the shape parameter. We apply this method to data from a prospective observation study, the Diagnostic Innovations in Glaucoma Study, to present a statistically significant association between structural and functional change rates that leads to a better understanding of the progression of glaucoma over time. PMID:26075565

Derivation of stochastic differential equations for scrape-off layer plasma fluctuations from experimentally measured statistics

Energy Technology Data Exchange (ETDEWEB)

Mekkaoui, Abdessamad [IEK-4 Forschungszentrum Juelich 52428 (Germany)

2013-07-01

A method to derive stochastic differential equations for intermittent plasma density dynamics in magnetic fusion edge plasma is presented. It uses a measured first four moments (mean, variance, Skewness and Kurtosis) and the correlation time of turbulence to write a Pearson equation for the probability distribution function of fluctuations. The Fokker-Planck equation is then used to derive a Langevin equation for the plasma density fluctuations. A theoretical expectations are used as a constraints to fix the nonlinearity structure of the stochastic differential equation. In particular when the quadratically nonlinear dynamics is assumed, then it is shown that the plasma density is driven by a multiplicative Wiener process and evolves on the turbulence correlation time scale, while the linear growth is quadratically damped by the fluctuation level. Strong criteria for statistical discrimination of experimental time series are proposed as an alternative to the Kurtosis-Skewness scaling. This scaling is broadly used in contemporary literature to characterize edge turbulence, but it is inappropriate because a large family of distributions could share this scaling. Strong criteria allow us to focus on the relevant candidate distribution and approach a nonlinear structure of edge turbulence model.

Multipole Stack for the 800 MeV PS Booster

CERN Multimedia

1975-01-01

The 800 MeV PS Booster had seen first beam in its 4 superposed rings in 1972, routine operation began in 1973. In the strive for ever higher beam intensities, the need for additional multipole lenses became evident. After detailed studies, the manufacture of 8 stacks of multipoles was launched in 1974. Each stack consists of 4 superposed multipoles and each multipole has 4 concentric shells. From the innermost to the outermost shell, Type A contains octupole, skew-octupole, sextupole, skew-sextupole. Type B contains skew-octupole, skew-sextupole, vertical dipole, horizontal dipole. Completion of installation in 1976 opened the way to higher beam intensities. M. Battiaz is seen here with a multipole stack and its many electrical connections.

Market risk in commodity markets: a VaR approach

International Nuclear Information System (INIS)

Giot, P.

2003-01-01

We put forward Value-at-Risk models relevant for commodity traders who have long and short trading positions in commodity markets. In a 5-year out-of-sample study on aluminium, copper, nickel, Brent crude oil and WTI crude oil daily cash prices and cocoa nearby futures contracts, we assess the performance of the RiskMetrics, skewed Student APARCH and skewed student ARCH models. While the skewed Student APARCH model performs best in all cases, the skewed Student ARCH model delivers good results and its estimation does not require non-linear optimization procedures. As such this new model could be relatively easily integrated in a spreadsheet-like environment and used by market practitioners. (author)

Market risk in commodity markets. A VaR approach

Energy Technology Data Exchange (ETDEWEB)

Giot, Pierre [Department of Business Administration and CEREFIM at University of Namur, Rempart de la Vierge, 8, 5000 Namur (Belgium); Laurent, Sebastien [Center for Operations Research and Econometrics (CORE) at Universite Catholique de Louvain, Louvain (Belgium)

2003-09-01

We put forward Value-at-Risk models relevant for commodity traders who have long and short trading positions in commodity markets. In a 5-year out-of-sample study on aluminium, copper, nickel, Brent crude oil and WTI crude oil daily cash prices and cocoa nearby futures contracts, we assess the performance of the RiskMetrics, skewed Student APARCH and skewed student ARCH models. While the skewed Student APARCH model performs best in all cases, the skewed Student ARCH model delivers good results and its estimation does not require non-linear optimization procedures. As such this new model could be relatively easily integrated in a spreadsheet-like environment and used by market practitioners.

Market risk in commodity markets. A VaR approach

International Nuclear Information System (INIS)

Giot, Pierre; Laurent, Sebastien

2003-01-01

We put forward Value-at-Risk models relevant for commodity traders who have long and short trading positions in commodity markets. In a 5-year out-of-sample study on aluminium, copper, nickel, Brent crude oil and WTI crude oil daily cash prices and cocoa nearby futures contracts, we assess the performance of the RiskMetrics, skewed Student APARCH and skewed student ARCH models. While the skewed Student APARCH model performs best in all cases, the skewed Student ARCH model delivers good results and its estimation does not require non-linear optimization procedures. As such this new model could be relatively easily integrated in a spreadsheet-like environment and used by market practitioners

Crystal structures and Hirshfeld surface analyses of bis[N,N-bis(2-methoxyethyldithiocarbamato-κ2S,S′]di-n-butyltin(IV and [N-(2-methoxyethyl-N-methyldithiocarbamato-κ2S,S′]triphenyltin(IV

Directory of Open Access Journals (Sweden)

Rapidah Mohamad

2018-03-01

Full Text Available The crystal and molecular structures of the two title organotin dithiocarbamate compounds, [Sn(C4H92(C7H14NO2S22], (I, and [Sn(C6H53(C5H10NOS2], (II, are described. Both structures feature asymmetrically bound dithiocarbamate ligands leading to a skew-trapezoidal bipyramidal geometry for the metal atom in (I and a distorted tetrahedral geometry in (II. The complete molecule of (I is generated by a crystallographic twofold axis (Sn site symmetry 2. In the crystal of (I, molecules self-assemble into a supramolecular array parallel to (10-1 via methylene-C—H...O(methoxy interactions. In the crystal of (II, supramolecular dimers are formed via pairs of weak phenyl-C—H...π(phenyl contacts. In each of (I and (II, the specified assemblies connect into a three-dimensional architecture without directional interactions between them. Hirshfeld surface analyses confirm the importance of H...H contacts in the molecular packing of each of (I and (II, and in the case of (I, highlight the importance of short methoxy-H...H(butyl contacts between layers.

Structural, morphological and optical properties of pulsed laser deposited ZnSe/ZnSeO3 thin films

Science.gov (United States)

Hassan, Syed Ali; Bashir, Shazia; Zehra, Khushboo; Salman Ahmed, Qazi

2018-04-01

The effect of varying laser pulses on structural, morphological and optical behavior of Pulsed Laser Deposited (PLD) ZnSe/ZnSeO3 thin films has been investigated. The films were grown by employing Excimer laser (100 mJ, 248 nm, 18 ns, 30 Hz) at various number of laser pulses i.e. 3000, 4000, 5000 and 6000 with elevated substrate temperature of 300 °C. One film was grown at Room Temperature (RT) by employing 3000 number of laser pulses. In order to investigate the structural analysis of deposited films, XRD analysis was performed. It was observed that the room temperature is not favorable for the growth of crystalline film. However, elevated substrate temperature to 300°C, two phases with preferred orientation of ZnSeO3 (2 1 2) and ZnSe (3 3 1) were identified. AFM and SEM analysis were performed to explore the surface morphology of grown films. Morphological analysis also confirmed the non-uniform film growth at room temperature. At elevated substrate temperature (300 °C), the growth of dendritic rods and cubical crystalline structures are observed for lower number of laser pulses i.e. 3000 and 4000 respectively. With increased number of pulses i.e. 5000 and 6000, the films surface morphology becomes smooth which is confirmed by measurement of surface RMS roughness. Number of grains, skewness, kurtosis and other parameters have been evaluated by statistical analysis. In order to investigate the thickness, and optical properties of deposited films, ellipsometery and UV–Vis spectroscopy techniques were employed. The estimated band gap energy is 2.67 eV for the film grown at RT, whereas band gap values varies from 2.80 eV to 3.01 eV for the films grown at 300 °C with increasing number of laser pulses.

Note on Symplectic SVD-Like Decomposition

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AGOUJIL Said

2016-02-01

Full Text Available The aim of this study was to introduce a constructive method to compute a symplectic singular value decomposition (SVD-like decomposition of a 2n-by-m rectangular real matrix A, based on symplectic refectors.This approach used a canonical Schur form of skew-symmetric matrix and it allowed us to compute eigenvalues for the structured matrices as Hamiltonian matrix JAA^T.

Reference: 753 [Arabidopsis Phenome Database[Archive

Lifescience Database Archive (English)

Full Text Available otypes, XLG3 and AGB1 each positively regulate root waving and root skewing. Since these responses are regul...s of root-waving and root-skewing responses in plants and possibly interact in a tissue-specific or signal-s...pecific manner. Because plants harboring knockout mutations in the Galpha subunit gene, GPA1, exhibit wild-type root waving and skewi...ng, our results may indicate that the AGB1 subunit funct

Controlling nosocomial infection based on structure of hospital social networks.

Science.gov (United States)

Ueno, Taro; Masuda, Naoki

2008-10-07

Nosocomial infection (i.e. infection in healthcare facilities) raises a serious public health problem, as implied by the existence of pathogens characteristic to healthcare facilities such as methicillin-resistant Staphylococcus aureus and hospital-mediated outbreaks of influenza and severe acute respiratory syndrome. For general communities, epidemic modeling based on social networks is being recognized as a useful tool. However, disease propagation may occur in a healthcare facility in a manner different from that in a urban community setting due to different network architecture. We simulate stochastic susceptible-infected-recovered dynamics on social networks, which are based on observations in a hospital in Tokyo, to explore effective containment strategies against nosocomial infection. The observed social networks in the hospital have hierarchical and modular structure in which dense substructure such as departments, wards, and rooms, are globally but only loosely connected, and do not reveal extremely right-skewed distributions of the number of contacts per individual. We show that healthcare workers, particularly medical doctors, are main vectors (i.e. transmitters) of diseases on these networks. Intervention methods that restrict interaction between medical doctors and their visits to different wards shrink the final epidemic size more than intervention methods that directly protect patients, such as isolating patients in single rooms. By the same token, vaccinating doctors with priority rather than patients or nurses is more effective. Finally, vaccinating individuals with large betweenness centrality (frequency of mediating connection between pairs of individuals along the shortest paths) is superior to vaccinating ones with large connectedness to others or randomly chosen individuals, which was suggested by previous model studies.

A proportional integral estimator-based clock synchronization protocol for wireless sensor networks.

Science.gov (United States)

Yang, Wenlun; Fu, Minyue

2017-11-01

Clock synchronization is an issue of vital importance in applications of WSNs. This paper proposes a proportional integral estimator-based protocol (EBP) to achieve clock synchronization for wireless sensor networks. As each local clock skew gradually drifts, synchronization accuracy will decline over time. Compared with existing consensus-based approaches, the proposed synchronization protocol improves synchronization accuracy under time-varying clock skews. Moreover, by restricting synchronization error of clock skew into a relative small quantity, it could reduce periodic re-synchronization frequencies. At last, a pseudo-synchronous implementation for skew compensation is introduced as synchronous protocol is unrealistic in practice. Numerical simulations are shown to illustrate the performance of the proposed protocol. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Are fund of hedge fund returns asymmetric?

OpenAIRE

Lynch, Margaret; Hutson, Elaine; Stevenson, Max

2004-01-01

We examine the return distributions of 332 funds of hedge funds and associated indices. Over half of the sample is significantly skewed according to the skewness statistic, and these are split 50/50 positive and negative. However, we argue that the skewness statistic can lead to erroneous inferences regarding the nature of the return distribution, because the test statistic is based on the normal distribution. Using a series of tests that make minimal assumptions about the shape of the ...

Clock generation and distribution for the 130-nm Itanium$^{R}$ 2 processor with 6-MB on-die L3 cache

CERN Document Server

Tam, S; Limaye, R D

2004-01-01

The clock generation and distribution system for the 130-nm Itanium 2 processor operates at 1.5 GHz with a skew of 24 ps. The Itanium 2 processor features 6 MB of on-die L3 cache and has a die size of 374 mm/sup 2/. Fuse-based clock de-skew enables post-silicon clock optimization to gain higher frequency. This paper describes the clock generation, global clock distribution, local clocking, and the clock skew optimization feature.

Characterization of the Complete Mitochondrial Genome Sequence of the Globose Head Whiptail Cetonurus globiceps (Gadiformes: Macrouridae and Its Phylogenetic Analysis.

Directory of Open Access Journals (Sweden)

Xiaofeng Shi

Full Text Available The particular environmental characteristics of deep water such as its immense scale and high pressure systems, presents technological problems that have prevented research to broaden our knowledge of deep-sea fish. Here, we described the mitogenome sequence of a deep-sea fish, Cetonurus globiceps. The genome is 17,137 bp in length, with a standard set of 22 transfer RNA genes (tRNAs, two ribosomal RNA genes, 13 protein-coding genes, and two typical non-coding control regions. Additionally, a 70 bp tRNA(Thr-tRNA(Pro intergenic spacer is present. The C. globiceps mitogenome exhibited strand-specific asymmetry in nucleotide composition. The AT-skew and GC-skew values in the whole genome of C. globiceps were 0 and -0.2877, respectively, revealing that the H-strand had equal amounts of A and T and that the overall nucleotide composition was C skewed. All of the tRNA genes could be folded into cloverleaf secondary structures, while the secondary structure of tRNA(Ser(AGY lacked a discernible dihydrouridine stem. By comparing this genome sequence with the recognition sites in teleost species, several conserved sequence blocks were identified in the control region. However, the GTGGG-box, the typical characteristic of conserved sequence block E (CSB-E, was absent. Notably, tandem repeats were identified in the 3' portion of the control region. No similar repetitive motifs are present in most of other gadiform species. Phylogenetic analysis based on 12 protein coding genes provided strong support that C. globiceps was the most derived in the clade. Some relationships however, are in contrast with those presented in previous studies. This study enriches our knowledge of mitogenomes of the genus Cetonurus and provides valuable information on the evolution of Macrouridae mtDNA and deep-sea fish.

A strategy to load balancing for non-connectivity MapReduce job

Science.gov (United States)

Zhou, Huaping; Liu, Guangzong; Gui, Haixia

2017-09-01

MapReduce has been widely used in large scale and complex datasets as a kind of distributed programming model. Original Hash partitioning function in MapReduce often results the problem of data skew when data distribution is uneven. To solve the imbalance of data partitioning, we proposes a strategy to change the remaining partitioning index when data is skewed. In Map phase, we count the amount of data which will be distributed to each reducer, then Job Tracker monitor the global partitioning information and dynamically modify the original partitioning function according to the data skew model, so the Partitioner can change the index of these partitioning which will cause data skew to the other reducer that has less load in the next partitioning process, and can eventually balance the load of each node. Finally, we experimentally compare our method with existing methods on both synthetic and real datasets, the experimental results show our strategy can solve the problem of data skew with better stability and efficiency than Hash method and Sampling method for non-connectivity MapReduce task.

Textural characteristics of foreshore sediments along Karnataka shoreline, west coast of India

Digital Repository Service at National Institute of Oceanography (India)

Dora, G.U.; SanilKumar, V.; Philip, C.S.; Johnson, G.; Vinayaraj, P.; Gowthaman, R.

skewed to coarse skewed with platykurtic, mesokurtic and leptokurtic characters. Grain characteristics varied spatially and temporally along with beach orientation, foreshore slope and wave action. A negative correlation between mean and sorting...

Beyond Zar: the use and abuse of classification statistics for otolith chemistry.

Science.gov (United States)

Jones, C M; Palmer, M; Schaffler, J J

2017-02-01

Classification method performance was evaluated using otolith chemistry of juvenile Atlantic menhaden Brevoortia tyrannus when assumptions of data normality were met and were violated. Four methods were tested [linear discriminant function analysis (LDFA), quadratic discriminant function analysis (QDFA), random forest (RF) and artificial neural networks (ANN)] using computer simulation to determine their performance when variable-group means ranged from small to large and their performance under conditions of typical skewness to double the amount of skewness typically observed. Using the kappa index, the parametric methods performed best after applying appropriate data transformation, gaining 2% better performance with LDFA performing slightly better than QDFA. RF performed as well as QDFA and showed no difference in performance between raw and transformed data while the performance of ANN was the poorest and worse with raw data. All methods performed well when group differences were large, but parametric methods outperformed machine-learning methods. When data were skewed the performance of all methods declined and worsened with greater skewness, but RF performed consistently as well or better than the other methods in the presence of skewness. The parametric methods were found to be more powerful when assumptions of normality can be met and can be used confidently when skewness and kurtosis are minimized. When these assumptions cannot be minimized, then machine-algorithm methods should also be tried. © 2016 The Fisheries Society of the British Isles.

Brain size and urbanization in birds

Institute of Scientific and Technical Information of China (English)

Anders; Pape; M?ller; Johannes; Erritz?e

2015-01-01

Background: Brain size may affect the probability of invasion of urban habitats if a relatively larger brain entails superior ability to adapt to novel environments. However, once urbanized urban environments may provide poor quality food that has negative consequences for normal brain development resulting in an excess of individuals with small brains.Methods: Here we analyze the independent effects of mean, standard deviation and skewness in brain mass for invasion of urban habitats by 108 species of birds using phylogenetic multiple regression analyses weighted by sample size.Results: There was no significant difference in mean brain mass between urbanized and non-urbanized species or between urban and rural populations of the same species, and mean brain mass was not significantly correlated with time since urbanization. Bird species that became urbanized had a greater standard deviation in brain mass than non-urbanized species, and the standard deviation in brain mass increased with time since urbanization. Brain mass was significantly left skewed in species that remained rural, while there was no significant skew in urbanized species. The degree of left skew was greater in urban than in rural populations of the same species, and successfully urbanized species decreased the degree of left skew with time since urbanization. This is consistent with the hypothesis that sub-optimal brain development was more common in rural habitats resulting in disproportionately many individuals with very smal brains.Conclusions: These findings do not support the hypothesis that large brains promote urbanization, but suggest that skewness has played a role in the initial invasion of urban habitats, and that variance and skew in brain mass have increased as species have become urbanized.

Brain size and urbanization in birds

Institute of Scientific and Technical Information of China (English)

Anders Pape Mller; Johannes Erritze

2015-01-01

Background:Brain size may affect the probability of invasion of urban habitats if a relatively larger brain entails superior ability to adapt to novel environments. However, once urbanized urban environments may provide poor quality food that has negative consequences for normal brain development resulting in an excess of individuals with small brains. Methods:Here we analyze the independent effects of mean, standard deviation and skewness in brain mass for invasion of urban habitats by 108 species of birds using phylogenetic multiple regression analyses weighted by sample size. Results:There was no significant difference in mean brain mass between urbanized and non-urbanized species or between urban and rural populations of the same species, and mean brain mass was not significantly correlated with time since urbanization. Bird species that became urbanized had a greater standard deviation in brain mass than non-urbanized species, and the standard deviation in brain mass increased with time since urbanization. Brain mass was significantly left skewed in species that remained rural, while there was no significant skew in urbanized species. The degree of left skew was greater in urban than in rural populations of the same species, and successfully urbanized species decreased the degree of left skew with time since urbanization. This is consistent with the hypothesis that sub-optimal brain development was more common in rural habitats resulting in disproportionately many individuals with very smal brains. Conclusions:These findings do not support the hypothesis that large brains promote urbanization, but suggest that skewness has played a role in the initial invasion of urban habitats, and that variance and skew in brain mass have increased as species have become urbanized.

BACKTESTING VALUE AT RISK MODELS IN THE PRESENCE OF STRUCTURAL BREAK ON THE ROMANIAN AND HUNGARIAN STOCK MARKETS

Directory of Open Access Journals (Sweden)

Cociuba Mihail Ioan

2014-07-01

Full Text Available Transactions on financial markets are associated with variability, risk and uncertainty, so quantification of risk has a great importance. Beside Standard Deviation and Variance, one of the most involved risk measure methods is Value-at-Risk (VaR. In this study, we use daily return for the stock index from Romania (BET and Hungary (BUX for the 01:2007 - 02:2013 periods in order to test the influence of structural breaks on the VaR metrics. We find out that the ARCH phenomenon is present, so we use the GARCH family models. The structural breaks in the series mean and variance are identified using the Zivot-Andrews test and PELT algorithm, the structural break dates are captured using dummy variables in the GARCH models (struc-GARCH, the selection of models is done using the informational criterion [Akaike, Schwarz, Log-likelihood]. The results of present research show a greater volatility associated with a higher risk level in case of Romanian stock index. The stock market indices return follows a negatively skewed and leptokurtic distributions forms either in two cases, so is unspecific a normal distribution. After applying above mentioned tests we can conclude that there are eight structural breaks in BET index returns variance and there are five breakpoints in case of BUX. The breakpoints in mean show very closely results in time, for BET in February 2009 and for BUX March 2009. Backtesting VaR models are done by measuring the number of times the loss is greater than the VaR forecast. The first step for unconditional coverage testing consists in comparing of fraction of VaR violation for a particular risk model. The independence testing it is very important tool in back-testing, because it is not the same that the VaR violations are differentiated in time or there are clustered in some certain period. By checking the independence test, we have the possibility to discover and reject the model with clustered hit sequence. Testing the influence

Magnetic measurements of the correction and adjustment magnets of the main ring

International Nuclear Information System (INIS)

Trbojevic, D.

1986-07-01

Correction magnets correct the field imperfections and alignment errors of the main quadrupole and bend magnets. For reducing and controlling chromaticity there are 186 sextupoles and 78 octupoles, while for suppressing various resonances there are 12 normal and 18 skew sextupoles and 24 normal and 19 skew quadrupoles. Beam positions are individually controlled by 108 horizontal and 108 skew dipoles. This report includes results of the all Main Ring correction and adjustment magnet harmonic measurements. The measurement principle and basic equations are described

Biometric and morphometric studies of Perna viridis and Perna indica along the southwest coast of India: a statistical approach

Digital Repository Service at National Institute of Oceanography (India)

Jayalakshmy, K.V.; Nair, M.; DileepKumar, R.; Vijayan, M.

morphometric gradient groups (spat and adult), indicating the different phenotypic plasticity between them. The factor scores classified P. indica as a unimodal, positively skewed leptokurtic population and P. viridis as a unimodal, negatively skewed...

Electrical structures in the northwest margin of the Junggar basin: Implications for its late Paleozoic geodynamics

Science.gov (United States)

Zhang, Sheng; Xu, Yixian; Jiang, Li; Yang, Bo; Liu, Ying; Griffin, W. L.; Luo, Yong; Huang, Rong; Zhou, Yong; Zhang, Liangliang

2017-10-01

Recent geological, geochemical and geophysical data have inclined to support the presence of a remnant Paleozoic oceanic lithosphere beneath the Western Junggar, southwestern Chinese Altaids. However, regional high-resolution geophysical data have been rarely deployed to image its geometry, making it difficult to trace its evolution and final geodynamic setting. Presently, two magnetotelluric (MT) profiles are deployed across the northwest margin of the Junggar basin and the southern Darbut belt to image the electrical structure of the crust and lithospheric mantle. High-quality data at 102 sites and the quasi-2D indications of phase tensor skew angles and impedance phase ellipses for relatively short periods (up to 500 s) allow us to invert the two profile data by a 2-D scheme. The resistivity cross-section of a NW-SE striking LINE2 sheds light on a fossil intraoceanic subduction system, and reveals the Miaoergou intrusions as a bowl-like pluton, indicating that the multi-phase intrusions primarily formed in a post-collisional setting. The resistivity cross-section of striking NE-SW LINE1 reveals a possible oceanic slab with relatively lower resistivity underlying the low-resistivity sedimentary strata and high-resistivity mélange. Given that the profile of LINE1 cuts the out-rise zone of a subducted slab developed during the late Paleozoic, the 2-D resistivity model may thus represent the zone that have experienced heterogeneous deformation, reflecting subduction with barrier variation parallel to the ancient trench. Moreover, as shown in previous results, the new MT data also illustrate that the Darbut Fault is a thin-skinned structure, which has been erased at depths during the subsequent magmatism.

Diversity of dermal denticle structure in sharks: Skin surface roughness and three-dimensional morphology.

Science.gov (United States)

Ankhelyi, Madeleine V; Wainwright, Dylan K; Lauder, George V

2018-05-29

Shark skin is covered with numerous placoid scales or dermal denticles. While previous research has used scanning electron microscopy and histology to demonstrate that denticles vary both around the body of a shark and among species, no previous study has quantified three-dimensional (3D) denticle structure and surface roughness to provide a quantitative analysis of skin surface texture. We quantified differences in denticle shape and size on the skin of three individual smooth dogfish sharks (Mustelus canis) using micro-CT scanning, gel-based surface profilometry, and histology. On each smooth dogfish, we imaged between 8 and 20 distinct areas on the body and fins, and obtained further comparative skin surface data from leopard, Atlantic sharpnose, shortfin mako, spiny dogfish, gulper, angel, and white sharks. We generated 3D images of individual denticles and measured denticle volume, surface area, and crown angle from the micro-CT scans. Surface profilometry was used to quantify metrology variables such as roughness, skew, kurtosis, and the height and spacing of surface features. These measurements confirmed that denticles on different body areas of smooth dogfish varied widely in size, shape, and spacing. Denticles near the snout are smooth, paver-like, and large relative to denticles on the body. Body denticles on smooth dogfish generally have between one and three distinct ridges, a diamond-like surface shape, and a dorsoventral gradient in spacing and roughness. Ridges were spaced on average 56 µm apart, and had a mean height of 6.5 µm, comparable to denticles from shortfin mako sharks, and with narrower spacing and lower heights than other species measured. We observed considerable variation in denticle structure among regions on the pectoral, dorsal, and caudal fins, including a leading-to-trailing edge gradient in roughness for each region. Surface roughness in smooth dogfish varied around the body from 3 to 42 microns. © 2018 Wiley Periodicals, Inc.

Signatures of self-assembly in size distributions of wood members in dam structures of Castor canadensis

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David M. Blersch

2014-12-01

Full Text Available Beavers (Castor canadensis construct dams on rivers throughout most of their historical range in North America, and their impact on water patterns in the landscape is considerable. Dam formation by beavers involves two processes: (1 intentional construction through the selection and placement of wood and sediment, which facilitates (2 the passive capture and accretion of suspended wood and sediment. The second process is a self-assembly mechanism that the beavers leverage by utilizing energy subsidies of watershed transport processes. The relative proportion of beaver activity to self-assembly processes in dam construction, however, is unknown. Here we show that lotic self-assembly processes account for a substantial portion of the work expended in beaver dam construction. We found through comprehensive measurement of the stick dimensions that the distributions for diameter, length, and volume are log-normal. By noting evidence of teeth markings, we determined that size distributions skewed significantly larger for wood handled by beavers compared to those that were not. Subsequent mass calculations suggest that beavers perform 50%–70% of the work of wood member placement for dam assembly, with riparian self-assembly processes contributing the remainder. Additionally, our results establish a benchmark for assessing the proportion of self-assembly work in similar riparian structures. Keywords: Beaver dam, Construction, Castor canadensis, Self-assembly, Distribution, Wood

Recurrent emergence of structural variants of LTR retrotransposon CsRn1 evolving novel expression strategy and their selective expansion in a carcinogenic liver fluke, Clonorchis sinensis.

Science.gov (United States)

Kim, Seon-Hee; Kong, Yoon; Bae, Young-An

2017-06-01

Autonomous retrotransposons, in which replication and transcription are coupled, encode the essential gag and pol genes as a fusion or separate overlapping form(s) that are expressed in single transcripts regulated by a common upstream promoter. The element-specific expression strategies have driven development of relevant translational recoding mechanisms including ribosomal frameshifting to satisfy the protein stoichiometry critical for the assembly of infectious virus-like particles. Retrotransposons with different recoding strategies exhibit a mosaic distribution pattern across the diverse families of reverse transcribing elements, even though their respective distributions are substantially skewed towards certain family groups. However, only a few investigations to date have focused on the emergence of retrotransposons evolving novel expression strategy and causal genetic drivers of the structural variants. In this study, the bulk of genomic and transcribed sequences of a Ty3/gypsy-like CsRn1 retrotransposon in Clonorchis sinensis were analyzed for the comprehensive examination of its expression strategy. Our results demonstrated that structural variants with single open reading frame (ORF) have recurrently emerged from precedential CsRn1 copies encoding overlapping gag-pol ORFs by a single-nucleotide insertion in an upstream region of gag stop codon. In the parasite genome, some of the newly evolved variants appeared to undergo proliferative burst as active master lineages together with their ancestral copies. The genetic event was similarly observed in Opisthorchis viverrini, the closest neighbor of C. sinensis, whereas the resulting structural variants might have failed to overcome purifying selection and comprised minor remnant copies in the Opisthorchis genome. Copyright © 2017 Elsevier B.V. All rights reserved.

The mitochondrial genome of the entomophagous endoparasite Xenosvesparum (Insecta: Strepsiptera)

Energy Technology Data Exchange (ETDEWEB)

Carapelli, Antonio; Vannini, Laura; Nardi, Francesco; Boore,Jeffrey L.; Beani, Laura; Dallai, Romano; Frati, Francesco

2005-12-01

In this study, the nearly complete sequence (14,519 bp) of the mitochondrial DNA (mtDNA) of the entomophagous endoparasite Xenos vesparum (Insecta: Strepsiptera) is described. All protein coding genes (PCGs) are in the arrangement known to be ancestral for insects, but three tRNA genes (trnA, trnS(gcu), and trnL(uag)) have transposed to derived positions and there are three tandem copies of trnH, each of which is potentially functional. All of these rearrangements except for that of trnL(uag) is within the short span between nad3 and nad4 and there are numerous blocks of unassignable sequence in this region, perhaps as remnants of larger scale predisposing rearrangements. X. vesparum mtDNA nucleotide composition is strongly biased toward As and Ts, as is typical for insect mtDNAs. There is also significant strand skew in the distribution of these nucleotides, with the J-strand being richer in A than T and in C than G, and the N-strand showing an opposite skew for complementary pairs of nucleotides. The hypothetical secondary structure of the 16S rRNA has also been reconstructed, obtaining a structural model similar to that of other insects.

P1-9: Relationship between Color Shifts in Land's Two-Color Method and Higher- and Lower-Level Visual Information

Directory of Open Access Journals (Sweden)

Saki Iwaida

2012-10-01

Full Text Available Land's two-color method gives rise to apparent full-color perception, even though only two colors (e.g., red and gray are used. Previous studies indicate that chromatic adaptation, color memory, and inductive effects contribute to the shifts of color perception from real to illusory colors (e.g., Kuriki, 2006 Vision Research 46 3055–3066. This paper investigates the relationship between the color shifts induced by Land images and the skewness of the luminance histogram. In Experiment 1, several Land images are created based on a yellow ball, and the magnitude of the color shifts of the images are measured. The results of Experiment 1 show a significant correlation between the magnitude of the color shifts and skewness, suggesting that skewness is critical for the color shifts. In Experiment 2, we test the hypothesis that color shifts depends on just skewness; the color shifts should be invariant even if the Land images are scrambled. However, the results of Experiment 2 demonstrate that scrambled Land images exhibit less intense color shifts, suggesting that color shifts are determined by the object's overall shape or surface gloss, not just skewness. Taken together, we conclude that both low-level visual processes, such as those associated with luminance histogram skew, and high-level cognitive functions, such as object interpretation or understanding of surface gloss, are involved in the color shift of Land images.

Optimum Stratification of a Skewed Population

OpenAIRE

D.K. Rao; M.G.M. Khan; K.G. Reddy

2014-01-01

The focus of this paper is to develop a technique of solving a combined problem of determining Optimum Strata Boundaries(OSB) and Optimum Sample Size (OSS) of each stratum, when the population understudy isskewed and the study variable has a Pareto frequency distribution. The problem of determining the OSB isformulated as a Mathematical Programming Problem (MPP) which is then solved by dynamic programming technique. A numerical example is presented to illustrate the compu...

Global coupling and decoupling of the APS storage ring

International Nuclear Information System (INIS)

Chae, Yong-Chul; Liu, Jianyang; Teng, L.C.

1995-01-01

This Paper describes a study of controlling the coupling between the horizontal and the vertical betatron oscillations in the APS storage ring. First, we investigate the strengthening of coupling using two families of skew quadrupoles. Using smooth approximation, we obtained the formulae to estimate the coupling ratio defined as the ratio of the vertical and horizontal emittances or, for a single particle, the ratio of the maximum values of the Courant Snyder invariants. Since we knew that the coupling is mostly enhanced by the 21st harmonic content of skew quadrupole distribution, we carried out the harmonic analysis in order to find the optimum arrangement of the skew quadrupoles. The numerical results from tracking a single particle are presented for the various configurations of skew quadrupoles. Second, we describe the global decoupling procedure to minimize the unwanted coupling effects. These are mainly due to the random roll errors of normal quadrupoles. It is shown that even with the rather large rms roll error of 2 mrad we can reduce the Coupling from 70 percent to 10 percent with a skew quadrupole strength which is one order of magnitude lower than the typical normal quadrupole strength

Stable isotope evidence for formation from magmatic fluids of the mineralized breccias in the Los Bronces and El Teniente copper deposits, Central Chile

International Nuclear Information System (INIS)

Skewes, M.A; Arevalo, A; Holmgren, C.; Stern, C.R

2001-01-01

The giant Miocene and Pliocene Rio Blanco-Los Bronces (Warnaars et al., 1985; Serrano et al., 1996; Vargas et al., 1999) and El Teniente (Camus, 1975; Cuadra, 1986; Skewes and Arevalo, 2000) copper deposits of central Chile are among the largest copper deposits in the world. Hypogene copper ore is more significant than supergene ore in these deposits, and most of the hypogene copper occurs in the matrix of multiple clusters of breccias (Skewes and Stern, 1994; 1995). The origin of the large mineralized breccia pipes in these and other Andean copper deposits has been attributed to the explosive expansion of magmatic aqueous fluids derived from cooling plutons (Emmons, 1938; Kents, 1964; Warnaars et al., 1985; Sillitoe, 1985; Skewes and Stern, 1994, 1995). Warnaars et al. (1985) and Skewes and Stern (1996) suggested that mineral deposition in the matrix of these breccias took place by the rapid cooling of the same magmatic fluids that generated the brecciation. Highly saline, high-temperature magmatic fluid inclusions occur in quartz and tourmaline in the matrix of these breccias (Holmgren et al., 1988; Vargas et al., 1999; Skewes et al., 2001) (au)

Forecasting Value-at-Risk under Different Distributional Assumptions

Directory of Open Access Journals (Sweden)

Manuela Braione

2016-01-01

Full Text Available Financial asset returns are known to be conditionally heteroskedastic and generally non-normally distributed, fat-tailed and often skewed. These features must be taken into account to produce accurate forecasts of Value-at-Risk (VaR. We provide a comprehensive look at the problem by considering the impact that different distributional assumptions have on the accuracy of both univariate and multivariate GARCH models in out-of-sample VaR prediction. The set of analyzed distributions comprises the normal, Student, Multivariate Exponential Power and their corresponding skewed counterparts. The accuracy of the VaR forecasts is assessed by implementing standard statistical backtesting procedures used to rank the different specifications. The results show the importance of allowing for heavy-tails and skewness in the distributional assumption with the skew-Student outperforming the others across all tests and confidence levels.

Two-family compensation of linear horizontal/vertical coupling

International Nuclear Information System (INIS)

Peterson, J.

1991-10-01

Many existing circular accelerators have been able to adequately compensate their horizontal/vertical coupling by one or two families of skew-quadrupole corrector magnets. For example, the HERA proton storage ring at DESY has used just two skew quadrupoles correctors, the SPS at CERN can operate with just one skew quadrupole corrector, and the Tevatron at Fermilab with two families of skew quadrupoles. At first sight just two corrector families seem unlikely to be enough, since there are four independent horizontal/vertical coupling coefficients in the 4 x 4 transfer from one point to any other in the ring. Thus, for the general case four families of correctors would seem to be necessary. It will be shown that the adequacy of two-family correction for storage rings in a consequence of operating near the diagonal of the tune diagram

Accumulation risk assessment for the flooding hazard

Science.gov (United States)

Roth, Giorgio; Ghizzoni, Tatiana; Rudari, Roberto

2010-05-01

distribution as a special or limiting case (e.g., the skew-normal or skew-t distributions). The present contribution constitutes an attempt to provide a better estimation of the joint probability distribution able to describe flood events in a multi-site multi-basin fashion. This goal will be pursued through the multivariate skew-t distribution, which allows to analytically define the joint probability distribution. Performances of the skew-t distribution will be discussed with reference to the Tanaro River in Northwestern Italy. To enhance the characteristics of the correlation structure, both nested and non-nested gauging stations will be selected, with significantly different contributing areas.

Reading Statistics And Research

OpenAIRE

Akbulut, Reviewed By Yavuz

2008-01-01

The book demonstrates the best and most conservative ways to decipher and critique research reports particularly for social science researchers. In addition, new editions of the book are always better organized, effectively structured and meticulously updated in line with the developments in the field of research statistics. Even the most trivial issues are revisited and updated in new editions. For instance, purchaser of the previous editions might check the interpretation of skewness and ku...

Population genomic structure and adaptation in the zoonotic malaria parasite Plasmodium knowlesi

KAUST Repository

Assefa, Samuel

2015-10-06

Malaria cases caused by the zoonotic parasite Plasmodium knowlesi are being increasingly reported throughout Southeast Asia and in travelers returning from the region. To test for evidence of signatures of selection or unusual population structure in this parasite, we surveyed genome sequence diversity in 48 clinical isolates recently sampled from Malaysian Borneo and in five lines maintained in laboratory rhesus macaques after isolation in the 1960s from Peninsular Malaysia and the Philippines. Overall genomewide nucleotide diversity (π = 6.03 × 10) was much higher than has been seen in worldwide samples of either of the major endemic malaria parasite species Plasmodium falciparum and Plasmodium vivax. A remarkable substructure is revealed within P. knowlesi, consisting of two major sympatric clusters of the clinical isolates and a third cluster comprising the laboratory isolates. There was deep differentiation between the two clusters of clinical isolates [mean genomewide fixation index (F) = 0.21, with 9,293 SNPs having fixed differences of F = 1.0]. This differentiation showed marked heterogeneity across the genome, with mean F values of different chromosomes ranging from 0.08 to 0.34 and with further significant variation across regions within several chromosomes. Analysis of the largest cluster (cluster 1, 38 isolates) indicated long-term population growth, with negatively skewed allele frequency distributions (genomewide average Tajima\\'s D = -1.35). Against this background there was evidence of balancing selection on particular genes, including the circumsporozoite protein (csp) gene, which had the top Tajima\\'s D value (1.57), and scans of haplotype homozygosity implicate several genomic regions as being under recent positive selection.

Population genomic structure and adaptation in the zoonotic malaria parasite Plasmodium knowlesi

KAUST Repository

Assefa, Samuel; Lim, Caeul; Preston, Mark D.; Duffy, Craig W.; Nair, Mridul; Adroub, Sabir; Kadir, Khamisah A.; Goldberg, Jonathan M.; Neafsey, Daniel E.; Divis, Paul; Clark, Taane G.; Duraisingh, Manoj T.; Conway, David J.; Pain, Arnab; Singh, Balbir

2015-01-01

Malaria cases caused by the zoonotic parasite Plasmodium knowlesi are being increasingly reported throughout Southeast Asia and in travelers returning from the region. To test for evidence of signatures of selection or unusual population structure in this parasite, we surveyed genome sequence diversity in 48 clinical isolates recently sampled from Malaysian Borneo and in five lines maintained in laboratory rhesus macaques after isolation in the 1960s from Peninsular Malaysia and the Philippines. Overall genomewide nucleotide diversity (π = 6.03 × 10) was much higher than has been seen in worldwide samples of either of the major endemic malaria parasite species Plasmodium falciparum and Plasmodium vivax. A remarkable substructure is revealed within P. knowlesi, consisting of two major sympatric clusters of the clinical isolates and a third cluster comprising the laboratory isolates. There was deep differentiation between the two clusters of clinical isolates [mean genomewide fixation index (F) = 0.21, with 9,293 SNPs having fixed differences of F = 1.0]. This differentiation showed marked heterogeneity across the genome, with mean F values of different chromosomes ranging from 0.08 to 0.34 and with further significant variation across regions within several chromosomes. Analysis of the largest cluster (cluster 1, 38 isolates) indicated long-term population growth, with negatively skewed allele frequency distributions (genomewide average Tajima's D = -1.35). Against this background there was evidence of balancing selection on particular genes, including the circumsporozoite protein (csp) gene, which had the top Tajima's D value (1.57), and scans of haplotype homozygosity implicate several genomic regions as being under recent positive selection.

Turbulent structures of non-Newtonian solutions containing rigid polymers

Science.gov (United States)

Mohammadtabar, M.; Sanders, R. S.; Ghaemi, S.

2017-10-01

The turbulent structure of a channel flow of Xanthan Gum (XG) polymer solution is experimentally investigated and compared with water flow at a Reynolds number of Re = 7200 (based on channel height and properties of water) and Reτ = 220 (based on channel height and friction velocity, uτ0). The polymer concentration is varied from 75, 100, and 125 ppm to reach the point of maximum drag reduction (MDR). Measurements are carried out using high-resolution, two-component Particle Image Velocimetry (PIV) to capture the inner and outer layer turbulence. The measurements showed that the logarithmic layer shifts away from the wall with increasing polymer concentration. The slopes of the mean velocity profile for flows containing 100 and 125 ppm XG are greater than that measured for XG at 75 ppm, which is parallel with the slope obtained for deionized water. The increase in slope results in thickening buffer layer. At MDR, the streamwise Reynolds stresses are as large as those of the Newtonian flow while the wall-normal Reynolds stresses and Reynolds shear stresses are significantly attenuated. The sweep-dominated region in the immediate vicinity of the wall extends further from the wall with increasing polymer concentration. The near-wall skewness intensifies towards positive streamwise fluctuations and covers a larger wall-normal length at larger drag reduction values. The quadrant analysis at y + 0 = 25 shows that the addition of polymers inclines the principal axis of v versus u plot to almost zero (horizontal) as the joint probability density function of fluctuations becomes symmetric with respect to the u axis at MDR. The reduction of turbulence production is mainly associated with the attenuation of the ejection motions. The spatial-correlation of the fluctuating velocity field shows that increasing the polymer concentration increases the spatial coherence of u fluctuations in the streamwise direction while they appear to have the opposite effect in the wall

Developmental aspects of English argument structure constructions for Korean-speaking second language learners: Usage-based constructional approaches to language development

Directory of Open Access Journals (Sweden)

Gyu-Ho Shin

2017-01-01

Full Text Available This study investigates developmental aspects of English Argument Structure Constructions (ASCs for Korean-speaking second language (L2 learners, providing evidence of how they manifest human domain-general cognitive systems during language acquisition via usage-based constructional approaches to language development. Participants were instructed on six English ASC types with their representative verbs for three months. The data from grammaticality preference tasks, writing tests, and free-writing tasks were analysed. Comprehension data from the grammaticality preference tasks showed significant improvement in understanding ASCs after instruction, supporting sentence-level generalisations for language comprehension independent of individual verbs. The production data from the writing tests demonstrated more frequent use of two-argument constructions than three-argument ones, which indicates the internal complexity between ASC types. The results of the writing tests also displayed skewed exploitation of verbs representative of the target ASCs, implying a frequency-sensitive nature of language acquisition. All production data further revealed active use of prefabricated chunks and incorporation of new and old language items. Taken all together, these observations suggest language learners’ merging narrowly stabilised L2 routines with other (non-linguistic resources as necessary, sustaining efficiency in a sentence-building process, under the superintendence of cognitive factors when satisfying communicative intents.

Ultrasonic Transducer Design for the Axial Flaw Detection of Dissimilar Metal Weld

International Nuclear Information System (INIS)

Yoon, Byung Sik; Kim, Yong Sik; Yang, Seung Han

2011-01-01

Dissimilar metal welds in nuclear power plant are known as very susceptible to PWSCC flaws, and periodically inspected by the qualified inspector and qualified procedure during in-service inspection period. According to field survey data, the majority of their DMWs are located on tapered nozzle or adjacent to a tapered component. These types of configurations restrict examination access and also limit examination volume coverage. Additionally, circumferential scan for axially oriented flaw is very difficult to detect located on tapered surface because the transducer can't receive flaw response from reflector for miss-orientation. To overcome this miss-orientation, it is necessary adapt skewed ultrasonic transducer accommodate tapered surface. The skewed refracted longitudinal ultrasonic transducer designed by modeling and manufactured from the modelling result for axial flaw detection. Experimental results showed that the skewed refracted longitudinal ultrasonic transducer get higher flaw response than non-skewed refracted longitudinal ultrasonic transducer

Planar four node Piezoelectric elements with drilling degrees of freedom

CSIR Research Space (South Africa)

Long, CS

2006-03-12

Full Text Available retains the skew-symmetric part of the stress tensor, while in the second; the skew part of stress is eliminated from the functional. The finite elements derived from two of the variational formulations derived in this paper are investigated. The first...

Sex ratios of Mountain Plovers from egg production to fledging

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Margaret M. Riordan

2015-12-01

Full Text Available Skewed sex ratios can have negative implications for population growth if they do not match a species' life history. A skewed tertiary sex ratio has been detected in a population of Mountain Plover (Charadrius montanus, a grassland shorebird experiencing population declines. To study the cause of the observed male skew, we examined three early life stages between egg and fledgling in eastern Colorado from 2010 to 2012. This allows us to distinguish between egg production and chick survival as an explanation for the observed skew. We examined the primary sex ratio in eggs produced and the secondary sex ratio in hatched chicks to see if the sex ratio bias occurs before hatching. We also determined the sex ratio at fledging to reveal sex-specific mortality of nestlings. The primary sex ratio was 1.01 (± 0.01 males per female. The secondary sex ratio consisted of 1.10 (± 0.02 males per female. The probability of a chick surviving to fledging differed between males (0.55 ± 0.13 and females (0.47 ± 0.15, but the precision of these survival estimates was low. Sex ratios in early life stages of the Mountain Plover do not explain the skewed sex ratio observed in adults in this breeding population.

Detection of Doppler Microembolic Signals Using High Order Statistics

Directory of Open Access Journals (Sweden)

Maroun Geryes

2016-01-01

Full Text Available Robust detection of the smallest circulating cerebral microemboli is an efficient way of preventing strokes, which is second cause of mortality worldwide. Transcranial Doppler ultrasound is widely considered the most convenient system for the detection of microemboli. The most common standard detection is achieved through the Doppler energy signal and depends on an empirically set constant threshold. On the other hand, in the past few years, higher order statistics have been an extensive field of research as they represent descriptive statistics that can be used to detect signal outliers. In this study, we propose new types of microembolic detectors based on the windowed calculation of the third moment skewness and fourth moment kurtosis of the energy signal. During energy embolus-free periods the distribution of the energy is not altered and the skewness and kurtosis signals do not exhibit any peak values. In the presence of emboli, the energy distribution is distorted and the skewness and kurtosis signals exhibit peaks, corresponding to the latter emboli. Applied on real signals, the detection of microemboli through the skewness and kurtosis signals outperformed the detection through standard methods. The sensitivities and specificities reached 78% and 91% and 80% and 90% for the skewness and kurtosis detectors, respectively.

Nanoscale high-content analysis using compositional heterogeneities of single proteoliposomes

DEFF Research Database (Denmark)

Mathiasen, Signe; Christensen, Sune M.; Fung, Juan José

2014-01-01

Proteoliposome reconstitution is a standard method to stabilize purified transmembrane proteins in membranes for structural and functional assays. Here we quantified intrareconstitution heterogeneities in single proteoliposomes using fluorescence microscopy. Our results suggest that compositional...... heterogeneities can severely skew ensemble-average proteoliposome measurements but also enable ultraminiaturized high-content screens. We took advantage of this screening capability to map the oligomerization energy of the β2-adrenergic receptor using ∼10(9)-fold less protein than conventional assays....

Application of Piezocomposite Twin, Side by Side, Phased Array UT Probes for the Inspection of Stainless Steel

International Nuclear Information System (INIS)

Delaide, M.; Dumas, Ph

2005-01-01

UT probes to be used for the examination of coarse-grain structure must allow to detect and size cracks, with a high reliability level. The combination of TRL probes, with phased array and piezocomposite technologies allows to improve probes performances and inspection speed. Single element crystals are replaced by matrix arrays, allowing to deflect and skew the beams, to change the inspection depth. This paper describes the designing, the manufacturing and the characterisation of several probes

Global coupling and decoupling of the APS storage ring

Energy Technology Data Exchange (ETDEWEB)

Chae, Y.C.; Liu, J.; Teng, L.C.

1993-07-01

This paper describes a study of controlling the coupling between the horizontal and the vertical betatron oscillations in the 7-GeV Advanced Photon Source (APS) storage ring. First, we investigate the strengthening of coupling using two families of skew quadrupoles. Twenty skew quadrupoles are arranged in the 40 sectors of the storage ring and powered in such a way so as to generate both quadrature components of the required 21st harmonic. The numerical results from tracking a single particle are presented for the various configurations of skew quadrupoles. Second, we describe the global decoupling procedure to minimize the unwanted coupling effects. These are mainly due to the random roll errors of normal quadruples. It is shown that even with the rather large rms roll error of 2 mrad, the coupling effects can be compensated for with 20 skew quadrupoles each having maximum strength one order of magnitude lower than the typical normal quadrupole strength.

Dominance and queen succession in captive colonies of the eusocial naked mole-rat, Heterocephalus glaber.

Science.gov (United States)

Clarke, F M; Faulkes, C G

1997-07-22

Naked mole-rat colonies exhibit a high reproductive skew, breeding being typically restricted to one female (the 'queen') and one to three males. Other colony members are reproductively suppressed, although this suppression can be reversed following the removal or death of the queen. We examined dominance and queen succession within captive colonies to investigate the relationship between urinary testosterone and cortisol, dominance rank and reproductive status; and to determine if behavioural and/or physiological parameters can be used as predictors of queen succession. Social structure was characterized by a linear dominance hierarchy before and after queen removal. Prior to queen removal, dominance rank was negatively correlated with body weight and urinary testosterone and cortisol titres in males and females. Queen removal results in social instability and aggression between high ranking individuals. Dominance rank appears to be a good predictor of reproductive status: queens are the highest ranking colony females and are succeeded by the next highest ranking females. The intense dominance-related aggression that accompanies reproductive succession in naked mole-rats provides empirical support for optimal skew theory.

R-ChIP Using Inactive RNase H Reveals Dynamic Coupling of R-loops with Transcriptional Pausing at Gene Promoters.

Science.gov (United States)

Chen, Liang; Chen, Jia-Yu; Zhang, Xuan; Gu, Ying; Xiao, Rui; Shao, Changwei; Tang, Peng; Qian, Hao; Luo, Daji; Li, Hairi; Zhou, Yu; Zhang, Dong-Er; Fu, Xiang-Dong

2017-11-16

R-loop, a three-stranded RNA/DNA structure, has been linked to induced genome instability and regulated gene expression. To enable precision analysis of R-loops in vivo, we develop an RNase-H-based approach; this reveals predominant R-loop formation near gene promoters with strong G/C skew and propensity to form G-quadruplex in non-template DNA, corroborating with all biochemically established properties of R-loops. Transcription perturbation experiments further indicate that R-loop induction correlates to transcriptional pausing. Interestingly, we note that most mapped R-loops are each linked to a nearby free RNA end; by using a ribozyme to co-transcriptionally cleave nascent RNA, we demonstrate that such a free RNA end coupled with a G/C-skewed sequence is necessary and sufficient to induce R-loop. These findings provide a topological solution for RNA invasion into duplex DNA and suggest an order for R-loop initiation and elongation in an opposite direction to that previously proposed. Copyright © 2017 Elsevier Inc. All rights reserved.

The influence of initial beliefs on judgments of probability.

Science.gov (United States)

Yu, Erica C; Lagnado, David A

2012-01-01

This study aims to investigate whether experimentally induced prior beliefs affect processing of evidence including the updating of beliefs under uncertainty about the unknown probabilities of outcomes and the structural, outcome-generating nature of the environment. Participants played a gambling task in the form of computer-simulated slot machines and were given information about the slot machines' possible outcomes without their associated probabilities. One group was induced with a prior belief about the outcome space that matched the space of actual outcomes to be sampled; the other group was induced with a skewed prior belief that included the actual outcomes and also fictional higher outcomes. In reality, however, all participants sampled evidence from the same underlying outcome distribution, regardless of priors given. Before and during sampling, participants expressed their beliefs about the outcome distribution (values and probabilities). Evaluation of those subjective probability distributions suggests that all participants' judgments converged toward the observed outcome distribution. However, despite observing no supporting evidence for fictional outcomes, a significant proportion of participants in the skewed priors condition expected them in the future. A probe of the participants' understanding of the underlying outcome-generating processes indicated that participants' judgments were based on the information given in the induced priors and consequently, a significant proportion of participants in the skewed condition believed the slot machines were not games of chance while participants in the control condition believed the machines generated outcomes at random. Beyond Bayesian or heuristic belief updating, priors not only contribute to belief revision but also affect one's deeper understanding of the environment.

Nucleotide composition bias and codon usage trends of gene ...

Indian Academy of Sciences (India)

2015-06-10

Jun 10, 2015 ... In a wide variety of organisms, synonymous codons are selected with different ... In addition, a series of GC skew and AT skew data was calculated for codon positions 1, ..... bias from different perspectives. Interestingly .... This study was supported by programme for Changjiang Scholars and Innovative ...

Prognostic value of X-chromosome inactivation in symptomatic female carriers of dystrophinopathy

Directory of Open Access Journals (Sweden)

Juan-Mateu Jonàs

2012-10-01

Full Text Available Abstract Background Between 8% and 22% of female carriers of DMD mutations exhibit clinical symptoms of variable severity. Development of symptoms in DMD mutation carriers without chromosomal rearrangements has been attributed to skewed X-chromosome inactivation (XCI favouring predominant expression of the DMD mutant allele. However the prognostic use of XCI analysis is controversial. We aimed to evaluate the correlation between X-chromosome inactivation and development of clinical symptoms in a series of symptomatic female carriers of dystrophinopathy. Methods We reviewed the clinical, pathological and genetic features of twenty-four symptomatic carriers covering a wide spectrum of clinical phenotypes. DMD gene analysis was performed using MLPA and whole gene sequencing in blood DNA and muscle cDNA. Blood and muscle DNA was used for X-chromosome inactivation (XCI analysis thought the AR methylation assay in symptomatic carriers and their female relatives, asymptomatic carriers as well as non-carrier females. Results Symptomatic carriers exhibited 49.2% more skewed XCI profiles than asymptomatic carriers. The extent of XCI skewing in blood tended to increase in line with the severity of muscle symptoms. Skewed XCI patterns were found in at least one first-degree female relative in 78.6% of symptomatic carrier families. No mutations altering XCI in the XIST gene promoter were found. Conclusions Skewed XCI is in many cases familial inherited. The extent of XCI skewing is related to phenotype severity. However, the assessment of XCI by means of the AR methylation assay has a poor prognostic value, probably because the methylation status of the AR gene in muscle may not reflect in all cases the methylation status of the DMD gene.

Predicting species diversity of benthic communities within turbid nearshore using full-waveform bathymetric LiDAR and machine learners.

Directory of Open Access Journals (Sweden)

Antoine Collin

Full Text Available Epi-macrobenthic species richness, abundance and composition are linked with type, assemblage and structural complexity of seabed habitat within coastal ecosystems. However, the evaluation of these habitats is highly hindered by limitations related to both waterborne surveys (slow acquisition, shallow water and low reactivity and water clarity (turbid for most coastal areas. Substratum type/diversity and bathymetric features were elucidated using a supervised method applied to airborne bathymetric LiDAR waveforms over Saint-Siméon-Bonaventure's nearshore area (Gulf of Saint-Lawrence, Québec, Canada. High-resolution underwater photographs were taken at three hundred stations across an 8-km(2 study area. Seven models based upon state-of-the-art machine learning techniques such as Naïve Bayes, Regression Tree, Classification Tree, C 4.5, Random Forest, Support Vector Machine, and CN2 learners were tested for predicting eight epi-macrobenthic species diversity metrics as a function of the class number. The Random Forest outperformed other models with a three-discretized Simpson index applied to epi-macrobenthic communities, explaining 69% (Classification Accuracy of its variability by mean bathymetry, time range and skewness derived from the LiDAR waveform. Corroborating marine ecological theory, areas with low Simpson epi-macrobenthic diversity responded to low water depths, high skewness and time range, whereas higher Simpson diversity relied upon deeper bottoms (correlated with stronger hydrodynamics and low skewness and time range. The degree of species heterogeneity was therefore positively linked with the degree of the structural complexity of the benthic cover. This work underpins that fully exploited bathymetric LiDAR (not only bathymetrically derived by-products, coupled with proficient machine learner, is able to rapidly predict habitat characteristics at a spatial resolution relevant to epi-macrobenthos diversity, ranging from clear to

An asymmetric emittance electron source for the GALAXIE dielectric-laser accelerator injector

Energy Technology Data Exchange (ETDEWEB)

Valloni, A.; Cahill, A.; Fukusawa, A.; Musumeci, P.; Spataro, B.; Yakub, A.; Rosenzweig, J. B. [Dept. of Physics and Astronomy, University of California, Los Angeles, 405 Hilgard Ave., Los Angeles, CA 90034 (United States); Accelerator Division, Laboratori Nazionali di Frascati (INFN-LNF), Via E. Fermi 40, Frascati (RM) 00044 (Italy); Dept. of Physics and Astronomy, University of California, Los Angeles, 405 Hilgard Ave., Los Angeles, CA 90034 (United States)

2012-12-21

The GALAXIE project is a program to develop an all-optical, very high field accelerator and undulator integrated SASE FEL system based on dielectric laser-excited structures that support >GV/m fields. These structures are very wide in one direction to allow adequate charge given beam loading considerations, but also having small (subwavelength) apertures in the narrow direction. Such small vertical dimensions yield strict restrictions on the emittance in this direction, while no such constraint exists in the wide transverse direction. However, the overall beam brightness is restricted by the performance requirements on the FEL. To meet these demands, we are studying a very high field gun with a magnetized cathode, yielding a beam with angular momentum content. This beam is then subject to a skew-quad triplet that splits the emittances; this process is reversed to give a round beam after acceleration. This symmetric emittance beam avoids gain-degrading multiple-transverse-mode operation of the FEL, which also demands that the effects of the angular momentum in the beam be mitigated. In this paper we discuss the RF design of an X-band gun to be operated at {approx}200 MV/m peak field giving a 1 pC magnetized beam with unprecedented brightness. We examine the design of the focusing and skew-quad systems, investigating the associated beam dynamics and efficacy of emittance splitting.

Fine structure symmetry-breaking in decaying passive scalars advected by laminar shear flow

Science.gov (United States)

Bernardi, Francesca; Aminian, Manuchehr; Camassa, Roberto; Harris, Daniel; McLaughlin, Richard; UNC Joint Applied Mathematics; Marine Sciences Fluids Lab Team

2017-11-01

We investigate the dispersion of a passive scalar in laminar shear flow through rectangular and elliptical channels. We show through simulation, analysis and experiments that the cross-sectional aspect ratio sets the sign of the average skewness at long times, which describes the longitudinal asymmetry of the tracer distribution. We then extend the results to study the entire tracer distribution rather than only its longitudinal moments. With an analytical approach, we show that it is possible to describe the behavior of the tracer distribution at long time at any location in the cross-section, in turn highlighting the mechanism by which symmetry is broken. Future directions will be discussed. ONR Grant DURIP N00014-12-1-0749. NSF Grants RTG DMS-0943851, CMG ARC-1025523, DMS-1009750, and DMS-1517879.

The mathematics of mitering and its artful application

NARCIS (Netherlands)

Verhoeff, T.; Verhoeff, K.; Sarhangi, R.; Séquin, C.

2008-01-01

We give a systematic presentation of the mathematics behind the classic miter joint and variants, like the skew miter joint and the (skew) fold joint. The latter is especially useful for connecting strips at an angle. We also address the problems that arise from constructing a closed 3D path from

T4 fibrations over Calabi–Yau two-folds and non-Kähler manifolds in string theory

Directory of Open Access Journals (Sweden)

Hai Lin

2016-08-01

Full Text Available We construct a geometric model of eight-dimensional manifolds and realize them in the context of type II string theory. These eight-manifolds are constructed by non-trivial T4 fibrations over Calabi–Yau two-folds. These give rise to eight-dimensional non-Kähler Hermitian manifolds with SU(4 structure. The eight-manifold is also a circle fibration over a seven-dimensional G2 manifold with skew torsion. The eight-manifolds of this type appear as internal manifolds with SU(4 structure in type IIB string theory with F3 and F7 fluxes. These manifolds have generalized calibrated cycles in the presence of fluxes.

Incidence of genome structure, DNA asymmetry, and cell physiology on T-DNA integration in chromosomes of the phytopathogenic fungus Leptosphaeria maculans.

Science.gov (United States)

Bourras, Salim; Meyer, Michel; Grandaubert, Jonathan; Lapalu, Nicolas; Fudal, Isabelle; Linglin, Juliette; Ollivier, Benedicte; Blaise, Françoise; Balesdent, Marie-Hélène; Rouxel, Thierry

2012-08-01

The ever-increasing generation of sequence data is accompanied by unsatisfactory functional annotation, and complex genomes, such as those of plants and filamentous fungi, show a large number of genes with no predicted or known function. For functional annotation of unknown or hypothetical genes, the production of collections of mutants using Agrobacterium tumefaciens-mediated transformation (ATMT) associated with genotyping and phenotyping has gained wide acceptance. ATMT is also widely used to identify pathogenicity determinants in pathogenic fungi. A systematic analysis of T-DNA borders was performed in an ATMT-mutagenized collection of the phytopathogenic fungus Leptosphaeria maculans to evaluate the features of T-DNA integration in its particular transposable element-rich compartmentalized genome. A total of 318 T-DNA tags were recovered and analyzed for biases in chromosome and genic compartments, existence of CG/AT skews at the insertion site, and occurrence of microhomologies between the T-DNA left border (LB) and the target sequence. Functional annotation of targeted genes was done using the Gene Ontology annotation. The T-DNA integration mainly targeted gene-rich, transcriptionally active regions, and it favored biological processes consistent with the physiological status of a germinating spore. T-DNA integration was strongly biased toward regulatory regions, and mainly promoters. Consistent with the T-DNA intranuclear-targeting model, the density of T-DNA insertion correlated with CG skew near the transcription initiation site. The existence of microhomologies between promoter sequences and the T-DNA LB flanking sequence was also consistent with T-DNA integration to host DNA mediated by homologous recombination based on the microhomology-mediated end-joining pathway.