Science.gov

Sample records for pairwise covariance adds

  1. A Basic Computer Program for Calculating Simultaneous Pairwise Comparisons in Analysis of Covariance.

    ERIC Educational Resources Information Center

    Powers, Stephen; Jones, Patricia

    1986-01-01

    This paper describes a computer program which tests all pairwise comparisons of adjusted means in analysis of covariance by using Tukey-Kramer Test. The program contains: means of covariate, adjusted means of the criterion measure, sample size, mean square error, and the desired percentile point on the Studentized range distribution. (JAZ)

  2. Kv7 channels regulate pairwise spiking covariability in health and disease.

    PubMed

    Ocker, Gabriel Koch; Doiron, Brent

    2014-07-15

    Low-threshold M currents are mediated by the Kv7 family of potassium channels. Kv7 channels are important regulators of spiking activity, having a direct influence on the firing rate, spike time variability, and filter properties of neurons. How Kv7 channels affect the joint spiking activity of populations of neurons is an important and open area of study. Using a combination of computational simulations and analytic calculations, we show that the activation of Kv7 conductances reduces the covariability between spike trains of pairs of neurons driven by common inputs. This reduction is beyond that explained by the lowering of firing rates and involves an active cancellation of common fluctuations in the membrane potentials of the cell pair. Our theory shows that the excess covariance reduction is due to a Kv7-induced shift from low-pass to band-pass filtering of the single neuron spike train response. Dysfunction of Kv7 conductances is related to a number of neurological diseases characterized by both elevated firing rates and increased network-wide correlations. We show how changes in the activation or strength of Kv7 conductances give rise to excess correlations that cannot be compensated for by synaptic scaling or homeostatic modulation of passive membrane properties. In contrast, modulation of Kv7 activation parameters consistent with pharmacological treatments for certain hyperactivity disorders can restore normal firing rates and spiking correlations. Our results provide key insights into how regulation of a ubiquitous potassium channel class can control the coordination of population spiking activity. PMID:24790164

  3. Add HOC?: dendritic nonlinearities shape higher-than-pairwise correlations and improve coding in noisy (spiking) neural populations

    NASA Astrophysics Data System (ADS)

    Zylberberg, Joel; Shea-Brown, Eric

    2013-03-01

    Recent experiments with relatively large neural populations show significant higher-order correlations (HOC): the data are poorly fit by pair-wise maximum entropy models, but well-fit by higher-order models. We seek to understand how HOC are shaped by the properties of networks and of the neurons therein, and how these HOC affect population coding. In our presentation, we will demonstrate that dendritic non-linearities similar to those observed in physiology experiments are equivalent to beyond-pairwise interactions in a spin-glass-type statistical model: they can either increase, or decrease, the magnitude of the HOC relative to the pair-wise correlations. We will then discuss a population coding model with parameterized pairwise- and higher-order interactions, revealing the conditions under which the beyond-pairwise interactions (dendritic nonlinearities) can increase the mutual information between a given set of stimuli, and the population responses. For jointly Gaussian stimuli, coding performance can be slightly improved by shaping the output HOC via dendritic nonlinearities, if the neural firing rates are low. For skewed stimulus distributions, like the distribution of luminance values in natural images, the performance gains are much larger. This work was supported by NSF grant DMS-1056125 and a Career Award at the Scientific Interface from the Burroughs-Wellcome Fund.

  4. Pairwise-Comparison Software

    NASA Technical Reports Server (NTRS)

    Ricks, Wendell R.

    1995-01-01

    Pairwise comparison (PWC) is computer program that collects data for psychometric scaling techniques now used in cognitive research. It applies technique of pairwise comparisons, which is one of many techniques commonly used to acquire the data necessary for analyses. PWC administers task, collects data from test subject, and formats data for analysis. Written in Turbo Pascal v6.0.

  5. Constraining cosmology with pairwise velocity estimator

    NASA Astrophysics Data System (ADS)

    Ma, Yin-Zhe; Li, Min; He, Ping

    2015-11-01

    In this paper, we develop a full statistical method for the pairwise velocity estimator previously proposed, and apply Cosmicflows-2 catalogue to this method to constrain cosmology. We first calculate the covariance matrix for line-of-sight velocities for a given catalogue, and then simulate the mock full-sky surveys from it, and then calculate the variance for the pairwise velocity field. By applying the 8315 independent galaxy samples and compressed 5224 group samples from Cosmicflows-2 catalogue to this statistical method, we find that the joint constraint on Ωm0.6h and σ8 is completely consistent with the WMAP 9-year and Planck 2015 best-fitting cosmology. Currently, there is no evidence for the modified gravity models or any dynamic dark energy models from this practice, and the error-bars need to be reduced in order to provide any concrete evidence against/to support ΛCDM cosmology.

  6. Earth Observing System Covariance Realism

    NASA Technical Reports Server (NTRS)

    Zaidi, Waqar H.; Hejduk, Matthew D.

    2016-01-01

    The purpose of covariance realism is to properly size a primary object's covariance in order to add validity to the calculation of the probability of collision. The covariance realism technique in this paper consists of three parts: collection/calculation of definitive state estimates through orbit determination, calculation of covariance realism test statistics at each covariance propagation point, and proper assessment of those test statistics. An empirical cumulative distribution function (ECDF) Goodness-of-Fit (GOF) method is employed to determine if a covariance is properly sized by comparing the empirical distribution of Mahalanobis distance calculations to the hypothesized parent 3-DoF chi-squared distribution. To realistically size a covariance for collision probability calculations, this study uses a state noise compensation algorithm that adds process noise to the definitive epoch covariance to account for uncertainty in the force model. Process noise is added until the GOF tests pass a group significance level threshold. The results of this study indicate that when outliers attributed to persistently high or extreme levels of solar activity are removed, the aforementioned covariance realism compensation method produces a tuned covariance with up to 80 to 90% of the covariance propagation timespan passing (against a 60% minimum passing threshold) the GOF tests-a quite satisfactory and useful result.

  7. Covariant Transform

    NASA Astrophysics Data System (ADS)

    Kisil, Vladimir V.

    2011-03-01

    Dedicated to the memory of Cora Sadosky The paper develops theory of covariant transform, which is inspired by the wavelet construction. It was observed that many interesting types of wavelets (or coherent states) arise from group representations which are not square integrable or vacuum vectors which are not admissible. Covariant transform extends an applicability of the popular wavelets construction to classic examples like the Hardy space H2, Banach spaces, covariant functional calculus and many others.

  8. A pairwise interaction model for multivariate functional and longitudinal data

    PubMed Central

    Chiou, Jeng-Min; Müller, Hans-Georg

    2016-01-01

    Functional data vectors consisting of samples of multivariate data where each component is a random function are encountered increasingly often but have not yet been comprehensively investigated. We introduce a simple pairwise interaction model that leads to an interpretable and straightforward decomposition of multivariate functional data and of their variation into component-specific processes and pairwise interaction processes. The latter quantify the degree of pairwise interactions between the components of the functional data vectors, while the component-specific processes reflect the functional variation of a particular functional vector component that cannot be explained by the other components. Thus the proposed model provides an extension of the usual notion of a covariance or correlation matrix for multivariate vector data to functional data vectors and generates an interpretable functional interaction map. The decomposition provided by the model can also serve as a basis for subsequent analysis, such as study of the network structure of functional data vectors. The decomposition of the total variance into componentwise and interaction contributions can be quantified by an \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{upgreek} \\usepackage{mathrsfs} \\setlength{\\oddsidemargin}{-69pt} \\begin{document} }{}$R^2$\\end{document}-like decomposition. We provide consistency results for the proposed methods and illustrate the model by applying it to sparsely sampled longitudinal data from the Baltimore Longitudinal Study of Aging, examining the relationships between body mass index and blood fats. PMID:27279664

  9. Generalized Linear Covariance Analysis

    NASA Technical Reports Server (NTRS)

    Carpenter, James R.; Markley, F. Landis

    2014-01-01

    This talk presents a comprehensive approach to filter modeling for generalized covariance analysis of both batch least-squares and sequential estimators. We review and extend in two directions the results of prior work that allowed for partitioning of the state space into solve-for'' and consider'' parameters, accounted for differences between the formal values and the true values of the measurement noise, process noise, and textita priori solve-for and consider covariances, and explicitly partitioned the errors into subspaces containing only the influence of the measurement noise, process noise, and solve-for and consider covariances. In this work, we explicitly add sensitivity analysis to this prior work, and relax an implicit assumption that the batch estimator's epoch time occurs prior to the definitive span. We also apply the method to an integrated orbit and attitude problem, in which gyro and accelerometer errors, though not estimated, influence the orbit determination performance. We illustrate our results using two graphical presentations, which we call the variance sandpile'' and the sensitivity mosaic,'' and we compare the linear covariance results to confidence intervals associated with ensemble statistics from a Monte Carlo analysis.

  10. Generalized Linear Covariance Analysis

    NASA Technical Reports Server (NTRS)

    Carpenter, J. Russell; Markley, F. Landis

    2008-01-01

    We review and extend in two directions the results of prior work on generalized covariance analysis methods. This prior work allowed for partitioning of the state space into "solve-for" and "consider" parameters, allowed for differences between the formal values and the true values of the measurement noise, process noise, and a priori solve-for and consider covariances, and explicitly partitioned the errors into subspaces containing only the influence of the measurement noise, process noise, and a priori solve-for and consider covariances. In this work, we explicitly add sensitivity analysis to this prior work, and relax an implicit assumption that the batch estimator s anchor time occurs prior to the definitive span. We also apply the method to an integrated orbit and attitude problem, in which gyro and accelerometer errors, though not estimated, influence the orbit determination performance. We illustrate our results using two graphical presentations, which we call the "variance sandpile" and the "sensitivity mosaic," and we compare the linear covariance results to confidence intervals associated with ensemble statistics from a Monte Carlo analysis.

  11. Combining Multiple Pairwise Structure-based Alignments

    SciTech Connect

    2014-11-12

    CombAlign is a new Python code that generates a gapped, one-to-many, multiple structure-based sequence alignment(MSSA) given a set of pairwise structure-based alignments. In order to better define regions of similarity among related protein structures, it is useful to detect the residue-residue correspondences among a set of pairwise structure alignments. Few codes exist for constructing a one-to-many, multiple sequence alignment derived from a set of structure alignments, and we perceived a need for creating a new tool for combing pairwise structure alignments that would allow for insertion of gaps in the reference structure.

  12. Market structure explained by pairwise interactions

    NASA Astrophysics Data System (ADS)

    Bury, Thomas

    2013-03-01

    Financial markets are a typical example of complex systems where interactions between constituents lead to many remarkable features. Here we give empirical evidence, by making as few assumptions as possible, that the market microstructure capturing almost all of the available information in the data of stock markets does not involve higher order than pairwise interactions. We give an economic interpretation of this pairwise model. We show that it accurately recovers the empirical correlation coefficients; thus the collective behaviors are quantitatively described by models that capture the observed pairwise correlations but no higher-order interactions. Furthermore, we show that an order-disorder transition occurs, as predicted by the pairwise model. Last, we make the link with the graph-theoretic description of stock markets recovering the non-random and scale-free topology, shrinking length during crashes and meaningful clustering features, as expected.

  13. Doctoral Program Selection Using Pairwise Comparisons.

    ERIC Educational Resources Information Center

    Tadisina, Suresh K.; Bhasin, Vijay

    1989-01-01

    The application of a pairwise comparison methodology (Saaty's Analytic Hierarchy Process) to the doctoral program selection process is illustrated. A hierarchy for structuring and facilitating the doctoral program selection decision is described. (Author/MLW)

  14. Combining Multiple Pairwise Structure-based Alignments

    Energy Science and Technology Software Center (ESTSC)

    2014-11-12

    CombAlign is a new Python code that generates a gapped, one-to-many, multiple structure-based sequence alignment(MSSA) given a set of pairwise structure-based alignments. In order to better define regions of similarity among related protein structures, it is useful to detect the residue-residue correspondences among a set of pairwise structure alignments. Few codes exist for constructing a one-to-many, multiple sequence alignment derived from a set of structure alignments, and we perceived a need for creating a newmore » tool for combing pairwise structure alignments that would allow for insertion of gaps in the reference structure.« less

  15. Preference Learning and Ranking by Pairwise Comparison

    NASA Astrophysics Data System (ADS)

    Fürnkranz, Johannes; Hüllermeier, Eyke

    This chapter provides an overview of recent work on preference learning and ranking via pairwise classification. The learning by pairwise comparison (LPC) paradigm is the natural machine learning counterpart to the relational approach to preference modeling and decision making. From a machine learning point of view, LPC is especially appealing as it decomposes a possibly complex prediction problem into a certain number of learning problems of the simplest type, namely binary classification. We explain how to approach different preference learning problems, such as label and instance ranking, within the framework of LPC. We primarily focus on methodological aspects, but also address theoretical questions as well as algorithmic and complexity issues.

  16. PAIRWISE BLENDING OF HIGH LEVEL WASTE (HLW)

    SciTech Connect

    CERTA, P.J.

    2006-02-22

    The primary objective of this study is to demonstrate a mission scenario that uses pairwise and incidental blending of high level waste (HLW) to reduce the total mass of HLW glass. Secondary objectives include understanding how recent refinements to the tank waste inventory and solubility assumptions affect the mass of HLW glass and how logistical constraints may affect the efficacy of HLW blending.

  17. Cost functions for pairwise data clustering

    NASA Astrophysics Data System (ADS)

    Angelini, L.; Nitti, L.; Pellicoro, M.; Stramaglia, S.

    2001-07-01

    Cost functions for non-hierarchical pairwise clustering are introduced, in the probabilistic autoencoder framework, by the request of maximal average similarity between input and the output of the autoencoder. Clustering is thus formulated as the problem of finding the ground state of Potts spins Hamiltonians. The partition, provided by this procedure, identifies clusters with dense connected regions in the data space.

  18. Design, Implementation and Deployment of PAIRwise

    ERIC Educational Resources Information Center

    Knight, Allan; Almeroth, Kevin; Bimber, Bruce

    2008-01-01

    Increased access to the Internet has dramatically increased the sources from which students can deliberately or accidentally copy information. This article discusses our motivation to design, implement, and deploy an Internet based plagiarism detection system, called PAIRwise, to address this growing problem. We give details as to how we detect…

  19. On multitarget pairwise-Markov models

    NASA Astrophysics Data System (ADS)

    Mahler, Ronald

    2015-05-01

    Single- and multi-target tracking are both typically based on strong independence assumptions regarding both the target states and sensor measurements. In particular, both are theoretically based on the hidden Markov chain (HMC) model. That is, the target process is a Markov chain that is observed by an independent observation process. Since HMC assumptions are invalid in many practical applications, the pairwise Markov chain (PMC) model has been proposed as a way to weaken those assumptions. In this paper it is shown that the PMC model can be directly generalized to multitarget problems. Since the resulting tracking filters are computationally intractable, the paper investigates generalizations of the cardinalized probability hypothesis density (CPHD) filter to applications with PMC models.

  20. Model Fit after Pairwise Maximum Likelihood

    PubMed Central

    Barendse, M. T.; Ligtvoet, R.; Timmerman, M. E.; Oort, F. J.

    2016-01-01

    Maximum likelihood factor analysis of discrete data within the structural equation modeling framework rests on the assumption that the observed discrete responses are manifestations of underlying continuous scores that are normally distributed. As maximizing the likelihood of multivariate response patterns is computationally very intensive, the sum of the log–likelihoods of the bivariate response patterns is maximized instead. Little is yet known about how to assess model fit when the analysis is based on such a pairwise maximum likelihood (PML) of two–way contingency tables. We propose new fit criteria for the PML method and conduct a simulation study to evaluate their performance in model selection. With large sample sizes (500 or more), PML performs as well the robust weighted least squares analysis of polychoric correlations. PMID:27148136

  1. Model Fit after Pairwise Maximum Likelihood.

    PubMed

    Barendse, M T; Ligtvoet, R; Timmerman, M E; Oort, F J

    2016-01-01

    Maximum likelihood factor analysis of discrete data within the structural equation modeling framework rests on the assumption that the observed discrete responses are manifestations of underlying continuous scores that are normally distributed. As maximizing the likelihood of multivariate response patterns is computationally very intensive, the sum of the log-likelihoods of the bivariate response patterns is maximized instead. Little is yet known about how to assess model fit when the analysis is based on such a pairwise maximum likelihood (PML) of two-way contingency tables. We propose new fit criteria for the PML method and conduct a simulation study to evaluate their performance in model selection. With large sample sizes (500 or more), PML performs as well the robust weighted least squares analysis of polychoric correlations. PMID:27148136

  2. Pairwise polymer blends for oral drug delivery.

    PubMed

    Marks, Joyann A; Wegiel, Lindsay A; Taylor, Lynne S; Edgar, Kevin J

    2014-09-01

    Blends of polymers with complementary properties hold promise for addressing the diverse, demanding polymer performance requirements in amorphous solid dispersions (ASDs), but we lack comprehensive property understanding for blends of important ASD polymers. Herein, we prepare pairwise blends of commercially available polymers polyvinylpyrrolidone (PVP), the cationic acrylate copolymer Eudragit 100 (E100), hydroxypropyl methylcellulose acetate succinate (HPMCAS), carboxymethyl cellulose acetate butyrate (CMCAB), hydroxypropyl methylcellulose (HPMC), and the new derivative cellulose acetate adipate propionate (CAAdP). This study identifies miscible binary blends that may find use, for example, in ASDs for solubility and bioavailability enhancement of poorly water-soluble drugs. Differential scanning calorimetry, FTIR spectroscopy, and film clarity were used to determine blend miscibility. Several polymer combinations including HPMCAS/PVP, HPMC/CMCAB, and PVP/HPMC appear to be miscible in all proportions. In contrast, blends of E100/PVP and E100/HPMC showed a miscibility gap. Combinations of water-soluble and hydrophobic polymers like these may permit effective balancing of ASD performance criteria such as release rate and polymer-drug interaction to prevent nucleation and crystal growth of poorly soluble drugs. Miscible polymer combinations described herein will enable further study of their drug delivery capabilities, and provide a potentially valuable set of ASD formulation tools. PMID:24823790

  3. Disequilibrium mapping: Composite likelihood for pairwise disequilibrium

    SciTech Connect

    Devlin, B.; Roeder, K.; Risch, N.

    1996-08-15

    The pattern of linkage disequilibrium between a disease locus and a set of marker loci has been shown to be a useful tool for geneticists searching for disease genes. Several methods have been advanced to utilize the pairwise disequilibrium between the disease locus and each of a set of marker loci. However, none of the methods take into account the information from all pairs simultaneously while also modeling the variability in the disequilibrium values due to the evolutionary dynamics of the population. We propose a Composite Likelihood CL model that has these features when the physical distances between the marker loci are known or can be approximated. In this instance, and assuming that there is a single disease mutation, the CL model depends on only three parameters, the recombination fraction between the disease locus and an arbitrary marker locus, {theta}, the age of the mutation, and a variance parameter. When the CL is maximized over a grid of {theta}, it provides a graph that can direct the search for the disease locus. We also show how the CL model can be generalized to account for multiple disease mutations. Evolutionary simulations demonstrate the power of the analyses, as well as their potential weaknesses. Finally, we analyze the data from two mapped diseases, cystic fibrosis and diastrophic dysplasia, finding that the CL method performs well in both cases. 28 refs., 6 figs., 4 tabs.

  4. Predicting community composition from pairwise interactions

    NASA Astrophysics Data System (ADS)

    Friedman, Jonathan; Higgins, Logan; Gore, Jeff

    The ability to predict the structure of complex, multispecies communities is crucial for understanding the impact of species extinction and invasion on natural communities, as well as for engineering novel, synthetic communities. Communities are often modeled using phenomenological models, such as the classical generalized Lotka-Volterra (gLV) model. While a lot of our intuition comes from such models, their predictive power has rarely been tested experimentally. To directly assess the predictive power of this approach, we constructed synthetic communities comprised of up to 8 soil bacteria. We measured the outcome of competition between all species pairs, and used these measurements to predict the composition of communities composed of more than 2 species. The pairwise competitions resulted in a diverse set of outcomes, including coexistence, exclusion, and bistability, and displayed evidence for both interference and facilitation. Most pair outcomes could be captured by the gLV framework, and the composition of multispecies communities could be predicted for communities composed solely of such pairs. Our results demonstrate the predictive ability and utility of simple phenomenology, which enables accurate predictions in the absence of mechanistic details.

  5. Cross-Modal Subspace Learning via Pairwise Constraints.

    PubMed

    He, Ran; Zhang, Man; Wang, Liang; Ji, Ye; Yin, Qiyue

    2015-12-01

    In multimedia applications, the text and image components in a web document form a pairwise constraint that potentially indicates the same semantic concept. This paper studies cross-modal learning via the pairwise constraint and aims to find the common structure hidden in different modalities. We first propose a compound regularization framework to address the pairwise constraint, which can be used as a general platform for developing cross-modal algorithms. For unsupervised learning, we propose a multi-modal subspace clustering method to learn a common structure for different modalities. For supervised learning, to reduce the semantic gap and the outliers in pairwise constraints, we propose a cross-modal matching method based on compound ℓ21 regularization. Extensive experiments demonstrate the benefits of joint text and image modeling with semantically induced pairwise constraints, and they show that the proposed cross-modal methods can further reduce the semantic gap between different modalities and improve the clustering/matching accuracy. PMID:26259218

  6. Auto covariance computer

    NASA Technical Reports Server (NTRS)

    Hepner, T. E.; Meyers, J. F. (Inventor)

    1985-01-01

    A laser velocimeter covariance processor which calculates the auto covariance and cross covariance functions for a turbulent flow field based on Poisson sampled measurements in time from a laser velocimeter is described. The device will process a block of data that is up to 4096 data points in length and return a 512 point covariance function with 48-bit resolution along with a 512 point histogram of the interarrival times which is used to normalize the covariance function. The device is designed to interface and be controlled by a minicomputer from which the data is received and the results returned. A typical 4096 point computation takes approximately 1.5 seconds to receive the data, compute the covariance function, and return the results to the computer.

  7. Diabetes Steals Years, Adds Disabilities

    MedlinePlus

    ... news/fullstory_158312.html Diabetes Steals Years, Adds Disabilities Middle-aged adults will lose more than 3 ... with diabetes die earlier and suffer longer with disabilities than men and women without the blood-sugar ...

  8. Galilean covariant harmonic oscillator

    NASA Technical Reports Server (NTRS)

    Horzela, Andrzej; Kapuscik, Edward

    1993-01-01

    A Galilean covariant approach to classical mechanics of a single particle is described. Within the proposed formalism, all non-covariant force laws defining acting forces which become to be defined covariantly by some differential equations are rejected. Such an approach leads out of the standard classical mechanics and gives an example of non-Newtonian mechanics. It is shown that the exactly solvable linear system of differential equations defining forces contains the Galilean covariant description of harmonic oscillator as its particular case. Additionally, it is demonstrated that in Galilean covariant classical mechanics the validity of the second Newton law of dynamics implies the Hooke law and vice versa. It is shown that the kinetic and total energies transform differently with respect to the Galilean transformations.

  9. Pairwise interactions of colloids in two-dimensional geometric confinement.

    PubMed

    Park, Bum Jun; Lee, Bomsock; Yu, Taekyung

    2014-12-28

    We present the pairwise interaction behaviour of colloids confined to two-dimensional (2D) colloidal cages using optical laser tweezers. A single probe particle inside hexagonal cage particles at a planar oil-water interface is allowed to diffuse freely and the spring constant is extracted from its trajectories. To evaluate the effect of multibody interactions, the pair interactions between the probe particle and each cage particle are directly measured by using optical tweezers. Based on pairwise additivity, Monte Carlo simulations are used to compare the values of the spring constant obtained from experiments and simulations. We find that the multibody interactions negligibly occur and thus the particle interactions confined to such colloidal cages are highly pairwise. This work demonstrates that the use of the pairwise assumption in numerical simulations is rational when interparticle repulsive interactions are sufficiently strong, such as the particle interactions at fluid-fluid interfaces. PMID:25363564

  10. When do microcircuits produce beyond-pairwise correlations?

    PubMed Central

    Barreiro, Andrea K.; Gjorgjieva, Julijana; Rieke, Fred; Shea-Brown, Eric

    2014-01-01

    Describing the collective activity of neural populations is a daunting task. Recent empirical studies in retina, however, suggest a vast simplification in how multi-neuron spiking occurs: the activity patterns of retinal ganglion cell (RGC) populations under some conditions are nearly completely captured by pairwise interactions among neurons. In other circumstances, higher-order statistics are required and appear to be shaped by input statistics and intrinsic circuit mechanisms. Here, we study the emergence of higher-order interactions in a model of the RGC circuit in which correlations are generated by common input. We quantify the impact of higher-order interactions by comparing the responses of mechanistic circuit models vs. “null” descriptions in which all higher-than-pairwise correlations have been accounted for by lower order statistics; these are known as pairwise maximum entropy (PME) models. We find that over a broad range of stimuli, output spiking patterns are surprisingly well captured by the pairwise model. To understand this finding, we study an analytically tractable simplification of the RGC model. We find that in the simplified model, bimodal input signals produce larger deviations from pairwise predictions than unimodal inputs. The characteristic light filtering properties of the upstream RGC circuitry suppress bimodality in light stimuli, thus removing a powerful source of higher-order interactions. This provides a novel explanation for the surprising empirical success of pairwise models. PMID:24567715

  11. PWC - PAIRWISE COMPARISON SOFTWARE: SOFTWARE PROGRAM FOR PAIRWISE COMPARISON TASK FOR PSYCHOMETRIC SCALING AND COGNITIVE RESEARCH

    NASA Technical Reports Server (NTRS)

    Ricks, W. R.

    1994-01-01

    PWC is used for pair-wise comparisons in both psychometric scaling techniques and cognitive research. The cognitive tasks and processes of a human operator of automated systems are now prominent considerations when defining system requirements. Recent developments in cognitive research have emphasized the potential utility of psychometric scaling techniques, such as multidimensional scaling, for representing human knowledge and cognitive processing structures. Such techniques involve collecting measurements of stimulus-relatedness from human observers. When data are analyzed using this scaling approach, an n-dimensional representation of the stimuli is produced. This resulting representation is said to describe the subject's cognitive or perceptual view of the stimuli. PWC applies one of the many techniques commonly used to acquire the data necessary for these types of analyses: pair-wise comparisons. PWC administers the task, collects the data from the test subject, and formats the data for analysis. It therefore addresses many of the limitations of the traditional "pen-and-paper" methods. By automating the data collection process, subjects are prevented from going back to check previous responses, the possibility of erroneous data transfer is eliminated, and the burden of the administration and taking of the test is eased. By using randomization, PWC ensures that subjects see the stimuli pairs presented in random order, and that each subject sees pairs in a different random order. PWC is written in Turbo Pascal v6.0 for IBM PC compatible computers running MS-DOS. The program has also been successfully compiled with Turbo Pascal v7.0. A sample executable is provided. PWC requires 30K of RAM for execution. The standard distribution medium for this program is a 5.25 inch 360K MS-DOS format diskette. Two electronic versions of the documentation are included on the diskette: one in ASCII format and one in MS Word for Windows format. PWC was developed in 1993.

  12. A General Pairwise Interaction Model Provides an Accurate Description of In Vivo Transcription Factor Binding Sites

    PubMed Central

    Santolini, Marc; Mora, Thierry; Hakim, Vincent

    2014-01-01

    The identification of transcription factor binding sites (TFBSs) on genomic DNA is of crucial importance for understanding and predicting regulatory elements in gene networks. TFBS motifs are commonly described by Position Weight Matrices (PWMs), in which each DNA base pair contributes independently to the transcription factor (TF) binding. However, this description ignores correlations between nucleotides at different positions, and is generally inaccurate: analysing fly and mouse in vivo ChIPseq data, we show that in most cases the PWM model fails to reproduce the observed statistics of TFBSs. To overcome this issue, we introduce the pairwise interaction model (PIM), a generalization of the PWM model. The model is based on the principle of maximum entropy and explicitly describes pairwise correlations between nucleotides at different positions, while being otherwise as unconstrained as possible. It is mathematically equivalent to considering a TF-DNA binding energy that depends additively on each nucleotide identity at all positions in the TFBS, like the PWM model, but also additively on pairs of nucleotides. We find that the PIM significantly improves over the PWM model, and even provides an optimal description of TFBS statistics within statistical noise. The PIM generalizes previous approaches to interdependent positions: it accounts for co-variation of two or more base pairs, and predicts secondary motifs, while outperforming multiple-motif models consisting of mixtures of PWMs. We analyse the structure of pairwise interactions between nucleotides, and find that they are sparse and dominantly located between consecutive base pairs in the flanking region of TFBS. Nonetheless, interactions between pairs of non-consecutive nucleotides are found to play a significant role in the obtained accurate description of TFBS statistics. The PIM is computationally tractable, and provides a general framework that should be useful for describing and predicting TFBSs beyond

  13. Reliable clock estimation using linear weighted fusion based on pairwise broadcast synchronization

    SciTech Connect

    Shi, Xin Zhao, Xiangmo Hui, Fei Ma, Junyan Yang, Lan

    2014-10-06

    Clock synchronization in wireless sensor networks (WSNs) has been studied extensively in recent years and many protocols are put forward based on the point of statistical signal processing, which is an effective way to optimize accuracy. However, the accuracy derived from the statistical data can be improved mainly by sufficient packets exchange, which will consume the limited power resources greatly. In this paper, a reliable clock estimation using linear weighted fusion based on pairwise broadcast synchronization is proposed to optimize sync accuracy without expending additional sync packets. As a contribution, a linear weighted fusion scheme for multiple clock deviations is constructed with the collaborative sensing of clock timestamp. And the fusion weight is defined by the covariance of sync errors for different clock deviations. Extensive simulation results show that the proposed approach can achieve better performance in terms of sync overhead and sync accuracy.

  14. Covariant mutually unbiased bases

    NASA Astrophysics Data System (ADS)

    Carmeli, Claudio; Schultz, Jussi; Toigo, Alessandro

    2016-06-01

    The connection between maximal sets of mutually unbiased bases (MUBs) in a prime-power dimensional Hilbert space and finite phase-space geometries is well known. In this article, we classify MUBs according to their degree of covariance with respect to the natural symmetries of a finite phase-space, which are the group of its affine symplectic transformations. We prove that there exist maximal sets of MUBs that are covariant with respect to the full group only in odd prime-power dimensional spaces, and in this case, their equivalence class is actually unique. Despite this limitation, we show that in dimension 2r covariance can still be achieved by restricting to proper subgroups of the symplectic group, that constitute the finite analogues of the oscillator group. For these subgroups, we explicitly construct the unitary operators yielding the covariance.

  15. Covariance mapping techniques

    NASA Astrophysics Data System (ADS)

    Frasinski, Leszek J.

    2016-08-01

    Recent technological advances in the generation of intense femtosecond pulses have made covariance mapping an attractive analytical technique. The laser pulses available are so intense that often thousands of ionisation and Coulomb explosion events will occur within each pulse. To understand the physics of these processes the photoelectrons and photoions need to be correlated, and covariance mapping is well suited for operating at the high counting rates of these laser sources. Partial covariance is particularly useful in experiments with x-ray free electron lasers, because it is capable of suppressing pulse fluctuation effects. A variety of covariance mapping methods is described: simple, partial (single- and multi-parameter), sliced, contingent and multi-dimensional. The relationship to coincidence techniques is discussed. Covariance mapping has been used in many areas of science and technology: inner-shell excitation and Auger decay, multiphoton and multielectron ionisation, time-of-flight and angle-resolved spectrometry, infrared spectroscopy, nuclear magnetic resonance imaging, stimulated Raman scattering, directional gamma ray sensing, welding diagnostics and brain connectivity studies (connectomics). This review gives practical advice for implementing the technique and interpreting the results, including its limitations and instrumental constraints. It also summarises recent theoretical studies, highlights unsolved problems and outlines a personal view on the most promising research directions.

  16. Misunderstanding analysis of covariance.

    PubMed

    Miller, G A; Chapman, J P

    2001-02-01

    Despite numerous technical treatments in many venues, analysis of covariance (ANCOVA) remains a widely misused approach to dealing with substantive group differences on potential covariates, particularly in psychopathology research. Published articles reach unfounded conclusions, and some statistics texts neglect the issue. The problem with ANCOVA in such cases is reviewed. In many cases, there is no means of achieving the superficially appealing goal of "correcting" or "controlling for" real group differences on a potential covariate. In hopes of curtailing misuse of ANCOVA and promoting appropriate use, a nontechnical discussion is provided, emphasizing a substantive confound rarely articulated in textbooks and other general presentations, to complement the mathematical critiques already available. Some alternatives are discussed for contexts in which ANCOVA is inappropriate or questionable. PMID:11261398

  17. The covariant chiral ring

    NASA Astrophysics Data System (ADS)

    Bourget, Antoine; Troost, Jan

    2016-03-01

    We construct a covariant generating function for the spectrum of chiral primaries of symmetric orbifold conformal field theories with N = (4 , 4) supersymmetry in two dimensions. For seed target spaces K3 and T 4, the generating functions capture the SO(21) and SO(5) representation theoretic content of the chiral ring respectively. Via string dualities, we relate the transformation properties of the chiral ring under these isometries of the moduli space to the Lorentz covariance of perturbative string partition functions in flat space.

  18. Discovering Pair-wise Synergies in Microarray Data

    PubMed Central

    Chen, Yuan; Cao, Dan; Gao, Jun; Yuan, Zheming

    2016-01-01

    Informative gene selection can have important implications for the improvement of cancer diagnosis and the identification of new drug targets. Individual-gene-ranking methods ignore interactions between genes. Furthermore, popular pair-wise gene evaluation methods, e.g. TSP and TSG, are helpless for discovering pair-wise interactions. Several efforts to discover pair-wise synergy have been made based on the information approach, such as EMBP and FeatKNN. However, the methods which are employed to estimate mutual information, e.g. binarization, histogram-based and KNN estimators, depend on known data or domain characteristics. Recently, Reshef et al. proposed a novel maximal information coefficient (MIC) measure to capture a wide range of associations between two variables that has the property of generality. An extension from MIC(X; Y) to MIC(X1; X2; Y) is therefore desired. We developed an approximation algorithm for estimating MIC(X1; X2; Y) where Y is a discrete variable. MIC(X1; X2; Y) is employed to detect pair-wise synergy in simulation and cancer microarray data. The results indicate that MIC(X1; X2; Y) also has the property of generality. It can discover synergic genes that are undetectable by reference feature selection methods such as MIC(X; Y) and TSG. Synergic genes can distinguish different phenotypes. Finally, the biological relevance of these synergic genes is validated with GO annotation and OUgene database. PMID:27470995

  19. Discovering Pair-wise Synergies in Microarray Data.

    PubMed

    Chen, Yuan; Cao, Dan; Gao, Jun; Yuan, Zheming

    2016-01-01

    Informative gene selection can have important implications for the improvement of cancer diagnosis and the identification of new drug targets. Individual-gene-ranking methods ignore interactions between genes. Furthermore, popular pair-wise gene evaluation methods, e.g. TSP and TSG, are helpless for discovering pair-wise interactions. Several efforts to discover pair-wise synergy have been made based on the information approach, such as EMBP and FeatKNN. However, the methods which are employed to estimate mutual information, e.g. binarization, histogram-based and KNN estimators, depend on known data or domain characteristics. Recently, Reshef et al. proposed a novel maximal information coefficient (MIC) measure to capture a wide range of associations between two variables that has the property of generality. An extension from MIC(X; Y) to MIC(X1; X2; Y) is therefore desired. We developed an approximation algorithm for estimating MIC(X1; X2; Y) where Y is a discrete variable. MIC(X1; X2; Y) is employed to detect pair-wise synergy in simulation and cancer microarray data. The results indicate that MIC(X1; X2; Y) also has the property of generality. It can discover synergic genes that are undetectable by reference feature selection methods such as MIC(X; Y) and TSG. Synergic genes can distinguish different phenotypes. Finally, the biological relevance of these synergic genes is validated with GO annotation and OUgene database. PMID:27470995

  20. Five key factors determining pairwise correlations in visual cortex

    PubMed Central

    Sahani, Maneesh; Carandini, Matteo

    2015-01-01

    The responses of cortical neurons to repeated presentation of a stimulus are highly variable, yet correlated. These “noise correlations” reflect a low-dimensional structure of population dynamics. Here, we examine noise correlations in 22,705 pairs of neurons in primary visual cortex (V1) of anesthetized cats, during ongoing activity and in response to artificial and natural visual stimuli. We measured how noise correlations depend on 11 factors. Because these factors are themselves not independent, we distinguished their influences using a nonlinear additive model. The model revealed that five key factors play a predominant role in determining pairwise correlations. Two of these are distance in cortex and difference in sensory tuning: these are known to decrease correlation. A third factor is firing rate: confirming most earlier observations, it markedly increased pairwise correlations. A fourth factor is spike width: cells with a broad spike were more strongly correlated amongst each other. A fifth factor is spike isolation: neurons with worse isolation were more correlated, even if they were recorded on different electrodes. For pairs of neurons with poor isolation, this last factor was the main determinant of correlations. These results were generally independent of stimulus type and timescale of analysis, but there were exceptions. For instance, pairwise correlations depended on difference in orientation tuning more during responses to gratings than to natural stimuli. These results consolidate disjoint observations in a vast literature on pairwise correlations and point towards regularities of population coding in sensory cortex. PMID:26019310

  1. Graph theory for analyzing pair-wise data: application to geophysical model parameters estimated from interferometric synthetic aperture radar data at Okmok volcano, Alaska

    NASA Astrophysics Data System (ADS)

    Reinisch, Elena C.; Cardiff, Michael; Feigl, Kurt L.

    2016-07-01

    Graph theory is useful for analyzing time-dependent model parameters estimated from interferometric synthetic aperture radar (InSAR) data in the temporal domain. Plotting acquisition dates (epochs) as vertices and pair-wise interferometric combinations as edges defines an incidence graph. The edge-vertex incidence matrix and the normalized edge Laplacian matrix are factors in the covariance matrix for the pair-wise data. Using empirical measures of residual scatter in the pair-wise observations, we estimate the relative variance at each epoch by inverting the covariance of the pair-wise data. We evaluate the rank deficiency of the corresponding least-squares problem via the edge-vertex incidence matrix. We implement our method in a MATLAB software package called GraphTreeTA available on GitHub (https://github.com/feigl/gipht). We apply temporal adjustment to the data set described in Lu et al. (Geophys Res Solid Earth 110, 2005) at Okmok volcano, Alaska, which erupted most recently in 1997 and 2008. The data set contains 44 differential volumetric changes and uncertainties estimated from interferograms between 1997 and 2004. Estimates show that approximately half of the magma volume lost during the 1997 eruption was recovered by the summer of 2003. Between June 2002 and September 2003, the estimated rate of volumetric increase is (6.2 ± 0.6) × 10^6~m^3/year . Our preferred model provides a reasonable fit that is compatible with viscoelastic relaxation in the five years following the 1997 eruption. Although we demonstrate the approach using volumetric rates of change, our formulation in terms of incidence graphs applies to any quantity derived from pair-wise differences, such as range change, range gradient, or atmospheric delay.

  2. Using Analysis of Covariance (ANCOVA) with Fallible Covariates

    ERIC Educational Resources Information Center

    Culpepper, Steven Andrew; Aguinis, Herman

    2011-01-01

    Analysis of covariance (ANCOVA) is used widely in psychological research implementing nonexperimental designs. However, when covariates are fallible (i.e., measured with error), which is the norm, researchers must choose from among 3 inadequate courses of action: (a) know that the assumption that covariates are perfectly reliable is violated but…

  3. Constraints on Gravity and Dark Energy from the Pairwise Kinematic Sunyaev-Zel'dovich Effect

    NASA Astrophysics Data System (ADS)

    Mueller, Eva-Maria; de Bernardis, Francesco; Bean, Rachel; Niemack, Michael D.

    2015-07-01

    We calculate the constraints on dark energy and cosmic modifications to gravity achievable with upcoming cosmic microwave background (CMB) surveys sensitive to the Sunyaev-Zel’dovich (SZ) effects. The analysis focuses on using the mean pairwise velocity of clusters as observed through the kinematic SZ effect (kSZ), an approach based on the same methods used for the first detection of the kSZ effect, and includes a detailed derivation and discussion of this statistic’s covariance under a variety of different survey assumptions. The potential of current, Stage II, and upcoming, Stages III and IV, CMB observations are considered, in combination with contemporaneous spectroscopic and photometric galaxy observations. A detailed assessment is made of the sensitivity to the assumed statistical and systematic uncertainties in the optical depth determination, the magnitude and uncertainty in the minimum detectable mass, and the importance of pairwise velocity correlations at small separations, where nonlinear effects can start to arise. In combination with Stage III constraints on the expansion history, such as those projected by the Dark Energy Task Force, we forecast 5% and 3% for fractional errors on the growth factor, γ, for Stage III and IV surveys, respectively, and 2% constraints on the growth rate, fg, for a Stage IV survey for 0.2\\lt z\\lt 0.6. The results suggest that kSZ measurements of cluster peculiar velocities, obtained from cross-correlation with upcoming spectroscopic galaxy surveys, could provide robust tests of dark energy and theories of gravity on cosmic scales.

  4. Covariant approximation averaging

    NASA Astrophysics Data System (ADS)

    Shintani, Eigo; Arthur, Rudy; Blum, Thomas; Izubuchi, Taku; Jung, Chulwoo; Lehner, Christoph

    2015-06-01

    We present a new class of statistical error reduction techniques for Monte Carlo simulations. Using covariant symmetries, we show that correlation functions can be constructed from inexpensive approximations without introducing any systematic bias in the final result. We introduce a new class of covariant approximation averaging techniques, known as all-mode averaging (AMA), in which the approximation takes account of contributions of all eigenmodes through the inverse of the Dirac operator computed from the conjugate gradient method with a relaxed stopping condition. In this paper we compare the performance and computational cost of our new method with traditional methods using correlation functions and masses of the pion, nucleon, and vector meson in Nf=2 +1 lattice QCD using domain-wall fermions. This comparison indicates that AMA significantly reduces statistical errors in Monte Carlo calculations over conventional methods for the same cost.

  5. Covariant deformed oscillator algebras

    NASA Technical Reports Server (NTRS)

    Quesne, Christiane

    1995-01-01

    The general form and associativity conditions of deformed oscillator algebras are reviewed. It is shown how the latter can be fulfilled in terms of a solution of the Yang-Baxter equation when this solution has three distinct eigenvalues and satisfies a Birman-Wenzl-Murakami condition. As an example, an SU(sub q)(n) x SU(sub q)(m)-covariant q-bosonic algebra is discussed in some detail.

  6. Partial covariate adjusted regression

    PubMed Central

    Şentürk, Damla; Nguyen, Danh V.

    2008-01-01

    Covariate adjusted regression (CAR) is a recently proposed adjustment method for regression analysis where both the response and predictors are not directly observed (Şentürk and Müller, 2005). The available data has been distorted by unknown functions of an observable confounding covariate. CAR provides consistent estimators for the coefficients of the regression between the variables of interest, adjusted for the confounder. We develop a broader class of partial covariate adjusted regression (PCAR) models to accommodate both distorted and undistorted (adjusted/unadjusted) predictors. The PCAR model allows for unadjusted predictors, such as age, gender and demographic variables, which are common in the analysis of biomedical and epidemiological data. The available estimation and inference procedures for CAR are shown to be invalid for the proposed PCAR model. We propose new estimators and develop new inference tools for the more general PCAR setting. In particular, we establish the asymptotic normality of the proposed estimators and propose consistent estimators of their asymptotic variances. Finite sample properties of the proposed estimators are investigated using simulation studies and the method is also illustrated with a Pima Indians diabetes data set. PMID:20126296

  7. The Bayesian Covariance Lasso

    PubMed Central

    Khondker, Zakaria S; Zhu, Hongtu; Chu, Haitao; Lin, Weili; Ibrahim, Joseph G.

    2012-01-01

    Estimation of sparse covariance matrices and their inverse subject to positive definiteness constraints has drawn a lot of attention in recent years. The abundance of high-dimensional data, where the sample size (n) is less than the dimension (d), requires shrinkage estimation methods since the maximum likelihood estimator is not positive definite in this case. Furthermore, when n is larger than d but not sufficiently larger, shrinkage estimation is more stable than maximum likelihood as it reduces the condition number of the precision matrix. Frequentist methods have utilized penalized likelihood methods, whereas Bayesian approaches rely on matrix decompositions or Wishart priors for shrinkage. In this paper we propose a new method, called the Bayesian Covariance Lasso (BCLASSO), for the shrinkage estimation of a precision (covariance) matrix. We consider a class of priors for the precision matrix that leads to the popular frequentist penalties as special cases, develop a Bayes estimator for the precision matrix, and propose an efficient sampling scheme that does not precalculate boundaries for positive definiteness. The proposed method is permutation invariant and performs shrinkage and estimation simultaneously for non-full rank data. Simulations show that the proposed BCLASSO performs similarly as frequentist methods for non-full rank data. PMID:24551316

  8. A piecewise lookup table for calculating nonbonded pairwise atomic interactions.

    PubMed

    Luo, Jinping; Liu, Lijun; Su, Peng; Duan, Pengbo; Lu, Daihui

    2015-11-01

    A critical challenge for molecular dynamics simulations of chemical or biological systems is to improve the calculation efficiency while retaining sufficient accuracy. The main bottleneck in improving the efficiency is the evaluation of nonbonded pairwise interactions. We propose a new piecewise lookup table method for rapid and accurate calculation of interatomic nonbonded pairwise interactions. The piecewise lookup table allows nonuniform assignment of table nodes according to the slope of the potential function and the pair interaction distribution. The proposed method assigns the nodes more reasonably than in general lookup tables, and thus improves the accuracy while requiring fewer nodes. To obtain the same level of accuracy, our piecewise lookup table accelerates the calculation via the efficient usage of cache memory. This new method is straightforward to implement and should be broadly applicable. Graphical Abstract Illustration of piecewise lookup table method. PMID:26481475

  9. A Pairwise Preferential Interaction Model for Understanding Peptide Aggregation

    PubMed Central

    Kang, Myungshim

    2010-01-01

    A pairwise preferential interaction model (PPIM), based on Kirkwood–Buff integrals, is developed to quantify and characterize the interactions between some of the functional groups commonly observed in peptides. The existing experimental data are analyzed to determine the preferential interaction (PI) parameters for different amino acid and small peptide systems in aqueous solutions. The PIs between the different functional groups present in the peptides are then isolated and quantified by assuming simple pairwise additivity. The PPIM approach provides consistent estimates for the pair interactions between the same functional groups obtained from different solute molecules. Furthermore, these interactions appear to be chemically intuitive. It is argued that this type of approach can provide valuable information concerning specific functional group correlations which could give rise to peptide aggregation. PMID:20694045

  10. Simulations of the Pairwise Kinematic Sunyaev–Zel’dovich Signal

    NASA Astrophysics Data System (ADS)

    Flender, Samuel; Bleem, Lindsey; Finkel, Hal; Habib, Salman; Heitmann, Katrin; Holder, Gilbert

    2016-06-01

    The pairwise kinematic Sunyaev–Zel’dovich (kSZ) signal from galaxy clusters is a probe of their line of sight momenta, and thus a potentially valuable source of cosmological information. In addition to the momenta, the amplitude of the measured signal depends on the properties of the intracluster gas and observational limitations such as errors in determining cluster centers and redshifts. In this work, we simulate the pairwise kSZ signal of clusters at z\\lt 1, using the output from a cosmological N-body simulation and including the properties of the intracluster gas via a model that can be varied in post-processing. We find that modifications to the gas profile due to star formation and feedback reduce the pairwise kSZ amplitude of clusters by ˜ 50%, relative to the naive “gas traces mass” assumption. We demonstrate that miscentering can reduce the overall amplitude of the pairwise kSZ signal by up to 10%, while redshift errors can lead to an almost complete suppression of the signal at small separations. We confirm that a high-significance detection is expected from the combination of data from current generation, high-resolution cosmic microwave background experiments, such as the South Pole Telescope, and cluster samples from optical photometric surveys, such as the Dark Energy Survey. Furthermore, we forecast that future experiments such as Advanced ACTPol in conjunction with data from the Dark Energy Spectroscopic Instrument will yield detection significances of at least 20σ , and up to 57σ in an optimistic scenario. Our simulated maps are publicly available at http://www.hep.anl.gov/cosmology/ksz.html.

  11. Simulations of the Pairwise Kinematic Sunyaev–Zel’dovich Signal

    NASA Astrophysics Data System (ADS)

    Flender, Samuel; Bleem, Lindsey; Finkel, Hal; Habib, Salman; Heitmann, Katrin; Holder, Gilbert

    2016-06-01

    The pairwise kinematic Sunyaev–Zel’dovich (kSZ) signal from galaxy clusters is a probe of their line of sight momenta, and thus a potentially valuable source of cosmological information. In addition to the momenta, the amplitude of the measured signal depends on the properties of the intracluster gas and observational limitations such as errors in determining cluster centers and redshifts. In this work, we simulate the pairwise kSZ signal of clusters at z\\lt 1, using the output from a cosmological N-body simulation and including the properties of the intracluster gas via a model that can be varied in post-processing. We find that modifications to the gas profile due to star formation and feedback reduce the pairwise kSZ amplitude of clusters by ∼ 50%, relative to the naive “gas traces mass” assumption. We demonstrate that miscentering can reduce the overall amplitude of the pairwise kSZ signal by up to 10%, while redshift errors can lead to an almost complete suppression of the signal at small separations. We confirm that a high-significance detection is expected from the combination of data from current generation, high-resolution cosmic microwave background experiments, such as the South Pole Telescope, and cluster samples from optical photometric surveys, such as the Dark Energy Survey. Furthermore, we forecast that future experiments such as Advanced ACTPol in conjunction with data from the Dark Energy Spectroscopic Instrument will yield detection significances of at least 20σ , and up to 57σ in an optimistic scenario. Our simulated maps are publicly available at http://www.hep.anl.gov/cosmology/ksz.html.

  12. Robust Subjective Visual Property Prediction from Crowdsourced Pairwise Labels.

    PubMed

    Fu, Yanwei; Hospedales, Timothy M; Xiang, Tao; Xiong, Jiechao; Gong, Shaogang; Wang, Yizhou; Yao, Yuan

    2016-03-01

    The problem of estimating subjective visual properties from image and video has attracted increasing interest. A subjective visual property is useful either on its own (e.g. image and video interestingness) or as an intermediate representation for visual recognition (e.g. a relative attribute). Due to its ambiguous nature, annotating the value of a subjective visual property for learning a prediction model is challenging. To make the annotation more reliable, recent studies employ crowdsourcing tools to collect pairwise comparison labels. However, using crowdsourced data also introduces outliers. Existing methods rely on majority voting to prune the annotation outliers/errors. They thus require a large amount of pairwise labels to be collected. More importantly as a local outlier detection method, majority voting is ineffective in identifying outliers that can cause global ranking inconsistencies. In this paper, we propose a more principled way to identify annotation outliers by formulating the subjective visual property prediction task as a unified robust learning to rank problem, tackling both the outlier detection and learning to rank jointly. This differs from existing methods in that (1) the proposed method integrates local pairwise comparison labels together to minimise a cost that corresponds to global inconsistency of ranking order, and (2) the outlier detection and learning to rank problems are solved jointly. This not only leads to better detection of annotation outliers but also enables learning with extremely sparse annotations. PMID:27046498

  13. Weak signal detection in hyperspectral imagery using sparse matrix transform (SMT) covariance estimation

    SciTech Connect

    Theiler, James P; Cao, Guangzhi; Bouman, Charles A

    2009-01-01

    Many detection algorithms in hyperspectral image analysis, from well-characterized gaseous and solid targets to deliberately uncharacterized anomalies and anomlous changes, depend on accurately estimating the covariance matrix of the background. In practice, the background covariance is estimated from samples in the image, and imprecision in this estimate can lead to a loss of detection power. In this paper, we describe the sparse matrix transform (SMT) and investigate its utility for estimating the covariance matrix from a limited number of samples. The SMT is formed by a product of pairwise coordinate (Givens) rotations, which can be efficiently estimated using greedy optimization. Experiments on hyperspectral data show that the estimate accurately reproduces even small eigenvalues and eigenvectors. In particular, we find that using the SMT to estimate the covariance matrix used in the adaptive matched filter leads to consistently higher signal-to-noise ratios.

  14. Covariant magnetic connection hypersurfaces

    NASA Astrophysics Data System (ADS)

    Pegoraro, F.

    2016-04-01

    > In the single fluid, non-relativistic, ideal magnetohydrodynamic (MHD) plasma description, magnetic field lines play a fundamental role by defining dynamically preserved `magnetic connections' between plasma elements. Here we show how the concept of magnetic connection needs to be generalized in the case of a relativistic MHD description where we require covariance under arbitrary Lorentz transformations. This is performed by defining 2-D magnetic connection hypersurfaces in the 4-D Minkowski space. This generalization accounts for the loss of simultaneity between spatially separated events in different frames and is expected to provide a powerful insight into the 4-D geometry of electromagnetic fields when .

  15. Pairwise association of neopentane as a function of hydrostatic pressure

    NASA Astrophysics Data System (ADS)

    Graziano, Giuseppe

    2014-11-01

    It is shown that the contact-minimum configuration of two neopentane molecules is favoured on increasing hydrostatic pressure over the range 1-4000 atm, at room temperature, in line with the methane results (Graziano, 2014). This is due to the decrease in water accessible surface area accompanying the association, that leads to a gain in configurational/translational entropy of water molecules, whose magnitude increases with hydrostatic pressure. Of course, the strengthening of pairwise hydrophobic interaction cannot shed light on the pressure-induced denaturation of globular proteins.

  16. Firefox add-ons for medical reference.

    PubMed

    Hoy, Matthew B

    2010-07-01

    Firefox is a Web browser created by the Mozilla project, an open-source software group. Features of the browser include automated updates, advanced security and standards compliance, and the ability to add functionality through add-ons and extensions. First introduced in 2004, Firefox now accounts for roughly 30% of the browser market. This article will focus primarily on add-ons and extensions available for the browser that are useful to medical researchers. PMID:20677067

  17. Stardust Navigation Covariance Analysis

    NASA Astrophysics Data System (ADS)

    Menon, Premkumar R.

    2000-01-01

    The Stardust spacecraft was launched on February 7, 1999 aboard a Boeing Delta-II rocket. Mission participants include the National Aeronautics and Space Administration (NASA), the Jet Propulsion Laboratory (JPL), Lockheed Martin Astronautics (LMA) and the University of Washington. The primary objective of the mission is to collect in-situ samples of the coma of comet Wild-2 and return those samples to the Earth for analysis. Mission design and operational navigation for Stardust is performed by the Jet Propulsion Laboratory (JPL). This paper will describe the extensive JPL effort in support of the Stardust pre-launch analysis of the orbit determination component of the mission covariance study. A description of the mission and it's trajectory will be provided first, followed by a discussion of the covariance procedure and models. Predicted accuracy's will be examined as they relate to navigation delivery requirements for specific critical events during the mission. Stardust was launched into a heliocentric trajectory in early 1999. It will perform an Earth Gravity Assist (EGA) on January 15, 2001 to acquire an orbit for the eventual rendezvous with comet Wild-2. The spacecraft will fly through the coma (atmosphere) on the dayside of Wild-2 on January 2, 2004. At that time samples will be obtained using an aerogel collector. After the comet encounter Stardust will return to Earth when the Sample Return Capsule (SRC) will separate and land at the Utah Test Site (UTTR) on January 15, 2006. The spacecraft will however be deflected off into a heliocentric orbit. The mission is divided into three phases for the covariance analysis. They are 1) Launch to EGA, 2) EGA to Wild-2 encounter and 3) Wild-2 encounter to Earth reentry. Orbit determination assumptions for each phase are provided. These include estimated and consider parameters and their associated a-priori uncertainties. Major perturbations to the trajectory include 19 deterministic and statistical maneuvers

  18. ADD Teacher Inservice Project. Final Grant Report.

    ERIC Educational Resources Information Center

    Edwards, Mark C.; Schulz, Eldon G.

    The report describes activities and achievements of the Attention Deficit Disorder (ADD) Teacher Inservice Project. The inservice program was developed using a formal process to identify the critical issues related to ADD awareness, assessment, and intervention. Program content was designed to address critical issues identified in the research…

  19. Inviting Calm Within: ADD, Neurology, and Mindfulness

    ERIC Educational Resources Information Center

    Riner, Phillip S.; Tanase, Madalina

    2014-01-01

    The fourth edition of the "Diagnostic and Statistical Manual of Mental Disorders" ("DSM IV") describes ADD as behaviorally observed impairments in attention, impulsivity, and hyperactivity. Officially known as AD/HD, we use ADD here because we are dealing primarily with attention, organizational, and impulsivity issues. A more…

  20. 76 FR 47240 - ``Add Us In'' Initiative

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-04

    ... of Disability Employment Policy ``Add Us In'' Initiative AGENCY: Office of Disability Employment.... Department of Labor (``DOL'' or ``Department''), Office of Disability Employment Policy (ODEP) announces the... historically excluded communities, to employ youth and adults with disabilities. Add Us In aims to...

  1. A Statistically Justified Pairwise ML Method for Incomplete Nonnormal Data: A Comparison With Direct ML and Pairwise ADF

    ERIC Educational Resources Information Center

    Savalei, Victoria; Bentler, Peter M.

    2005-01-01

    This article proposes a new approach to the statistical analysis of pairwisepresent covariance structure data. The estimator is based on maximizing the complete data likelihood function, and the associated test statistic and standard errors are corrected for misspecification using Satorra-Bentler corrections. A Monte Carlo study was conducted to…

  2. Prediction of Spatiotemporal Patterns of Neural Activity from Pairwise Correlations

    NASA Astrophysics Data System (ADS)

    Marre, O.; El Boustani, S.; Frégnac, Y.; Destexhe, A.

    2009-04-01

    We designed a model-based analysis to predict the occurrence of population patterns in distributed spiking activity. Using a maximum entropy principle with a Markovian assumption, we obtain a model that accounts for both spatial and temporal pairwise correlations among neurons. This model is tested on data generated with a Glauber spin-glass system and is shown to correctly predict the occurrence probabilities of spatiotemporal patterns significantly better than Ising models only based on spatial correlations. This increase of predictability was also observed on experimental data recorded in parietal cortex during slow-wave sleep. This approach can also be used to generate surrogates that reproduce the spatial and temporal correlations of a given data set.

  3. Time-Frequency Analysis Reveals Pairwise Interactions in Insect Swarms

    NASA Astrophysics Data System (ADS)

    Puckett, James G.; Ni, Rui; Ouellette, Nicholas T.

    2015-06-01

    The macroscopic emergent behavior of social animal groups is a classic example of dynamical self-organization, and is thought to arise from the local interactions between individuals. Determining these interactions from empirical data sets of real animal groups, however, is challenging. Using multicamera imaging and tracking, we studied the motion of individual flying midges in laboratory mating swarms. By performing a time-frequency analysis of the midge trajectories, we show that the midge behavior can be segmented into two distinct modes: one that is independent and composed of low-frequency maneuvers, and one that consists of higher-frequency nearly harmonic oscillations conducted in synchrony with another midge. We characterize these pairwise interactions, and make a hypothesis as to their biological function.

  4. Time-Frequency Analysis Reveals Pairwise Interactions in Insect Swarms.

    PubMed

    Puckett, James G; Ni, Rui; Ouellette, Nicholas T

    2015-06-26

    The macroscopic emergent behavior of social animal groups is a classic example of dynamical self-organization, and is thought to arise from the local interactions between individuals. Determining these interactions from empirical data sets of real animal groups, however, is challenging. Using multicamera imaging and tracking, we studied the motion of individual flying midges in laboratory mating swarms. By performing a time-frequency analysis of the midge trajectories, we show that the midge behavior can be segmented into two distinct modes: one that is independent and composed of low-frequency maneuvers, and one that consists of higher-frequency nearly harmonic oscillations conducted in synchrony with another midge. We characterize these pairwise interactions, and make a hypothesis as to their biological function. PMID:26197145

  5. Calibration of Smartphone-Based Weather Measurements Using Pairwise Gossip

    PubMed Central

    Zamora, Jane Louie Fresco; Kashihara, Shigeru; Yamaguchi, Suguru

    2015-01-01

    Accurate and reliable daily global weather reports are necessary for weather forecasting and climate analysis. However, the availability of these reports continues to decline due to the lack of economic support and policies in maintaining ground weather measurement systems from where these reports are obtained. Thus, to mitigate data scarcity, it is required to utilize weather information from existing sensors and built-in smartphone sensors. However, as smartphone usage often varies according to human activity, it is difficult to obtain accurate measurement data. In this paper, we present a heuristic-based pairwise gossip algorithm that will calibrate smartphone-based pressure sensors with respect to fixed weather stations as our referential ground truth. Based on actual measurements, we have verified that smartphone-based readings are unstable when observed during movement. Using our calibration algorithm on actual smartphone-based pressure readings, the updated values were significantly closer to the ground truth values. PMID:26421312

  6. Pairwise cobalt doping of boron carbides with cobaltocene

    SciTech Connect

    Ignatov, A. Yu.; Losovyj, Ya. B.; Carlson, L.; LaGraffe, D.; Brand, J. I.; Dowben, P. A.

    2007-10-15

    We have performed Co K-edge x-ray absorption fine structure and x-ray absorption near edge structure measurements of Co-doped plasma enhanced chemical vapor phase deposition (PECVD) grown 'C{sub 2}B{sub 10}H{sub x}' semiconducting boron carbides, using cobaltocene. Cobalt does not dope PECVD grown boron carbides as a random fragment of the cobaltocene source gas. The Co atoms are fivefold boron coordinated (R=2.10{+-}0.02 A) and are chemically bonded to the icosahedral cages of B{sub 10}CH{sub x} or B{sub 9}C{sub 2}H{sub y}. Pairwise Co doping occurs, with the cobalt atoms favoring sites some 5.28{+-}0.02 A apart.

  7. Prediction of Spatiotemporal Patterns of Neural Activity from Pairwise Correlations

    SciTech Connect

    Marre, O.; El Boustani, S.; Fregnac, Y.; Destexhe, A.

    2009-04-03

    We designed a model-based analysis to predict the occurrence of population patterns in distributed spiking activity. Using a maximum entropy principle with a Markovian assumption, we obtain a model that accounts for both spatial and temporal pairwise correlations among neurons. This model is tested on data generated with a Glauber spin-glass system and is shown to correctly predict the occurrence probabilities of spatiotemporal patterns significantly better than Ising models only based on spatial correlations. This increase of predictability was also observed on experimental data recorded in parietal cortex during slow-wave sleep. This approach can also be used to generate surrogates that reproduce the spatial and temporal correlations of a given data set.

  8. Pairwise cobalt doping of boron carbides with cobaltocene

    NASA Astrophysics Data System (ADS)

    Ignatov, A. Yu.; Losovyj, Ya. B.; Carlson, L.; LaGraffe, D.; Brand, J. I.; Dowben, P. A.

    2007-10-01

    We have performed Co K-edge x-ray absorption fine structure and x-ray absorption near edge structure measurements of Co-doped plasma enhanced chemical vapor phase deposition (PECVD) grown "C2B10Hx" semiconducting boron carbides, using cobaltocene. Cobalt does not dope PECVD grown boron carbides as a random fragment of the cobaltocene source gas. The Co atoms are fivefold boron coordinated (R=2.10±0.02Å) and are chemically bonded to the icosahedral cages of B10CHx or B9C2Hy. Pairwise Co doping occurs, with the cobalt atoms favoring sites some 5.28±0.02Å apart.

  9. Pairwise comparison and selection temperature in evolutionary game dynamics

    PubMed Central

    Traulsen, Arne; Pacheco, Jorge M.; Nowak, Martin A.

    2007-01-01

    Recently, the frequency dependent Moran process has been introduced in order to describe evolutionary game dynamics in finite populations. Here, an alternative to this process is investigated that is based on pairwise comparison between two individuals. We follow a long tradition in the physics community and introduce a temperature (of selection) to account for stochastic effects. We calculate the fixation probabilities and fixation times for any symmetric 2 × 2 game, for any intensity of selection and any initial number of mutants. The temperature can be used to gauge continuously from neutral drift to the extreme selection intensity known as imitation dynamics. For some payoff matrices the distribution of fixation times can become so broad that the average value is no longer very meaningful. PMID:17292423

  10. Latent Variable Model for Learning in Pairwise Markov Networks

    PubMed Central

    Amizadeh, Saeed; Hauskrecht, Milos

    2011-01-01

    Pairwise Markov Networks (PMN) are an important class of Markov networks which, due to their simplicity, are widely used in many applications such as image analysis, bioinformatics, sensor networks, etc. However, learning of Markov networks from data is a challenging task; there are many possible structures one must consider and each of these structures comes with its own parameters making it easy to overfit the model with limited data. To deal with the problem, recent learning methods build upon the L1 regularization to express the bias towards sparse network structures. In this paper, we propose a new and more flexible framework that let us bias the structure, that can, for example, encode the preference to networks with certain local substructures which as a whole exhibit some special global structure. We experiment with and show the benefit of our framework on two types of problems: learning of modular networks and learning of traffic networks models. PMID:22228193

  11. On the early epidemic dynamics for pairwise models.

    PubMed

    Llensa, Carlos; Juher, David; Saldaña, Joan

    2014-07-01

    The relationship between the basic reproduction number R0 and the exponential growth rate, specific to pair approximation models, is derived for the SIS, SIR and SEIR deterministic models without demography. These models are extended by including a random rewiring of susceptible individuals from infectious (and exposed) neighbours. The derived relationship between the exponential growth rate and R0 appears as formally consistent with those derived from homogeneous mixing models, enabling us to measure the transmission potential using the early growth rate of cases. On the other hand, the algebraic expression of R0 for the SEIR pairwise model shows that its value is affected by the average duration of the latent period, in contrast to what happens for the homogeneous mixing SEIR model. Numerical simulations on complex contact networks are performed to check the analytical assumptions and predictions. PMID:24607747

  12. Calibration of Smartphone-Based Weather Measurements Using Pairwise Gossip.

    PubMed

    Zamora, Jane Louie Fresco; Kashihara, Shigeru; Yamaguchi, Suguru

    2015-01-01

    Accurate and reliable daily global weather reports are necessary for weather forecasting and climate analysis. However, the availability of these reports continues to decline due to the lack of economic support and policies in maintaining ground weather measurement systems from where these reports are obtained. Thus, to mitigate data scarcity, it is required to utilize weather information from existing sensors and built-in smartphone sensors. However, as smartphone usage often varies according to human activity, it is difficult to obtain accurate measurement data. In this paper, we present a heuristic-based pairwise gossip algorithm that will calibrate smartphone-based pressure sensors with respect to fixed weather stations as our referential ground truth. Based on actual measurements, we have verified that smartphone-based readings are unstable when observed during movement. Using our calibration algorithm on actual smartphone-based pressure readings, the updated values were significantly closer to the ground truth values. PMID:26421312

  13. Congruence of Behavioral Symptomatology in Children with ADD/H, ADD/WO, and Learning Disabilities.

    ERIC Educational Resources Information Center

    Stanford, Lisa D.; Hynd, George W.

    1994-01-01

    This study compared parent and teacher behavioral ratings for 77 children (ages 5-16) diagnosed as having attention deficit disorder with hyperactivity (ADD/H), attention deficit disorder without hyperactivity (ADD/WO), or learning disabilities (LD). ADD/WO and LD children were rated similarly on symptoms of withdrawal and impulsivity but differed…

  14. A human platelet calcium calculator trained by pairwise agonist scanning.

    PubMed

    Lee, Mei Yan; Diamond, Scott L

    2015-02-01

    Since platelet intracellular calcium mobilization [Ca(t)]i controls granule release, cyclooxygenase-1 and integrin activation, and phosphatidylserine exposure, blood clotting simulations require prediction of platelet [Ca(t)]i in response to combinatorial agonists. Pairwise Agonist Scanning (PAS) deployed all single and pairwise combinations of six agonists (ADP, convulxin, thrombin, U46619, iloprost and GSNO used at 0.1, 1, and 10xEC50; 154 conditions including a null condition) to stimulate platelet P2Y1/P2Y12 GPVI, PAR1/PAR4, TP, IP receptors, and guanylate cyclase, respectively, in Factor Xa-inhibited (250 nM apixaban), diluted platelet rich plasma that had been loaded with the calcium dye Fluo-4 NW. PAS of 10 healthy donors provided [Ca(t)]i data for training 10 neural networks (NN, 2-layer/12-nodes) per donor. Trinary stimulations were then conducted at all 0.1x and 1xEC50 doses (160 conditions) as was a sampling of 45 higher ordered combinations (four to six agonists). The NN-ensemble average was a calcium calculator that accurately predicted [Ca (t)]i beyond the single and binary training set for trinary stimulations (R = 0.924). The 160 trinary synergy scores, a normalized metric of signaling crosstalk, were also well predicted (R = 0.850) as were the calcium dynamics (R = 0.871) and high-dimensional synergy scores (R = 0.695) for the 45 higher ordered conditions. The calculator even predicted sequential addition experiments (n = 54 conditions, R = 0.921). NN-ensemble is a fast calcium calculator, ideal for multiscale clotting simulations that include spatiotemporal concentrations of ADP, collagen, thrombin, thromboxane, prostacyclin, and nitric oxide. PMID:25723389

  15. A Human Platelet Calcium Calculator Trained by Pairwise Agonist Scanning

    PubMed Central

    Lee, Mei Yan; Diamond, Scott L.

    2015-01-01

    Since platelet intracellular calcium mobilization [Ca(t)]i controls granule release, cyclooxygenase-1 and integrin activation, and phosphatidylserine exposure, blood clotting simulations require prediction of platelet [Ca(t)]i in response to combinatorial agonists. Pairwise Agonist Scanning (PAS) deployed all single and pairwise combinations of six agonists (ADP, convulxin, thrombin, U46619, iloprost and GSNO used at 0.1, 1, and 10xEC50; 154 conditions including a null condition) to stimulate platelet P2Y1/P2Y12 GPVI, PAR1/PAR4, TP, IP receptors, and guanylate cyclase, respectively, in Factor Xa-inhibited (250 nM apixaban), diluted platelet rich plasma that had been loaded with the calcium dye Fluo-4 NW. PAS of 10 healthy donors provided [Ca(t)]i data for training 10 neural networks (NN, 2-layer/12-nodes) per donor. Trinary stimulations were then conducted at all 0.1x and 1xEC50 doses (160 conditions) as was a sampling of 45 higher ordered combinations (four to six agonists). The NN-ensemble average was a calcium calculator that accurately predicted [Ca (t)]i beyond the single and binary training set for trinary stimulations (R = 0.924). The 160 trinary synergy scores, a normalized metric of signaling crosstalk, were also well predicted (R = 0.850) as were the calcium dynamics (R = 0.871) and high-dimensional synergy scores (R = 0.695) for the 45 higher ordered conditions. The calculator even predicted sequential addition experiments (n = 54 conditions, R = 0.921). NN-ensemble is a fast calcium calculator, ideal for multiscale clotting simulations that include spatiotemporal concentrations of ADP, collagen, thrombin, thromboxane, prostacyclin, and nitric oxide. PMID:25723389

  16. The incredible shrinking covariance estimator

    NASA Astrophysics Data System (ADS)

    Theiler, James

    2012-05-01

    Covariance estimation is a key step in many target detection algorithms. To distinguish target from background requires that the background be well-characterized. This applies to targets ranging from the precisely known chemical signatures of gaseous plumes to the wholly unspecified signals that are sought by anomaly detectors. When the background is modelled by a (global or local) Gaussian or other elliptically contoured distribution (such as Laplacian or multivariate-t), a covariance matrix must be estimated. The standard sample covariance overfits the data, and when the training sample size is small, the target detection performance suffers. Shrinkage addresses the problem of overfitting that inevitably arises when a high-dimensional model is fit from a small dataset. In place of the (overfit) sample covariance matrix, a linear combination of that covariance with a fixed matrix is employed. The fixed matrix might be the identity, the diagonal elements of the sample covariance, or some other underfit estimator. The idea is that the combination of an overfit with an underfit estimator can lead to a well-fit estimator. The coefficient that does this combining, called the shrinkage parameter, is generally estimated by some kind of cross-validation approach, but direct cross-validation can be computationally expensive. This paper extends an approach suggested by Hoffbeck and Landgrebe, and presents efficient approximations of the leave-one-out cross-validation (LOOC) estimate of the shrinkage parameter used in estimating the covariance matrix from a limited sample of data.

  17. Covariant Electrodynamics in Vacuum

    NASA Astrophysics Data System (ADS)

    Wilhelm, H. E.

    1990-05-01

    The generalized Galilei covariant Maxwell equations and their EM field transformations are applied to the vacuum electrodynamics of a charged particle moving with an arbitrary velocity v in an inertial frame with EM carrier (ether) of velocity w. In accordance with the Galilean relativity principle, all velocities have absolute meaning (relative to the ether frame with isotropic light propagation), and the relative velocity of two bodies is defined by the linear relation uG = v1 - v2. It is shown that the electric equipotential surfaces of a charged particle are compressed in the direction parallel to its relative velocity v - w (mechanism for physical length contraction of bodies). The magnetic field H(r, t) excited in the ether by a charge e moving uniformly with velocity v is related to its electric field E(r, t) by the equation H=ɛ0(v - w)xE/[ 1 +w • (t>- w)/c20], which shows that (i) a magnetic field is excited only if the charge moves relative to the ether, and (ii) the magnetic field is weak if v - w is not comparable to the velocity of light c0 . It is remarkable that a charged particle can excite EM shock waves in the ether if |i> - w > c0. This condition is realizable for anti-parallel charge and ether velocities if |v-w| > c0- | w|, i.e., even if |v| is subluminal. The possibility of this Cerenkov effect in the ether is discussed for terrestrial and galactic situations

  18. Consistency of crisp and fuzzy pairwise comparison matrix using fuzzy preference programming

    NASA Astrophysics Data System (ADS)

    Aminuddin, Adam Shariff Adli; Nawawi, Mohd Kamal Mohd

    2014-12-01

    In this paper, the consistency of crisp pairwise comparison matrix is compared with the fuzzy pairwise comparison matrix of Analytic Network Process (ANP). The fuzzy input in the form of triangular membership function is converted into crisp value using Fuzzy Preference Programming (FPP) method which is implemented using MATLAB. The consistency ratio (CR) for both of the crisp and fuzzy pairwise comparison matrix is calculated using SuperDecisions. Main finding shows that the involvement of fuzzy elements into the decision maker's judgment can reduce the inconsistency of the pairwise comparison matrix compared with the crisp judgment.

  19. ADD psychosis as a separate entity.

    PubMed

    Bellak, L

    1985-01-01

    "Attention deficit disorder (ADD) psychosis" merits delineation as a separate entity. It constitutes the end result of the effects of a certain particular neurological deficit (ADD) on personality organization. It is my belief that about 10 percent of psychoses currently diagnosed most often schizophrenic and sometimes affective psychosis must best be considered a separate organic psychosis, i.e., an ADD psychosis. This ADD psychosis, then, is not merely a subgroup of schizophrenia, as I once thought. It merits a separate designation because its etiology, pathogenesis, and life history are different from those of the schizophrenic syndrome. The family histories are also different, as are the psychological findings. The treatment response is so different that it merits urgent consideration. Prognosis, both short range and long range, also seems different from those of the other psychoses. PMID:4081648

  20. Covariant Closed String Coherent States

    SciTech Connect

    Hindmarsh, Mark; Skliros, Dimitri

    2011-02-25

    We give the first construction of covariant coherent closed string states, which may be identified with fundamental cosmic strings. We outline the requirements for a string state to describe a cosmic string, and provide an explicit and simple map that relates three different descriptions: classical strings, light cone gauge quantum states, and covariant vertex operators. The resulting coherent state vertex operators have a classical interpretation and are in one-to-one correspondence with arbitrary classical closed string loops.

  1. Covariant closed string coherent states.

    PubMed

    Hindmarsh, Mark; Skliros, Dimitri

    2011-02-25

    We give the first construction of covariant coherent closed string states, which may be identified with fundamental cosmic strings. We outline the requirements for a string state to describe a cosmic string, and provide an explicit and simple map that relates three different descriptions: classical strings, light cone gauge quantum states, and covariant vertex operators. The resulting coherent state vertex operators have a classical interpretation and are in one-to-one correspondence with arbitrary classical closed string loops. PMID:21405564

  2. Differential Item Functioning Detection across Two Methods of Defining Group Comparisons: Pairwise and Composite Group Comparisons

    ERIC Educational Resources Information Center

    Sari, Halil Ibrahim; Huggins, Anne Corinne

    2015-01-01

    This study compares two methods of defining groups for the detection of differential item functioning (DIF): (a) pairwise comparisons and (b) composite group comparisons. We aim to emphasize and empirically support the notion that the choice of pairwise versus composite group definitions in DIF is a reflection of how one defines fairness in DIF…

  3. Equating a Large-Scale Writing Assessment Using Pairwise Comparisons of Performances

    ERIC Educational Resources Information Center

    Humphry, Stephen M.; McGrane, Joshua A.

    2015-01-01

    This paper presents a method for equating writing assessments using pairwise comparisons which does not depend upon conventional common-person or common-item equating designs. Pairwise comparisons have been successfully applied in the assessment of open-ended tasks in English and other areas such as visual art and philosophy. In this paper,…

  4. Multiplex pairwise assembly of array-derived DNA oligonucleotides

    PubMed Central

    Klein, Jason C.; Lajoie, Marc J.; Schwartz, Jerrod J.; Strauch, Eva-Maria; Nelson, Jorgen; Baker, David; Shendure, Jay

    2016-01-01

    While the cost of DNA sequencing has dropped by five orders of magnitude in the past decade, DNA synthesis remains expensive for many applications. Although DNA microarrays have decreased the cost of oligonucleotide synthesis, the use of array-synthesized oligos in practice is limited by short synthesis lengths, high synthesis error rates, low yield and the challenges of assembling long constructs from complex pools. Toward addressing these issues, we developed a protocol for multiplex pairwise assembly of oligos from array-synthesized oligonucleotide pools. To evaluate the method, we attempted to assemble up to 2271 targets ranging in length from 192–252 bases using pairs of array-synthesized oligos. Within sets of complexity ranging from 131–250 targets, we observed error-free assemblies for 90.5% of all targets. When all 2271 targets were assembled in one reaction, we observed error-free constructs for 70.6%. While the assembly method intrinsically increased accuracy to a small degree, we further increased accuracy by using a high throughput ‘Dial-Out PCR’ protocol, which combines Illumina sequencing with an in-house set of unique PCR tags to selectively amplify perfect assemblies from complex synthetic pools. This approach has broad applicability to DNA assembly and high-throughput functional screens. PMID:26553805

  5. Convergent cross-mapping and pairwise asymmetric inference

    NASA Astrophysics Data System (ADS)

    McCracken, James M.; Weigel, Robert S.

    2014-12-01

    Convergent cross-mapping (CCM) is a technique for computing specific kinds of correlations between sets of times series. It was introduced by Sugihara et al. [Science 338, 496 (2012)., 10.1126/science.1227079] and is reported to be "a necessary condition for causation" capable of distinguishing causality from standard correlation. We show that the relationships between CCM correlations proposed by Sugihara et al. do not, in general, agree with intuitive concepts of "driving" and as such should not be considered indicative of causality. It is shown that the fact that the CCM algorithm implies causality is a function of system parameters for simple linear and nonlinear systems. For example, in a circuit containing a single resistor and inductor, both voltage and current can be identified as the driver depending on the frequency of the source voltage. It is shown that the CCM algorithm, however, can be modified to identify relationships between pairs of time series that are consistent with intuition for the considered example systems for which CCM causality analysis provided nonintuitive driver identifications. This modification of the CCM algorithm is introduced as "pairwise asymmetric inference" (PAI) and examples of its use are presented.

  6. Convergent cross-mapping and pairwise asymmetric inference.

    PubMed

    McCracken, James M; Weigel, Robert S

    2014-12-01

    Convergent cross-mapping (CCM) is a technique for computing specific kinds of correlations between sets of times series. It was introduced by Sugihara et al. [Science 338, 496 (2012).] and is reported to be "a necessary condition for causation" capable of distinguishing causality from standard correlation. We show that the relationships between CCM correlations proposed by Sugihara et al. do not, in general, agree with intuitive concepts of "driving" and as such should not be considered indicative of causality. It is shown that the fact that the CCM algorithm implies causality is a function of system parameters for simple linear and nonlinear systems. For example, in a circuit containing a single resistor and inductor, both voltage and current can be identified as the driver depending on the frequency of the source voltage. It is shown that the CCM algorithm, however, can be modified to identify relationships between pairs of time series that are consistent with intuition for the considered example systems for which CCM causality analysis provided nonintuitive driver identifications. This modification of the CCM algorithm is introduced as "pairwise asymmetric inference" (PAI) and examples of its use are presented. PMID:25615160

  7. Multiplex pairwise assembly of array-derived DNA oligonucleotides.

    PubMed

    Klein, Jason C; Lajoie, Marc J; Schwartz, Jerrod J; Strauch, Eva-Maria; Nelson, Jorgen; Baker, David; Shendure, Jay

    2016-03-18

    While the cost of DNA sequencing has dropped by five orders of magnitude in the past decade, DNA synthesis remains expensive for many applications. Although DNA microarrays have decreased the cost of oligonucleotide synthesis, the use of array-synthesized oligos in practice is limited by short synthesis lengths, high synthesis error rates, low yield and the challenges of assembling long constructs from complex pools. Toward addressing these issues, we developed a protocol for multiplex pairwise assembly of oligos from array-synthesized oligonucleotide pools. To evaluate the method, we attempted to assemble up to 2271 targets ranging in length from 192-252 bases using pairs of array-synthesized oligos. Within sets of complexity ranging from 131-250 targets, we observed error-free assemblies for 90.5% of all targets. When all 2271 targets were assembled in one reaction, we observed error-free constructs for 70.6%. While the assembly method intrinsically increased accuracy to a small degree, we further increased accuracy by using a high throughput 'Dial-Out PCR' protocol, which combines Illumina sequencing with an in-house set of unique PCR tags to selectively amplify perfect assemblies from complex synthetic pools. This approach has broad applicability to DNA assembly and high-throughput functional screens. PMID:26553805

  8. Shrinkage estimators for covariance matrices.

    PubMed

    Daniels, M J; Kass, R E

    2001-12-01

    Estimation of covariance matrices in small samples has been studied by many authors. Standard estimators, like the unstructured maximum likelihood estimator (ML) or restricted maximum likelihood (REML) estimator, can be very unstable with the smallest estimated eigenvalues being too small and the largest too big. A standard approach to more stably estimating the matrix in small samples is to compute the ML or REML estimator under some simple structure that involves estimation of fewer parameters, such as compound symmetry or independence. However, these estimators will not be consistent unless the hypothesized structure is correct. If interest focuses on estimation of regression coefficients with correlated (or longitudinal) data, a sandwich estimator of the covariance matrix may be used to provide standard errors for the estimated coefficients that are robust in the sense that they remain consistent under misspecification of the covariance structure. With large matrices, however, the inefficiency of the sandwich estimator becomes worrisome. We consider here two general shrinkage approaches to estimating the covariance matrix and regression coefficients. The first involves shrinking the eigenvalues of the unstructured ML or REML estimator. The second involves shrinking an unstructured estimator toward a structured estimator. For both cases, the data determine the amount of shrinkage. These estimators are consistent and give consistent and asymptotically efficient estimates for regression coefficients. Simulations show the improved operating characteristics of the shrinkage estimators of the covariance matrix and the regression coefficients in finite samples. The final estimator chosen includes a combination of both shrinkage approaches, i.e., shrinking the eigenvalues and then shrinking toward structure. We illustrate our approach on a sleep EEG study that requires estimation of a 24 x 24 covariance matrix and for which inferences on mean parameters critically

  9. Nonreciprocal photonic crystal add-drop filter

    SciTech Connect

    Tao, Keyu; Xiao, Jun-Jun; Yin, Xiaobo

    2014-11-24

    We present a versatile add-drop integrated photonic filter (ADF) consisting of nonreciprocal waveguides in which the propagation of light is restricted in one predetermined direction. With the bus and add/drop waveguides symmetrically coupled through a cavity, the four-port device allows each individual port to add and/or drop a signal of the same frequency. The scheme is general and we demonstrate the nonreciprocal ADF with magneto-optical photonic crystals. The filter is immune to waveguide defects, allowing straightforward implementation of multi-channel ADFs by cascading the four-port designs. The results should find applications in wavelength-division multiplexing and related integrated photonic techniques.

  10. Shift-and-add for astronomical imaging

    NASA Technical Reports Server (NTRS)

    Ribak, Erez; Hege, E. Keith; Strobel, Nicolas V.; Christou, Julian C.

    1989-01-01

    Diffraction-limited astronomical images have been obtained utilizing a variant of the shift-and-add method. It is shown that the matched filter approach for extending the weighted shift-and-add method reduces specklegrams from extended objects and from an object dominated by photon noise. The method is aberration-insensitive and yields very high dynamic range results. The iterative method for arriving at the matched filter does not automatically converge in the case of photon-noisy specklegrams for objects with more than one maximum.

  11. A class of covariate-dependent spatiotemporal covariance functions

    PubMed Central

    Reich, Brian J; Eidsvik, Jo; Guindani, Michele; Nail, Amy J; Schmidt, Alexandra M.

    2014-01-01

    In geostatistics, it is common to model spatially distributed phenomena through an underlying stationary and isotropic spatial process. However, these assumptions are often untenable in practice because of the influence of local effects in the correlation structure. Therefore, it has been of prolonged interest in the literature to provide flexible and effective ways to model non-stationarity in the spatial effects. Arguably, due to the local nature of the problem, we might envision that the correlation structure would be highly dependent on local characteristics of the domain of study, namely the latitude, longitude and altitude of the observation sites, as well as other locally defined covariate information. In this work, we provide a flexible and computationally feasible way for allowing the correlation structure of the underlying processes to depend on local covariate information. We discuss the properties of the induced covariance functions and discuss methods to assess its dependence on local covariate information by means of a simulation study and the analysis of data observed at ozone-monitoring stations in the Southeast United States. PMID:24772199

  12. Educational Interventions for Students with ADD.

    ERIC Educational Resources Information Center

    Salend, Spencer J.; Elhoweris, Hala; van Garderen, Delinda

    2003-01-01

    Principles of educational interventions for students with attention deficit disorder (ADD) include: (1) giving complete and thorough directions; (2) individualizing in-class and homework assignments; (3) motivating students; (4) promoting active responding and monitoring understanding; (5) employing content enhancements; (6) offering learning…

  13. 76 FR 49508 - ``Add Us In'' Initiative

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-10

    ... Federal Register on August 4, 2011 at 76 FR 150. Specifically, we are correcting the Funding Opportunity... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF LABOR Office of Disability Employment Program ``Add Us In'' Initiative AGENCY: Office of Disability...

  14. Cross-Section Covariance Data Processing with the AMPX Module PUFF-IV

    SciTech Connect

    Wiarda, Dorothea; Leal, Luiz C; Dunn, Michael E

    2011-01-01

    The ENDF community is endeavoring to release an updated version of the ENDF/B-VII library (ENDF/B-VII.1). In the new release several new evaluations containing covariance information have been added, as the community strives to add covariance information for use in programs like the TSUNAMI (Tools for Sensitivity and Uncertainty Analysis Methodology Implementation) sequence of SCALE (Ref 1). The ENDF/B formatted files are processed into libraries to be used in transport calculations using the AMPX code system (Ref 2) or the NJOY code system (Ref 3). Both codes contain modules to process covariance matrices: PUFF-IV for AMPX and ERRORR in the case of NJOY. While the cross section processing capability between the two code systems has been widely compared, the same is not true for the covariance processing. This paper compares the results for the two codes using the pre-release version of ENDF/B-VII.1.

  15. Are Eddy Covariance series stationary?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Spectral analysis via a discrete Fourier transform is used often to examine eddy covariance series for cycles (eddies) of interest. Generally the analysis is performed on hourly or half-hourly data sets collected at 10 or 20 Hz. Each original series is often assumed to be stationary. Also automated ...

  16. Generalization of Pairwise Models to non-Markovian Epidemics on Networks

    NASA Astrophysics Data System (ADS)

    Kiss, Istvan Z.; Röst, Gergely; Vizi, Zsolt

    2015-08-01

    In this Letter, a generalization of pairwise models to non-Markovian epidemics on networks is presented. For the case of infectious periods of fixed length, the resulting pairwise model is a system of delay differential equations, which shows excellent agreement with results based on stochastic simulations. Furthermore, we analytically compute a new R0 -like threshold quantity and an analytical relation between this and the final epidemic size. Additionally, we show that the pairwise model and the analytic results can be generalized to an arbitrary distribution of the infectious times, using integro-differential equations, and this leads to a general expression for the final epidemic size. By showing the rigorous link between non-Markovian dynamics and pairwise delay differential equations, we provide the framework for a more systematic understanding of non-Markovian dynamics.

  17. An IRT Approach to Constructing and Scoring Pairwise Preference Items Involving Stimuli on Different Dimensions: The Multi-Unidimensional Pairwise-Preference Model

    ERIC Educational Resources Information Center

    Stark, Stephen; Chernyshenko, Oleksandr S.; Drasgow, Fritz

    2005-01-01

    This article proposes an item response theory (IRT) approach to constructing and scoring multidimensional pairwise preference items. Individual statements are administered and calibrated using a unidimensional single-stimulus model. Tests are created by combining multidimensional items with a small number of unidimensional pairings needed to…

  18. Minimal unitary (covariant) scattering theory

    SciTech Connect

    Lindesay, J.V.; Markevich, A.

    1983-06-01

    In the minimal three particle equations developed by Lindesay the two body input amplitude was an on shell relativistic generalization of the non-relativistic scattering model characterized by a single mass parameter ..mu.. which in the two body (m + m) system looks like an s-channel bound state (..mu.. < 2m) or virtual state (..mu.. > 2m). Using this driving term in covariant Faddeev equations generates a rich covariant and unitary three particle dynamics. However, the simplest way of writing the relativisitic generalization of the Faddeev equations can take the on shell Mandelstam parameter s = 4(q/sup 2/ + m/sup 2/), in terms of which the two particle input is expressed, to negative values in the range of integration required by the dynamics. This problem was met in the original treatment by multiplying the two particle input amplitude by THETA(s). This paper provides what we hope to be a more direct way of meeting the problem.

  19. Covariant jump conditions in electromagnetism

    NASA Astrophysics Data System (ADS)

    Itin, Yakov

    2012-02-01

    A generally covariant four-dimensional representation of Maxwell's electrodynamics in a generic material medium can be achieved straightforwardly in the metric-free formulation of electromagnetism. In this setup, the electromagnetic phenomena are described by two tensor fields, which satisfy Maxwell's equations. A generic tensorial constitutive relation between these fields is an independent ingredient of the theory. By use of different constitutive relations (local and non-local, linear and non-linear, etc.), a wide area of applications can be covered. In the current paper, we present the jump conditions for the fields and for the energy-momentum tensor on an arbitrarily moving surface between two media. From the differential and integral Maxwell equations, we derive the covariant boundary conditions, which are independent of any metric and connection. These conditions include the covariantly defined surface current and are applicable to an arbitrarily moving smooth curved boundary surface. As an application of the presented jump formulas, we derive a Lorentzian type metric as a condition for existence of the wave front in isotropic media. This result holds for ordinary materials as well as for metamaterials with negative material constants.

  20. Structural covariance in schizophrenia and first-episode psychosis: An approach based on graph analysis.

    PubMed

    Zugman, André; Assunção, Idaiane; Vieira, Gilson; Gadelha, Ary; White, Thomas P; Oliveira, Pedro Paulo M; Noto, Cristiano; Crossley, Nicolas; Mcguire, Philip; Cordeiro, Quirino; Belangero, Sintia I O; Bressan, Rodrigo A; Jackowski, Andrea P; Sato, João Ricardo

    2015-12-01

    Schizophrenia is a neurodevelopmental disorder that produces abnormalities across different brain regions. Measuring structural covariance with MRI is a well-established approach to investigate common changes in distinct systems. We investigated structural covariance in schizophrenia in a large Brazilian sample of individuals with chronic schizophrenia (n = 143), First Episode Psychosis (n = 32), and matched healthy controls (n = 82) using a combination of graph analysis and computational neuroanatomy. Firstly, we proposed the connectivity-closeness and integrity-closeness centrality measures and them compared healthy controls with chronic schizophrenia regarding these metrics. We then conducted a second analysis on the mapped regions comparing the pairwise difference between the three groups. Our results show that compared with controls, both patient groups (in pairwise comparisons) had a reduced integrity-closeness in pars orbitalis and insula, suggesting that the relationship between these areas and other brain regions is increased in schizophrenia. No differences were found between the First Episode Psychosis and Schizophrenia groups. Since in schizophrenia the brain is affected as a whole, this may mirror that these regions may be related to the generalized structural alteration seen in schizophrenia. PMID:26458012

  1. Covariance Evaluation Methodology for Neutron Cross Sections

    SciTech Connect

    Herman,M.; Arcilla, R.; Mattoon, C.M.; Mughabghab, S.F.; Oblozinsky, P.; Pigni, M.; Pritychenko, b.; Songzoni, A.A.

    2008-09-01

    We present the NNDC-BNL methodology for estimating neutron cross section covariances in thermal, resolved resonance, unresolved resonance and fast neutron regions. The three key elements of the methodology are Atlas of Neutron Resonances, nuclear reaction code EMPIRE, and the Bayesian code implementing Kalman filter concept. The covariance data processing, visualization and distribution capabilities are integral components of the NNDC methodology. We illustrate its application on examples including relatively detailed evaluation of covariances for two individual nuclei and massive production of simple covariance estimates for 307 materials. Certain peculiarities regarding evaluation of covariances for resolved resonances and the consistency between resonance parameter uncertainties and thermal cross section uncertainties are also discussed.

  2. Connecting Math and Motion: A Covariational Approach

    NASA Astrophysics Data System (ADS)

    Culbertson, Robert J.; Thompson, A. S.

    2006-12-01

    We define covariational reasoning as the ability to correlate changes in two connected variables. For example, the ability to describe the height of fluid in an odd-shaped vessel as a function of fluid volume requires covariational reasoning skills. Covariational reasoning ability is an essential resource for gaining a deep understanding of the physics of motion. We have developed an approach for teaching physical science to in-service math and science high school teachers that emphasizes covariational reasoning. Several examples of covariation and results from a small cohort of local teachers will be presented.

  3. Phase-covariant quantum benchmarks

    SciTech Connect

    Calsamiglia, J.; Aspachs, M.; Munoz-Tapia, R.; Bagan, E.

    2009-05-15

    We give a quantum benchmark for teleportation and quantum storage experiments suited for pure and mixed test states. The benchmark is based on the average fidelity over a family of phase-covariant states and certifies that an experiment cannot be emulated by a classical setup, i.e., by a measure-and-prepare scheme. We give an analytical solution for qubits, which shows important differences with standard state estimation approach, and compute the value of the benchmark for coherent and squeezed states, both pure and mixed.

  4. Beta Diversity of Plant-Pollinator Networks and the Spatial Turnover of Pairwise Interactions

    PubMed Central

    Carstensen, Daniel W.; Sabatino, Malena; Trøjelsgaard, Kristian; Morellato, Leonor Patricia C.

    2014-01-01

    Interactions between species form complex networks that vary across space and time. Even without spatial or temporal constraints mutualistic pairwise interactions may vary, or rewire, across space but this variability is not well understood. Here, we quantify the beta diversity of species and interactions and test factors influencing the probability of turnover of pairwise interactions across space. We ask: 1) whether beta diversity of plants, pollinators, and interactions follow a similar trend across space, and 2) which interaction properties and site characteristics are related to the probability of turnover of pairwise interactions. Geographical distance was positively correlated with plant and interaction beta diversity. We find that locally frequent interactions are more consistent across space and that local flower abundance is important for the realization of pairwise interactions. While the identity of pairwise interactions is highly variable across space, some species-pairs form interactions that are locally frequent and spatially consistent. Such interactions represent cornerstones of interacting communities and deserve special attention from ecologists and conservation planners alike. PMID:25384058

  5. User's manual for Axisymmetric Diffuser Duct (ADD) code. Volume 1: General ADD code description

    NASA Technical Reports Server (NTRS)

    Anderson, O. L.; Hankins, G. B., Jr.; Edwards, D. E.

    1982-01-01

    This User's Manual contains a complete description of the computer codes known as the AXISYMMETRIC DIFFUSER DUCT code or ADD code. It includes a list of references which describe the formulation of the ADD code and comparisons of calculation with experimental flows. The input/output and general use of the code is described in the first volume. The second volume contains a detailed description of the code including the global structure of the code, list of FORTRAN variables, and descriptions of the subroutines. The third volume contains a detailed description of the CODUCT code which generates coordinate systems for arbitrary axisymmetric ducts.

  6. User's manual for Axisymmetric Diffuser Duct (ADD) code. Volume 3: ADD code coordinate generator

    NASA Technical Reports Server (NTRS)

    Anderson, O. L.; Hankins, G. B., Jr.; Edwards, D. E.

    1982-01-01

    This User's Manual contains a complete description of the computer codes known as the Axisymmetric Diffuser Duct (ADD) code. It includes a list of references which describe the formulation of the ADD code and comparisons of calculation with experimental flows. The input/output and general use of the code is described in the first volume. The second volume contains a detailed description of the code including the global structure of the code, list of FORTRAN variables, and descriptions of the subroutines. The third volume contains a detailed description of the CODUCT code which generates coordinate systems for arbitrary axisymmetric ducts.

  7. Beyond Rainbow-Ladder in a covariant three-body Bethe-Salpeter approach: Baryons

    NASA Astrophysics Data System (ADS)

    Sanchis-Alepuz, Hèlios; Kubrak, Stanislav D.; Fischer, Christian S.

    2014-06-01

    We report on recent results of a calculation of the nucleon and delta masses in a covariant bound-state approach, where to the simple rainbow-ladder gluon-exchange interaction kernel we add a pion-exchange contribution to account for pion cloud effects. We observe good agreement with lattice data at large pion masses. At the physical point our masses are too large by about five percent, signaling the need for more structure in the gluon part of the interaction.

  8. Using Joint Interviews to Add Analytic Value.

    PubMed

    Polak, Louisa; Green, Judith

    2016-10-01

    Joint interviewing has been frequently used in health research, and is the subject of a growing methodological literature. We review this literature, and build on it by drawing on a case study of how people make decisions about taking statins. This highlights two ways in which a dyadic approach to joint interviewing can add analytic value compared with individual interviewing. First, the analysis of interaction within joint interviews can help to explicate tacit knowledge and to illuminate the range of often hard-to-access resources that are drawn upon in making decisions. Second, joint interviews mitigate some of the weaknesses of interviewing as a method for studying practices; we offer a cautious defense of the often-tacit assumption that the "naturalness" of joint interviews strengthens their credibility as the basis for analytic inferences. We suggest that joint interviews are a particularly appropriate method for studying complex shared practices such as making health decisions. PMID:25850721

  9. Independents add gas reserves, forego romance

    SciTech Connect

    Gill, D.

    1981-08-01

    Incentive pricing for low-permeability reservoirs and tax advantages for drilling them are 2 big reasons why more independents may start making a special effort to add gas reserves to their inventories. If so, it will be a change from past practices, which saw independents build up big gas positions by circumstance rather than by intention. There are always major refiners ready and willing to buy whole crude oil reservoirs from small producers, but purchasers willing to take gas fields in a single investment are few and far between. Lower-than-normal return on equity during the first 20 years, plus the heavy front-end cost of a frac necessary to produce the tight gas might dissuade independents from drilling tight gas sands, but those liabilities are offset by the higher price tight gas gets and the peculiar tax advantages of exploring for it that make a nice fit with the small operator's way of doing business.

  10. Pairwise Force Smoothed Particle Hydrodynamics model for multiphase flow: Surface tension and contact line dynamics

    NASA Astrophysics Data System (ADS)

    Tartakovsky, Alexandre M.; Panchenko, Alexander

    2016-01-01

    We present a novel formulation of the Pairwise Force Smoothed Particle Hydrodynamics (PF-SPH) model and use it to simulate two- and three-phase flows in bounded domains. In the PF-SPH model, the Navier-Stokes equations are discretized with the Smoothed Particle Hydrodynamics (SPH) method, and the Young-Laplace boundary condition at the fluid-fluid interface and the Young boundary condition at the fluid-fluid-solid interface are replaced with pairwise forces added into the Navier-Stokes equations. We derive a relationship between the parameters in the pairwise forces and the surface tension and static contact angle. Next, we demonstrate the model's accuracy under static and dynamic conditions. Finally, we use the Pf-SPH model to simulate three phase flow in a porous medium.

  11. SDT: A Virus Classification Tool Based on Pairwise Sequence Alignment and Identity Calculation

    PubMed Central

    Muhire, Brejnev Muhizi; Varsani, Arvind; Martin, Darren Patrick

    2014-01-01

    The perpetually increasing rate at which viral full-genome sequences are being determined is creating a pressing demand for computational tools that will aid the objective classification of these genome sequences. Taxonomic classification approaches that are based on pairwise genetic identity measures are potentially highly automatable and are progressively gaining favour with the International Committee on Taxonomy of Viruses (ICTV). There are, however, various issues with the calculation of such measures that could potentially undermine the accuracy and consistency with which they can be applied to virus classification. Firstly, pairwise sequence identities computed based on multiple sequence alignments rather than on multiple independent pairwise alignments can lead to the deflation of identity scores with increasing dataset sizes. Also, when gap-characters need to be introduced during sequence alignments to account for insertions and deletions, methodological variations in the way that these characters are introduced and handled during pairwise genetic identity calculations can cause high degrees of inconsistency in the way that different methods classify the same sets of sequences. Here we present Sequence Demarcation Tool (SDT), a free user-friendly computer program that aims to provide a robust and highly reproducible means of objectively using pairwise genetic identity calculations to classify any set of nucleotide or amino acid sequences. SDT can produce publication quality pairwise identity plots and colour-coded distance matrices to further aid the classification of sequences according to ICTV approved taxonomic demarcation criteria. Besides a graphical interface version of the program for Windows computers, command-line versions of the program are available for a variety of different operating systems (including a parallel version for cluster computing platforms). PMID:25259891

  12. Efficient Fast Stereo Acoustic Echo Cancellation Based on Pairwise Optimal Weight Realization Technique

    NASA Astrophysics Data System (ADS)

    Yukawa, Masahiro; Murakoshi, Noriaki; Yamada, Isao

    2006-12-01

    In stereophonic acoustic echo cancellation (SAEC) problem, fast and accurate tracking of echo path is strongly required for stable echo cancellation. In this paper, we propose a class of efficient fast SAEC schemes with linear computational complexity (with respect to filter length). The proposed schemes are based on pairwise optimal weight realization (POWER) technique, thus realizing a "best" strategy (in the sense of pairwise and worst-case optimization) to use multiple-state information obtained by preprocessing. Numerical examples demonstrate that the proposed schemes significantly improve the convergence behavior compared with conventional methods in terms of system mismatch as well as echo return loss enhancement (ERLE).

  13. Parameter inference with estimated covariance matrices

    NASA Astrophysics Data System (ADS)

    Sellentin, Elena; Heavens, Alan F.

    2016-02-01

    When inferring parameters from a Gaussian-distributed data set by computing a likelihood, a covariance matrix is needed that describes the data errors and their correlations. If the covariance matrix is not known a priori, it may be estimated and thereby becomes a random object with some intrinsic uncertainty itself. We show how to infer parameters in the presence of such an estimated covariance matrix, by marginalizing over the true covariance matrix, conditioned on its estimated value. This leads to a likelihood function that is no longer Gaussian, but rather an adapted version of a multivariate t-distribution, which has the same numerical complexity as the multivariate Gaussian. As expected, marginalization over the true covariance matrix improves inference when compared with Hartlap et al.'s method, which uses an unbiased estimate of the inverse covariance matrix but still assumes that the likelihood is Gaussian.

  14. COVARIANCE ASSISTED SCREENING AND ESTIMATION

    PubMed Central

    Ke, By Tracy; Jin, Jiashun; Fan, Jianqing

    2014-01-01

    Consider a linear model Y = X β + z, where X = Xn,p and z ~ N(0, In). The vector β is unknown and it is of interest to separate its nonzero coordinates from the zero ones (i.e., variable selection). Motivated by examples in long-memory time series (Fan and Yao, 2003) and the change-point problem (Bhattacharya, 1994), we are primarily interested in the case where the Gram matrix G = X′X is non-sparse but sparsifiable by a finite order linear filter. We focus on the regime where signals are both rare and weak so that successful variable selection is very challenging but is still possible. We approach this problem by a new procedure called the Covariance Assisted Screening and Estimation (CASE). CASE first uses a linear filtering to reduce the original setting to a new regression model where the corresponding Gram (covariance) matrix is sparse. The new covariance matrix induces a sparse graph, which guides us to conduct multivariate screening without visiting all the submodels. By interacting with the signal sparsity, the graph enables us to decompose the original problem into many separated small-size subproblems (if only we know where they are!). Linear filtering also induces a so-called problem of information leakage, which can be overcome by the newly introduced patching technique. Together, these give rise to CASE, which is a two-stage Screen and Clean (Fan and Song, 2010; Wasserman and Roeder, 2009) procedure, where we first identify candidates of these submodels by patching and screening, and then re-examine each candidate to remove false positives. For any procedure β̂ for variable selection, we measure the performance by the minimax Hamming distance between the sign vectors of β̂ and β. We show that in a broad class of situations where the Gram matrix is non-sparse but sparsifiable, CASE achieves the optimal rate of convergence. The results are successfully applied to long-memory time series and the change-point model. PMID:25541567

  15. Covariant density functional theory: The role of the pion

    SciTech Connect

    Lalazissis, G. A.; Karatzikos, S.; Serra, M.; Otsuka, T.; Ring, P.

    2009-10-15

    We investigate the role of the pion in covariant density functional theory. Starting from conventional relativistic mean field (RMF) theory with a nonlinear coupling of the {sigma} meson and without exchange terms we add pions with a pseudovector coupling to the nucleons in relativistic Hartree-Fock approximation. In order to take into account the change of the pion field in the nuclear medium the effective coupling constant of the pion is treated as a free parameter. It is found that the inclusion of the pion to this sort of density functionals does not destroy the overall description of the bulk properties by RMF. On the other hand, the noncentral contribution of the pion (tensor coupling) does have effects on single particle energies and on binding energies of certain nuclei.

  16. Covariance-enhanced discriminant analysis

    PubMed Central

    XU, PEIRONG; ZHU, JI; ZHU, LIXING; LI, YI

    2016-01-01

    Summary Linear discriminant analysis has been widely used to characterize or separate multiple classes via linear combinations of features. However, the high dimensionality of features from modern biological experiments defies traditional discriminant analysis techniques. Possible interfeature correlations present additional challenges and are often underused in modelling. In this paper, by incorporating possible interfeature correlations, we propose a covariance-enhanced discriminant analysis method that simultaneously and consistently selects informative features and identifies the corresponding discriminable classes. Under mild regularity conditions, we show that the method can achieve consistent parameter estimation and model selection, and can attain an asymptotically optimal misclassification rate. Extensive simulations have verified the utility of the method, which we apply to a renal transplantation trial.

  17. Spatio-temporal covariability in coho salmon ( Oncorhynchus kisutch) survival, from California to southeast Alaska

    NASA Astrophysics Data System (ADS)

    Teo, Steven L. H.; Botsford, Louis W.; Hastings, Alan

    2009-12-01

    One of the motivations of the GLOBEC Northeast Pacific program is to understand the apparent inverse relationship between the increase in salmon catches in the Gulf of Alaska and concurrent declines in the California Current System (CCS). We therefore used coded wire tag (CWT) data to examine the spatial and temporal patterns of covariability in the survival of hatchery coho salmon along the coast from California to southeast Alaska between release years 1980 and 2004. There is substantial covariability in coho salmon survival between neighboring regions along the coast, and there is clear evidence for increased covariability within two main groups - a northern and southern group. The dividing line between the groups lies approximately at the north end of Vancouver Island. However, CWT survivals do not support inverse covariability in hatchery coho salmon survival between southeast Alaska and the CCS over this 25 year time span. Instead, the hatchery coho survival in southeast Alaska is relatively uncorrelated with coho survival in the California Current System on inter-annual time scales. The 50% correlation and e-folding scales (distances at which magnitude of correlations decreases to 50% and e -1 (32.8%), respectively) of pairwise correlations between individual hatcheries were 150 and 217 km, which are smaller than that reported for sockeye, pink, and chum salmon. The 50% correlation scale of coho salmon is also substantially smaller than those reported for upwelling indices and sea surface temperature. There are also periods of 5-10 years with high covariability between adjacent regions on the scale of hundreds of km, which may be of biological and physical significance.

  18. Input nonlinearities can shape beyond-pairwise correlations and improve information transmission by neural populations

    NASA Astrophysics Data System (ADS)

    Zylberberg, Joel; Shea-Brown, Eric

    2015-12-01

    While recent recordings from neural populations show beyond-pairwise, or higher-order, correlations (HOC), we have little understanding of how HOC arise from network interactions and of how they impact encoded information. Here, we show that input nonlinearities imply HOC in spin-glass-type statistical models. We then discuss one such model with parametrized pairwise- and higher-order interactions, revealing conditions under which beyond-pairwise interactions increase the mutual information between a given stimulus type and the population responses. For jointly Gaussian stimuli, coding performance is improved by shaping output HOC only when neural firing rates are constrained to be low. For stimuli with skewed probability distributions (like natural image luminances), performance improves for all firing rates. Our work suggests surprising connections between nonlinear integration of neural inputs, stimulus statistics, and normative theories of population coding. Moreover, it suggests that the inclusion of beyond-pairwise interactions could improve the performance of Boltzmann machines for machine learning and signal processing applications.

  19. Revisiting the classification of curtoviruses based on genome-wide pairwise identity.

    PubMed

    Varsani, Arvind; Martin, Darren P; Navas-Castillo, Jesús; Moriones, Enrique; Hernández-Zepeda, Cecilia; Idris, Ali; Murilo Zerbini, F; Brown, Judith K

    2014-07-01

    Members of the genus Curtovirus (family Geminiviridae) are important pathogens of many wild and cultivated plant species. Until recently, relatively few full curtovirus genomes have been characterised. However, with the 19 full genome sequences now available in public databases, we revisit the proposed curtovirus species and strain classification criteria. Using pairwise identities coupled with phylogenetic evidence, revised species and strain demarcation guidelines have been instituted. Specifically, we have established 77 % genome-wide pairwise identity as a species demarcation threshold and 94 % genome-wide pairwise identity as a strain demarcation threshold. Hence, whereas curtovirus sequences with >77 % genome-wide pairwise identity would be classified as belonging to the same species, those sharing >94 % identity would be classified as belonging to the same strain. We provide step-by-step guidelines to facilitate the classification of newly discovered curtovirus full genome sequences and a set of defined criteria for naming new species and strains. The revision yields three curtovirus species: Beet curly top virus (BCTV), Spinach severe surly top virus (SpSCTV) and Horseradish curly top virus (HrCTV). PMID:24463952

  20. Input nonlinearities can shape beyond-pairwise correlations and improve information transmission by neural populations.

    PubMed

    Zylberberg, Joel; Shea-Brown, Eric

    2015-12-01

    While recent recordings from neural populations show beyond-pairwise, or higher-order, correlations (HOC), we have little understanding of how HOC arise from network interactions and of how they impact encoded information. Here, we show that input nonlinearities imply HOC in spin-glass-type statistical models. We then discuss one such model with parametrized pairwise- and higher-order interactions, revealing conditions under which beyond-pairwise interactions increase the mutual information between a given stimulus type and the population responses. For jointly Gaussian stimuli, coding performance is improved by shaping output HOC only when neural firing rates are constrained to be low. For stimuli with skewed probability distributions (like natural image luminances), performance improves for all firing rates. Our work suggests surprising connections between nonlinear integration of neural inputs, stimulus statistics, and normative theories of population coding. Moreover, it suggests that the inclusion of beyond-pairwise interactions could improve the performance of Boltzmann machines for machine learning and signal processing applications. PMID:26764727

  1. A Scaling Study by Pair-Wise Comparison Method: Friend Choosing in Adolescents

    ERIC Educational Resources Information Center

    Özmercan, Esra Eminoglu; Kumandas, Hatice

    2016-01-01

    This study aims to identify the perception levels of characteristics considered important to choose friends by adolescents from secondary education and to scale them with pair-wise comparison judgements. In this respect, this study was conducted with 100 10th grade students from a state vocational high school located in Marmara region in Turkey.…

  2. A Covariance Generation Methodology for Fission Product Yields

    NASA Astrophysics Data System (ADS)

    Terranova, N.; Serot, O.; Archier, P.; Vallet, V.; De Saint Jean, C.; Sumini, M.

    2016-03-01

    Recent safety and economical concerns for modern nuclear reactor applications have fed an outstanding interest in basic nuclear data evaluation improvement and completion. It has been immediately clear that the accuracy of our predictive simulation models was strongly affected by our knowledge on input data. Therefore strong efforts have been made to improve nuclear data and to generate complete and reliable uncertainty information able to yield proper uncertainty propagation on integral reactor parameters. Since in modern nuclear data banks (such as JEFF-3.1.1 and ENDF/BVII.1) no correlations for fission yields are given, in the present work we propose a covariance generation methodology for fission product yields. The main goal is to reproduce the existing European library and to add covariance information to allow proper uncertainty propagation in depletion and decay heat calculations. To do so, we adopted the Generalized Least Square Method (GLSM) implemented in CONRAD (COde for Nuclear Reaction Analysis and Data assimilation), developed at CEA-Cadarache. Theoretical values employed in the Bayesian parameter adjustment are delivered thanks to a convolution of different models, representing several quantities in fission yield calculations: the Brosa fission modes for pre-neutron mass distribution, a simplified Gaussian model for prompt neutron emission probability, theWahl systematics for charge distribution and the Madland-England model for the isomeric ratio. Some results will be presented for the thermal fission of U-235, Pu-239 and Pu-241.

  3. User's manual for Axisymmetric Diffuser Duct (ADD) code. Volume II. Detailed ADD code description

    SciTech Connect

    Anderson, O.L.; Hankins, G.B. Jr.; Edwards, D.E.

    1982-02-01

    This section of the manual is intended for the special user who wishes to modify the ADD code or adopt the ADD code to a different computer. An overview of the code is provided in terms of the principal tasks. These principal tasks are clearly labeled in the main program ALTMN and agree with the tasks listed in the Global Task Chart and the Global Tree Structure. Internal flags, as opposed to input options, are described. These flags are set by the code and control the calculation flow between different subroutines. Flags used only within a subroutine are described in the detailed subroutine descriptions. Special problems associated with machine specific language are also described in this Section. The operation of a general I/O routine, which uses UNIVAC library I/O routine NTRAN, and a description of the data files is given. This general I/O routine has been developed to allow NTRAN compatibility with ANSI standard DEFINE FILE for easy conversion. The ADD code also uses a standard spline smoothing routine ICSVKU provided by International Mathematical and Statistical Libraries, Inc. The use of this subroutine is described. All labelled COMMON block and DIMENSION statements are set by INCLUDE statements. Block sizes and EQUIVALENCE statements are set by PARAMETER statements. The use of these in the code is described.

  4. Genetic diversity and species diversity of stream fishes covary across a land-use gradient

    USGS Publications Warehouse

    Blum, M.J.; Bagley, M.J.; Walters, D.M.; Jackson, S.A.; Daniel, F.B.; Chaloud, D.J.; Cade, B.S.

    2012-01-01

    Genetic diversity and species diversity are expected to covary according to area and isolation, but may not always covary with environmental heterogeneity. In this study, we examined how patterns of genetic and species diversity in stream fishes correspond to local and regional environmental conditions. To do so, we compared population size, genetic diversity and divergence in central stonerollers (Campostoma anomalum) to measures of species diversity and turnover in stream fish assemblages among similarly sized watersheds across an agriculture-forest land-use gradient in the Little Miami River basin (Ohio, USA). Significant correlations were found in many, but not all, pair-wise comparisons. Allelic richness and species richness were strongly correlated, for example, but diversity measures based on allele frequencies and assemblage structure were not. In-stream conditions related to agricultural land use were identified as significant predictors of genetic diversity and species diversity. Comparisons to population size indicate, however, that genetic diversity and species diversity are not necessarily independent and that variation also corresponds to watershed location and glaciation history in the drainage basin. Our findings demonstrate that genetic diversity and species diversity can covary in stream fish assemblages, and illustrate the potential importance of scaling observations to capture responses to hierarchical environmental variation. More comparisons according to life history variation could further improve understanding of conditions that give rise to parallel variation in genetic diversity and species diversity, which in turn could improve diagnosis of anthropogenic influences on aquatic ecosystems. ?? 2011 Springer-Verlag.

  5. Quality Quantification of Evaluated Cross Section Covariances

    SciTech Connect

    Varet, S.; Dossantos-Uzarralde, P.

    2015-01-15

    Presently, several methods are used to estimate the covariance matrix of evaluated nuclear cross sections. Because the resulting covariance matrices can be different according to the method used and according to the assumptions of the method, we propose a general and objective approach to quantify the quality of the covariance estimation for evaluated cross sections. The first step consists in defining an objective criterion. The second step is computation of the criterion. In this paper the Kullback-Leibler distance is proposed for the quality quantification of a covariance matrix estimation and its inverse. It is based on the distance to the true covariance matrix. A method based on the bootstrap is presented for the estimation of this criterion, which can be applied with most methods for covariance matrix estimation and without the knowledge of the true covariance matrix. The full approach is illustrated on the {sup 85}Rb nucleus evaluations and the results are then used for a discussion on scoring and Monte Carlo approaches for covariance matrix estimation of the cross section evaluations.

  6. REGRESSION METHODS FOR DATA WITH INCOMPLETE COVARIATES

    EPA Science Inventory

    Modern statistical methods in chronic disease epidemiology allow simultaneous regression of disease status on several covariates. hese methods permit examination of the effects of one covariate while controlling for those of others that may be causally related to the disease. owe...

  7. Particle emission from covariant phase space

    SciTech Connect

    Bambah, B.A. )

    1992-12-01

    Using Lorentz-covariant sources, we calculate the multiplicity distribution of {ital n} pair correlated particles emerging from a Lorentz-covariant phase-space volume. We use the Kim-Wigner formalism and identify these sources as the squeezed states of a relativistic harmonic oscillator. The applications of this to multiplicity distributions in particle physics is discussed.

  8. Group Theory of Covariant Harmonic Oscillators

    ERIC Educational Resources Information Center

    Kim, Y. S.; Noz, Marilyn E.

    1978-01-01

    A simple and concrete example for illustrating the properties of noncompact groups is presented. The example is based on the covariant harmonic-oscillator formalism in which the relativistic wave functions carry a covariant-probability interpretation. This can be used in a group theory course for graduate students who have some background in…

  9. Non-pairwise additivity of the leading-order dispersion energy

    SciTech Connect

    Hollett, Joshua W.

    2015-02-28

    The leading-order (i.e., dipole-dipole) dispersion energy is calculated for one-dimensional (1D) and two-dimensional (2D) infinite lattices, and an infinite 1D array of infinitely long lines, of doubly occupied locally harmonic wells. The dispersion energy is decomposed into pairwise and non-pairwise additive components. By varying the force constant and separation of the wells, the non-pairwise additive contribution to the dispersion energy is shown to depend on the overlap of density between neighboring wells. As well separation is increased, the non-pairwise additivity of the dispersion energy decays. The different rates of decay for 1D and 2D lattices of wells is explained in terms of a Jacobian effect that influences the number of nearest neighbors. For an array of infinitely long lines of wells spaced 5 bohrs apart, and an inter-well spacing of 3 bohrs within a line, the non-pairwise additive component of the leading-order dispersion energy is −0.11 kJ mol{sup −1} well{sup −1}, which is 7% of the total. The polarizability of the wells and the density overlap between them are small in comparison to that of the atomic densities that arise from the molecular density partitioning used in post-density-functional theory (DFT) damped dispersion corrections, or DFT-D methods. Therefore, the nonadditivity of the leading-order dispersion observed here is a conservative estimate of that in molecular clusters.

  10. Effect modification by time-varying covariates.

    PubMed

    Robins, James M; Hernán, Miguel A; Rotnitzky, Andrea

    2007-11-01

    Marginal structural models (MSMs) allow estimation of effect modification by baseline covariates, but they are less useful for estimating effect modification by evolving time-varying covariates. Rather, structural nested models (SNMs) were specifically designed to estimate effect modification by time-varying covariates. In their paper, Petersen et al. (Am J Epidemiol 2007;166:985-993) describe history-adjusted MSMs as a generalized form of MSM and argue that history-adjusted MSMs allow a researcher to easily estimate effect modification by time-varying covariates. However, history-adjusted MSMs can result in logically incompatible parameter estimates and hence in contradictory substantive conclusions. Here the authors propose a more restrictive definition of history-adjusted MSMs than the one provided by Petersen et al. and compare the advantages and disadvantages of using history-adjusted MSMs, as opposed to SNMs, to examine effect modification by time-dependent covariates. PMID:17875581

  11. Adjoints and Low-rank Covariance Representation

    NASA Technical Reports Server (NTRS)

    Tippett, Michael K.; Cohn, Stephen E.

    2000-01-01

    Quantitative measures of the uncertainty of Earth System estimates can be as important as the estimates themselves. Second moments of estimation errors are described by the covariance matrix, whose direct calculation is impractical when the number of degrees of freedom of the system state is large. Ensemble and reduced-state approaches to prediction and data assimilation replace full estimation error covariance matrices by low-rank approximations. The appropriateness of such approximations depends on the spectrum of the full error covariance matrix, whose calculation is also often impractical. Here we examine the situation where the error covariance is a linear transformation of a forcing error covariance. We use operator norms and adjoints to relate the appropriateness of low-rank representations to the conditioning of this transformation. The analysis is used to investigate low-rank representations of the steady-state response to random forcing of an idealized discrete-time dynamical system.

  12. Global multiple protein-protein interaction network alignment by combining pairwise network alignments

    PubMed Central

    2015-01-01

    Background A wealth of protein interaction data has become available in recent years, creating an urgent need for powerful analysis techniques. In this context, the problem of finding biologically meaningful correspondences between different protein-protein interaction networks (PPIN) is of particular interest. The PPIN of a species can be compared with that of other species through the process of PPIN alignment. Such an alignment can provide insight into basic problems like species evolution and network component function determination, as well as translational problems such as target identification and elucidation of mechanisms of disease spread. Furthermore, multiple PPINs can be aligned simultaneously, expanding the analytical implications of the result. While there are several pairwise network alignment algorithms, few methods are capable of multiple network alignment. Results We propose SMAL, a MNA algorithm based on the philosophy of scaffold-based alignment. SMAL is capable of converting results from any global pairwise alignment algorithms into a MNA in linear time. Using this method, we have built multiple network alignments based on combining pairwise alignments from a number of publicly available (pairwise) network aligners. We tested SMAL using PPINs of eight species derived from the IntAct repository and employed a number of measures to evaluate performance. Additionally, as part of our experimental investigations, we compared the effectiveness of SMAL while aligning up to eight input PPINs, and examined the effect of scaffold network choice on the alignments. Conclusions A key advantage of SMAL lies in its ability to create MNAs through the use of pairwise network aligners for which native MNA implementations do not exist. Experiments indicate that the performance of SMAL was comparable to that of the native MNA implementation of established methods such as IsoRankN and SMETANA. However, in terms of computational time, SMAL was significantly faster

  13. The covariate-adjusted frequency plot.

    PubMed

    Holling, Heinz; Böhning, Walailuck; Böhning, Dankmar; Formann, Anton K

    2016-04-01

    Count data arise in numerous fields of interest. Analysis of these data frequently require distributional assumptions. Although the graphical display of a fitted model is straightforward in the univariate scenario, this becomes more complex if covariate information needs to be included into the model. Stratification is one way to proceed, but has its limitations if the covariate has many levels or the number of covariates is large. The article suggests a marginal method which works even in the case that all possible covariate combinations are different (i.e. no covariate combination occurs more than once). For each covariate combination the fitted model value is computed and then summed over the entire data set. The technique is quite general and works with all count distributional models as well as with all forms of covariate modelling. The article provides illustrations of the method for various situations and also shows that the proposed estimator as well as the empirical count frequency are consistent with respect to the same parameter. PMID:23376964

  14. A Ranking Procedure by Incomplete Pairwise Comparisons Using Information Entropy and Dempster-Shafer Evidence Theory

    PubMed Central

    Pan, Dongbo; Lu, Xi; Liu, Juan; Deng, Yong

    2014-01-01

    Decision-making, as a way to discover the preference of ranking, has been used in various fields. However, owing to the uncertainty in group decision-making, how to rank alternatives by incomplete pairwise comparisons has become an open issue. In this paper, an improved method is proposed for ranking of alternatives by incomplete pairwise comparisons using Dempster-Shafer evidence theory and information entropy. Firstly, taking the probability assignment of the chosen preference into consideration, the comparison of alternatives to each group is addressed. Experiments verified that the information entropy of the data itself can determine the different weight of each group's choices objectively. Numerical examples in group decision-making environments are used to test the effectiveness of the proposed method. Moreover, the divergence of ranking mechanism is analyzed briefly in conclusion section. PMID:25250393

  15. Pairwise-Svm for On-Board Urban Road LIDAR Classification

    NASA Astrophysics Data System (ADS)

    Shu, Zhen; Sun, Kai; Qiu, Kaijin; Ding, Kou

    2016-06-01

    The common method of LiDAR classifications is Markov random fields (MRF). Based on construction of MRF energy function, spectral and directional features are extracted for on-board urban point clouds. The MRF energy function is consisted of unary and pairwise potentials. The unary terms are computed by SVM classifictaion. The initial labeling is mainly processed through geometrical shapes. The pairwise potential is estimated by Naïve Bayes. From training data, the probability of adjacent objects is computed by prior knowledge. The final labeling method is reweighted message-passing to minimization the energy function. The MRF model is difficult to process the large-scale misclassification. We propose a super-voxel clustering method for over-segment and grouping segment for large objects. Trees, poles ground, and building are classified in this paper. The experimental results show that this method improves the accuracy of classification and speed of computation.

  16. A ranking procedure by incomplete pairwise comparisons using information entropy and Dempster-Shafer evidence theory.

    PubMed

    Pan, Dongbo; Lu, Xi; Liu, Juan; Deng, Yong

    2014-01-01

    Decision-making, as a way to discover the preference of ranking, has been used in various fields. However, owing to the uncertainty in group decision-making, how to rank alternatives by incomplete pairwise comparisons has become an open issue. In this paper, an improved method is proposed for ranking of alternatives by incomplete pairwise comparisons using Dempster-Shafer evidence theory and information entropy. Firstly, taking the probability assignment of the chosen preference into consideration, the comparison of alternatives to each group is addressed. Experiments verified that the information entropy of the data itself can determine the different weight of each group's choices objectively. Numerical examples in group decision-making environments are used to test the effectiveness of the proposed method. Moreover, the divergence of ranking mechanism is analyzed briefly in conclusion section. PMID:25250393

  17. Efficient mapping of genomic sequences to optimize multiple pairwise alignment in hybrid cluster platforms.

    PubMed

    Montañola, Alberto; Roig, Concepció; Hernández, Porfidio

    2014-01-01

    Multiple sequence alignment (MSA), used in biocomputing to study similarities between different genomic sequences, is known to require important memory and computation resources. Nowadays, researchers are aligning thousands of these sequences, creating new challenges in order to solve the problem using the available resources efficiently. Determining the efficient amount of resources to allocate is important to avoid waste of them, thus reducing the economical costs required in running for example a specific cloud instance. The pairwise alignment is the initial key step of the MSA problem, which will compute all pair alignments needed. We present a method to determine the optimal amount of memory and computation resources to allocate by the pairwise alignment, and we will validate it through a set of experimental results for different possible inputs. These allow us to determine the best parameters to configure the applications in order to use effectively the available resources of a given system. PMID:25339085

  18. Pairwise Comparisons of Mitochondrial DNA Sequences in Subdivided Populations and Implications for Early Human Evolution

    PubMed Central

    Marjoram, P.; Donnelly, P.

    1994-01-01

    We consider the effect on the distribution of pairwise differences between mitochondrial DNA sequences of the incorporation into the underlying population genetics model of two particular effects that seem realistic for human populations. The first is that the population size was roughly constant before growing to its current level. The second is that the population is geographically subdivided rather than panmictic. In each case these features tend to encourage multimodal distributions of pairwise differences, in contrast to existing, unimodal datasets. We argue that population genetics models currently used to analyze such data may thus fail to reflect important features of human mitochondrial DNA evolution. These may include selection on the mitochondrial genome, more realistic mutation mechanisms, or special population or migration dynamics. Particularly in view of the variability inherent in the single available human mitochondrial genealogy, it is argued that until these effects are better understood, inferences from such data should be rather cautious. PMID:8150290

  19. PTM Along Track Algorithm to Maintain Spacing During Same Direction Pair-Wise Trajectory Management Operations

    NASA Technical Reports Server (NTRS)

    Carreno, Victor A.

    2015-01-01

    Pair-wise Trajectory Management (PTM) is a cockpit based delegated responsibility separation standard. When an air traffic service provider gives a PTM clearance to an aircraft and the flight crew accepts the clearance, the flight crew will maintain spacing and separation from a designated aircraft. A PTM along track algorithm will receive state information from the designated aircraft and from the own ship to produce speed guidance for the flight crew to maintain spacing and separation

  20. Hilbert-Schmidt Measure of Pairwise Quantum Discord for Three-Qubit X States

    NASA Astrophysics Data System (ADS)

    Daoud, M.; Laamara, R. Ahl; Seddik, S.

    2015-10-01

    The Hilbert-Schmidt distance between a mixed three-qubit state and its closest state is used to quantify the amount of pairwise quantum correlations in a tripartite system. Analytical expressions of geometric quantum discord are derived. A particular attention is devoted to two special classes of three-qubit X states. They include three-qubit states of W, GHZ and Bell type. We also discuss the monogamy property of geometric quantum discord in some mixed three-qubit systems.

  1. Covariation bias in panic-prone individuals.

    PubMed

    Pauli, P; Montoya, P; Martz, G E

    1996-11-01

    Covariation estimates between fear-relevant (FR; emergency situations) or fear-irrelevant (FI; mushrooms and nudes) stimuli and an aversive outcome (electrical shock) were examined in 10 high-fear (panic-prone) and 10 low-fear respondents. When the relation between slide category and outcome was random (illusory correlation), only high-fear participants markedly overestimated the contingency between FR slides and shocks. However, when there was a high contingency of shocks following FR stimuli (83%) and a low contingency of shocks following FI stimuli (17%), the group difference vanished. Reversal of contingencies back to random induced a covariation bias for FR slides in high- and low-fear respondents. Results indicate that panic-prone respondents show a covariation bias for FR stimuli and that the experience of a high contingency between FR slides and aversive outcomes may foster such a covariation bias even in low-fear respondents. PMID:8952200

  2. Reconciling Covariances with Reliable Orbital Uncertainty

    NASA Astrophysics Data System (ADS)

    Folcik, Z.; Lue, A.; Vatsky, J.

    2011-09-01

    There is a common suspicion that formal covariances do not represent a realistic measure of orbital uncertainties. By devising metrics for measuring the representations of orbit error, we assess under what circumstances such lore is justified as well as the root cause of the discrepancy between the mathematics of orbital uncertainty and its practical implementation. We offer a scheme by which formal covariances may be adapted to be an accurate measure of orbital uncertainties and show how that adaptation performs against both simulated and real space-object data. We also apply these covariance adaptation methods to the process of observation association using many simulated and real data test cases. We demonstrate that covariance-informed observation association can be reliable, even in the case when only two tracks are available. Satellite breakup and collision event catalog maintenance could benefit from the automation made possible with these association methods.

  3. Hierarchical semi-numeric method for pairwise fuzzy group decision making.

    PubMed

    Marimin, M; Umano, M; Hatono, I; Tamura, H

    2002-01-01

    Gradual improvements to a single-level semi-numeric method, i.e., linguistic labels preference representation by fuzzy sets computation for pairwise fuzzy group decision making are summarized. The method is extended to solve multiple criteria hierarchical structure pairwise fuzzy group decision-making problems. The problems are hierarchically structured into focus, criteria, and alternatives. Decision makers express their evaluations of criteria and alternatives based on each criterion by using linguistic labels. The labels are converted into and processed in triangular fuzzy numbers (TFNs). Evaluations of criteria yield relative criteria weights. Evaluations of the alternatives, based on each criterion, yield a degree of preference for each alternative or a degree of satisfaction for each preference value. By using a neat ordered weighted average (OWA) or a fuzzy weighted average operator, solutions obtained based on each criterion are aggregated into final solutions. The hierarchical semi-numeric method is suitable for solving a larger and more complex pairwise fuzzy group decision-making problem. The proposed method has been verified and applied to solve some real cases and is compared to Saaty's (1996) analytic hierarchy process (AHP) method. PMID:18244875

  4. Pairwise Kinship Analysis by the Index of Chromosome Sharing Using High-Density Single Nucleotide Polymorphisms

    PubMed Central

    Morimoto, Chie; Manabe, Sho; Kawaguchi, Takahisa; Kawai, Chihiro; Fujimoto, Shuntaro; Hamano, Yuya; Yamada, Ryo; Matsuda, Fumihiko; Tamaki, Keiji

    2016-01-01

    We developed a new approach for pairwise kinship analysis in forensic genetics based on chromosomal sharing between two individuals. Here, we defined “index of chromosome sharing” (ICS) calculated using 174,254 single nucleotide polymorphism (SNP) loci typed by SNP microarray and genetic length of the shared segments from the genotypes of two individuals. To investigate the expected ICS distributions from first- to fifth-degree relatives and unrelated pairs, we used computationally generated genotypes to consider the effect of linkage disequilibrium and recombination. The distributions were used for probabilistic evaluation of the pairwise kinship analysis, such as likelihood ratio (LR) or posterior probability, without allele frequencies and haplotype frequencies. Using our method, all actual sample pairs from volunteers showed significantly high LR values (i.e., ≥ 108); therefore, we can distinguish distant relationships (up to the fifth-degree) from unrelated pairs based on LR. Moreover, we can determine accurate degrees of kinship in up to third-degree relationships with a probability of > 80% using the criterion of posterior probability ≥ 0.90, even if the kinship of the pair is totally unpredictable. This approach greatly improves pairwise kinship analysis of distant relationships, specifically in cases involving identification of disaster victims or missing persons. PMID:27472558

  5. Discovering Focus: Helping Students with ADD (Attention Deficit Disorder)

    ERIC Educational Resources Information Center

    Valkenburg, Jim

    2012-01-01

    Attention Deficit Disorder (ADD) is a neurological disorder which effects learning and that has a confusing set of diagnostic symptoms and an even more confusing set of remedies ranging from medication to meditation to nothing at all. Current neurological research suggests, however, that there are strategies that the individual with ADD can use to…

  6. Social Capital: Does It Add to the Health Inequalities Debate?

    ERIC Educational Resources Information Center

    Chappell, Neena L.; Funk, Laura M.

    2010-01-01

    This paper empirically examines the relationship between advantage, social capital and health status to assess (a) whether social capital adds explanatory power to what we already know about the relationship between advantage and health and (b) whether social capital adds anything beyond its component parts, namely social participation and trust.…

  7. Phase-covariant quantum cloning of qudits

    SciTech Connect

    Fan Heng; Imai, Hiroshi; Matsumoto, Keiji; Wang, Xiang-Bin

    2003-02-01

    We study the phase-covariant quantum cloning machine for qudits, i.e., the input states in a d-level quantum system have complex coefficients with arbitrary phase but constant module. A cloning unitary transformation is proposed. After optimizing the fidelity between input state and single qudit reduced density operator of output state, we obtain the optimal fidelity for 1 to 2 phase-covariant quantum cloning of qudits and the corresponding cloning transformation.

  8. Noncommutative Gauge Theory with Covariant Star Product

    SciTech Connect

    Zet, G.

    2010-08-04

    We present a noncommutative gauge theory with covariant star product on a space-time with torsion. In order to obtain the covariant star product one imposes some restrictions on the connection of the space-time. Then, a noncommutative gauge theory is developed applying this product to the case of differential forms. Some comments on the advantages of using a space-time with torsion to describe the gravitational field are also given.

  9. Covariant action for type IIB supergravity

    NASA Astrophysics Data System (ADS)

    Sen, Ashoke

    2016-07-01

    Taking clues from the recent construction of the covariant action for type II and heterotic string field theories, we construct a manifestly Lorentz covariant action for type IIB supergravity, and discuss its gauge fixing maintaining manifest Lorentz invariance. The action contains a (non-gravitating) free 4-form field besides the usual fields of type IIB supergravity. This free field, being completely decoupled from the interacting sector, has no physical consequence.

  10. Covariate analysis of bivariate survival data

    SciTech Connect

    Bennett, L.E.

    1992-01-01

    The methods developed are used to analyze the effects of covariates on bivariate survival data when censoring and ties are present. The proposed method provides models for bivariate survival data that include differential covariate effects and censored observations. The proposed models are based on an extension of the univariate Buckley-James estimators which replace censored data points by their expected values, conditional on the censoring time and the covariates. For the bivariate situation, it is necessary to determine the expectation of the failure times for one component conditional on the failure or censoring time of the other component. Two different methods have been developed to estimate these expectations. In the semiparametric approach these expectations are determined from a modification of Burke's estimate of the bivariate empirical survival function. In the parametric approach censored data points are also replaced by their conditional expected values where the expected values are determined from a specified parametric distribution. The model estimation will be based on the revised data set, comprised of uncensored components and expected values for the censored components. The variance-covariance matrix for the estimated covariate parameters has also been derived for both the semiparametric and parametric methods. Data from the Demographic and Health Survey was analyzed by these methods. The two outcome variables are post-partum amenorrhea and breastfeeding; education and parity were used as the covariates. Both the covariate parameter estimates and the variance-covariance estimates for the semiparametric and parametric models will be compared. In addition, a multivariate test statistic was used in the semiparametric model to examine contrasts. The significance of the statistic was determined from a bootstrap distribution of the test statistic.

  11. Sequential BART for imputation of missing covariates.

    PubMed

    Xu, Dandan; Daniels, Michael J; Winterstein, Almut G

    2016-07-01

    To conduct comparative effectiveness research using electronic health records (EHR), many covariates are typically needed to adjust for selection and confounding biases. Unfortunately, it is typical to have missingness in these covariates. Just using cases with complete covariates will result in considerable efficiency losses and likely bias. Here, we consider the covariates missing at random with missing data mechanism either depending on the response or not. Standard methods for multiple imputation can either fail to capture nonlinear relationships or suffer from the incompatibility and uncongeniality issues. We explore a flexible Bayesian nonparametric approach to impute the missing covariates, which involves factoring the joint distribution of the covariates with missingness into a set of sequential conditionals and applying Bayesian additive regression trees to model each of these univariate conditionals. Using data augmentation, the posterior for each conditional can be sampled simultaneously. We provide details on the computational algorithm and make comparisons to other methods, including parametric sequential imputation and two versions of multiple imputation by chained equations. We illustrate the proposed approach on EHR data from an affiliated tertiary care institution to examine factors related to hyperglycemia. PMID:26980459

  12. Low-dimensional Representation of Error Covariance

    NASA Technical Reports Server (NTRS)

    Tippett, Michael K.; Cohn, Stephen E.; Todling, Ricardo; Marchesin, Dan

    2000-01-01

    Ensemble and reduced-rank approaches to prediction and assimilation rely on low-dimensional approximations of the estimation error covariances. Here stability properties of the forecast/analysis cycle for linear, time-independent systems are used to identify factors that cause the steady-state analysis error covariance to admit a low-dimensional representation. A useful measure of forecast/analysis cycle stability is the bound matrix, a function of the dynamics, observation operator and assimilation method. Upper and lower estimates for the steady-state analysis error covariance matrix eigenvalues are derived from the bound matrix. The estimates generalize to time-dependent systems. If much of the steady-state analysis error variance is due to a few dominant modes, the leading eigenvectors of the bound matrix approximate those of the steady-state analysis error covariance matrix. The analytical results are illustrated in two numerical examples where the Kalman filter is carried to steady state. The first example uses the dynamics of a generalized advection equation exhibiting nonmodal transient growth. Failure to observe growing modes leads to increased steady-state analysis error variances. Leading eigenvectors of the steady-state analysis error covariance matrix are well approximated by leading eigenvectors of the bound matrix. The second example uses the dynamics of a damped baroclinic wave model. The leading eigenvectors of a lowest-order approximation of the bound matrix are shown to approximate well the leading eigenvectors of the steady-state analysis error covariance matrix.

  13. Covariance Modifications to Subspace Bases

    SciTech Connect

    Harris, D B

    2008-11-19

    Adaptive signal processing algorithms that rely upon representations of signal and noise subspaces often require updates to those representations when new data become available. Subspace representations frequently are estimated from available data with singular value (SVD) decompositions. Subspace updates require modifications to these decompositions. Updates can be performed inexpensively provided they are low-rank. A substantial literature on SVD updates exists, frequently focusing on rank-1 updates (see e.g. [Karasalo, 1986; Comon and Golub, 1990, Badeau, 2004]). In these methods, data matrices are modified by addition or deletion of a row or column, or data covariance matrices are modified by addition of the outer product of a new vector. A recent paper by Brand [2006] provides a general and efficient method for arbitrary rank updates to an SVD. The purpose of this note is to describe a closely-related method for applications where right singular vectors are not required. This note also describes the SVD updates to a particular scenario of interest in seismic array signal processing. The particular application involve updating the wideband subspace representation used in seismic subspace detectors [Harris, 2006]. These subspace detectors generalize waveform correlation algorithms to detect signals that lie in a subspace of waveforms of dimension d {ge} 1. They potentially are of interest because they extend the range of waveform variation over which these sensitive detectors apply. Subspace detectors operate by projecting waveform data from a detection window into a subspace specified by a collection of orthonormal waveform basis vectors (referred to as the template). Subspace templates are constructed from a suite of normalized, aligned master event waveforms that may be acquired by a single sensor, a three-component sensor, an array of such sensors or a sensor network. The template design process entails constructing a data matrix whose columns contain the

  14. Spacetime states and covariant quantum theory

    NASA Astrophysics Data System (ADS)

    Reisenberger, Michael; Rovelli, Carlo

    2002-06-01

    In its usual presentation, classical mechanics appears to give time a very special role. But it is well known that mechanics can be formulated so as to treat the time variable on the same footing as the other variables in the extended configuration space. Such covariant formulations are natural for relativistic gravitational systems, where general covariance conflicts with the notion of a preferred physical-time variable. The standard presentation of quantum mechanics, in turn, again gives time a very special role, raising well known difficulties for quantum gravity. Is there a covariant form of (canonical) quantum mechanics? We observe that the preferred role of time in quantum theory is the consequence of an idealization: that measurements are instantaneous. Canonical quantum theory can be given a covariant form by dropping this idealization. States prepared by noninstantaneous measurements are described by ``spacetime smeared states.'' The theory can be formulated in terms of these states, without making any reference to a special time variable. The quantum dynamics is expressed in terms of the propagator, an object covariantly defined on the extended configuration space.

  15. TDRS-K to Add to Vital Space Network

    NASA Video Gallery

    NASA officials discuss the launch of the TDRS-K spacecraft to add to the space network that enables communications between the International Space Station and Earth-orbiting satellites and ground c...

  16. Top 5 Ways to Help Students with ADD/ADHD

    ERIC Educational Resources Information Center

    Johnson, Kathy

    2011-01-01

    This article suggests five ways to help students with ADD/ADHD. These are: (1) Integrate the primitive reflexes; (2) Diet; (3) Visual attention; (4) Help for auditory attention; and (5) Cognitive training.

  17. Poor Sleep May Not Add to Cholesterol Problems, Study Finds

    MedlinePlus

    ... nih.gov/medlineplus/news/fullstory_157561.html Poor Sleep May Not Add to Cholesterol Problems, Study Finds ... disease risk factors such as high cholesterol, because sleep apnea -- another type of sleep disorder -- has been ...

  18. FAST NEUTRON COVARIANCES FOR EVALUATED DATA FILES.

    SciTech Connect

    HERMAN, M.; OBLOZINSKY, P.; ROCHMAN, D.; KAWANO, T.; LEAL, L.

    2006-06-05

    We describe implementation of the KALMAN code in the EMPIRE system and present first covariance data generated for Gd and Ir isotopes. A complete set of covariances, in the full energy range, was produced for the chain of 8 Gadolinium isotopes for total, elastic, capture, total inelastic (MT=4), (n,2n), (n,p) and (n,alpha) reactions. Our correlation matrices, based on combination of model calculations and experimental data, are characterized by positive mid-range and negative long-range correlations. They differ from the model-generated covariances that tend to show strong positive long-range correlations and those determined solely from experimental data that result in nearly diagonal matrices. We have studied shapes of correlation matrices obtained in the calculations and interpreted them in terms of the underlying reaction models. An important result of this study is the prediction of narrow energy ranges with extremely small uncertainties for certain reactions (e.g., total and elastic).

  19. Gram-Schmidt algorithms for covariance propagation

    NASA Technical Reports Server (NTRS)

    Thornton, C. L.; Bierman, G. J.

    1977-01-01

    This paper addresses the time propagation of triangular covariance factors. Attention is focused on the square-root free factorization, P = UD(transpose of U), where U is unit upper triangular and D is diagonal. An efficient and reliable algorithm for U-D propagation is derived which employs Gram-Schmidt orthogonalization. Partitioning the state vector to distinguish bias and coloured process noise parameters increase mapping efficiency. Cost comparisons of the U-D, Schmidt square-root covariance and conventional covariance propagation methods are made using weighted arithmetic operation counts. The U-D time update is shown to be less costly than the Schmidt method; and, except in unusual circumstances, it is within 20% of the cost of conventional propagation.

  20. Gram-Schmidt algorithms for covariance propagation

    NASA Technical Reports Server (NTRS)

    Thornton, C. L.; Bierman, G. J.

    1975-01-01

    This paper addresses the time propagation of triangular covariance factors. Attention is focused on the square-root free factorization, P = UDU/T/, where U is unit upper triangular and D is diagonal. An efficient and reliable algorithm for U-D propagation is derived which employs Gram-Schmidt orthogonalization. Partitioning the state vector to distinguish bias and colored process noise parameters increases mapping efficiency. Cost comparisons of the U-D, Schmidt square-root covariance and conventional covariance propagation methods are made using weighted arithmetic operation counts. The U-D time update is shown to be less costly than the Schmidt method; and, except in unusual circumstances, it is within 20% of the cost of conventional propagation.

  1. A pairwise likelihood-based approach for changepoint detection in multivariate time series models

    PubMed Central

    Ma, Ting Fung; Yau, Chun Yip

    2016-01-01

    This paper develops a composite likelihood-based approach for multiple changepoint estimation in multivariate time series. We derive a criterion based on pairwise likelihood and minimum description length for estimating the number and locations of changepoints and for performing model selection in each segment. The number and locations of the changepoints can be consistently estimated under mild conditions and the computation can be conducted efficiently with a pruned dynamic programming algorithm. Simulation studies and real data examples demonstrate the statistical and computational efficiency of the proposed method. PMID:27279666

  2. Geometric measure of pairwise quantum discord for superpositions of multipartite generalized coherent states

    NASA Astrophysics Data System (ADS)

    Daoud, M.; Ahl Laamara, R.

    2012-07-01

    We give the explicit expressions of the pairwise quantum correlations present in superpositions of multipartite coherent states. A special attention is devoted to the evaluation of the geometric quantum discord. The dynamics of quantum correlations under a dephasing channel is analyzed. A comparison of geometric measure of quantum discord with that of concurrence shows that quantum discord in multipartite coherent states is more resilient to dissipative environments than is quantum entanglement. To illustrate our results, we consider some special superpositions of Weyl-Heisenberg, SU(2) and SU(1,1) coherent states which interpolate between Werner and Greenberger-Horne-Zeilinger states.

  3. A violation of the covariant entropy bound?

    NASA Astrophysics Data System (ADS)

    Masoumi, Ali; Mathur, Samir D.

    2015-04-01

    Several arguments suggest that the entropy density at high energy density ρ should be given by the expression s =K √{ρ /G } , where K is a constant of order unity. On the other hand the covariant entropy bound requires that the entropy on a light sheet be bounded by A /4 G , where A is the area of the boundary of the sheet. We find that in a suitably chosen cosmological geometry, the above expression for s violates the covariant entropy bound. We consider different possible explanations for this fact, in particular, the possibility that entropy bounds should be defined in terms of volumes of regions rather than areas of surfaces.

  4. Covariance Analysis of Gamma Ray Spectra

    SciTech Connect

    Trainham, R.; Tinsley, J.

    2013-01-01

    The covariance method exploits fluctuations in signals to recover information encoded in correlations which are usually lost when signal averaging occurs. In nuclear spectroscopy it can be regarded as a generalization of the coincidence technique. The method can be used to extract signal from uncorrelated noise, to separate overlapping spectral peaks, to identify escape peaks, to reconstruct spectra from Compton continua, and to generate secondary spectral fingerprints. We discuss a few statistical considerations of the covariance method and present experimental examples of its use in gamma spectroscopy.

  5. Covariance analysis of gamma ray spectra

    SciTech Connect

    Trainham, R.; Tinsley, J.

    2013-01-15

    The covariance method exploits fluctuations in signals to recover information encoded in correlations which are usually lost when signal averaging occurs. In nuclear spectroscopy it can be regarded as a generalization of the coincidence technique. The method can be used to extract signal from uncorrelated noise, to separate overlapping spectral peaks, to identify escape peaks, to reconstruct spectra from Compton continua, and to generate secondary spectral fingerprints. We discuss a few statistical considerations of the covariance method and present experimental examples of its use in gamma spectroscopy.

  6. Sparse Multivariate Regression With Covariance Estimation

    PubMed Central

    Rothman, Adam J.; Levina, Elizaveta; Zhu, Ji

    2014-01-01

    We propose a procedure for constructing a sparse estimator of a multivariate regression coefficient matrix that accounts for correlation of the response variables. This method, which we call multivariate regression with covariance estimation (MRCE), involves penalized likelihood with simultaneous estimation of the regression coefficients and the covariance structure. An efficient optimization algorithm and a fast approximation are developed for computing MRCE. Using simulation studies, we show that the proposed method outperforms relevant competitors when the responses are highly correlated. We also apply the new method to a finance example on predicting asset returns. An R-package containing this dataset and code for computing MRCE and its approximation are available online. PMID:24963268

  7. Parametric number covariance in quantum chaotic spectra

    NASA Astrophysics Data System (ADS)

    Vinayak, Kumar, Sandeep; Pandey, Akhilesh

    2016-03-01

    We study spectral parametric correlations in quantum chaotic systems and introduce the number covariance as a measure of such correlations. We derive analytic results for the classical random matrix ensembles using the binary correlation method and obtain compact expressions for the covariance. We illustrate the universality of this measure by presenting the spectral analysis of the quantum kicked rotors for the time-reversal invariant and time-reversal noninvariant cases. A local version of the parametric number variance introduced earlier is also investigated.

  8. Covariant Spectator Theory and Hadron Structure

    NASA Astrophysics Data System (ADS)

    Peña, M. T.; Leitão, Sofia; Biernat, Elmar P.; Stadler, Alfred; Ribeiro, J. E.; Gross, Franz

    2016-06-01

    We present the first results of a study on meson spectroscopy using a covariant formalism based on the Covariant Spectator Theory. Our approach is derived directly in Minkowski space and it approximates the Bethe-Salpeter equation by taking effectively into account the contributions from both ladder and crossed ladder diagrams in the q{bar{q}} interaction kernel. A general Lorentz structure of the kernel is tested and chiral constraints on the kernel are discussed. Results for the pion form factor are also presented.

  9. Parametric number covariance in quantum chaotic spectra.

    PubMed

    Vinayak; Kumar, Sandeep; Pandey, Akhilesh

    2016-03-01

    We study spectral parametric correlations in quantum chaotic systems and introduce the number covariance as a measure of such correlations. We derive analytic results for the classical random matrix ensembles using the binary correlation method and obtain compact expressions for the covariance. We illustrate the universality of this measure by presenting the spectral analysis of the quantum kicked rotors for the time-reversal invariant and time-reversal noninvariant cases. A local version of the parametric number variance introduced earlier is also investigated. PMID:27078354

  10. Multilevel summation with B-spline interpolation for pairwise interactions in molecular dynamics simulations.

    PubMed

    Hardy, David J; Wolff, Matthew A; Xia, Jianlin; Schulten, Klaus; Skeel, Robert D

    2016-03-21

    The multilevel summation method for calculating electrostatic interactions in molecular dynamics simulations constructs an approximation to a pairwise interaction kernel and its gradient, which can be evaluated at a cost that scales linearly with the number of atoms. The method smoothly splits the kernel into a sum of partial kernels of increasing range and decreasing variability with the longer-range parts interpolated from grids of increasing coarseness. Multilevel summation is especially appropriate in the context of dynamics and minimization, because it can produce continuous gradients. This article explores the use of B-splines to increase the accuracy of the multilevel summation method (for nonperiodic boundaries) without incurring additional computation other than a preprocessing step (whose cost also scales linearly). To obtain accurate results efficiently involves technical difficulties, which are overcome by a novel preprocessing algorithm. Numerical experiments demonstrate that the resulting method offers substantial improvements in accuracy and that its performance is competitive with an implementation of the fast multipole method in general and markedly better for Hamiltonian formulations of molecular dynamics. The improvement is great enough to establish multilevel summation as a serious contender for calculating pairwise interactions in molecular dynamics simulations. In particular, the method appears to be uniquely capable for molecular dynamics in two situations, nonperiodic boundary conditions and massively parallel computation, where the fast Fourier transform employed in the particle-mesh Ewald method falls short. PMID:27004867

  11. A Pairwise Naïve Bayes Approach to Bayesian Classification

    PubMed Central

    Betensky, Rebecca A.

    2016-01-01

    Despite the relatively high accuracy of the naïve Bayes (NB) classifier, there may be several instances where it is not optimal, i.e. does not have the same classification performance as the Bayes classifier utilizing the joint distribution of the examined attributes. However, the Bayes classifier can be computationally intractable due to its required knowledge of the joint distribution. Therefore, we introduce a “pairwise naïve” Bayes (PNB) classifier that incorporates all pairwise relationships among the examined attributes, but does not require specification of the joint distribution. In this paper, we first describe the necessary and sufficient conditions under which the PNB classifier is optimal. We then discuss sufficient conditions for which the PNB classifier, and not NB, is optimal for normal attributes. Through simulation and actual studies, we evaluate the performance of our proposed classifier relative to the Bayes and NB classifiers, along with the HNB, AODE, LBR and TAN classifiers, using normal density and empirical estimation methods. Our applications show that the PNB classifier using normal density estimation yields the highest accuracy for data sets containing continuous attributes. We conclude that it offers a useful compromise between the Bayes and NB classifiers. PMID:27087730

  12. Canonical Force Distributions in Pairwise Interatomic Interactions from the Perspective of the Hellmann-Feynman Theorem.

    PubMed

    Walton, Jay R; Rivera-Rivera, Luis A; Lucchese, Robert R; Bevan, John W

    2016-05-26

    Force-based canonical approaches have recently given a unified but different viewpoint on the nature of bonding in pairwise interatomic interactions. Differing molecular categories (covalent, ionic, van der Waals, hydrogen, and halogen bonding) of representative interatomic interactions with binding energies ranging from 1.01 to 1072.03 kJ/mol have been modeled canonically giving a rigorous semiempirical verification to high accuracy. However, the fundamental physical basis expected to provide the inherent characteristics of these canonical transformations has not yet been elucidated. Subsequently, it was shown through direct numerical differentiation of these potentials that their associated force curves have canonical shapes. However, this approach to analyzing force results in inherent loss of accuracy coming from numerical differentiation of the potentials. We now show that this serious obstruction can be avoided by directly demonstrating the canonical nature of force distributions from the perspective of the Hellmann-Feynman theorem. This requires only differentiation of explicitly known Coulombic potentials, and we discuss how this approach to canonical forces can be used to further explain the nature of chemical bonding in pairwise interatomic interactions. All parameter values used in the canonical transformation are determined through explicit physical based algorithms, and it does not require direct consideration of electron correlation effects. PMID:27143175

  13. COLLECTIVE PAIRWISE CLASSIFICATION FOR MULTI-WAY ANALYSIS OF DISEASE AND DRUG DATA

    PubMed Central

    ZITNIK, MARINKA; ZUPAN, BLAZ

    2015-01-01

    Interactions between drugs, drug targets or diseases can be predicted on the basis of molecular, clinical and genomic features by, for example, exploiting similarity of disease pathways, chemical structures, activities across cell lines or clinical manifestations of diseases. A successful way to better understand complex interactions in biomedical systems is to employ collective relational learning approaches that can jointly model diverse relationships present in multiplex data. We propose a novel collective pairwise classification approach for multi-way data analysis. Our model leverages the superiority of latent factor models and classifies relationships in a large relational data domain using a pairwise ranking loss. In contrast to current approaches, our method estimates probabilities, such that probabilities for existing relationships are higher than for assumed-to-be-negative relationships. Although our method bears correspondence with the maximization of non-differentiable area under the ROC curve, we were able to design a learning algorithm that scales well on multi-relational data encoding interactions between thousands of entities. We use the new method to infer relationships from multiplex drug data and to predict connections between clinical manifestations of diseases and their underlying molecular signatures. Our method achieves promising predictive performance when compared to state-of-the-art alternative approaches and can make “category-jumping” predictions about diseases from genomic and clinical data generated far outside the molecular context. PMID:26776175

  14. Evaluation of Jackknife and Bootstrap for Defining Confidence Intervals for Pairwise Agreement Measures

    PubMed Central

    Severiano, Ana; Carriço, João A.; Robinson, D. Ashley; Ramirez, Mário; Pinto, Francisco R.

    2011-01-01

    Several research fields frequently deal with the analysis of diverse classification results of the same entities. This should imply an objective detection of overlaps and divergences between the formed clusters. The congruence between classifications can be quantified by clustering agreement measures, including pairwise agreement measures. Several measures have been proposed and the importance of obtaining confidence intervals for the point estimate in the comparison of these measures has been highlighted. A broad range of methods can be used for the estimation of confidence intervals. However, evidence is lacking about what are the appropriate methods for the calculation of confidence intervals for most clustering agreement measures. Here we evaluate the resampling techniques of bootstrap and jackknife for the calculation of the confidence intervals for clustering agreement measures. Contrary to what has been shown for some statistics, simulations showed that the jackknife performs better than the bootstrap at accurately estimating confidence intervals for pairwise agreement measures, especially when the agreement between partitions is low. The coverage of the jackknife confidence interval is robust to changes in cluster number and cluster size distribution. PMID:21611165

  15. Crystal Structure of the lamda Repressor and a Model for Pairwise Cooperative Operator Binding

    SciTech Connect

    Stayrook,S.; Jaru-Ampornpan, P.; Ni, J.; Hochschild, A.; Lewis, M.

    2008-01-01

    Bacteriophage {lambda} has for many years been a model system for understanding mechanisms of gene regulation1. A 'genetic switch' enables the phage to transition from lysogenic growth to lytic development when triggered by specific environmental conditions. The key component of the switch is the cI repressor, which binds to two sets of three operator sites on the chromosome that are separated by about 2,400 base pairs (bp)2, 3. A hallmark of the system is the pairwise cooperativity of repressor binding4. In the absence of detailed structural information, it has been difficult to understand fully how repressor molecules establish the cooperativity complex. Here we present the X-ray crystal structure of the intact cI repressor dimer bound to a DNA operator site. The structure of the repressor, determined by multiple isomorphous replacement methods, reveals an unusual overall architecture that allows it to adopt a conformation that appears to facilitate pairwise cooperative binding to adjacent operator sites.

  16. A water market simulator considering pair-wise trades between agents

    NASA Astrophysics Data System (ADS)

    Huskova, I.; Erfani, T.; Harou, J. J.

    2012-04-01

    In many basins in England no further water abstraction licences are available. Trading water between water rights holders has been recognized as a potentially effective and economically efficient strategy to mitigate increasing scarcity. A screening tool that could assess the potential for trade through realistic simulation of individual water rights holders would help assess the solution's potential contribution to local water management. We propose an optimisation-driven water market simulator that predicts pair-wise trade in a catchment and represents its interaction with natural hydrology and engineered infrastructure. A model is used to emulate licence-holders' willingness to engage in short-term trade transactions. In their simplest form agents are represented using an economic benefit function. The working hypothesis is that trading behaviour can be partially predicted based on differences in marginal values of water over space and time and estimates of transaction costs on pair-wise trades. We discuss the further possibility of embedding rules, norms and preferences of the different water user sectors to more realistically represent the behaviours, motives and constraints of individual licence holders. The potential benefits and limitations of such a social simulation (agent-based) approach is contrasted with our simulator where agents are driven by economic optimization. A case study based on the Dove River Basin (UK) demonstrates model inputs and outputs. The ability of the model to suggest impacts of water rights policy reforms on trading is discussed.

  17. PipTools: a computational toolkit to annotate and analyze pairwise comparisons of genomic sequences.

    PubMed

    Elnitski, Laura; Riemer, Cathy; Petrykowska, Hanna; Florea, Liliana; Schwartz, Scott; Miller, Webb; Hardison, Ross

    2002-12-01

    Sequence conservation between species is useful both for locating coding regions of genes and for identifying functional noncoding segments. Hence interspecies alignment of genomic sequences is an important computational technique. However, its utility is limited without extensive annotation. We describe a suite of software tools, PipTools, and related programs that facilitate the annotation of genes and putative regulatory elements in pairwise alignments. The alignment server PipMaker uses the output of these tools to display detailed information needed to interpret alignments. These programs are provided in a portable format for use on common desktop computers and both the toolkit and the PipMaker server can be found at our Web site (http://bio.cse.psu.edu/). We illustrate the utility of the toolkit using annotation of a pairwise comparison of the mouse MHC class II and class III regions with orthologous human sequences and subsequently identify conserved, noncoding sequences that are DNase I hypersensitive sites in chromatin of mouse cells. PMID:12504859

  18. Pairwise control of exchange interaction between individual spins in a triple quantum dot

    NASA Astrophysics Data System (ADS)

    Granger, G.; Studenikin, Sergei; Aers, G.; Kam, A.; Zawadzki, P.; Gaudreau, L.; Wasilewski, R.; Pioro-Ladriere, M.; Sachrajda, A.

    2012-02-01

    The original spin qubit proposal [1] suggested a linear array of spins for quantum computations and the exchange interaction for 2 qubit operations. An essential component of the proposal was the ability to control pairwise the exchange interaction between neighbouring pairs of spins. In this work we experimentally demonstrate such a pairwise control of the exchange interaction between three spins localized in a triple quantum dot (TQD) device. The TQD potential was formed using electrostatic lateral split-gate technology on a GaAs/GaAlAs heterostructure with a high-mobility two-dimensional electron gas [2]. We employ fast pulsing technique based on the Landau-Zener-Stuckelberg (LZS) approach for creating and manipulating coherent superpositions of three spin quantum states [3]. We show that we are able to maintain coherence when increasing the exchange coupling of one spin with another while simultaneously decreasing its coupling with the third.[4pt] [1] D. Loss, and D.P. DiVincenzo, Phys. Rev. A57, 120-126 (1998).[0pt] [2] L. Gaudreau , et al., Appl. Phys. Lett. v.95, 193101 (2009). [0pt] [3] J.R. Petta, H. Lu, and A.C. Gossard, Science v.327, 669-672 (2010).

  19. Multilevel summation with B-spline interpolation for pairwise interactions in molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Hardy, David J.; Wolff, Matthew A.; Xia, Jianlin; Schulten, Klaus; Skeel, Robert D.

    2016-03-01

    The multilevel summation method for calculating electrostatic interactions in molecular dynamics simulations constructs an approximation to a pairwise interaction kernel and its gradient, which can be evaluated at a cost that scales linearly with the number of atoms. The method smoothly splits the kernel into a sum of partial kernels of increasing range and decreasing variability with the longer-range parts interpolated from grids of increasing coarseness. Multilevel summation is especially appropriate in the context of dynamics and minimization, because it can produce continuous gradients. This article explores the use of B-splines to increase the accuracy of the multilevel summation method (for nonperiodic boundaries) without incurring additional computation other than a preprocessing step (whose cost also scales linearly). To obtain accurate results efficiently involves technical difficulties, which are overcome by a novel preprocessing algorithm. Numerical experiments demonstrate that the resulting method offers substantial improvements in accuracy and that its performance is competitive with an implementation of the fast multipole method in general and markedly better for Hamiltonian formulations of molecular dynamics. The improvement is great enough to establish multilevel summation as a serious contender for calculating pairwise interactions in molecular dynamics simulations. In particular, the method appears to be uniquely capable for molecular dynamics in two situations, nonperiodic boundary conditions and massively parallel computation, where the fast Fourier transform employed in the particle-mesh Ewald method falls short.

  20. Invariance of covariances arises out of noise

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

    Correlated neural activity is a known feature of the brain [1] and evidence increases that it is closely linked to information processing [2]. The temporal shape of covariances has early been related to synaptic interactions and to common input shared by pairs of neurons [3]. Recent theoretical work explains the small magnitude of covariances in inhibition dominated recurrent networks by active decorrelation [4, 5, 6]. For binary neurons the mean-field approach takes random fluctuations into account to accurately predict the average activity in such networks [7] and expressions for covariances follow from a master equation [8], both briefly reviewed here for completeness. In our recent work we have shown how to map different network models, including binary networks, onto linear dynamics [9]. Binary neurons with a strong non-linear Heaviside gain function are inaccessible to the classical treatment [8]. Here we show how random fluctuations generated by the network effectively linearize the system and implement a self-regulating mechanism, that renders population-averaged covariances independent of the interaction strength and keeps the system away from instability.

  1. Covariant Photon Quantization in the SME

    NASA Astrophysics Data System (ADS)

    Colladay, D.

    2014-01-01

    The Gupta-Bleuler quantization procedure is applied to the SME photon sector. A direct application of the method to the massless case fails due to an unavoidable incompleteness in the polarization states. A mass term can be included into the photon lagrangian to rescue the quantization procedure and maintain covariance.

  2. Economical phase-covariant cloning of qudits

    SciTech Connect

    Buscemi, Francesco; D'Ariano, Giacomo Mauro; Macchiavello, Chiara

    2005-04-01

    We derive the optimal N{yields}M phase-covariant quantum cloning for equatorial states in dimension d with M=kd+N, k integer. The cloning maps are optimal for both global and single-qudit fidelity. The map is achieved by an 'economical' cloning machine, which works without ancilla.

  3. Gauge field theory of covariant strings

    NASA Astrophysics Data System (ADS)

    Kaku, Michio

    1986-03-01

    We present a gauge covariant second-quantized field theory of strings which is explicitly invariant under the gauge transformations generated by the Virasoro algebra. Unlike the old field theory strings [1] this new formulation is Lorentz covariant as well as gauge covariant under the continuous group Diff( S1) and its central extension. We derive the free action: L=Φ(X) †P[i∂ τ-(L 0-1)]PΦ(X) , in the same way that Feynman derived the Schrödinger equation from the path integral formalism. The action is manifestly invariant under the gauge transformation δΦ(X)= limit∑n=1∞ɛ -nL -nΦ(X) , where P is a projection operator which annihilates spurious states. We give three distinct formulations of this operator P to all orders, the first based on extracting the operator from the functional formulation of the Nambu-Goto action, and the second and third based on inverting the Shapovalov matrix on a Verma module. This gauge covariant formulation can be easily extended to the Green-Schwarz superstring [2,3]. One element application of these methods is to re-express the old Neveu-Schwarz-Ramond model as a field theory which is manifestly invariant under space-time supersymmetric transformations.

  4. Covariates of Sesame Street Viewing by Preschoolers.

    ERIC Educational Resources Information Center

    Spaner, Steven D.

    A study was made of nine covariates as to their discriminating power between preschoolers who watch Sesame Street regularly and preschoolers who do not watch Sesame Street, Surveyed were 372 3-4 year old children on 9 variables. The nine variables were: race, socioeconomic status, number of siblings, child's birth order, maternal age, maternal…

  5. Observed Score Linear Equating with Covariates

    ERIC Educational Resources Information Center

    Branberg, Kenny; Wiberg, Marie

    2011-01-01

    This paper examined observed score linear equating in two different data collection designs, the equivalent groups design and the nonequivalent groups design, when information from covariates (i.e., background variables correlated with the test scores) was included. The main purpose of the study was to examine the effect (i.e., bias, variance, and…

  6. Nuclear moments in covariant density functional theory

    NASA Astrophysics Data System (ADS)

    Meng, J.; Zhao, P. W.; Zhang, S. Q.; Hu, J. N.; Li, J.

    2014-05-01

    Recent progresses on microscopic and self-consistent description of the nuclear moments in covariant density functional theory based on a point-coupling interaction are briefly reviewed. In particular, the electric quadrupole moments of Cd isotopes and the magnetic moments of Pb isotopes are discussed.

  7. Hawking fluxes, back reaction and covariant anomalies

    NASA Astrophysics Data System (ADS)

    Kulkarni, Shailesh

    2008-11-01

    Starting from the chiral covariant effective action approach of Banerjee and Kulkarni (2008 Phys. Lett. B 659 827), we provide a derivation of the Hawking radiation from a charged black hole in the presence of gravitational back reaction. The modified expressions for charge and energy flux, due to the effect of one-loop back reaction are obtained.

  8. A Covariance NMR Toolbox for MATLAB and OCTAVE

    NASA Astrophysics Data System (ADS)

    Short, Timothy; Alzapiedi, Leigh; Brüschweiler, Rafael; Snyder, David

    2011-03-01

    The Covariance NMR Toolbox is a new software suite that provides a streamlined implementation of covariance-based analysis of multi-dimensional NMR data. The Covariance NMR Toolbox uses the MATLAB or, alternatively, the freely available GNU OCTAVE computer language, providing a user-friendly environment in which to apply and explore covariance techniques. Covariance methods implemented in the toolbox described here include direct and indirect covariance processing, 4D covariance, generalized indirect covariance (GIC), and Z-matrix transform. In order to provide compatibility with a wide variety of spectrometer and spectral analysis platforms, the Covariance NMR Toolbox uses the NMRPipe format for both input and output files. Additionally, datasets small enough to fit in memory are stored as arrays that can be displayed and further manipulated in a versatile manner within MATLAB or OCTAVE.

  9. A covariance NMR toolbox for MATLAB and OCTAVE.

    PubMed

    Short, Timothy; Alzapiedi, Leigh; Brüschweiler, Rafael; Snyder, David

    2011-03-01

    The Covariance NMR Toolbox is a new software suite that provides a streamlined implementation of covariance-based analysis of multi-dimensional NMR data. The Covariance NMR Toolbox uses the MATLAB or, alternatively, the freely available GNU OCTAVE computer language, providing a user-friendly environment in which to apply and explore covariance techniques. Covariance methods implemented in the toolbox described here include direct and indirect covariance processing, 4D covariance, generalized indirect covariance (GIC), and Z-matrix transform. In order to provide compatibility with a wide variety of spectrometer and spectral analysis platforms, the Covariance NMR Toolbox uses the NMRPipe format for both input and output files. Additionally, datasets small enough to fit in memory are stored as arrays that can be displayed and further manipulated in a versatile manner within MATLAB or OCTAVE. PMID:21215669

  10. Cellular and Circuit Mechanisms Maintain Low Spike Co-Variability and Enhance Population Coding in Somatosensory Cortex

    PubMed Central

    Ly, Cheng; Middleton, Jason W.; Doiron, Brent

    2012-01-01

    The responses of cortical neurons are highly variable across repeated presentations of a stimulus. Understanding this variability is critical for theories of both sensory and motor processing, since response variance affects the accuracy of neural codes. Despite this influence, the cellular and circuit mechanisms that shape the trial-to-trial variability of population responses remain poorly understood. We used a combination of experimental and computational techniques to uncover the mechanisms underlying response variability of populations of pyramidal (E) cells in layer 2/3 of rat whisker barrel cortex. Spike trains recorded from pairs of E-cells during either spontaneous activity or whisker deflected responses show similarly low levels of spiking co-variability, despite large differences in network activation between the two states. We developed network models that show how spike threshold non-linearities dilute E-cell spiking co-variability during spontaneous activity and low velocity whisker deflections. In contrast, during high velocity whisker deflections, cancelation mechanisms mediated by feedforward inhibition maintain low E-cell pairwise co-variability. Thus, the combination of these two mechanisms ensure low E-cell population variability over a wide range of whisker deflection velocities. Finally, we show how this active decorrelation of population variability leads to a drastic increase in the population information about whisker velocity. The prevalence of spiking non-linearities and feedforward inhibition in the nervous system suggests that the mechanisms for low network variability presented in our study may generalize throughout the brain. PMID:22408615

  11. Covariance modeling in geodetic applications of collocation

    NASA Astrophysics Data System (ADS)

    Barzaghi, Riccardo; Cazzaniga, Noemi; De Gaetani, Carlo; Reguzzoni, Mirko

    2014-05-01

    Collocation method is widely applied in geodesy for estimating/interpolating gravity related functionals. The crucial problem of this approach is the correct modeling of the empirical covariance functions of the observations. Different methods for getting reliable covariance models have been proposed in the past by many authors. However, there are still problems in fitting the empirical values, particularly when different functionals of T are used and combined. Through suitable linear combinations of positive degree variances a model function that properly fits the empirical values can be obtained. This kind of condition is commonly handled by solver algorithms in linear programming problems. In this work the problem of modeling covariance functions has been dealt with an innovative method based on the simplex algorithm. This requires the definition of an objective function to be minimized (or maximized) where the unknown variables or their linear combinations are subject to some constraints. The non-standard use of the simplex method consists in defining constraints on model covariance function in order to obtain the best fit on the corresponding empirical values. Further constraints are applied so to have coherence with model degree variances to prevent possible solutions with no physical meaning. The fitting procedure is iterative and, in each iteration, constraints are strengthened until the best possible fit between model and empirical functions is reached. The results obtained during the test phase of this new methodology show remarkable improvements with respect to the software packages available until now. Numerical tests are also presented to check for the impact that improved covariance modeling has on the collocation estimate.

  12. Construction of Covariance Functions with Variable Length Fields

    NASA Technical Reports Server (NTRS)

    Gaspari, Gregory; Cohn, Stephen E.; Guo, Jing; Pawson, Steven

    2005-01-01

    This article focuses on construction, directly in physical space, of three-dimensional covariance functions parametrized by a tunable length field, and on an application of this theory to reproduce the Quasi-Biennial Oscillation (QBO) in the Goddard Earth Observing System, Version 4 (GEOS-4) data assimilation system. These Covariance models are referred to as multi-level or nonseparable, to associate them with the application where a multi-level covariance with a large troposphere to stratosphere length field gradient is used to reproduce the QBO from sparse radiosonde observations in the tropical lower stratosphere. The multi-level covariance functions extend well-known single level covariance functions depending only on a length scale. Generalizations of the first- and third-order autoregressive covariances in three dimensions are given, providing multi-level covariances with zero and three derivatives at zero separation, respectively. Multi-level piecewise rational covariances with two continuous derivatives at zero separation are also provided. Multi-level powerlaw covariances are constructed with continuous derivatives of all orders. Additional multi-level covariance functions are constructed using the Schur product of single and multi-level covariance functions. A multi-level powerlaw covariance used to reproduce the QBO in GEOS-4 is described along with details of the assimilation experiments. The new covariance model is shown to represent the vertical wind shear associated with the QBO much more effectively than in the baseline GEOS-4 system.

  13. Linear covariance analysis for gimbaled pointing systems

    NASA Astrophysics Data System (ADS)

    Christensen, Randall S.

    Linear covariance analysis has been utilized in a wide variety of applications. Historically, the theory has made significant contributions to navigation system design and analysis. More recently, the theory has been extended to capture the combined effect of navigation errors and closed-loop control on the performance of the system. These advancements have made possible rapid analysis and comprehensive trade studies of complicated systems ranging from autonomous rendezvous to vehicle ascent trajectory analysis. Comprehensive trade studies are also needed in the area of gimbaled pointing systems where the information needs are different from previous applications. It is therefore the objective of this research to extend the capabilities of linear covariance theory to analyze the closed-loop navigation and control of a gimbaled pointing system. The extensions developed in this research include modifying the linear covariance equations to accommodate a wider variety of controllers. This enables the analysis of controllers common to gimbaled pointing systems, with internal states and associated dynamics as well as actuator command filtering and auxiliary controller measurements. The second extension is the extraction of power spectral density estimates from information available in linear covariance analysis. This information is especially important to gimbaled pointing systems where not just the variance but also the spectrum of the pointing error impacts the performance. The extended theory is applied to a model of a gimbaled pointing system which includes both flexible and rigid body elements as well as input disturbances, sensor errors, and actuator errors. The results of the analysis are validated by direct comparison to a Monte Carlo-based analysis approach. Once the developed linear covariance theory is validated, analysis techniques that are often prohibitory with Monte Carlo analysis are used to gain further insight into the system. These include the creation

  14. Inferring Pairwise Interactions from Biological Data Using Maximum-Entropy Probability Models

    PubMed Central

    Stein, Richard R.; Marks, Debora S.; Sander, Chris

    2015-01-01

    Maximum entropy-based inference methods have been successfully used to infer direct interactions from biological datasets such as gene expression data or sequence ensembles. Here, we review undirected pairwise maximum-entropy probability models in two categories of data types, those with continuous and categorical random variables. As a concrete example, we present recently developed inference methods from the field of protein contact prediction and show that a basic set of assumptions leads to similar solution strategies for inferring the model parameters in both variable types. These parameters reflect interactive couplings between observables, which can be used to predict global properties of the biological system. Such methods are applicable to the important problems of protein 3-D structure prediction and association of gene–gene networks, and they enable potential applications to the analysis of gene alteration patterns and to protein design. PMID:26225866

  15. Broadband continuous wave source localization via pair-wise, cochleagram processing

    NASA Astrophysics Data System (ADS)

    Nosal, Eva-Marie; Frazer, L. Neil

    2005-04-01

    A pair-wise processor has been developed for the passive localization of broadband continuous-wave underwater sources. The algorithm uses sparse hydrophone arrays and does not require previous knowledge of the source signature. It is applicable in multiple source situations. A spectrogram/cochleagram version of the algorithm has been developed in order to utilize higher frequencies at longer ranges where signal incoherence, and limited computational resources, preclude the use of full waveforms. Simulations demonstrating the robustness of the algorithm with respect to noise and environmental mismatch will be presented, together with initial results from the analysis of humpback whale song recorded at the Pacific Missile Range Facility off Kauai. [Work supported by MHPCC and ONR.

  16. Market Competitiveness Evaluation of Mechanical Equipment with a Pairwise Comparisons Hierarchical Model

    PubMed Central

    Hou, Fujun

    2016-01-01

    This paper provides a description of how market competitiveness evaluations concerning mechanical equipment can be made in the context of multi-criteria decision environments. It is assumed that, when we are evaluating the market competitiveness, there are limited number of candidates with some required qualifications, and the alternatives will be pairwise compared on a ratio scale. The qualifications are depicted as criteria in hierarchical structure. A hierarchical decision model called PCbHDM was used in this study based on an analysis of its desirable traits. Illustration and comparison shows that the PCbHDM provides a convenient and effective tool for evaluating the market competitiveness of mechanical equipment. The researchers and practitioners might use findings of this paper in application of PCbHDM. PMID:26783751

  17. a Unified Perspective on the Nature of Pairwise Interatomic Interactions from Ar2 to Carbon Monoxide.

    NASA Astrophysics Data System (ADS)

    Rosales, Charles K.; Rivera-Rivera, Luis A.; McElmurry, Blake A.; Lucchese, Robert R.; Bevan, John W.; Walton, Jay R.

    2014-06-01

    A method is developed that gives a unified perspective on the nature of a wide range of pairwise interatomic interactions. The approach is applied to the diatomic molecules CO, H2+, H2, HF, LiH, Li2, O2, and Ar2, and one-dimensional cuts through the potentials of OC-HBr, OC-HF, OC-HCCH, OC-HCN, OC-HCl, OC-HI, OC-BrCl, and OC-Cl2. Systems selected for investigation illustrate different bound categories varying from van der Waals, halogen bonded, hydrogen bonded to strongly bound covalently bound carbon monoxide with binding energies varying over almost three orders of magnitude, from 99.3 wn to 90683 wn. Accurate semi-empirically determined Rydberg-Klein-Rees or morphed interatomic potentials are used in transformations for this wide range of species to a reduced potential demonstrating commonality in their fundamental nature.

  18. A Maximum-Likelihood Method for the Estimation of Pairwise Relatedness in Structured Populations

    PubMed Central

    Anderson, Amy D.; Weir, Bruce S.

    2007-01-01

    A maximum-likelihood estimator for pairwise relatedness is presented for the situation in which the individuals under consideration come from a large outbred subpopulation of the population for which allele frequencies are known. We demonstrate via simulations that a variety of commonly used estimators that do not take this kind of misspecification of allele frequencies into account will systematically overestimate the degree of relatedness between two individuals from a subpopulation. A maximum-likelihood estimator that includes FST as a parameter is introduced with the goal of producing the relatedness estimates that would have been obtained if the subpopulation allele frequencies had been known. This estimator is shown to work quite well, even when the value of FST is misspecified. Bootstrap confidence intervals are also examined and shown to exhibit close to nominal coverage when FST is correctly specified. PMID:17339212

  19. Trade-off relations of Bell violations among pairwise qubit systems

    NASA Astrophysics Data System (ADS)

    Qin, Hui-Hui; Fei, Shao-Ming; Li-Jost, Xianqing

    2015-12-01

    We investigate the nonlocality distributions among multiqubit systems based on the maximal violations of the Clauser-Horne-Shimony-Holt (CHSH) inequality of reduced pairwise qubit systems. We present a trade-off relation satisfied by these maximal violations, which gives rise to restrictions on the distribution of nonlocality among the subqubit systems. For a three-qubit system, it is impossible that all pairs of qubits violate the CHSH inequality, and once a pair of qubits violates the CHSH inequality maximally, the other two pairs of qubits must both obey the CHSH inequality. Detailed examples are given to illustrate the trade-off relations, and the trade-off relations are generalized to arbitrary multiqubit systems.

  20. Pairwise Quantum Discord for a Symmetric Multi-Qubit System in Different Types of Noisy Channels

    NASA Astrophysics Data System (ADS)

    Guo, You-Neng; Zeng, Ke; Wang, Guo-You

    2016-06-01

    We study the pairwise quantum discord (QD) for a symmetric multi-qubit system in different types of noisy channels, such as phase-flip, amplitude damping, phase-damping, and depolarizing channels. Using the QD and geometric quantum discord (GMQD) to quantify quantum correlations, some analytical and numerical results are presented. The results show that, the QD dynamics is strongly related to the number of spin particles N as well as the initial parameter 𝜃 of the one-axis twisting collective state. With the number of spin particles N increasing, the amount of the QD increases. However, when the amount of the QD arrives at a stable maximal value, the QD is independence of the number of spin particles N increasing. The behavior of the QD is symmetrical during a period 0 ≤ 𝜃 ≤ 2 π. Moreover, we compare the QD dynamics with the GMQD for a symmetric multi-qubit system in different types of noisy channels.

  1. Market Competitiveness Evaluation of Mechanical Equipment with a Pairwise Comparisons Hierarchical Model.

    PubMed

    Hou, Fujun

    2016-01-01

    This paper provides a description of how market competitiveness evaluations concerning mechanical equipment can be made in the context of multi-criteria decision environments. It is assumed that, when we are evaluating the market competitiveness, there are limited number of candidates with some required qualifications, and the alternatives will be pairwise compared on a ratio scale. The qualifications are depicted as criteria in hierarchical structure. A hierarchical decision model called PCbHDM was used in this study based on an analysis of its desirable traits. Illustration and comparison shows that the PCbHDM provides a convenient and effective tool for evaluating the market competitiveness of mechanical equipment. The researchers and practitioners might use findings of this paper in application of PCbHDM. PMID:26783751

  2. Atomic pairwise distribution function analysis of the amorphous phase prepared by different manufacturing routes.

    PubMed

    Boetker, Johan P; Koradia, Vishal; Rades, Thomas; Rantanen, Jukka; Savolainen, Marja

    2012-01-01

    Amlodipine besilate, a calcium channel antagonist, exists in several solid forms. Processing of anhydrate and dihydrate forms of this drug may lead to solid state changes, and is therefore the focus of this study. Milling was performed for the anhydrate form, whereas the dihydrate form was subjected to quench cooling thereby creating an amorphous form of the drug from both starting materials. The milled and quench cooled samples were, together with the crystalline starting materials, analyzed with X-ray powder diffraction (XRPD), Raman spectroscopy and atomic pair-wise distribution function (PDF) analysis of the XRPD pattern. When compared to XRPD and Raman spectroscopy, the PDF analysis was superior in displaying the difference between the amorphous samples prepared by milling and quench cooling approaches of the two starting materials. PMID:24300182

  3. On the sufficiency of pairwise interactions in maximum entropy models of networks

    NASA Astrophysics Data System (ADS)

    Nemenman, Ilya; Merchan, Lina

    Biological information processing networks consist of many components, which are coupled by an even larger number of complex multivariate interactions. However, analyses of data sets from fields as diverse as neuroscience, molecular biology, and behavior have reported that observed statistics of states of some biological networks can be approximated well by maximum entropy models with only pairwise interactions among the components. Based on simulations of random Ising spin networks with p-spin (p > 2) interactions, here we argue that this reduction in complexity can be thought of as a natural property of some densely interacting networks in certain regimes, and not necessarily as a special property of living systems. This work was supported in part by James S. McDonnell Foundation Grant No. 220020321.

  4. On the Sufficiency of Pairwise Interactions in Maximum Entropy Models of Networks

    NASA Astrophysics Data System (ADS)

    Merchan, Lina; Nemenman, Ilya

    2016-03-01

    Biological information processing networks consist of many components, which are coupled by an even larger number of complex multivariate interactions. However, analyses of data sets from fields as diverse as neuroscience, molecular biology, and behavior have reported that observed statistics of states of some biological networks can be approximated well by maximum entropy models with only pairwise interactions among the components. Based on simulations of random Ising spin networks with p-spin (p>2) interactions, here we argue that this reduction in complexity can be thought of as a natural property of densely interacting networks in certain regimes, and not necessarily as a special property of living systems. By connecting our analysis to the theory of random constraint satisfaction problems, we suggest a reason for why some biological systems may operate in this regime.

  5. Weak pairwise correlations imply strongly correlated network states in a neural population

    PubMed Central

    Schneidman, Elad; Berry, Michael J.; Segev, Ronen; Bialek, William

    2006-01-01

    Biological networks have so many possible states that exhaustive sampling is impossible. Successful analysis thus depends on simplifying hypotheses, but experiments on many systems hint that complicated, higher-order interactions among large groups of elements have an important role. Here we show, in the vertebrate retina, that weak correlations between pairs of neurons coexist with strongly collective behaviour in the responses of ten or more neurons. We find that this collective behaviour is described quantitatively by models that capture the observed pairwise correlations but assume no higher-order interactions. These maximum entropy models are equivalent to Ising models, and predict that larger networks are completely dominated by correlation effects. This suggests that the neural code has associative or error-correcting properties, and we provide preliminary evidence for such behaviour. As a first test for the generality of these ideas, we show that similar results are obtained from networks of cultured cortical neurons. PMID:16625187

  6. Feature-based pairwise retinal image registration by radial distortion correction

    NASA Astrophysics Data System (ADS)

    Lee, Sangyeol; Abràmoff, Michael D.; Reinhardt, Joseph M.

    2007-03-01

    Fundus camera imaging is widely used to document disorders such as diabetic retinopathy and macular degeneration. Multiple retinal images can be combined together through a procedure known as mosaicing to form an image with a larger field of view. Mosaicing typically requires multiple pairwise registrations of partially overlapped images. We describe a new method for pairwise retinal image registration. The proposed method is unique in that the radial distortion due to image acquisition is corrected prior to the geometric transformation. Vessel lines are detected using the Hessian operator and are used as input features to the registration. Since the overlapping region is typically small in a retinal image pair, only a few correspondences are available, thus limiting the applicable model to an afine transform at best. To recover the distortion due to curved-surface of retina and lens optics, a combined approach of an afine model with a radial distortion correction is proposed. The parameters of the image acquisition and radial distortion models are estimated during an optimization step that uses Powell's method driven by the vessel line distance. Experimental results using 20 pairs of green channel images acquired from three subjects with a fundus camera confirmed that the afine model with distortion correction could register retinal image pairs to within 1.88+/-0.35 pixels accuracy (mean +/- standard deviation) assessed by vessel line error, which is 17% better than the afine-only approach. Because the proposed method needs only two correspondences, it can be applied to obtain good registration accuracy even in the case of small overlap between retinal image pairs.

  7. How well can polarization models of pairwise nonadditive forces describe liquid water?

    PubMed

    Akin-Ojo, Omololu; Szalewicz, Krzysztof

    2013-01-14

    Properties of liquid water have been computed using a near-exact rigid-monomer two-body (pairwise-additive) force field and the same field supplemented by a simple, non-empirical polarization model of pairwise nonadditive many-body forces. The inclusion of nonadditive polarization forces leads to a dramatic decrease, sometimes by an order of magnitude, of the deviations of water properties computed using classical molecular dynamics from experiment results. The remaining deviations are typically of the order of 10%. The model correctly predicts the temperature dependence of the properties except for the density of supercooled water. This good performance is achieved despite the known failure of the polarization model in reproducing trimer nonadditive interaction energies, confirmed here by showing that for a random set of trimers with all O-O separations smaller than 3.4 Å, selected from simulation snapshots, the average error of the model relative to accurate ab initio values is 71%. However, the errors gradually decrease for larger trimers, more abundant in liquid, and one can estimate that the polarization model should reproduce the exact liquid interaction energy to within about 6%. Although this accuracy is consistent with the observed performance of the polarization model, it does not explain the dramatic improvements over the two-body model. These improvements are due to the restructuring of liquid into tetrahedral arrangements instigated by the nonadditive polarization forces. The deviations of our predictions from experiments are generally also consistent with the estimated contributions from leading neglected effects other than the exchange nonadditive forces: the monomer flexibility and quantum nuclear motion effects. PMID:23320692

  8. Parasail: SIMD C library for global, semi-global, and local pairwise sequence alignments

    DOE PAGESBeta

    Daily, Jeffrey A.

    2016-02-10

    Sequence alignment algorithms are a key component of many bioinformatics applications. Though various fast Smith-Waterman local sequence alignment implementations have been developed for x86 CPUs, most are embedded into larger database search tools. In addition, fast implementations of Needleman-Wunsch global sequence alignment and its semi-global variants are not as widespread. This article presents the first software library for local, global, and semi-global pairwise intra-sequence alignments and improves the performance of previous intra-sequence implementations. As a result, a faster intra-sequence pairwise alignment implementation is described and benchmarked. Using a 375 residue query sequence a speed of 136 billion cell updates permore » second (GCUPS) was achieved on a dual Intel Xeon E5-2670 12-core processor system, the highest reported for an implementation based on Farrar’s ’striped’ approach. When using only a single thread, parasail was 1.7 times faster than Rognes’s SWIPE. For many score matrices, parasail is faster than BLAST. The software library is designed for 64 bit Linux, OS X, or Windows on processors with SSE2, SSE41, or AVX2. Source code is available from https://github.com/jeffdaily/parasail under the Battelle BSD-style license. In conclusion, applications that require optimal alignment scores could benefit from the improved performance. For the first time, SIMD global, semi-global, and local alignments are available in a stand-alone C library.« less

  9. Understanding molecular crystals with dispersion-inclusive density functional theory: pairwise corrections and beyond.

    PubMed

    Kronik, Leeor; Tkatchenko, Alexandre

    2014-11-18

    CONSPECTUS: Molecular crystals are ubiquitous in many areas of science and engineering, including biology and medicine. Until recently, our ability to understand and predict their structure and properties using density functional theory was severely limited by the lack of approximate exchange-correlation functionals able to achieve sufficient accuracy. Here we show that there are many cases where the simple, minimally empirical pairwise correction scheme of Tkatchenko and Scheffler provides a useful prediction of the structure and properties of molecular crystals. After a brief introduction of the approach, we demonstrate its strength through some examples taken from our recent work. First, we show the accuracy of the approach using benchmark data sets of molecular complexes. Then we show its efficacy for structural determination using the hemozoin crystal, a challenging system possessing a wide range of strong and weak binding scenarios. Next, we show that it is equally useful for response properties by considering the elastic constants exhibited by the supramolecular diphenylalanine peptide solid and the infrared signature of water libration movements in brushite. Throughout, we emphasize lessons learned not only for the methodology but also for the chemistry and physics of the crystals in question. We further show that in many other scenarios where the simple pairwise correction scheme is not sufficiently accurate, one can go beyond it by employing a computationally inexpensive many-body dispersive approach that results in useful, quantitative accuracy, even in the presence of significant screening and/or multibody contributions to the dispersive energy. We explain the principles of the many-body approach and demonstrate its accuracy for benchmark data sets of small and large molecular complexes and molecular solids. PMID:24901508

  10. Are ionic liquids pairwise in gas phase? A cluster approach and in situ IR study.

    PubMed

    Dong, Kun; Zhao, Lidong; Wang, Qian; Song, Yuting; Zhang, Suojiang

    2013-04-28

    In this work, we discussed the vaporization and gas species of ionic liquids (ILs) by a cluster approach of quantum statistical thermodynamics proposed by R. Luwig (Phys. Chem. Chem. Phys., 10, 4333), which is a controversial issue up to date. Based on the different sized clusters (2-12 ion-pairs) of the condensed phase, the molar enthalpies of vaporization (ΔvapH, 298.15 K, 1bar) of four representative ILs, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][NTf2]) 1-ethyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide ([Emmim][NTf2]) 1-ethyl-3-methylimidazolium chloride ([Emim]Cl) and ethylammonium nitrate ([EtAm][NO3]), were calculated. The predicted ΔvapH were increased remarkably; even the values of [EtAm][NO3] were larger than 700 kJ mol(-1) when the charged isolated ions were assumed to be gas species. However, the ΔvapH were close to experimental measurements when the gas species assumed to be anion-cation pairwise, indicating that the different conformational ion-pairs can coexist in the gas phase when the IL is evaporated. Particularly for the protic IL, [EtAm][NO3], even the neutral precursor molecules by proton transfer can occur in gas phase. In addition, it's found that the effect of hydrogen bonds on the vaporization cannot be negligible by comparing the ΔvapH of [Emim][NTf2] with [Emmim][NTf2]. The in situ and calculated IR spectra provided the further proof that the ions are pairwise in gas phase. PMID:23493905

  11. Analysis of Geographic and Pairwise Distances among Chinese Cashmere Goat Populations

    PubMed Central

    Liu, Jian-Bin; Wang, Fan; Lang, Xia; Zha, Xi; Sun, Xiao-Ping; Yue, Yao-Jing; Feng, Rui-Lin; Yang, Bo-Hui; Guo, Jian

    2013-01-01

    This study investigated the geographic and pairwise distances of nine Chinese local Cashmere goat populations through the analysis of 20 microsatellite DNA markers. Fluorescence PCR was used to identify the markers, which were selected based on their significance as identified by the Food and Agriculture Organization of the United Nations (FAO) and the International Society for Animal Genetics (ISAG). In total, 206 alleles were detected; the average allele number was 10.30; the polymorphism information content of loci ranged from 0.5213 to 0.7582; the number of effective alleles ranged from 4.0484 to 4.6178; the observed heterozygosity was from 0.5023 to 0.5602 for the practical sample; the expected heterozygosity ranged from 0.5783 to 0.6464; and Allelic richness ranged from 4.7551 to 8.0693. These results indicated that Chinese Cashmere goat populations exhibited rich genetic diversity. Further, the Wright’s F-statistics of subpopulation within total (FST) was 0.1184; the genetic differentiation coefficient (GST) was 0.0940; and the average gene flow (Nm) was 2.0415. All pairwise FST values among the populations were highly significant (p<0.01 or p<0.001), suggesting that the populations studied should all be considered to be separate breeds. Finally, the clustering analysis divided the Chinese Cashmere goat populations into at least four clusters, with the Hexi and Yashan goat populations alone in one cluster. These results have provided useful, practical, and important information for the future of Chinese Cashmere goat breeding. PMID:25049794

  12. Low-Fidelity Covariances: Neutron Cross Section Covariance Estimates for 387 Materials

    DOE Data Explorer

    The Low-fidelity Covariance Project (Low-Fi) was funded in FY07-08 by DOEÆs Nuclear Criticality Safety Program (NCSP). The project was a collaboration among ANL, BNL, LANL, and ORNL. The motivation for the Low-Fi project stemmed from an imbalance in supply and demand of covariance data. The interest in, and demand for, covariance data has been in a continual uptrend over the past few years. Requirements to understand application-dependent uncertainties in simulated quantities of interest have led to the development of sensitivity / uncertainty and data adjustment software such as TSUNAMI [1] at Oak Ridge. To take full advantage of the capabilities of TSUNAMI requires general availability of covariance data. However, the supply of covariance data has not been able to keep up with the demand. This fact is highlighted by the observation that the recent release of the much-heralded ENDF/B-VII.0 included covariance data for only 26 of the 393 neutron evaluations (which is, in fact, considerably less covariance data than was included in the final ENDF/B-VI release).[Copied from R.C. Little et al., "Low-Fidelity Covariance Project", Nuclear Data Sheets 109 (2008) 2828-2833] The Low-Fi covariance data are now available at the National Nuclear Data Center. They are separate from ENDF/B-VII.0 and the NNDC warns that this information is not approved by CSEWG. NNDC describes the contents of this collection as: "Covariance data are provided for radiative capture (or (n,ch.p.) for light nuclei), elastic scattering (or total for some actinides), inelastic scattering, (n,2n) reactions, fission and nubars over the energy range from 10(-5{super}) eV to 20 MeV. The library contains 387 files including almost all (383 out of 393) materials of the ENDF/B-VII.0. Absent are data for (7{super})Li, (232{super})Th, (233,235,238{super})U and (239{super})Pu as well as (223,224,225,226{super})Ra, while (nat{super})Zn is replaced by (64,66,67,68,70{super})Zn

  13. Covariance Spectroscopy Applied to Nuclear Radiation Detection

    SciTech Connect

    Trainham, R., Tinsley, J., Keegan, R., Quam, W.

    2011-09-01

    Covariance spectroscopy is a method of processing second order moments of data to obtain information that is usually absent from average spectra. In nuclear radiation detection it represents a generalization of nuclear coincidence techniques. Correlations and fluctuations in data encode valuable information about radiation sources, transport media, and detection systems. Gaining access to the extra information can help to untangle complicated spectra, uncover overlapping peaks, accelerate source identification, and even sense directionality. Correlations existing at the source level are particularly valuable since many radioactive isotopes emit correlated gammas and neutrons. Correlations also arise from interactions within detector systems, and from scattering in the environment. In particular, correlations from Compton scattering and pair production within a detector array can be usefully exploited in scenarios where direct measurement of source correlations would be unfeasible. We present a covariance analysis of a few experimental data sets to illustrate the utility of the concept.

  14. RNA sequence analysis using covariance models.

    PubMed Central

    Eddy, S R; Durbin, R

    1994-01-01

    We describe a general approach to several RNA sequence analysis problems using probabilistic models that flexibly describe the secondary structure and primary sequence consensus of an RNA sequence family. We call these models 'covariance models'. A covariance model of tRNA sequences is an extremely sensitive and discriminative tool for searching for additional tRNAs and tRNA-related sequences in sequence databases. A model can be built automatically from an existing sequence alignment. We also describe an algorithm for learning a model and hence a consensus secondary structure from initially unaligned example sequences and no prior structural information. Models trained on unaligned tRNA examples correctly predict tRNA secondary structure and produce high-quality multiple alignments. The approach may be applied to any family of small RNA sequences. Images PMID:8029015

  15. Covariance and the hierarchy of frame bundles

    NASA Technical Reports Server (NTRS)

    Estabrook, Frank B.

    1987-01-01

    This is an essay on the general concept of covariance, and its connection with the structure of the nested set of higher frame bundles over a differentiable manifold. Examples of covariant geometric objects include not only linear tensor fields, densities and forms, but affinity fields, sectors and sector forms, higher order frame fields, etc., often having nonlinear transformation rules and Lie derivatives. The intrinsic, or invariant, sets of forms that arise on frame bundles satisfy the graded Cartan-Maurer structure equations of an infinite Lie algebra. Reduction of these gives invariant structure equations for Lie pseudogroups, and for G-structures of various orders. Some new results are introduced for prolongation of structure equations, and for treatment of Riemannian geometry with higher-order moving frames. The use of invariant form equations for nonlinear field physics is implicitly advocated.

  16. On covariance structure in noisy, big data

    NASA Astrophysics Data System (ADS)

    Paffenroth, Randy C.; Nong, Ryan; Du Toit, Philip C.

    2013-09-01

    Herein we describe theory and algorithms for detecting covariance structures in large, noisy data sets. Our work uses ideas from matrix completion and robust principal component analysis to detect the presence of low-rank covariance matrices, even when the data is noisy, distorted by large corruptions, and only partially observed. In fact, the ability to handle partial observations combined with ideas from randomized algorithms for matrix decomposition enables us to produce asymptotically fast algorithms. Herein we will provide numerical demonstrations of the methods and their convergence properties. While such methods have applicability to many problems, including mathematical finance, crime analysis, and other large-scale sensor fusion problems, our inspiration arises from applying these methods in the context of cyber network intrusion detection.

  17. Economical phase-covariant cloning with multiclones

    NASA Astrophysics Data System (ADS)

    Zhang, Wen-Hai; Ye, Liu

    2009-09-01

    This paper presents a very simple method to derive the explicit transformations of the optimal economical 1 to M phase-covariant cloning. The fidelity of clones reaches the theoretic bound [D'Ariano G M and Macchiavello C 2003 Phys. Rev. A 67 042306]. The derived transformations cover the previous contributions [Delgado Y, Lamata L et al., 2007 Phys. Rev. Lett. 98 150502] in which M must be odd.

  18. Covariance expressions for eigenvalue and eigenvector problems

    NASA Astrophysics Data System (ADS)

    Liounis, Andrew J.

    There are a number of important scientific and engineering problems whose solutions take the form of an eigenvalue--eigenvector problem. Some notable examples include solutions to linear systems of ordinary differential equations, controllability of linear systems, finite element analysis, chemical kinetics, fitting ellipses to noisy data, and optimal estimation of attitude from unit vectors. In many of these problems, having knowledge of the eigenvalue and eigenvector Jacobians is either necessary or is nearly as important as having the solution itself. For instance, Jacobians are necessary to find the uncertainty in a computed eigenvalue or eigenvector estimate. This uncertainty, which is usually represented as a covariance matrix, has been well studied for problems similar to the eigenvalue and eigenvector problem, such as singular value decomposition. There has been substantially less research on the covariance of an optimal estimate originating from an eigenvalue-eigenvector problem. In this thesis we develop two general expressions for the Jacobians of eigenvalues and eigenvectors with respect to the elements of their parent matrix. The expressions developed make use of only the parent matrix and the eigenvalue and eigenvector pair under consideration. In addition, they are applicable to any general matrix (including complex valued matrices, eigenvalues, and eigenvectors) as long as the eigenvalues are simple. Alongside this, we develop expressions that determine the uncertainty in a vector estimate obtained from an eigenvalue-eigenvector problem given the uncertainty of the terms of the matrix. The Jacobian expressions developed are numerically validated with forward finite, differencing and the covariance expressions are validated using Monte Carlo analysis. Finally, the results from this work are used to determine covariance expressions for a variety of estimation problem examples and are also applied to the design of a dynamical system.

  19. Covariant quantum mechanics applied to noncommutative geometry

    NASA Astrophysics Data System (ADS)

    Astuti, Valerio

    2015-08-01

    We here report a result obtained in collaboration with Giovanni Amelino-Camelia, first shown in the paper [1]. Applying the manifestly covariant formalism of quantum mechanics to the much studied Snyder spacetime [2] we show how it is trivial in every physical observables, this meaning that every measure in this spacetime gives the same results that would be obtained in the flat Minkowski spacetime.

  20. Partial covariance mapping techniques at FELs

    NASA Astrophysics Data System (ADS)

    Frasinski, Leszek

    2014-05-01

    The development of free-electron lasers (FELs) is driven by the desire to access the structure and chemical dynamics of biomolecules with atomic resolution. Short, intense FEL pulses have the potential to record x-ray diffraction images before the molecular structure is destroyed by radiation damage. However, even during the shortest, few-femtosecond pulses currently available, there are some significant changes induced by massive ionisation and onset of Coulomb explosion. To interpret the diffraction images it is vital to gain insight into the electronic and nuclear dynamics during multiple core and valence ionisations that compete with Auger cascades. This paper focuses on a technique that is capable to probe these processes. The covariance mapping technique is well suited to the high intensity and low repetition rate of FEL pulses. While the multitude of charges ejected at each pulse overwhelm conventional coincidence methods, an improved technique of partial covariance mapping can cope with hundreds of photoelectrons or photoions detected at each FEL shot. The technique, however, often reveals spurious, uninteresting correlations that spoil the maps. This work will discuss the strengths and limitations of various forms of covariance mapping techniques. Quantitative information extracted from the maps will be linked to theoretical modelling of ionisation and fragmentation paths. Special attention will be given to critical experimental parameters, such as counting rate, FEL intensity fluctuations, vacuum impurities or detector efficiency and nonlinearities. Methods of assessing and optimising signal-to-noise ratio will be described. Emphasis will be put on possible future developments such as multidimensional covariance mapping, compensation for various experimental instabilities and improvements in the detector response. This work has been supported the EPSRC, UK (grants EP/F021232/1 and EP/I032517/1).

  1. Accommodating College Students with Learning Disabilities: ADD, ADHD, and Dyslexia

    ERIC Educational Resources Information Center

    Vickers, Melana Zyla

    2010-01-01

    Universities are providing extra time on tests, quiet exam rooms, in-class note-takers, and other assistance to college students with modest learning disabilities. But these policies are shrouded in secrecy. This paper, "Accommodating College Students with Learning Disabilities: ADD, ADHD, and Dyslexia," by Melana Zyla Vickers, examines the nature…

  2. Mode-routed fiber-optic add-drop filter

    NASA Technical Reports Server (NTRS)

    Moslehi, Behzad (Inventor); Black, Richard James (Inventor); Shaw, Herbert John (Inventor)

    2000-01-01

    New elements mode-converting two-mode grating and mode-filtering two-mode coupler are disclosed and used as elements in a system for communications, add-drop filtering, and strain sensing. Methods of fabrication for these new two-mode gratings and mode-filtering two-mode couplers are also disclosed.

  3. ADD and ADHD: An Overview for School Counselors. ERIC Digest.

    ERIC Educational Resources Information Center

    Pledge, Deanna S.

    School counselors are often consultants for parents and teachers on problems that children and adolescents face. Attention deficit disorder (ADD) is one such problem. It is frequently misunderstood, presenting a challenge for parents and teachers alike. The counselor is a resource for initial identification and interventions at home and in the…

  4. Four Simple Ways to Add Movement in Daily Lessons

    ERIC Educational Resources Information Center

    Helgeson, John

    2011-01-01

    Adding movement to classroom activities not only engages students, but also may improve the classroom climate and reduce disruptions. In this article, the author discusses four simple activities to add movement in daily lessons. These activities are: (1) Vocabulary/Notes around the Room; (2) Cooperative Learning: Posting Task Assignments; (3)…

  5. ERDA's portfolio: solar add-on device construction manuals

    SciTech Connect

    Barron, J.J.; Cole, W.J.

    1981-01-01

    The New York State Energy Research and Development Authority (ERDA) has developed a portfolio of eight (8) instructional manuals for the construction of the following solar add-on devices: thermosiphoning hot water system; standard domestic hot water system; bread box type hot water system; add-on greenhouse space heating system (with mass); add-on sunspace space heating system (without mass); thermosiphoning air panel space heating system; fan assisted air panel space heating system; Trombe wall space heating system. In addition to step-by-step instructions and illustrations of device construction, each manual contains a list of materials and specifications (including estimated costs in 1980 dollars and sources of supply), guidelines for appropriate siting and installation, and energy performance estimates under optimal and non-optimal conditions. This portfolio of solar add-on devices is directed toward the do-it-yourself homeowner, builders and home improvement contractors, and weatherization organizations. Each instruction manual is a complete, self-contained module suitable for distribution separately or as part of the portfolio. Each manual also has an educational module associated with it including color slides, which is designed for use by community colleges, industrial high schools and adult educational programs. An outline is presented of the content of the design packages,as well as a description of ERDA's plans for distribution of the designs and educating the public on their use, and information on how to obtain individual construction manuals or the entire portfolio.

  6. ENVIRONMENTAL TECHNOLOGY VERIFICATION: ADD-ON NOX CONTROLS

    EPA Science Inventory

    The paper discusses the environmental technology verification (ETV) of add-on nitrogen oxide (NOx) controls. Research Triangle Institute (RTI) is EPA's cooperating partner for the Air Pollution Control Technology (APCT) Program, one of a dozen ETV pilot programs. Verification of ...

  7. Enhancing Teaching using MATLAB Add-Ins for Excel

    ERIC Educational Resources Information Center

    Hamilton, Paul V.

    2004-01-01

    In this paper I will illustrate how to extend the capabilities of Microsoft Excel spreadsheets with add-ins created by MATLAB. Excel provides a broad array of fundamental tools but often comes up short when more sophisticated scenarios are involved. To overcome this short-coming of Excel while retaining its ease of use, I will describe how…

  8. How HR Leaders Can Add Value to an Organization

    ERIC Educational Resources Information Center

    Smallwood, Norm; Ulrich, Dave

    2006-01-01

    Generally speaking, it is safe to say that human resource leaders whole-heartedly believe that the HR function should add value to an organization. However, many wonder where to start. In this article, the authors outline three ways in which the HR function, and the HR leader, can create sustained value for an organization and its stakeholders.

  9. Medicalised Pupils: The Case of ADD/ADHD

    ERIC Educational Resources Information Center

    Kristjansson, Kristjan

    2009-01-01

    Recent decades have seen an increasing number of life's problems conceptualised and interpreted through the prism of disease; among them are those affecting pupils at school. Witness the cases of hyperactivity and deficient attention, so often diagnosed as ADD/ADHD. Research indicates that there is at least some tendency towards overdiagnosis of…

  10. Using Covariance Analysis to Assess Pointing Performance

    NASA Technical Reports Server (NTRS)

    Bayard, David; Kang, Bryan

    2009-01-01

    A Pointing Covariance Analysis Tool (PCAT) has been developed for evaluating the expected performance of the pointing control system for NASA s Space Interferometry Mission (SIM). The SIM pointing control system is very complex, consisting of multiple feedback and feedforward loops, and operating with multiple latencies and data rates. The SIM pointing problem is particularly challenging due to the effects of thermomechanical drifts in concert with the long camera exposures needed to image dim stars. Other pointing error sources include sensor noises, mechanical vibrations, and errors in the feedforward signals. PCAT models the effects of finite camera exposures and all other error sources using linear system elements. This allows the pointing analysis to be performed using linear covariance analysis. PCAT propagates the error covariance using a Lyapunov equation associated with time-varying discrete and continuous-time system matrices. Unlike Monte Carlo analysis, which could involve thousands of computational runs for a single assessment, the PCAT analysis performs the same assessment in a single run. This capability facilitates the analysis of parametric studies, design trades, and "what-if" scenarios for quickly evaluating and optimizing the control system architecture and design.

  11. Covariance tracking: architecture optimizations for embedded systems

    NASA Astrophysics Data System (ADS)

    Romero, Andrés; Lacassagne, Lionel; Gouiffès, Michèle; Zahraee, Ali Hassan

    2014-12-01

    Covariance matching techniques have recently grown in interest due to their good performances for object retrieval, detection, and tracking. By mixing color and texture information in a compact representation, it can be applied to various kinds of objects (textured or not, rigid or not). Unfortunately, the original version requires heavy computations and is difficult to execute in real time on embedded systems. This article presents a review on different versions of the algorithm and its various applications; our aim is to describe the most crucial challenges and particularities that appeared when implementing and optimizing the covariance matching algorithm on a variety of desktop processors and on low-power processors suitable for embedded systems. An application of texture classification is used to compare different versions of the region descriptor. Then a comprehensive study is made to reach a higher level of performance on multi-core CPU architectures by comparing different ways to structure the information, using single instruction, multiple data (SIMD) instructions and advanced loop transformations. The execution time is reduced significantly on two dual-core CPU architectures for embedded computing: ARM Cortex-A9 and Cortex-A15 and Intel Penryn-M U9300 and Haswell-M 4650U. According to our experiments on covariance tracking, it is possible to reach a speedup greater than ×2 on both ARM and Intel architectures, when compared to the original algorithm, leading to real-time execution.

  12. Development of covariance capabilities in EMPIRE code

    SciTech Connect

    Herman,M.; Pigni, M.T.; Oblozinsky, P.; Mughabghab, S.F.; Mattoon, C.M.; Capote, R.; Cho, Young-Sik; Trkov, A.

    2008-06-24

    The nuclear reaction code EMPIRE has been extended to provide evaluation capabilities for neutron cross section covariances in the thermal, resolved resonance, unresolved resonance and fast neutron regions. The Atlas of Neutron Resonances by Mughabghab is used as a primary source of information on uncertainties at low energies. Care is taken to ensure consistency among the resonance parameter uncertainties and those for thermal cross sections. The resulting resonance parameter covariances are formatted in the ENDF-6 File 32. In the fast neutron range our methodology is based on model calculations with the code EMPIRE combined with experimental data through several available approaches. The model-based covariances can be obtained using deterministic (Kalman) or stochastic (Monte Carlo) propagation of model parameter uncertainties. We show that these two procedures yield comparable results. The Kalman filter and/or the generalized least square fitting procedures are employed to incorporate experimental information. We compare the two approaches analyzing results for the major reaction channels on {sup 89}Y. We also discuss a long-standing issue of unreasonably low uncertainties and link it to the rigidity of the model.

  13. Development of Covariance Capabilities in EMPIRE Code

    SciTech Connect

    Herman, M. Pigni, M.T.; Oblozinsky, P.; Mughabghab, S.F.; Mattoon, C.M.; Capote, R.; Cho, Young-Sik; Trkov, A.

    2008-12-15

    The nuclear reaction code EMPIRE has been extended to provide evaluation capabilities for neutron cross section covariances in the thermal, resolved resonance, unresolved resonance and fast neutron regions. The Atlas of Neutron Resonances by Mughabghab is used as a primary source of information on uncertainties at low energies. Care is taken to ensure consistency among the resonance parameter uncertainties and those for thermal cross sections. The resulting resonance parameter covariances are formatted in the ENDF-6 File 32. In the fast neutron range our methodology is based on model calculations with the code EMPIRE combined with experimental data through several available approaches. The model-based covariances can be obtained using deterministic (Kalman) or stochastic (Monte Carlo) propagation of model parameter uncertainties. We show that these two procedures yield comparable results. The Kalman filter and/or the generalized least square fitting procedures are employed to incorporate experimental information. We compare the two approaches analyzing results for the major reaction channels on {sup 89}Y. We also discuss a long-standing issue of unreasonably low uncertainties and link it to the rigidity of the model.

  14. Shrinkage covariance matrix approach for microarray data

    NASA Astrophysics Data System (ADS)

    Karjanto, Suryaefiza; Aripin, Rasimah

    2013-04-01

    Microarray technology was developed for the purpose of monitoring the expression levels of thousands of genes. A microarray data set typically consists of tens of thousands of genes (variables) from just dozens of samples due to various constraints including the high cost of producing microarray chips. As a result, the widely used standard covariance estimator is not appropriate for this purpose. One such technique is the Hotelling's T2 statistic which is a multivariate test statistic for comparing means between two groups. It requires that the number of observations (n) exceeds the number of genes (p) in the set but in microarray studies it is common that n < p. This leads to a biased estimate of the covariance matrix. In this study, the Hotelling's T2 statistic with the shrinkage approach is proposed to estimate the covariance matrix for testing differential gene expression. The performance of this approach is then compared with other commonly used multivariate tests using a widely analysed diabetes data set as illustrations. The results across the methods are consistent, implying that this approach provides an alternative to existing techniques.

  15. Covariant Perturbation Expansion of Off-Diagonal Heat Kernel

    NASA Astrophysics Data System (ADS)

    Gou, Yu-Zi; Li, Wen-Du; Zhang, Ping; Dai, Wu-Sheng

    2016-07-01

    Covariant perturbation expansion is an important method in quantum field theory. In this paper an expansion up to arbitrary order for off-diagonal heat kernels in flat space based on the covariant perturbation expansion is given. In literature, only diagonal heat kernels are calculated based on the covariant perturbation expansion.

  16. Earth Observation System Flight Dynamics System Covariance Realism

    NASA Technical Reports Server (NTRS)

    Zaidi, Waqar H.; Tracewell, David

    2016-01-01

    This presentation applies a covariance realism technique to the National Aeronautics and Space Administration (NASA) Earth Observation System (EOS) Aqua and Aura spacecraft based on inferential statistics. The technique consists of three parts: collection calculation of definitive state estimates through orbit determination, calculation of covariance realism test statistics at each covariance propagation point, and proper assessment of those test statistics.

  17. ANALYSIS OF COVARIANCE WITH SPATIALLY CORRELATED SECONDARY VARIABLES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Data sets which contain measurements on a spatially referenced response and covariate are analyzed using either co-kriging or spatial analysis of covariance. While co-kriging accounts for the correlation structure of the covariate, it is purely a predictive tool. Alternatively, spatial analysis of c...

  18. Covariate Selection in Propensity Scores Using Outcome Proxies

    ERIC Educational Resources Information Center

    Kelcey, Ben

    2011-01-01

    This study examined the practical problem of covariate selection in propensity scores (PSs) given a predetermined set of covariates. Because the bias reduction capacity of a confounding covariate is proportional to the concurrent relationships it has with the outcome and treatment, particular focus is set on how we might approximate…

  19. Eliciting Systematic Rule Use in Covariation Judgment [the Early Years].

    ERIC Educational Resources Information Center

    Shaklee, Harriet; Paszek, Donald

    Related research suggests that children may show some simple understanding of event covariations by the early elementary school years. The present experiments use a rule analysis methodology to investigate covariation judgments of children in this age range. In Experiment 1, children in second, third and fourth grade judged covariations on 12…

  20. Hidden Covariation Detection Produces Faster, Not Slower, Social Judgments

    ERIC Educational Resources Information Center

    Barker, Lynne A.; Andrade, Jackie

    2006-01-01

    In P. Lewicki's (1986b) demonstration of hidden covariation detection (HCD), responses of participants were slower to faces that corresponded with a covariation encountered previously than to faces with novel covariations. This slowing contrasts with the typical finding that priming leads to faster responding and suggests that HCD is a unique type…

  1. Covariant balance laws in continua with microstructure

    NASA Astrophysics Data System (ADS)

    Yavari, Arash; Marsden, Jerrold E.

    2009-02-01

    The purpose of this paper is to extend the Green-Naghdi-Rivlin balance of energy method to continua with microstructure. The key idea is to replace the group of Galilean transformations with the group of diffeomorphisms of the ambient space. A key advantage is that one obtains in a natural way all the needed balance laws on both the macro and micro levels along with two Doyle-Erickson formulas. We model a structured continuum as a triplet of Riemannian manifolds: a material manifold, the ambient space manifold of material particles and a director field manifold. The Green-Naghdi-Rivlin theorem and its extensions for structured continua are critically reviewed. We show that when the ambient space is Euclidean and when the microstructure manifold is the tangent space of the ambient space manifold, postulating a single balance of energy law and its invariance under time-dependent isometries of the ambient space, one obtains conservation of mass, balances of linear and angular momenta but not a separate balance of linear momentum. We develop a covariant elasticity theory for structured continua by postulating that energy balance is invariant under time-dependent spatial diffeomorphisms of the ambient space, which in this case is the product of two Riemannian manifolds. We then introduce two types of constrained continua in which microstructure manifold is linked to the reference and ambient space manifolds. In the case when at every material point, the microstructure manifold is the tangent space of the ambient space manifold at the image of the material point, we show that the assumption of covariance leads to balances of linear and angular momenta with contributions from both forces and micro-forces along with two Doyle-Ericksen formulas. We show that generalized covariance leads to two balances of linear momentum and a single coupled balance of angular momentum. Using this theory, we covariantly obtain the balance laws for two specific examples, namely elastic

  2. Quantum energy inequalities and local covariance II: categorical formulation

    NASA Astrophysics Data System (ADS)

    Fewster, Christopher J.

    2007-11-01

    We formulate quantum energy inequalities (QEIs) in the framework of locally covariant quantum field theory developed by Brunetti, Fredenhagen and Verch, which is based on notions taken from category theory. This leads to a new viewpoint on the QEIs, and also to the identification of a new structural property of locally covariant quantum field theory, which we call local physical equivalence. Covariant formulations of the numerical range and spectrum of locally covariant fields are given and investigated, and a new algebra of fields is identified, in which fields are treated independently of their realisation on particular spacetimes and manifestly covariant versions of the functional calculus may be formulated.

  3. Estimation of Hardy-Weinberg and pairwise disequilibrium in the apolipoprotein AI-CIII-AIV gene cluster.

    PubMed Central

    Haviland, M B; Kessling, A M; Davignon, J; Sing, C F

    1991-01-01

    Departures from Hardy-Weinberg (HW) equilibria and pairwise disequilibria were estimated in a sample of unrelated healthy individuals typed for six RFLPs in the apo AI-CIII-AIV gene region. The sample was composed of males and females, selected for health, from two populations, those of exclusively French-Canadian (FC) and those of some non-French-Canadian (NFC) ancestry. An approach suggested by Weir and Cockerham, which includes estimates of nonrandom association (disequilibria) between three and four alleles at two loci as well as the traditional associations between two alleles, at two loci was used. The pattern of departures from HW equilibria suggested that the genetic structures of the FC and NFC are different. Departure from HW equilibrium at an RFLP locus could not be predicted from information about other loci in the same gene region. Nonrandom associations were also evident from the pairwise analyses. Two pairs of loci had significant diallelic disequilibria, while two other pairs had significant triallelic disequilibria. All of the RFLP pairs had at least one measure of disequilibrium at its maximum value determined by allele frequencies. Inferences about pairwise disequilibria depended on the statistical approach used. Sizes of the pairwise disequilibria were not correlated with the physical distance between loci. The impact of these disequilibria on RFLP-phenotype association studies is discussed. PMID:1678249

  4. Intraspecific and interspecific pair-wise seedling competition between exotic annual grasses and native perennials: Plant-soil relationships

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Few studies have examined plant-soil relationships in competitive arenas between exotic and native plants in the western United States. A pair-wise competitive design was used to evaluate plant-soil relationships between seedings of the exotic annual grasses Bromus tectorum and Taentherium caput-med...

  5. The structure of pairwise correlation in mouse primary visual cortex reveals functional organization in the absence of an orientation map.

    PubMed

    Denman, Daniel J; Contreras, Diego

    2014-10-01

    Neural responses to sensory stimuli are not independent. Pairwise correlation can reduce coding efficiency, occur independent of stimulus representation, or serve as an additional channel of information, depending on the timescale of correlation and the method of decoding. Any role for correlation depends on its magnitude and structure. In sensory areas with maps, like the orientation map in primary visual cortex (V1), correlation is strongly related to the underlying functional architecture, but it is unclear whether this correlation structure is an essential feature of the system or arises from the arrangement of cells in the map. We assessed the relationship between functional architecture and pairwise correlation by measuring both synchrony and correlated spike count variability in mouse V1, which lacks an orientation map. We observed significant pairwise synchrony, which was organized by distance and relative orientation preference between cells. We also observed nonzero correlated variability in both the anesthetized (0.16) and awake states (0.18). Our results indicate that the structure of pairwise correlation is maintained in the absence of an underlying anatomical organization and may be an organizing principle of the mammalian visual system preserved by nonrandom connectivity within local networks. PMID:23689635

  6. Pair-Wise Trajectory Management-Oceanic (PTM-O) . [Concept of Operations—Version 3.9

    NASA Technical Reports Server (NTRS)

    Jones, Kenneth M.

    2014-01-01

    This document describes the Pair-wise Trajectory Management-Oceanic (PTM-O) Concept of Operations (ConOps). Pair-wise Trajectory Management (PTM) is a concept that includes airborne and ground-based capabilities designed to enable and to benefit from, airborne pair-wise distance-monitoring capability. PTM includes the capabilities needed for the controller to issue a PTM clearance that resolves a conflict for a specific pair of aircraft. PTM avionics include the capabilities needed for the flight crew to manage their trajectory relative to specific designated aircraft. Pair-wise Trajectory Management PTM-Oceanic (PTM-O) is a regional specific application of the PTM concept. PTM is sponsored by the National Aeronautics and Space Administration (NASA) Concept and Technology Development Project (part of NASA's Airspace Systems Program). The goal of PTM is to use enhanced and distributed communications and surveillance along with airborne tools to permit reduced separation standards for given aircraft pairs, thereby increasing the capacity and efficiency of aircraft operations at a given altitude or volume of airspace.

  7. Higher Curvature Effects in the ADD and RS Models

    SciTech Connect

    Rizzo, Thomas G.; /SLAC

    2006-07-05

    Over the last few years several extra-dimensional models have been introduced in attempt to deal with the hierarchy problem. These models can lead to rather unique and spectacular signatures at Terascale colliders such as the LHC and ILC. The ADD and RS models, though quite distinct, have many common feature including a constant curvature bulk, localized Standard Model(SM) fields and the assumption of the validity of the EH action as a description of gravitational interactions.

  8. Stereovision Imaging in Smart Mobile Phone Using Add on Prisms

    NASA Astrophysics Data System (ADS)

    Bar-Magen Numhauser, Jonathan; Zalevsky, Zeev

    2014-03-01

    In this work we present the use of a prism-based add on component installed on top of a smart phone to achieve stereovision capabilities using iPhone mobile operating system. Through these components and the combination of the appropriate application programming interface and mathematical algorithms the obtained results will permit the analysis of possible enhancements for new uses to such system, in a variety of areas including medicine and communications.

  9. Randomized Controlled Trials of Add-On Antidepressants in Schizophrenia

    PubMed Central

    Joffe, Grigori; Stenberg, Jan-Henry

    2015-01-01

    Background: Despite adequate treatment with antipsychotics, a substantial number of patients with schizophrenia demonstrate only suboptimal clinical outcome. To overcome this challenge, various psychopharmacological combination strategies have been used, including antidepressants added to antipsychotics. Methods: To analyze the efficacy of add-on antidepressants for the treatment of negative, positive, cognitive, depressive, and antipsychotic-induced extrapyramidal symptoms in schizophrenia, published randomized controlled trials assessing the efficacy of adjunctive antidepressants in schizophrenia were reviewed using the following parameters: baseline clinical characteristics and number of patients, their on-going antipsychotic treatment, dosage of the add-on antidepressants, duration of the trial, efficacy measures, and outcomes. Results: There were 36 randomized controlled trials reported in 41 journal publications (n=1582). The antidepressants used were the selective serotonin reuptake inhibitors, duloxetine, imipramine, mianserin, mirtazapine, nefazodone, reboxetin, trazodone, and bupropion. Mirtazapine and mianserin showed somewhat consistent efficacy for negative symptoms and both seemed to enhance neurocognition. Trazodone and nefazodone appeared to improve the antipsychotics-induced extrapyramidal symptoms. Imipramine and duloxetine tended to improve depressive symptoms. No clear evidence supporting selective serotonin reuptake inhibitors’ efficacy on any clinical domain of schizophrenia was found. Add-on antidepressants did not worsen psychosis. Conclusions: Despite a substantial number of randomized controlled trials, the overall efficacy of add-on antidepressants in schizophrenia remains uncertain mainly due to methodological issues. Some differences in efficacy on several schizophrenia domains seem, however, to exist and to vary by the antidepressant subgroups—plausibly due to differences in the mechanisms of action. Antidepressants may not worsen

  10. Inferring Meta-covariates in Classification

    NASA Astrophysics Data System (ADS)

    Harris, Keith; McMillan, Lisa; Girolami, Mark

    This paper develops an alternative method for gene selection that combines model based clustering and binary classification. By averaging the covariates within the clusters obtained from model based clustering, we define “meta-covariates” and use them to build a probit regression model, thereby selecting clusters of similarly behaving genes, aiding interpretation. This simultaneous learning task is accomplished by an EM algorithm that optimises a single likelihood function which rewards good performance at both classification and clustering. We explore the performance of our methodology on a well known leukaemia dataset and use the Gene Ontology to interpret our results.