3,165 research outputs found

    Boundary limit theory for functional local to unity regression

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    This paper studies functional local unit root models (FLURs) in which the autoregressive coeļ¬€icient may vary with time in the vicinity of unity. We extend conventional local to unity (LUR) models by allowing the localizing coeļ¬€icient to be a function which characterizes departures from unity that may occur within the sample in both stationary and explosive directions. Such models enhance the flexibility of the LUR framework by including break point, trending, and multi-directional departures from unit autoregressive coeļ¬€icients. We study the behavior of this model as the localizing function diverges, thereby determining the impact on the time series and on inference from the time series as the limits of the domain of deļ¬nition of the autoregressive coeļ¬€icient are approached. This boundary limit theory enables us to characterize the asymptotic form of power functions for associated unit root tests against functional alternatives. Both sequential and simultaneous limits (as the sample size and localizing coeļ¬€icient diverge) are developed. We ļ¬nd that asymptotics for the process, the autoregressive estimate, and its tt statistic have boundary limit behavior that diļ¬€ers from standard limit theory in both explosive and stationary cases. Some novel features of the boundary limit theory are the presence of a segmented limit process for the time series in the stationary direction and a degenerate process in the explosive direction. These features have material implications for autoregressive estimation and inference which are examined in the paper

    Exploring the Effect of Crowd Management Measures on Passengersā€™ Behaviour at Metro Stations

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    To reduce problems of interaction at the platform train interface (PTI) platform edge doors (PEDs) and markings on the platform are used as door positions indicators. The common methods to study the effect of these measures are based on average values of density using Fruinā€™s Level of Service (LOS), however identification cannot be made of which part of the PTI is more congested. To solve this problem, a new method is proposed. The method included a conceptual model in which the PTI was discretised into 40Ā cm square cells to identify which part of the platform is more congested. Passengersā€™ behaviour was recorded considering two situations before the train arrives: i) passengers waiting in front of the doors; ii) passengers waiting beside the doors. Observation was done at existing stations at Metro de Santiago and London Underground. Results show that PEDs changed the behaviour of passengers as they were located beside the doors rather than in front of them. In addition, when markings were used on the platform, then this behaviour was reinforced. Therefore, it is recommended to use this method to better design the PTI rather than the LOS which is used to design the whole platform. Further research is needed to study the effect of PEDs on passengers with reduced mobility

    Chiral Symmetry Breaking and External Fields in the Kuperstein-Sonnenschein Model

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    A novel holographic model of chiral symmetry breaking has been proposed by Kuperstein and Sonnenschein by embedding non-supersymmetric probe D7 and anti-D7 branes in the Klebanov-Witten background. We study the dynamics of the probe flavours in this model in the presence of finite temperature and a constant electromagnetic field. In keeping with the weakly coupled field theory intuition, we find the magnetic field promotes spontaneous breaking of chiral symmetry whereas the electric field restores it. The former effect is universally known as the "magnetic catalysis" in chiral symmetry breaking. In the presence of an electric field such a condensation is inhibited and a current flows. Thus we are faced with a steady-state situation rather than a system in equilibrium. We conjecture a definition of thermodynamic free energy for this steady-state phase and using this proposal we study the detailed phase structure when both electric and magnetic fields are present in two representative configurations: mutually perpendicular and parallel.Comment: 50 pages, multiple figures, minor typo fixed, references adde

    Holographic DC conductivities from the open string metric

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    We study the DC conductivities of various holographic models using the open string metric (OSM), which is an effective metric geometrizing density and electromagnetic field effect. We propose a new way to compute the nonlinear conductivity using OSM. As far as the final conductivity formula is concerned, it is equivalent to the Karch-O'Bannon's real-action method. However, it yields a geometrical insight and technical simplifications. Especially, a real-action condition is interpreted as a regular geometry condition of OSM. As applications of the OSM method, we study several holographic models on the quantum Hall effect and strange metal. By comparing a Lifshitz background and the Light-Cone AdS, we show how an extra parameter can change the temperature scaling behavior of conductivity. Finally we discuss how OSM can be used to study other transport coefficients, such as diffusion constant, and effective temperature induced by the effective world volume horizon.Comment: 33 page

    Conservation genomics reveals possible illegal trade routes and admixture across pangolin lineages in Southeast Asia

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    The use of genome-wide genetic markers is an emerging approach for informing evidence-based management decisions for highly threatened species. Pangolins are the most heavily trafficked mammals across illegal wildlife trade globally, but critically endangered Sunda pangolins (Manis javanica) have not been widely studied in insular Southeast Asia. We usedā€‰>ā€‰12,000 single nucleotide polymorphic markers (SNPs) to assign pangolin seizures from illegal trade of unknown origin to possible geographic sources via genetic clustering with pangolins of known origin. Our SNPs reveal three previously unrecognized genetic lineages of Sunda pangolins, possibly from Borneo, Java and Singapore/Sumatra. The seizure assignments suggest the majority of pangolins were traded from Borneo to Java. Using mitochondrial markers did not provide the same resolution of pangolin lineages, and to explore if admixture might explain these differences, we applied sophisticated tests of introgression usingā€‰>ā€‰2000 SNPs to investigate secondary gene flow between each of the three Sunda pangolin lineages. It is possible the admixture which we discovered is due to human-mediated movements of pangolins. Our findings impact a range of conservation actions, including tracing patterns of trade, repatriation of rescue animals, and conservation breeding. In order to conserve genetic diversity, we suggest that, pending further research, each pangolin lineage should as a precaution be protected and managed as an evolutionarily distinct conservation unit

    Association and interaction analyses of eight genes under asthma linkage peaks

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    Background: Linkage studies have implicated the 2q33, 9p21, 11q13 and 20q13 regions in the regulation of allergic disease. The aim of this study was to test genetic variants in candidate genes from these regions for association with specific asthma traits. Methods: Ninety-five single nucleotide polymorphisms (SNP) located in eight genes (CD28, CTLA4, ICOS, ADAM23, ADAMTSL1, MS4A2, CDH26 and HRH3) were genotyped in >5000 individuals from Australian (n = 1162), Dutch (n = 99) and Danish (n = 303) families. Traits tested included doctor-diagnosed asthma, atopy, airway obstruction, total serum immunoglobulin (Ig) E levels and eosinophilia. Association was tested using both multivariate and univariate methods, with gene-wide thresholds for significance determined through simulation. Gene-by-gene and gene-by-environment analyses were also performed. Results: There was no overall evidence for association with seven of the eight genes tested when considering all genetic variation assayed in each gene. The exception was MS4A2 on chromosome 11q13, which showed weak evidence for association with IgE (gene-wide P < 0.05, rs502581). There were no significant gene-by-gene or gene-by-environment interaction effects after accounting for the number of tests performed. Conclusions: The individual variants genotyped in the 2q33, 9p21 and 20q13 regions do not explain a large fraction of the variation in the quantitative traits tested or have a major impact on asthma or atopy risk. Our results are consistent with a weak effect of MS4A2 polymorphisms on the variation of total IgE levels. Ā© 2009 John Wiley & Sons A/S

    On Poincare and logarithmic Sobolev inequalities for a class of singular Gibbs measures

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    This note, mostly expository, is devoted to Poincar{\'e} and log-Sobolev inequalities for a class of Boltzmann-Gibbs measures with singular interaction. Such measures allow to model one-dimensional particles with confinement and singular pair interaction. The functional inequalities come from convexity. We prove and characterize optimality in the case of quadratic confinement via a factorization of the measure. This optimality phenomenon holds for all beta Hermite ensembles including the Gaussian unitary ensemble, a famous exactly solvable model of random matrix theory. We further explore exact solvability by reviewing the relation to Dyson-Ornstein-Uhlenbeck diffusion dynamics admitting the Hermite-Lassalle orthogonal polynomials as a complete set of eigenfunctions. We also discuss the consequence of the log-Sobolev inequality in terms of concentration of measure for Lipschitz functions such as maxima and linear statistics.Comment: Minor improvements. To appear in Geometric Aspects of Functional Analysis -- Israel Seminar (GAFA) 2017-2019", Lecture Notes in Mathematics 225

    Susceptibility to Peer Pressure, Self-Esteem, and Health Locus of Control as Correlates of Adolescent Substance Abuse

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    As part of a school-based alcohol misuse prevention study, questionnaires were ad ministered to 2,589 fifth and sixth grade students to determine levels of use of alcohol, marijuana, and cigarettes, intentions to use these substances, and problems resulting from alcohol misuse. The questionnaire also included 45 items concerning susceptibil ity to peer pressure, self-esteem, and health locus of control. These 45 items were factor analyzed separately for two groups formed by random assignment. Six factors were identified which were both internally consistent and replicable, and indices were constructed. The indices measuring susceptibility to peer pressure, self-esteem, and internal health locus of control were significantly and negatively correlated with most of the substance use, misuse, and intention items, and an external health locus of con trol index was not significantly related to most of the substance use, misuse, and inten tion items. The "Susceptibility to Peer Pressure" index correlated more highly with the adolescent substance use, misuse, and intention items than the self-esteem or the health locus of control indices, and it had the highest alpha coefficient. Implications for the design of school-based substance abuse prevention programs are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68065/2/10.1177_109019818701400207.pd
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