Variable selection and updating in model-based discriminant analysis for high dimensional data with food authenticity applications

Food authenticity studies are concerned with determining if food samples have been correctly labelled or not. Discriminant analysis methods are an integral part of the methodology for food authentication. Motivated by food authenticity applications, a model-based discriminant analysis method that includes variable selection is presented. The discriminant analysis model is fitted in a semi-supervised manner using both labeled and unlabeled data. The method is shown to give excellent classification performance on several high-dimensional multiclass food authenticity datasets with more variables than observations. The variables selected by the proposed method provide information about which variables are meaningful for classification purposes. A headlong search strategy for variable selection is shown to be efficient in terms of computation and achieves excellent classification performance. In applications to several food authenticity datasets, our proposed method outperformed default implementations of Random Forests, AdaBoost, transductive SVMs and Bayesian Multinomial Regression by substantial margins

The effects of inspiratory muscle training in older adults

Purpose: Declining inspiratory muscle function and structure and systemic low-level inflammation and oxidative stress may contribute to morbidity and mortality during normal ageing. Therefore, we examined the effects of inspiratory muscle training (IMT) in older adults on inspiratory muscle function and structure and systemic inflammation and oxidative stress, and re-examined the reported positive effects of IMT on respiratory muscle strength, inspiratory muscle endurance, spirometry, exercise performance, physical activity levels (PAL) and quality of life (QoL). Methods: Thirty-four healthy older adults (68 ± 3 years) with normal spirometry, respiratory muscle strength and physical fitness were divided equally into a pressure-threshold IMT or sham-hypoxic placebo group. Before and after an 8 week intervention, measurements were taken for dynamic inspiratory muscle function and inspiratory muscle endurance using a weighted plunger pressure-threshold loading device, diaphragm thickness using B-mode ultrasonography, plasma cytokine concentrations using immunoassays, DNA damage levels in peripheral blood mononuclear cells (PBMC) using Comet Assays, spirometry, maximal mouth pressures, exercise performance using a six minute walk test, PAL using a questionnaire and accelerometry, and QoL using a questionnaire

Deepening democracy within Ireland's social partnership

Ireland's social partnership process, now under attack from a number of quarters, has repeatedly been charged with being 'undemocratic' in that it undermines the sovereign position of elected political representatives, with key policy formulation and decision-making taking place in fora outside the institutions of representative democracy. These critiques echo those against new forms of networked governance more globally. A key question therefore is how (and if) democracy may be deepened within social partnership or its potential successor(s). This article addresses this question by employing a post-liberal democratic framework to examine social partnership in practice, and by drawing lessons from another partnership process, Malawi's PRSP. Drawing from Malawi's experience, it is argued that democracy can be deepened within social partnership when governance deliberations and negotiations are conducted under conditions of vibrant public debate and genuine perspective-based representation, and when the communicative and discursive norms are widened to allow for such representation

Refined saddle-point preconditioners for discretized Stokes problems

This paper is concerned with the implementation of efficient solution algorithms for elliptic problems with constraints. We establish theory which shows that including a simple scaling within well-established block diagonal preconditioners for Stokes problems can result in significantly faster convergence when applying the preconditioned MINRES method. The codes used in the numerical studies are available online

Unveiling the nature of INTEGRAL objects through optical spectroscopy. VIII. Identification of 44 newly detected hard X-ray sources

(abridged) Hard X-ray surveys performed by the INTEGRAL satellite have discovered a conspicuous fraction (up to 30%) of unidentified objects among the detected sources. Here we continue our identification program by selecting probable optical candidates using positional cross-correlation with soft X-ray, radio, and/or optical archives, and performing optical spectroscopy on them. As a result, we identified or more accurately characterized 44 counterparts of INTEGRAL sources: 32 active galactic nuclei, with redshift 0.019 < z < 0.6058, 6 cataclysmic variables (CVs), 5 high-mass X-ray binaries (2 of which in the Small Magellanic Cloud), and 1 low-mass X-ray binary. This was achieved by using 7 telescopes of various sizes and archival data from two online spectroscopic surveys. The main physical parameters of these hard X-ray sources were also determined using the available multiwavelength information. AGNs are the most abundant population among hard X-ray objects, and our results confirm this tendency when optical spectroscopy is used as an identification tool. The deeper sensitivity of recent INTEGRAL surveys enables one to begin detecting hard X-ray emission above 20 keV from sources such as LINER-type AGNs and non-magnetic CVs.Comment: 22 pages, 14 figures, 6 tables, accepted for publication on A&A, main journa

Unveiling the nature of INTEGRAL objects through optical spectroscopy. IX. 22 more identifications, and a glance into the far hard X-ray Universe

(Abridged) Since its launch in October 2002, the INTEGRAL satellite has revolutionized our knowledge of the hard X-ray sky thanks to its unprecedented imaging capabilities and source detection positional accuracy above 20 keV. Nevertheless, many of the newly-detected sources in the INTEGRAL sky surveys are of unknown nature. The combined use of available information at longer wavelengths (mainly soft X-rays and radio) and of optical spectroscopy on the putative counterparts of these new hard X-ray objects allows us to pinpoint their exact nature. Continuing our long-standing program that has been running since 2004, and using 6 different telescopes of various sizes, we report the classification through optical spectroscopy of 22 more unidentified or poorly studied high-energy sources detected with the IBIS instrument onboard INTEGRAL. We found that 16 of them are active galactic nuclei (AGNs), while the remaining 6 objects are within our Galaxy. Among the identified extragalactic sources, 14 are Type 1 AGNs; of these, 6 lie at redshift larger than 0.5 and one has z = 3.12, which makes it the second farthest object detected in the INTEGRAL surveys up to now. The remaining AGNs are of type 2, and one of them is a pair of interacting Seyfert 2 galaxies. The Galactic objects are identified as two cataclysmic variables, one high-mass X-ray binary, one symbiotic binary and two chromospherically active stars. We thus still find that AGNs are the most abundant population among hard X-ray objects identified through optical spectroscopy. Moreover, we note that the higher sensitivity of the more recent INTEGRAL surveys is now enabling the detection of high-redshift AGNs, thus allowing the exploration of the most distant hard X-ray emitting sources and possibly of the most extreme blazars.Comment: 18 pages, 9 figures, 8 tables, accepted for publication on Astronomy & Astrophysics, main journa

Random Convex Hulls and Extreme Value Statistics

In this paper we study the statistical properties of convex hulls of $N$ random points in a plane chosen according to a given distribution. The points may be chosen independently or they may be correlated. After a non-exhaustive survey of the somewhat sporadic literature and diverse methods used in the random convex hull problem, we present a unifying approach, based on the notion of support function of a closed curve and the associated Cauchy's formulae, that allows us to compute exactly the mean perimeter and the mean area enclosed by the convex polygon both in case of independent as well as correlated points. Our method demonstrates a beautiful link between the random convex hull problem and the subject of extreme value statistics. As an example of correlated points, we study here in detail the case when the points represent the vertices of $n$ independent random walks. In the continuum time limit this reduces to $n$ independent planar Brownian trajectories for which we compute exactly, for all $n$, the mean perimeter and the mean area of their global convex hull. Our results have relevant applications in ecology in estimating the home range of a herd of animals. Some of these results were announced recently in a short communication [Phys. Rev. Lett. {\bf 103}, 140602 (2009)].Comment: 61 pages (pedagogical review); invited contribution to the special issue of J. Stat. Phys. celebrating the 50 years of Yeshiba/Rutgers meeting

The ACS Virgo Cluster Survey X. Half-light Radii of Globular Clusters in Early-Type Galaxies: Environmental Dependencies and a Standard Ruler for Distance Estimation

We have measured half-light radii, r_h, for globular clusters (GCs) belonging to the 100 early-type galaxies observed in the ACS Virgo Cluster Survey and the elliptical galaxy NGC 4697. An analysis of the dependencies of the measured r_h on both the properties of the GCs themselves and their host galaxies reveals that the average r_h increases with increasing galactocentric distance or, alternatively, with decreasing galaxy surface brightness. For the first time, we find that the average r_h decreases with the host galaxy color. We also show that there is no evidence for a variation of r_h with the luminosity of the GCs. Finally, we find in agreement with previous observations that the average r_h depends on the color of GCs, with red GCs being ~17% smaller than their blue counterparts. We show that this difference is probably a consequence of an intrinsic mechanism, rather than projection effects, and that it is in good agreement with the mechanism proposed in Jordan (2004). We discuss these findings in light of two simple pictures for the origin of the r_h of GCs and show that both lead to a behavior in rough agreement with the observations. After accounting for the dependencies found we show that the average GC half-light radii can be successfully used as a standard ruler for distance estimation. We outline the methodology, and provide a calibration for its use. We find = 2.7 +- 0.35 pc for GCs with (g-z)=1.2 mag in a galaxy with color (g-z)_{gal}=1.5 mag and at an underlying surface z-band brightness of mu_z = 21 mag arcsec^{-2}. Using this technique, we place an upper limit of 3.4 Mpc on the 1-sigma line-of-sight depth of the Virgo Cluster. Finally, we examine the form of the r_h distribution for our sample galaxies and provide an analytic expression which successfully describes this distribution. (Abridged)Comment: 18 pages, 13 figures. Accepted for publication in ApJ. Also available at http://www.physics.rutgers.edu/~pcote/acs/publications.htm