Detection of Dispersed Radio Pulses: A machine learning approach to candidate identification and classification

Searching for extraterrestrial, transient signals in astronomical data sets is an active area of current research. However, machine learning techniques are lacking in the literature concerning single-pulse detection. This paper presents a new, two-stage approach for identifying and classifying dispersed pulse groups (DPGs) in single-pulse search output. The first stage identified DPGs and extracted features to characterize them using a new peak identification algorithm which tracks sloping tendencies around local maxima in plots of signal-to-noise ratio vs. dispersion measure. The second stage used supervised machine learning to classify DPGs. We created four benchmark data sets: one unbalanced and three balanced versions using three different imbalance treatments.We empirically evaluated 48 classifiers by training and testing binary and multiclass versions of six machine learning algorithms on each of the four benchmark versions. While each classifier had advantages and disadvantages, all classifiers with imbalance treatments had higher recall values than those with unbalanced data, regardless of the machine learning algorithm used. Based on the benchmarking results, we selected a subset of classifiers to classify the full, unlabelled data set of over 1.5 million DPGs identified in 42,405 observations made by the Green Bank Telescope. Overall, the classifiers using a multiclass ensemble tree learner in combination with two oversampling imbalance treatments were the most efficient; they identified additional known pulsars not in the benchmark data set and provided six potential discoveries, with significantly less false positives than the other classifiers.Comment: 13 pages, accepted for publication in MNRAS, ref. MN-15-1713-MJ.R

Application of Cytotoxicity Assays for Detection of Potentially Harmful Bioactive Compounds Produced by Freshwater Bloom-Forming Algae

Detection of harmful bioactive compounds produced by bloom-forming pelagic algae is important to assess the potential risks to communities. We applied two cell-based assays, an erythrocyte lysis assay (ELA) that assesses membrane integrity, and a RTgill-W1 cytotoxicity assay (RCA) that detects changes in cell metabolism, to evaluate the cytotoxic effects of: (1) individual toxins and noxious compounds; and (2) complex mixtures of compounds produced by cyanobacteria and chrysophyte isolates. ELA was insensitive to toxins and noxious compounds except at exceptionally high concentrations (EC50≥106 nM). RCA was sensitive to noxious compounds only, at concentrations greater than reported environmental averages (EC50≥103 nM). Cultured isolates produced bioactive compounds that had recognizable, dose dependent, toxic effects. Toxicity of these bioactive compounds depended on the taxa (cyanobacteria, not chrysophytes), growth stage (stationary phase more toxic than exponential phase), location (intracellular more toxic than extracellular), and iron status (iron-replete cells more toxic that iron-deplete cells)

Uniform Asymptotics for Polynomials Orthogonal With Respect to a General Class of Discrete Weights and Universality Results for Associated Ensembles: Announcement of Results

We compute the pointwise asymptotics of orthogonal polynomials with respect to a general class of pure point measures supported on finite sets as both the number of nodes of the measure and also the degree of the orthogonal polynomials become large. The class of orthogonal polynomials we consider includes as special cases the Krawtchouk and Hahn classical discrete orthogonal polynomials, but is far more general. In particular, we consider nodes that are not necessarily equally spaced. The asymptotic results are given with error bound for all points in the complex plane except for a finite union of discs of arbitrarily small but fixed radii. These exceptional discs are the neighborhoods of the so-called band edges of the associated equilibrium measure. As applications, we prove universality results for correlation functions of a general class of discrete orthogonal polynomial ensembles, and in particular we deduce asymptotic formulae with error bound for certain statistics relevant in the random tiling of a hexagon with rhombus-shaped tiles. The discrete orthogonal polynomials are characterized in terms of a a Riemann-Hilbert problem formulated for a meromorphic matrix with certain pole conditions. By extending the methods of [17, 22], we suggest a general and unifying approach to handle Riemann-Hilbert problems in the situation when poles of the unknown matrix are accumulating on some set in the asymptotic limit of interest.Comment: 28 pages, 7 figure

Session D1: Towards Effective, Bi-Directional Selective Fish Passage

Abstract: Barriers interfere with aquatic connectivity by preventing or limiting migratory fishes from spawning and other life history processes, and there is increasing pressure to restore connectivity. However, conflicting management objectives exist in many jurisdictions where barriers to fish movement inhibit the restoration of native fishes but protect native fish communities above barriers from undesirable invasive species. In the Laurentian Great Lakes, barriers are an important management tool in the control of invasive Sea Lampreys. Sea Lampreys remain highly destructive in the Great Lakes, and are a constant threat to a 7 billion dollar fishery. Developing selective, effective bi-directional fish passage to remove Sea Lampreys while allowing the passage of native fishes has become an issue of great importance for Great Lakes fisheries managers. To date, efforts have included a variety of approaches including velocity barriers, seasonal barriers, trap-and-sort fishways, and eel ladders. The integration of emerging technologies, such as push-pull and electrical and pheromone guidance and advances in engineering, such as eel-style ladder traps are providing hope that better selective, effective bi-directional fish passage solutions are possible. The Great Lakes Fishery Commission is developing a research theme specific to selective bi-directional fish passage in the hopes of resolving the conflict between aquatic fragmentation and invasive species control

A naturalistic study of medication reduction in a residential treatment setting

The primary aim of this pilot study was to ascertain if psychiatric medications could be reduced in a convenience sample of seriously emotionally disturbed children and adolescents over the course of residential treatment. We also sought to understand factors correlated with reduction in the number of medications during treatment. A review of the treatment of 141 patients (n = 112 admitted on medication and n = 29 admitted on no medication) admitted to, and discharged from, a residential treatment setting between 1992 and 2001 was undertaken. Significantly more children were discharged from treatment on no medications than were admitted to residential treatment on no medications. In children receiving more than 1 medication at admission, the number of combined medications was significantly reduced over the course of residential treatment. However, the majority of children admitted on medications continued on some psychiatric medications, indicating that psychopharmacology continued to play an important role in their treatment. In 112 patients admitted on psychoactive medications, our pilot data suggests that improvement in externalizing, internalizing, psychotic, and autistic psychopathology while in residential treatment, the presence of an intact family (adoptive or biological), the absence of a history of either sexual or physical abuse, and the type of medication used appear to be factors that correlate with a reduced use of medications in this population