Cardiac myoglobin deficit has evolved repeatedly in teleost fishes

Peer reviewedPublisher PD

Statistical Evidence for Three classes of Gamma-ray Bursts

Two different multivariate clustering techniques, the K-means partitioning method and the Dirichlet process of mixture modeling, have been applied to the BATSE Gamma-ray burst (GRB) catalog, to obtain the optimum number of coherent groups. In the standard paradigm, GRB are classified in only two groups, the long and short bursts. However, for both the clustering techniques, the optimal number of classes was found to be three, a result which is consistent with previous statistical analysis. In this classification, the long bursts are further divided into two groups which are primarily differentiated by their total fluence and duration and hence are named low and high fluence GRB. Analysis of GRB with known red-shifts and spectral parameters suggests that low fluence GRB have nearly constant isotropic energy output of 10^{52} ergs while for the high fluence ones, the energy output ranges from 10^{52} to 10^{54} ergs. It is speculated that the three kinds of GRBs reflect three different origins: mergers of neutron star systems, mergers between white dwarfs and neutron stars, and collapse of massive stars.Comment: 7 pages, accepted for publication in the Astrophysical Journal. Minor editorial change

Significance analysis and statistical mechanics: an application to clustering

This paper addresses the statistical significance of structures in random data: Given a set of vectors and a measure of mutual similarity, how likely does a subset of these vectors form a cluster with enhanced similarity among its elements? The computation of this cluster p-value for randomly distributed vectors is mapped onto a well-defined problem of statistical mechanics. We solve this problem analytically, establishing a connection between the physics of quenched disorder and multiple testing statistics in clustering and related problems. In an application to gene expression data, we find a remarkable link between the statistical significance of a cluster and the functional relationships between its genes.Comment: to appear in Phys. Rev. Let

A Dedicated M-Dwarf Planet Search Using The Hobby-Eberly Telescope

We present first results of our planet search program using the 9.2 meter Hobby-Eberly Telescope (HET) at McDonald Observatory to detect planets around M-type dwarf stars via high-precision radial velocity (RV) measurements. Although more than 100 extrasolar planets have been found around solar-type stars of spectral type F to K, there is only a single M-dwarf (GJ 876, Delfosse et al. 1998; Marcy et al. 1998; Marcy et al. 2001) known to harbor a planetary system. With the current incompleteness of Doppler surveys with respect to M-dwarfs, it is not yet possible to decide whether this is due to a fundamental difference in the formation history and overall frequency of planetary systems in the low-mass regime of the Hertzsprung-Russell diagram, or simply an observational bias. Our HET M-dwarf survey plans to survey 100 M-dwarfs in the next 3 to 4 years with the primary goal to answer this question. Here we present the results from the first year of the survey which show that our routine RV-precision for M-dwarfs is 6 m/s. We found that GJ 864 and GJ 913 are binary systems with yet undetermined periods, while 5 out of 39 M-dwarfs reveal a high RV-scatter and represent candidates for having short-periodic planetary companions. For one of them, GJ 436 (rms = 20.6 m/s), we have already obtained follow-up observations but no periodic signal is present in the RV-data.Comment: 12 pages, 14 figures, accepted for publication in the Astronomical Journa

Predictive Value of Biomarkers for Normal and Pathological Ageing in a Rat Model

Sub-optimal diets are widely known to be associated with disease. This study investigated two questions: first, whether a Western affluent diet affects long-term health in the rat, and second, whether, and to what extent, early changes in blood biomarkers can predict specific pathologies. A rat model was used in which animals were fed from weaning either a control diet or a high fat, low protein, energy dense Western affluent diet. Rats were harvested at either 12 or 18 months, and at these time points blood samples were taken and various clinical biomarkers measured using a hospital analyser or by ELISA. Predictive biomarkers should show small changes at early time points and larger changes at later time-points, and be associated with disease(s). Tissues were examined for overt pathology, and data were mined to establish links between pathologies and specific blood markers that might be used predictively. Results showed that the Western affluent diet is associated with ill-health, with a relative risk of developing disease 4.5 times higher than for the control diet. Furthermore we conclude that triacylglycerol, HDL cholesterol, the ratio of total cholesterol to HDL cholesterol, creatinine and alanine aminotransferase were good predictors of disease as across the cohorts they showed altered levels before the clinical development of pathologies, in agreement with our hypothesis

Revisiting rho 1 Cancri e: A New Mass Determination Of The Transiting super-Earth

We present a mass determination for the transiting super-Earth rho 1 Cancri e based on nearly 700 precise radial velocity (RV) measurements. This extensive RV data set consists of data collected by the McDonald Observatory planet search and published data from Lick and Keck observatories (Fischer et al. 2008). We obtained 212 RV measurements with the Tull Coude Spectrograph at the Harlan J. Smith 2.7 m Telescope and combined them with a new Doppler reduction of the 131 spectra that we have taken in 2003-2004 with the High-Resolution-Spectrograph (HRS) at the Hobby-Eberly Telescope (HET) for the original discovery of rho 1 Cancri e. Using this large data set we obtain a 5-planet Keplerian orbital solution for the system and measure an RV semi-amplitude of K = 6.29 +/- 0.21 m/s for rho 1 Cnc e and determine a mass of 8.37 +/- 0.38 M_Earth. The uncertainty in mass is thus less than 5%. This planet was previously found to transit its parent star (Winn et al. 2011, Demory et al. 2011), which allowed them to estimate its radius. Combined with the latest radius estimate from Gillon et al. (2012), we obtain a mean density of rho = 4.50 +/- 0.20 g/cm^3. The location of rho 1 Cnc e in the mass-radius diagram suggests that the planet contains a significant amount of volitales, possibly a water-rich envelope surrounding a rocky core.Comment: 16 pages, 5 figures, accepted for publication in the Astrophysical Journal (the 300+ RV measurements will be published as online tables or can be obtained from the author

Rainbow trout (Oncorhynchus mykiss) urea cycle and polyamine synthesis gene families show dynamic expression responses to inflammation

The research was supported by a studentship to T. Clark funded between the University of Aberdeen and BioMar Ltd.Peer reviewedPostprin

Elemental Abundances of Solar Sibling Candidates

Dynamical information along with survey data on metallicity and in some cases age have been used recently by some authors to search for candidates of stars that were born in the cluster where the Sun formed. We have acquired high resolution, high signal-to-noise ratio spectra for 30 of these objects to determine, using detailed elemental abundance analysis, if they could be true solar siblings. Only two of the candidates are found to have solar chemical composition. Updated modeling of the stars' past orbits in a realistic Galactic potential reveals that one of them, HD162826, satisfies both chemical and dynamical conditions for being a sibling of the Sun. Measurements of rare-element abundances for this star further confirm its solar composition, with the only possible exception of Sm. Analysis of long-term high-precision radial velocity data rules out the presence of hot Jupiters and confirms that this star is not in a binary system. We find that chemical tagging does not necessarily benefit from studying as many elements as possible, but instead from identifying and carefully measuring the abundances of those elements which show large star-to-star scatter at a given metallicity. Future searches employing data products from ongoing massive astrometric and spectroscopic surveys can be optimized by acknowledging this fact.Comment: ApJ, in press. Tables 2 and 4 are available in full in the "Other formats: source" downloa