Regularized Ordinal Regression and the ordinalNet R Package

Regularization techniques such as the lasso (Tibshirani 1996) and elastic net (Zou and Hastie 2005) can be used to improve regression model coefficient estimation and prediction accuracy, as well as to perform variable selection. Ordinal regression models are widely used in applications where the use of regularization could be beneficial; however, these models are not included in many popular software packages for regularized regression. We propose a coordinate descent algorithm to fit a broad class of ordinal regression models with an elastic net penalty. Furthermore, we demonstrate that each model in this class generalizes to a more flexible form, for instance to accommodate unordered categorical data. We introduce an elastic net penalty class that applies to both model forms. Additionally, this penalty can be used to shrink a non-ordinal model toward its ordinal counterpart. Finally, we introduce the R package ordinalNet, which implements the algorithm for this model class

Scalable data abstractions for distributed parallel computations

The ability to express a program as a hierarchical composition of parts is an essential tool in managing the complexity of software and a key abstraction this provides is to separate the representation of data from the computation. Many current parallel programming models use a shared memory model to provide data abstraction but this doesn't scale well with large numbers of cores due to non-determinism and access latency. This paper proposes a simple programming model that allows scalable parallel programs to be expressed with distributed representations of data and it provides the programmer with the flexibility to employ shared or distributed styles of data-parallelism where applicable. It is capable of an efficient implementation, and with the provision of a small set of primitive capabilities in the hardware, it can be compiled to operate directly on the hardware, in the same way stack-based allocation operates for subroutines in sequential machines

Narrow band optical heterodyne detection

Narrowband optical heterodyne detectio

Wavelet Analysis and Lognormal Distributions in GRBs

A wavelet analysis has been performed on 80 intense gamma-ray bursts GRBs) from the BATSE 3B catalog with durations longer than 2 seconds. The wavelet analysis applied novel features developed for edge detection in image processing and this filtering process was used to extract a fit to the irregular GRB profile from the background. A straightforward algorithm was subsequently used to identify statistically significant peaks in this profile. The areas and FWHM of 270 peaks that were characterised as isolated were found to be consistent with lognormal distributions. The distribution of time intervals between peak maxima for all 963 identified peaks in the GRBs is also presented.Comment: 5 pages, 4 figure

The nature of GRB-selected submillimeter galaxies: hot and young

We present detailed fits of the spectral energy distributions (SEDs) of four submillimeter (submm) galaxies selected by the presence of a gamma-ray burst (GRB) event (GRBs 980703, 000210, 000418 and 010222). These faint ~3 mJy submm emitters at redshift ~1 are characterized by an unusual combination of long- and short-wavelength properties, namely enhanced submm and/or radio emission combined with optical faintness and blue colors. We exclude an active galactic nucleus as the source of long-wavelength emission. From the SED fits we conclude that the four galaxies are young (ages <2 Gyr), highly starforming (star formation rates ~150 MSun/yr), low-mass (stellar masses ~10^10 MSun) and dusty (dust masses ~3x10^8 MSun). Their high dust temperatures (Td>45 K) indicate that GRB host galaxies are hotter, younger, and less massive counterparts to submm-selected galaxies detected so far. Future facilities like Herschel, JCMT/SCUBA-2 and ALMA will test this hypothesis enabling measurement of dust temperatures of fainter GRB-selected galaxies.Comment: 9 pages, 2 figures, submitted to ApJ, for SED templates, see http://archive.dark-cosmology.dk

Gamma-ray bursts and X-ray melting of material as a potential source of chondrules and planets

The intense radiation from a gamma-ray burst (GRB) is shown to be capable of melting stony material at distances up to 300 light years which subsequently cool to form chondrules. These conditions were created in the laboratory for the first time when millimeter sized pellets were placed in a vacuum chamber in the white synchrotron beam at the European Synchrotron Radiation Facility (ESRF). The pellets were rapidly heated in the X-ray and gamma-ray furnace to above 1400 C melted and cooled. This process heats from the inside unlike normal furnaces. The melted spherical samples were examined with a range of techniques and found to have microstructural properties similar to the chondrules that come from meteorites. This experiment demonstrates that GRBs can melt precursor material to form chondrules that may subsequently influence the formation of planets. This work extends the field of laboratory astrophysics to include high power synchrotron sources.Comment: 8 pages, 10 figures. Proceedings of the 5th INTEGRAL Workshop, Munich 16-20 February 2004. High resolution figures available at http://bermuda.ucd.ie/%7Esmcbreen/papers/duggan_01.pd

Systematic review and meta-analysis of the sero-epidemiological association between Epstein-Barr virus and rheumatoid arthritis

Acknowledgements The authors would like to thank Cynthia Fraser for helping run the literature search, Dr Neil Basu for providing advice on search terms for rheumatoid arthritis and to Xueli Jia, Katie Bannister and Kubra Boza for their help with foreign language papers. The authors would also like to thank the University of Aberdeen librarians at the Foresterhill medical library for their help in locating articles used for this systematic review and meta-analysis.Peer reviewedPublisher PD

Establishing the potential for using routine data on Incapacity Benefit to assess the local impact of policy initiatives

&lt;i&gt;Background&lt;/i&gt;: Incapacity Benefit (IB) is the key contributory benefit for people who are incapable of work because of illness or disability. &lt;i&gt;Methods&lt;/i&gt;: The aims were to establish the utility of routinely collected data for local evaluation and to provide a descriptive epidemiology of the IB population in Glasgow and Scotland for the period 2000–05 using data supplied by the Department for Work and Pensions. &lt;i&gt;Results&lt;/i&gt;: Glasgow's IB population is large in absolute and relative terms but is now falling, mainly due to a decrease in on flow. Claimants, tend to be older, have a poor work history and suffer from mental health problems. The rate of decline has been greater in Glasgow than Scotland, although the rate of on flow is still higher. &lt;i&gt;Conclusions&lt;/i&gt;: Department for Work and Pensions (DWP) data can be used locally to provide important insights into the dynamics of the IB population. However, to be truly useful, more work needs to be undertaken to combine the DWP data with other information

Dual partially harmonic tensors and Brauer-Schur-Weyl duality

Let $V$ be a $2m$-dimensional symplectic vector space over an algebraically closed field $K$. Let \mbb_n^{(f)} be the two-sided ideal of the Brauer algebra \mbb_n(-2m) over $K$ generated by $e_1e_3... e_{2f-1}$, where $0\leq f\leq [n/2]$. Let $\mathcal{HT}_{f}^{\otimes n}$ be the subspace of partially harmonic tensors of valence $f$ in $V^{\otimes n}$. In this paper, we prove that $\dim\mathcal{HT}_f^{\otimes n}$ and \dim\End_{KSp(V)}\Bigl(V^{\otimes n}/V^{\otimes n}\mbb_n^{(f)}\Bigr) are both independent of $K$, and the natural homomorphism from \mbb_n(-2m)/\mbb_n^{(f)} to \End_{KSp(V)}\Bigl(V^{\otimes n}/V^{\otimes n}\mbb_n^{(f)}\Bigr) is always surjective. We show that $\mathcal{HT}_{f}^{\otimes n}$ has a Weyl filtration and is isomorphic to the dual of V^{\otimes n}\mbb_n^{(f)}/V^{\otimes n}\mbb_n^{(f+1)} as a $Sp(V)$-(\mbb_n(-2m)/\mbb_n^{(f+1)})-bimodule. We obtain a $Sp(V)$-\mbb_n-bimodules filtration of $V^{\otimes n}$ such that each successive quotient is isomorphic to some \nabla(\lam)\otimes z_{g,\lam}\mbb_n with \lam\vdash n-2g, \ell(\lam)\leq m and $0\leq g\leq [n/2]$, where \nabla(\lam) is the co-Weyl module associated to \lam and z_{g,\lam} is an explicitly constructed maximal vector of weight \lam. As a byproduct, we show that each right \mbb_n-module z_{g,\lam}\mbb_n is integrally defined and stable under base change