Quality Assessment of Linked Datasets using Probabilistic Approximation

With the increasing application of Linked Open Data, assessing the quality of datasets by computing quality metrics becomes an issue of crucial importance. For large and evolving datasets, an exact, deterministic computation of the quality metrics is too time consuming or expensive. We employ probabilistic techniques such as Reservoir Sampling, Bloom Filters and Clustering Coefficient estimation for implementing a broad set of data quality metrics in an approximate but sufficiently accurate way. Our implementation is integrated in the comprehensive data quality assessment framework Luzzu. We evaluated its performance and accuracy on Linked Open Datasets of broad relevance.Comment: 15 pages, 2 figures, To appear in ESWC 2015 proceeding

Player Tracking and Stroke Recognition in Tennis Video

In this paper we present an investigation into the computer vision problem of tracking humans in digital video. The investigation domain is digital tennis footage and the aim is to track the tennis player and recognise the strokes played. The motivation behind this investigation is to eventually automate the task of digital tennis footage annotation so that metadata, such as the time codes and a description of the strokes played, are automatically appended to the video. This then enables a number of compelling applications, from simple search facilities for the home viewer, to more complex analysis tools suitable for a tennis coach. The system developed solves the problem of tennis player tracking and stroke recognition using relatively simple, and well known, image processing operations constrained by an a priori knowledge of the image capture conditions, the background scene, and the application domain

Virtue and austerity

Virtue ethics is often proposed as a third way in health-care ethics, that while consequentialism and deontology focus on action guidelines, virtue focuses on character; all three aim to help agents discern morally right action although virtue seems to have least to contribute to political issues, such as austerity. I claim: (1) This is a bad way to characterize virtue ethics. The 20th century renaissance of virtue ethics was first proposed as a response to the difficulty of making sense of ‘moral rightness’ outside a religious context. For Aristotle the right action is that which is practically best; that means best for the agent in order to live a flourishing life.There are no moral considerations besides this. (2) Properly characterized, virtue ethics can contribute to discussion of austerity. A criticism of virtue ethics is that fixed characteristics seem a bad idea in ever-changing environments; perhaps we should be generous in prosperity, selfish in austerity. Furthermore, empirical evidence suggests that people indeed do change with their environment. However, I argue that virtues concern fixed values not fixed behaviour; the values underlying virtue allow for different behaviour in different circumstances: in austerity, virtues still give the agent the best chance of flourishing. Two questions arise. (a) In austere environments might not injustice help an individual flourish by, say, obtaining material goods? No, because unjust acts undermine the type of society the agent needs for flourishing. (b) What good is virtue to those lacking the other means to flourish? The notion of degrees of flourishing shows that most people would benefit somewhat from virtue. However, in extreme circumstances virtue might harm rather than benefit the agent: such circumstances are to be avoided; virtue ethics thus has a political agenda to enable flourishing. This requires justice, a fortiori when in austerity

The star-formation rate in the host of GRB 990712

We have observed the host galaxy of GRB 990712 at 1.4 GHz with the Australia Telescope Compact Array, to obtain an estimate of its total star-formation rate. We do not detect a source at the position of the host. The 2 sigma upper limit of 70 microJy implies that the total star-formation rate is lower than 100 Msun/yr, using conservative values for the spectral index and cosmological parameters. This upper limit is in stark contrast with recent reports of radio/submillimeter-determined star-formation rates of roughly 500 Msun/yr for two other GRB host galaxies. Our observations present the deepest radio-determined star-formation rate limit on a GRB host galaxy yet, and show that also from the unobscured radio point-of-view, not every GRB host galaxy is a vigorous starburst.Comment: A&A Letters, in press, 5 pages; a high-resolution color gif version of the paper figure is also supplie

Discharge Readiness After Liver Transplant Is Not One Size Fits All

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/162709/2/lt25864_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/162709/1/lt25864.pd

Creation of Electron--Positron Wind in Gamma-Ray Bursts and Its Effect on the Early Afterglow Emission

We calculate the creation of electron--positron pairs in Gamma-Ray Bursts (GRBs) resulting from the collision between scattered and outward moving gamma-ray photons. The number of pairs exceeds the number of ambient medium electrons encountered by the GRB ejecta up to ~ 10^{16} cm from the center of explosion. The shock resulting from the interaction of the ejecta with the pair-wind may brighten the afterglow synchrotron emission during the first few minutes. Even without this effect, the peak intensity of the optical afterglow increases with the density of the surrounding medium. Therefore, observations of the optical flux at early times constrain the density of the circumburst medium. If the electron and magnetic field energies behind the forward shock sweeping-up the pair-wind and the circumburst medium are as inferred from fits to the broadband afterglow emission at 0.5-100 days, then the current upper limits on the optical counterpart emission, set by the ROTSE and LOTIS experiments, indicate that the circumburst medium within 0.01 pc is less dense than 100 cm^{-3} or, if a wind, corresponds to a progenitor mass-loss to wind speed ratio below 10^{-6} M_sun/yr/(1000 km/s).Comment: 9 pages, submitted to MNRAS in 200

Convergence of random zeros on complex manifolds

We show that the zeros of random sequences of Gaussian systems of polynomials of increasing degree almost surely converge to the expected limit distribution under very general hypotheses. In particular, the normalized distribution of zeros of systems of m polynomials of degree N, orthonormalized on a regular compact subset K of C^m, almost surely converge to the equilibrium measure on K as the degree N goes to infinity.Comment: 16 page

The host of the SN-less GRB 060505 in high resolution

The spiral host galaxy of GRB 060505 at z=0.089 was the site of a puzzling long duration burst without an accompanying supernova. Studies of the burst environment by Th\"one et al. (2008) suggested that this GRB came from the collapse of a massive star and that the GRB site was a region with properties different from the rest of the galaxy. We reobserved the galaxy in high spatial resolution using the VIMOS integral-field unit (IFU) at the VLT with a spaxel size of 0.67 arcsec. Furthermore, we use long slit high resolution data from HIRES/Keck at two different slit positions covering the GRB site, the center of the galaxy and an HII region next to the GRB region. We compare the properties of different HII regions in the galaxy with the GRB site and study the global and local kinematic properties of this galaxy. The resolved data show that the GRB site has the lowest metallicity in the galaxy with around 1/3 Z_solar, but its specific SFR (SSFR) of 7.4 M_solar/yr/L/L* and age (determined by the Halpha EW) are similar to other HII regions in the host. The galaxy shows a gradient in metallicity and SSFR from the bulge to the outskirts as it is common for spiral galaxies. This gives further support to the theory that GRBs prefer regions of higher star-formation and lower metallicity, which, in S-type galaxies, are more easily found in the spiral arms than in the centre. Kinematic measurements of the galaxy do not show evidence for large perturbations but a minor merger in the past cannot be excluded. This study confirms the collapsar origin of GRB060505 but reveals that the properties of the HII region surrounding the GRB were not unique to that galaxy. Spatially resolved observations are key to know the implications and interpretations of unresolved GRB hosts observations at higher redshifts.Comment: 15 pages, 16 figures, 6 tables; resubmitted to MNRAS after minor revision

Multi-color Optical and NIR Light Curves of 64 Stripped-Envelope Core-Collapse Supernovae

We present a densely-sampled, homogeneous set of light curves of 64 low redshift (z < 0.05) stripped-envelope supernovae (SN of type IIb, Ib, Ic and Ic-bl). These data were obtained between 2001 and 2009 at the Fred L. Whipple Observatory (FLWO) on Mt. Hopkins in Arizona, with the optical FLWO 1.2-m and the near-infrared PAIRITEL 1.3-m telescopes. Our dataset consists of 4543 optical photometric measurements on 61 SN, including a combination of UBVRI, UBVr'i', and u'BVr'i', and 2142 JHKs near-infrared measurements on 25 SN. This sample constitutes the most extensive multi-color data set of stripped-envelope SN to date. Our photometry is based on template-subtracted images to eliminate any potential host galaxy light contamination. This work presents these photometric data, compares them with data in the literature, and estimates basic statistical quantities: date of maximum, color, and photometric properties. We identify promising color trends that may permit the identification of stripped-envelope SN subtypes from their photometry alone. Many of these SN were observed spectroscopically by the CfA SN group, and the spectra are presented in a companion paper (Modjaz et al. 2014). A thorough exploration that combines the CfA photometry and spectroscopy of stripped-envelope core-collapse SN will be presented in a follow-up paper.Comment: 26 pages, 17 figures, 8 tables. Revised version resubmitted to ApJ Supplements after referee report. Additional online material is available through http://cosmo.nyu.edu/SNYU

The Afterglow, Energetics and Host Galaxy of the Short-Hard Gamma-Ray Burst 051221a

We present detailed optical, X-ray and radio observations of the bright afterglow of the short gamma-ray burst 051221a obtained with Gemini, Swift/XRT, and the Very Large Array, as well as optical spectra from which we measure the redshift of the burst, z=0.5464. At this redshift the isotropic-equivalent prompt energy release was about 1.5 x 10^51 erg, and using the standard afterglow synchrotron model we find that the blastwave kinetic energy is similar, E_K,iso ~ 8.4 x 10^51 erg. An observed jet break at t ~ 5 days indicates that the opening angle is ~ 7 degrees and the total beaming-corrected energy is therefore ~ 2.5 x 10^49 erg, comparable to the values inferred for previous short GRBs. We further show that the burst experienced an episode of energy injection by a factor of 3.4 between t=1.4 and 3.4 hours, which was accompanied by reverse shock emission in the radio band. This result provides continued evidence that the central engines of short GRBs may be active significantly longer than the duration of the burst and/or produce a wide range of Lorentz factors. Finally, we show that the host galaxy of GRB051221a is actively forming stars at a rate of about 1.6 M_solar/yr, but at the same time exhibits evidence for an appreciable population of old stars (~ 1 Gyr) and near solar metallicity. The lack of bright supernova emission and the low circumburst density (n ~ 10^-3 cm^-3) continue to support the idea that short bursts are not related to the death of massive stars and are instead consistent with a compact object merger. Given that the total energy release is a factor of ~ 10 larger than the predicted yield for a neutrino annihilation mechanism, this suggests that magnetohydrodynamic processes may be required to power the burst.Comment: Final version (to appear in ApJ on 20 September 2006