SPARQL is the W3C candidate recommendation query language for RDF. In this paper we address systematically the formal study of SPARQL, concentrating in its graph pattern facility. We consider for this study a fragment without literals and a simple version of filters which encompasses all the main issues yet is simple to formalize. We provide a

Object 944 Hidalgo is one of the asteroids most likely to be an extinct or dormant comet. Hidalgo's Tisserand invariant (T=2.07) suggests very strongly that this object originated either in the Kuiper belt or in the Oort cloud (Weissman et al. 2002). Our latest ground based results show significant rotational variability in the near-infrared

We present a Roche tomography reconstruction of the secondary star in the cataclysmic variable AE Aqr. The tomogram reveals several surface inhomogeneities that are due to the presence of large, cool star-spots. In addition to a number of lower latitude spots, the maps also show the presence of a large, high-latitude spot similar to that seen in

BF theory is a topological theory that can be seen as a natural generalization of 3-dimensional gravity to arbitrary dimensions. Here we show that the coupling to point particles that is natural in three dimensions generalizes in a direct way to BF theory in d dimensions coupled to (d-3)-branes. In the resulting model, the connection is flat except

We present Ks-band surface photometry of NGC 7690 (Hubble type Sab) and NGC 4593 (SBb). We find that, in both galaxies, a major part of the ``bulge'' is as flat as the disk and has approximately the same color as the inner disk. In other words, the ``bulges'' of these galaxies have disklike properties. We conclude that these are examples of `

We address the general problem of the luminosity-specific planetary nebula (PN) number, better known as the `α' ratio, given by α=NPN/Lgal, and its relationship with the age and metallicity of the parent stellar population. Our analysis relies on population synthesis models that account for simple stellar populations (SSPs), and more elaborate