Monsters and Babies from the FIRST/IRAS Survey

Radio continuum emission at cm wavelengths is relatively little affected by extinction. When combined with far-infrared (FIR) surveys this provides for a convenient and unbiased method to select (radio-loud) AGN and starbursts deeply embedded in gas and dust--rich galaxies. Such radio-selected FIR samples are useful for detailed investigations of the complex relationships between (radio) galaxy and starburst activity, and to determine whether ULIRGs are powered by hidden quasars (monsters) or young stars (babies). We present the results of a large program to obtain identifications and spectra of radio-selected, optically faint IRAS/FSC objects using the FIRST/VLA 20 cm survey. These objects are all radio-`quiet' in the sense that their radio power / FIR luminosities follow the well-known radio/FIR relationship for star forming galaxies. We compare these results to a previous study by our group of a sample of radio-`loud' IRAS/FSC ULIRGs selected from the Texas 365 MHz survey. Many of these objects also show evidence for dominant, A-type stellar populations, as well as high ionization lines usually associated with AGN. These radio-loud ULIRGs have properties intermediate between those of starbursts and quasars, suggesting a possible evolutionary connection. Deep Keck spectroscopic observations of three ULIRGs from these samples are presented, including high signal-to-noise spectropolarimetry. The polarimetry observations failed to show evidence of a hidden quasar in polarized (scattered) light in the two systems in which the stellar light was dominated by A-type stars. Although observations of a larger sample would be needed to allow a general conclusion, our current data suggest that a large fraction of ULIRGs may be powered by luminous starbursts, not by hidden, luminous AGN (quasars). [abridged]Comment: 6 Pages, including 2 PostScript figures. To appear in proceedings of "Ultraluminous Galaxies: Monsters and Babies", held at Ringberg Castle, Germany, 20-26 September 199

Anomalous HI kinematics in Centaurus A: evidence for jet-induced star formation

We present new 21-cm HI observations performed with ATCA of the large HI filament located about 15 kpc NE from the centre of Centaurus A and discovered by Schiminovich et al.(1994). This HI cloud is situated (in projection) near the radio jet of Centaurus A, as well as near a large filament of ionised gas of high excitation and turbulent velocities and near regions with young stars. The higher velocity and spatial resolution of the new data reveals that, apart from the smooth velocity gradient corresponding to the overall rotation of the cloud around Centaurus A, HI with anomalous velocities of about 100 km/s is present at the southern tip of this cloud. This is interpreted as evidence for an ongoing interaction between the radio jet and the HI cloud. Gas stripped from the HI cloud gives rise to the large filament of ionised gas and the star formation regions that are found downstream from the location of the interaction. The implied flow velocities are very similar to the observed anomalous HI velocities. Given the amount of HI with anomalous kinematics and the current star formation rate, the efficiency of jet-induced star formation is at most of the order of a percent.Comment: Accepted for publication in A&A, 7 pages, 4 figures. The full paper with high resolution images can be downloaded from http://www.astron.nl/~morganti/Papers/cena.paper.pd

Durability and service life of concrete repairs in the presence of cracks

Engineered Cementitious Composite (ECC) has been proposed to be one of the most promising repair materials due to its unique high ductility and tight crack width control. In concrete repairs, the shrinkage of repair materials is restrained by concrete substrate, and the repair material therefore often cracks. When ECC is used as repair material, the crack width is much smaller compared to normal concrete. The tight crack width of ECC retards the penetration of water and harmful substances and thus enhances the durability of concrete repairs. This paper is aimed to explore the chloride penetration in cracked ECC repairs and to assess the service life of the repair systems. Rapid chloride migration tests was conducted to investigate the chloride penetration profile. Based on the experimental results, the service life of repair systems was evaluated

Service life design for infrastructure

In the past few years more and more attention has been devoted to the safety and serviceability as well as durability and sustainability of structures. Meanwhile there are intensive research and development activities going on, e.g. on materials properties, deterioration mechanisms, geometric- and structural design, execution aspect and maintenance. Furthermore, codes and standards on service life design are being discussed and partially established world wide. It is now time to present a focused picture of the current status and future trends in this field, including theory, practice and education. The aim of the symposium is to provide a forum to researchers and practitioners for presenting the newest findings and to discuss new ideas on service life design and serviceability of infrastructural Works, effectiveness of service life design methods and experiences from the practice

From Branching to Linear Metric Domains (and back

is permitted for educational or research use on condition that this copyright notice is included in any copy. See back inner page for a list of recent publications in the BRICS Report Series. Copies may be obtained by contacting: BRIC

A generation-oriented workbench for performance grammar: Capturing linear order variability in German and Dutch

We describe a generation-oriented workbench for the Performance Grammar (PG) formalism, highlighting the treatment of certain word order and movement constraints in Dutch and German. PG enables a simple and uniform treatment of a heterogeneous collection of linear order phenomena in the domain of verb constructions (variably known as Cross-serial Dependencies, Verb Raising, Clause Union, Extraposition, Third Construction, Particle Hopping, etc.). The central data structures enabling this feature are clausal “topologies”: one-dimensional arrays associated with clauses, whose cells (“slots”) provide landing sites for the constituents of the clause. Movement operations are enabled by unification of lateral slots of topologies at adjacent levels of the clause hierarchy. The PGW generator assists the grammar developer in testing whether the implemented syntactic knowledge allows all and only the well-formed permutations of constituents

A generation-oriented workbench for performance grammar: Capturing linear order variability in German and Dutch

We describe a generation-oriented workbench for the Performance Grammar (PG) formalism, highlighting the treatment of certain word order and movement constraints in Dutch and German. PG enables a simple and uniform treatment of a heterogeneous collection of linear order phenomena in the domain of verb constructions (variably known as Cross-serial Dependencies, Verb Raising, Clause Union, Extraposition, Third Construction, Particle Hopping, etc.). The central data structures enabling this feature are clausal “topologies”: one-dimensional arrays associated with clauses, whose cells (“slots”) provide landing sites for the constituents of the clause. Movement operations are enabled by unification of lateral slots of topologies at adjacent levels of the clause hierarchy. The PGW generator assists the grammar developer in testing whether the implemented syntactic knowledge allows all and only the well-formed permutations of constituents

Extended reagions of radio emission not associated with the AGN phenomenon as sources of acceleration of cosmic rays: The case of cD galaxies

Diffuse, non-thermal extended emission not associated with the AGN phenomenon, found in many clusters of galaxies hosted by an AGN, are related to the acceleration of cosmic rays. In the current work we present preliminary evidence of absence of such formations in clusters of galaxies hosted by optically identified cD galaxies. Our subsample consists of three powerful low redshift radiogalaxies, centered in poor clusters of galaxies. We have searched for radio relics and (mini)halos which could be forming as a result of the confinement of cosmic rays by bubbles creayed by the AGN. We report on the work in progress.Comment: 4 pages, Conference HEPRO II

A Sample of 669 Ultra Steep Spectrum Radio Sources to Find High Redshift Radio Galaxies

Since radio sources with Ultra Steep Spectra (USS; alpha <~ -1.30; S ~ nu^alpha) are efficient tracers of high redshift radio galaxies (HzRGs), we have defined three samples of such USS sources using the recently completed WENSS, TEXAS, MRC, NVSS and PMN radio-surveys. Our combined sample contains 669 sources with S_1400 > 10 mJy and covers virtually the entire sky outside the Galactic plane (|b|>15). For our 2 largest samples, covering declination > -35, we selected only sources with angular sizes Theta < 1'. For 410 sources, we present radio-maps with 0.3" to ~5" resolution from VLA and ATCA observations or from the FIRST survey, which allows the optical identification of these radio sources. We find that the spectral index distribution of 143,000 sources from the WENSS and NVSS consists of a steep spectrum galaxy and a flat spectrum quasar population, with the relative contribution of flat spectrum sources doubling from S_1400 >0.1 Jy to S_1400 >2.5 Jy. The identification fraction of our USS sources on the POSS (R <~ 20) is as low as 15%, independent of spectral index alpha < -1.30. We further show that 85% of the USS sources that can be identified with an X-ray source are probably contained in galaxy clusters, and that alpha < -1.6 sources are excellent Galactic pulsar candidates, because the percentage of these sources is four times higher in the Galactic plane. Our sample has been constructed to start an intensive campaign to obtain a large sample of high redshift objects (z>3) that is selected in a way that does not suffer from dust extinction or any other optical bias [abridged].Comment: 28 Pages, 12 PostScript figures. Accepted for publication in Astronomy & Astrophysics Supplements. Appendices B, C & D available on http://www.strw.LeidenUniv.nl/~debreuck/paper