Wireworm Control using Fodder Rape and Mustard – evaluating the use of brassica green manures for the control of wireworm (Agriotes spp.) in organic crops

In a field experiment at ADAS Pwllpeiran in 2001, brassica green manures were grown for 6 weeks and dug in before planting King Edward potatoes, to see if they suppressed wireworm in the crop. There was a trend for potatoes grown after mustard to suffer less damage from both wireworms and slugs than potatoes grown after fodder rape or no green manure, but the differences were not significant. Further trials, with longer green manuring periods, are needed to establish if there is a benefit, and whether the breakdown products of brassica green manures are toxic to wireworms

Empirical Uncertainty Estimators for Astrometry from Digital Databases

In order to understand the positional uncertainties of arbitrary objects in several of the current major databases containing astrometric information, a sample of extragalactic radio sources with precise positions in the International Celestial Reference Frame (ICRF) is compared with the available positions of their optical counterparts. The discrepancies between the radio and various optical positions are used to derive empirical uncertainty estimators for the USNO-A2.0, USNO-A1.0, Guide Star Selection System (GSSS) images, and the first and second Digitized Sky Surveys (DSS-I and DSS-II). In addition, an estimate of the uncertainty when the USNO-A2.0 catalog is transferred to different image data is provided. These optical astrometric frame uncertainties can in some cases be the dominant error term when cross-identifying sources at different wavelengths.Comment: 12 pages including 2 figures and 1 table. Accepted for publication in The Astronomical Journal, October 1999. Values in Table 1 for DSS I corrected 99-07-1

The finite representation property for composition, intersection, domain and range

We prove that the nite representation property holds for rep- resentation by partial functions for the signature consisting of composition, intersection, domain and range and for any expansion of this signature by the antidomain, xset, preferential union, maximum iterate and opposite opera- tions. The proof shows that, for all these signatures, the size of base required is bounded by a double-exponential function of the size of the algebra. This establishes that representability of nite algebras is decidable for all these signatures. We also give an example of a signature for which the nite repre- sentation property fails to hold for representation by partial functions

The GSC-II-based survey of ancient cool white dwarfs I. The sample of spectroscopically confirmed WDs

The GSC-II white dwarf survey was designed to identify faint and high proper motion objects, which we used to define a new and independent sample of cool white dwarfs. With this survey we aim to derive new constraints on the halo white dwarf space density. Also, these data can provide information on the age of thick disk and halo through the analysis of the luminosity function. On the basis of astrometric and photometric parameters, we selected candidates with mu > 0.28 as/yr and R_F > 16 in an area of 1150 square degrees. Then, we separated white dwarfs from late type dwarfs and subdwarfs by means of the reduced proper motion diagram. Finally, spectroscopic follow-up observations were carried out to confirm the white dwarf nature of the selected candidates. We found 41 white dwarfs of which 24 are new discoveries. Here we present the full sample and for each object provide positions, absolute proper motions, photometry, and spectroscopy.Comment: 14 pages, 7 figures, submitted to A&

Five supernova survey galaxies in the southern hemisphere. II. The supernova rates

Based on the database compiled in the first article of this series, with 56 SN events discovered in 3838 galaxies of the southern hemisphere, we compute the rate of supernovae (SNe) of different types along the Hubble sequence normalized to the optical and near-infrared luminosities as well as to the stellar mass of the galaxies. We find that the rates of all SN types show a dependence on both morphology and colors of the galaxies, and therefore, on the star-formation activity. The rate of core-collapse (CC) SNe is confirmed to be closely related to the Star Formation Rate (SFR) and only indirectly to the total mass of the galaxies. The rate of SNe Ia can be explained by assuming that at least 15% of Ia events in spiral galaxies originates in relatively young stellar populations. We find that the rates show no modulation with nuclear activity or environment. The ratio of SN rates between types Ib/c and II shows no trend with spiral type.Comment: 13 pages, 2 figures, 5 tables, published in Astrophysics (English translation of Astrofizika