Are the Luminosities of RR Lyrae Stars Affected by Second Parameter Effects?

There is a serious discrepancy between the distance to the LMC derived from the Cepheid Period-Luminosity relation and that obtained by using the Galactic calibration for the luminosity of RR Lyrae stars. It is suggested that this problem might be due to the fact that second parameter effects make it inappropriate to apply Galactic calibrations to RR Lyrae variables in the Magellanic Clouds, i.e. Mv(RR) could depend on both [Fe/H] and on one or more second parameters.Comment: 10 pages as uuencoded compressed Postscript. Also available at http://www.dao.nrc.ca/DAO/SCIENCE/science.htm

Rotating solenoidal perfect fluids of Petrov type D

We prove that aligned Petrov type D perfect fluids for which the vorticity vector is not orthogonal to the plane of repeated principal null directions and for which the magnetic part of the Weyl tensor with respect to the fluid velocity has vanishing divergence, are necessarily purely electric or locally rotationally symmetric. The LRS metrics are presented explicitly.Comment: 6 pages, no figure

Perseverance of perverse subsidies and their impact on trade and the environment

Theoretical and empirical aspects of policy failures due to subsidies are discussed in the context of international trade. A general classification of subsidies that cause environmental externalities is presented. The economic and environmental impacts of producer subsidies on international trade are examined with partial equilibrium analysis. The magnitude and economic and environmental relevance of subsidies in various sectors is assessed on the basis of empirical indicators. Finally, suggestions are provided on how subsidy-related policy failures can be eliminated at national and international levels. © 2001 Elsevier Science B.V

Shapley-Ames Galaxies in the Blue and Infrared

The Shapley-Ames Catalog of 1276 galaxies with B < 12.5 is compared with the Sanders et al. all sky sample of the 629 galaxies with 60 m flux density > 5.24 Jy. The fraction of Shapley-Ames galaxies that are visible in the IR is found to increase from 0.006 for E or E/S0 galaxies to 0.384 for Sc galaxies. The subset of Shapley-Ames galaxies that are detected in the IR has a median blue luminosity that is ~0.8 mag fainter than that of all Shapley-Ames galaxies. Most of this difference is due to the fact that late-type galaxies (which contain dust and hot stars) are systematically less luminous in blue light than are early-type galaxies. Within individual stages along the Hubble sequence no significant differences are found between the luminosity distributions in blue light of galaxies that were detected in the infrared and those that were not. However, our data show a puzzling exception (significant at 99.9%) for SBc galaxies. For reasons that are not understood Shapley-Ames SBc galaxies, that are visible in the IR, are more luminous in blue light than those SBc galaxies that are not detected in the infrared. An other peculiarity of the data is that Shapley-Ames Sc galaxies galaxies are (at 99.6% confidence) more luminous than objects of type SBc .Comment: 11 pages. no figures. To be published in the Astronomical Journa

Shear-free perfect fluids with a solenoidal electric curvature

We prove that the vorticity or the expansion vanishes for any shear-free perfect fluid solution of the Einstein field equations where the pressure satisfies a barotropic equation of state and the spatial divergence of the electric part of the Weyl tensor is zero.Comment: 9 page

Purely radiative perfect fluids

We study `purely radiative' (div E = div H = 0) and geodesic perfect fluids with non-constant pressure and show that the Bianchi class A perfect fluids can be uniquely characterized --modulo the class of purely electric and (pseudo-)spherically symmetric universes-- as those models for which the magnetic and electric part of the Weyl tensor and the shear are simultaneously diagonalizable. For the case of constant pressure the same conclusion holds provided one also assumes that the fluid is irrotational.Comment: 12 pages, minor grammatical change

A New Method for the Determination of the Hubble Parameter

By chance, the slope of the Mv(max) versus (B-V)max relation for recent theoretical models of supernovae of Type Ia (SNe Ia) by Hoflich & Khokhlov is indistinguishable from the slope of a reddening line in the V versus B-V plane. This coincidence allows one to determine a parameter Mv*(max) for SNe Ia that is independent of both supernova detonation model and of interstellar reddening. Calibrating Mv*(max) with observations of SNe Ia by Hamuy et al. yields values of the Hubble parameter Ho in the range 55 - 60 km s-1 Mpc-1 . The discrepancy between this result, and values of Ho recently obtained from observations of Cepheids in the Virgo cluster, suggests that either (1) the Cepheid distance scale is wrong, (2) the SN Ia models of Hoflich & Khokhlov are too bright by ~ 0.75 mag near maximum light, or (3) their models are too red by \~ 0.25 mag in B-V.Comment: 12 pages and 1 figure as uuencoded compressed Postscript. Also available at http://www.dao.nrc.ca/DAO/SCIENCE/science.htm

Measuring the Economic Value of Two Habitat Defragmentation Policy Scenarios for the Veluwe, The Netherlands

This paper offers an economic value assessment of a nature protection programme in the Veluwe. This programme involves two defragmentation scenarios: the first scenario connects the central part of the Veluwe with the IJssel river forelands in a north-eastern direction, while the second scenario is focused on defragmentation in a south-western direction, where the Rhine river forelands are located. The valuation is based on a questionnaire that was administered during face-to-face interviews in the Veluwe area and through the Internet. We employ a contingent valuation approach to assess the respondents’ willingness to pay for the realisation of the defragmentation scenarios. It appears that the mean willingness to pay for the two defragmentation scenarios are € 59.7 and € 162.2 per respondent. These two willingness-to-pay estimates, which refer to a lump sum payment (or ‘once-and-for-all payment’), are based on a lognormal and Weibull distribution respectively. In addition to the willingness to pay, we also estimate recreation benefits of the Veluwe. To that end, we use the travel cost technique, the purpose of which is to arrive at an estimate of the site’s consumer surplus. According to this technique, the yearly recreational benefits are estimated between € 0.06 and € 0.45 per visitor. Whereas the former estimate is based on the fuel costs only, the latter covers also insurance and maintenance costs, and capital depreciation. Finally, we performed an aggregation of individual WTP estimates over Dutch households. With the resulting aggregate estimates we are able to compare the total costs and benefits of the two scenarios for habitat fragmentation in the Veluwe. The result of such a simple comparison turns out to critically depend on whether the mean or median estimate is used for aggregation. If aggregation of individual WTP estimates is based on mean values, then the benefits far exceed the estimated costs of defragmentation. In other words, based on an integrated economic-ecological analysis it makes sense to execute the defragmentation measures described in the scenarios. However, aggregate estimates obtained by using median values result in higher costs than aggregate estimates that are based on mean values. Even stronger, median-based estimates show that the costs of implementing scenario 2 are higher than the total benefits of this scenario.Economic value, Nature protection, Defragmentation policy, Veluwe