L^p boundedness of the wave operator for the one dimensional Schroedinger operator

Given a one dimensional perturbed Schroedinger operator H=-(d/dx)^2+V(x) we consider the associated wave operators W_+, W_- defined as the strong L^2 limits as s-> \pm\infty of the operators e^{isH} e^{-isH_0} We prove that the wave operators are bounded operators on L^p for all 1<p<\infty, provided (1+|x|)^2 V(x) is integrable, or else (1+|x|)V(x) is integrable and 0 is not a resonance. For p=\infty we obtain an estimate in terms of the Hilbert transform. Some applications to dispersive estimates for equations with variable rough coefficients are given.Comment: 26 page

Supermassive Binaries and Extragalactic Jets

Some quasars show Doppler shifted broad emission line peaks. I give new statistics of the occurrence of these peaks and show that, while the most spectacular cases are in quasars with strong radio jets inclined to the line of sight, they are also almost as common in radio-quiet quasars. Theories of the origin of the peaks are reviewed and it is argued that the displaced peaks are most likely produced by the supermassive binary model. The separations of the peaks in the 3C 390.3-type objects are consistent with orientation-dependent "unified models" of quasar activity. If the supermassive binary model is correct, all members of "the jet set" (astrophysical objects showing jets) could be binaries.Comment: 31 pages, PostScript, missing figure is in ApJ 464, L105 (see http://www.aas.org/ApJ/v464n2/5736/5736.html

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

Biocontrol of Pythium in the pea rhizosphere by antifungal metabolite producing and non-producing Pseudomonas strains

The definitive version is available at www.blackwell-synergy.com. Copyright Blackwell Publishing DOI : 10.1046/j.1365-2672.2001.01260.xFour well-described strains of Pseudomonas fluorescens were assessed for their effect upon pea growth and their antagonistic activity against large Pythium ultimum inocula. The effect of Pseudomonas strains upon the indigenous soil microflora, soil enzyme activities and plant growth in the presence and absence of Pythium is assessed. Pythium inoculation reduced the shoot and root weights, root length, and the number of lateral roots. The effect of Pythium was reduced by the Pseudomonas strains as follows: F113, SBW25 and CHAO increased the shoot weights (by 20%, 22% and 35% respectively); strains Q2-87, SBW25 and CHAO increased root weights (14%, 14% and 52%); Strains SBW25 and CHAO increased the root lengths (19% and 69%), and increased the number of lateral roots (14% and 29%). All the Pseudomonas strains reduced the number of lesions and the root and soil Pythium populations, whilst SBW25 and CHAO increased the number of lateral roots. Pythium inoculation increased root and soil microbial populations but the magnitude of this effect was Pseudomonas strain specific. Pythium increased the activity of C, N and P cycle enzymes, whilst the Pseudomonas strains reduced this effect, indicating reduced plant damage. Overall, strains SBW25 and CHAO had the greatest beneficial characteristics as these strains produced the greatest reductions in the side effects of Pythium infection (microbial populations and enzyme activities) and resulted in significantly improved plant growth. Surprisingly strain SBW25 does not produce antifungal metabolites, and its biocontrol activity was related to a greater colonisation ability in the rhizosphere.Peer reviewe

A SCUBA Galaxy in the Protocluster around 53W002 at z=2.4

We analyse an 850-um SCUBA map of the environment of the z=2.39 radio galaxy 53W002, which has been shown to reside in an over-density of Ly-alpha detected galaxies. We identify four luminous submillimeter (submm) sources within a 2.3' (1.2Mpc at z=2.39) diameter area around the radio galaxy (which itself is a weak submm source). We employ a 1.4-GHz map to accurately locate the counterpart of one of these sources, SMMJ17142+5016, and identify this source with a narrow-line AGN with an extended Ly-alpha halo at z=2.390 which is member of the structure around 53W002. Hence SMMJ17142+5016 is the first spectroscopically-confirmed, submm-selected companion to a high-redshift radio galaxy. We discuss the OHS JHK spectrum of this galaxy and in addition present five new constraints on its spectral energy distribution longward of 1um, using these to estimate its bolometric luminosity as ~8x10^12 Lo, or a star formation rate of ~1000Mo/yr if young stars provide the bulk of the luminosity. This result provides direct support for the statistical detection of over-densities of SCUBA galaxies around high-redshift radio galaxies and confirms theoretical predictions that SCUBA galaxies, as the progenitors of massive ellipticals, should be strongly clustered in the highest density regions of the distant Universe.Comment: ApJ, in press, 8 pages, 3 figure

Carbon fractions in the rhizosphere of pea inoculated with 2,4 diacetylphloroglucinol producing and non-producing Pseudomonas fluorescens F113

The definitive version is available at www.blackwell-synergy.com. Copyright Blackwell Publishing DOI : 10.1046/j.1365-2672.1999.00809.xThe aim of this work was to determine the effect of wild type and functionally modified Pseudomonas fluorescens strains on C fractions in the rhizosphere of pea. The lacZY marked F113 strain produces the antibiotic 2,4 diacetylphloroglucinol (DAPG) useful in plant disease control. The modified strain of F113 was repressed in production of DAPG, creating the DAPG negative strain F113 G22. The F113 treatment resulted in a significantly lower shoot/root ratio. The F113 G22 treatment had a significantly greater indigenous and total fluorescent Pseudomonas population than the control and F113 (DAPG+) treatment. Both strains significantly increased the water soluble carbohydrates and the total water soluble carbon in the pea rhizosphere soil. Strain F113 significantly increased the soil protein content relative to the control but not in relation to the F113 G22 treatment. The F113 treatment had a significantly greater organic acid content than the control and F113 G22 treatments, whilst the F113 G22 treatment was also significantly greater than the control. Both inocula resulted in significantly lower phosphate contents than the control. The F113 inocula significantly increased alkaline phosphatase, sulphatase and urease activities, and reduced glucosidase activities indicating increased carbon availability. Both inocula increased C availability, however, antibiotic production by strain F113 reduced the utilisation of organic acids released from the plant resulting in differing effects of the two strains on nutrient availability, plant growth, soil enzyme activities and Pseudomonas populations.Peer reviewe