PKS 1004+13: A High-Inclination, Highly-Absorbed Radio-Loud QSO -- The First Radio-Loud BAL QSO at Low Redshift?

The existence of BAL outflows in only radio-quiet QSOs was thought to be an important clue to mass ejection and the radio-loud - radio-quiet dichotomy. Recently a few radio-loud BAL QSOs have been discovered at high redshift. We present evidence that PKS 1004+13 is a radio-loud BAL QSO. It would be the first known at low-redshift (z = 0.24), and one of the most radio luminous. For PKS 1004+13, there appear to be broad absorption troughs of O VI, N V, Si IV, and C IV, indicating high-ionization outflows up to about 10,000 km/s. There are also two strong, broad (~500 km/s), high-ionization, associated absorption systems that show partial covering of the continuum source. The strong UV absorption we have detected suggests that the extreme soft-X-ray weakness of PKS 1004+13 is primarily the result of absorption. The large radio-lobe dominance indicates BAL and associated gas at high inclinations to the central engine axis, perhaps in a line-of-sight that passes through an accretion disk wind.Comment: To appear in Ap.J. Letters, 1999 (June or July); 4 pages, 5 figure

Aanzienlijk verschil in productie tussen rode klaverrassen: In het project Rode Klaver 2.0 zijn persistentie en productiviteit van rode klaver onderzocht.

In de biologische melkveehouderij wordt veel gesproken over teruglopende grasopbrengsten. Rode klaver kan helpen het tij te keren. Niet alleen op maaipercelen maar ook op maai/weide percelen waar wordt omgeweid. Naast productie en voederwaarde is persistentie van rode klaverrassen hierbij een belangrijk kenmerk

Methodological tests of the use of trace elements as tracers to assess root activity

peer-reviewedN.J.H. was funded by the Irish Research Council, co-funded by Marie Curie Actions under FP7. The field experiments A, B and G were supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under the grant agreements FP7-266018 (AnimalChange) and FP7- 244983 (MultiSward). Experiment F was supported by the German Science Foundation (FOR 456).Background and aims There is increasing interest in how resource utilisation in grassland ecosystems is affected by changes in plant diversity and abiotic conditions. Research to date has mainly focussed on aboveground responses and there is limited insight into belowground processes. The aim of this study was to test a number of assumptions for the valid use of the trace elements caesium, lithium, rubidium and strontium as tracers to assess the root activity of several grassland species. Methods We carried out a series of experiments addressing the reliability of soil labelling, injection density, incubation time, application rate and the comparability of different tracers in a multiple tracer method. Results The results indicate that it is possible to achieve a reliable labelling of soil depths. Tracer injection density affected the variability but not the mean level of plant tracer concentrations. Tracer application rates should be based on pilot studies, because of site- and species-specific responses. The trace elements did not meet prerequisites to be used in a multiple tracer method. Conclusions The use of trace elements as tracers is potentially a very useful tool to give insight into plant root activity at different soil depths. This work highlights some of the main benefits and pitfalls of the method and provides specific recommendations to assist the design of tracer experiments and interpretation of the results.N.J.H. was funded by the Irish Research Council, co-funded by Marie Curie Actions under FP7. The field experiments A, B and G were supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under the grant agreements FP7-266018 (AnimalChange) and FP7- 244983 (MultiSward). Experiment F was supported by the German Science Foundation (FOR 456).European Unio

Thermohaline mixing in low-mass giants: RGB and beyond

Thermohaline mixing has recently been proposed to occur in low mass red giants, with large consequence for the chemical yields of low mass stars. We investigate the role of thermohaline mixing during the evolution of stars between 1 Msun and 3 Msun. We use a stellar evolution code which includes rotational mixing and internal magnetic fields. We confirm that thermohaline mixing has the potential to destroy most of the helium 3 which is produced earlier on the main sequence during the red giant stage, in stars below 1.5Msun. We find this process to continue during core helium burning and beyond. We find rotational and magnetic mixing to be negligible compared to the thermohaline mixing in the relevant layers, even if the interaction of thermohaline motions with the differential rotation may be essential to establish the time scale of thermohaline mixing in red giants.Comment: Proceedings of the Conference "Unsolved problems in stellar physics" - Cambridge, July 200

The Electron Glass in a Switchable Mirror: Relaxation, Aging and Universality

The rare earth hydride YH$_{3-\delta}$ can be tuned through the metal-insulator transition both by changing $\delta$ and by illumination with ultraviolet light. The transition is dominated by strong electron-electron interactions, with transport in the insulator sensitive to both a Coulomb gap and persistent quantum fluctuations. Via a systematic variation of UV illumination time, photon flux, Coulomb gap depth, and temperature, we demonstrate that polycrystalline YH$_{3-\delta}$ serves as a model system for studying the properties of the interacting electron glass. Prominent among its features are logarithmic relaxation, aging, and universal scaling of the conductivity

Measuring the Reduced Shear

Neglecting the second order corrections in weak lensing measurements can lead to a few percent uncertainties on cosmic shears, and becomes more important for cluster lensing mass reconstructions. Existing methods which claim to measure the reduced shears are not necessarily accurate to the second order when a point spread function (PSF) is present. We show that the method of Zhang (2008) exactly measures the reduced shears at the second order level in the presence of PSF. A simple theorem is provided for further confirming our calculation, and for judging the accuracy of any shear measurement method at the second order based on its properties at the first order. The method of Zhang (2008) is well defined mathematically. It does not require assumptions on the morphologies of galaxies and the PSF. To reach a sub-percent level accuracy, the CCD pixel size is required to be not larger than 1/3 of the Full Width at Half Maximum (FWHM) of the PSF. Using a large ensemble (> 10^7) of mock galaxies of unrestricted morphologies, we find that contaminations to the shear signals from the noise of background photons can be removed in a well defined way because they are not correlated with the source shapes. The residual shear measurement errors due to background noise are consistent with zero at the sub-percent level even when the amplitude of such noise reaches about 1/10 of the source flux within the half-light radius of the source. This limit can in principle be extended further with a larger galaxy ensemble in our simulations. On the other hand, the source Poisson noise remains to be a cause of systematic errors. For a sub-percent level accuracy, our method requires the amplitude of the source Poisson noise to be less than 1/80 ~ 1/100 of the source flux within the half-light radius of the source, corresponding to collecting roughly 10^4 source photons.Comment: 18 pages, 3 figures, 4 tables, minor changes from the previous versio

Evidence for Non-Hydrostatic Gas from the Cluster X-ray to Lensing Mass Ratio

Using a uniform analysis procedure, we measure spatially resolved weak gravitational lensing and hydrostatic X-ray masses for a sample of 18 clusters of galaxies. We find a radial trend in the X-ray to lensing mass ratio: at r2500 we obtain a ratio MX/ML=1.03+/-0.07 which decreases to MX/ML=0.78+/-0.09 at r500. This difference is significant at 3 sigma once we account for correlations between the measurements. We show that correcting the lensing mass for excess correlated structure outside the virial radius slightly reduces, but does not eliminate this trend. An X-ray mass underestimate, perhaps due to nonthermal pressure support, can explain the residual trend. The trend is not correlated with the presence or absence of a cool core. We also examine the cluster gas fraction and find no correlation with ML, an important result for techniques that aim to determine cosmological parameters using the gas fraction.Comment: 8 pages, minor modifications, accepted for publication in MNRA

Assessing simulations of daily temperature and precipitation variability with global climate models for present and enhanced greenhouse climates

The enhanced greenhouse climates of five different global climate models are examined with reference to the ability of the models to characterize the frequency of extreme events on both a regional and global scale. Ten years of model output for both control and enhanced greenhouse conditions are utilized to derive return periods for extreme temperature and precipitation events and to characterize the variability of the model climate at both regional and global scales. Under enhanced greenhouse conditions, return periods for extreme precipitation events are shorter and there is a general increase in the intensity of precipitation and number of wet spells in most areas. There is a decrease in frequency of cold temperature extremes and an increase in hot extremes in many areas. The results show a reasonable level of agreement between the models in terms of global scale variability, but the difference between model simulations of precipitation on a regional scale suggests that model derived estimates of variability changes must be carefully justified

Ion distribution and ablation depth measurements of a fs-ps laser-irradiated solid tin target

The ablation of solid tin surfaces by an 800-nanometer-wavelength laser is studied for a pulse length range from 500 fs to 4.5 ps and a fluence range spanning 0.9 to 22 J/cm^2. The ablation depth and volume are obtained employing a high-numerical-aperture optical microscope, while the ion yield and energy distributions are obtained from a set of Faraday cups set up under various angles. We found a slight increase of the ion yield for an increasing pulse length, while the ablation depth is slightly decreasing. The ablation volume remained constant as a function of pulse length. The ablation depth follows a two-region logarithmic dependence on the fluence, in agreement with the available literature and theory. In the examined fluence range, the ion yield angular distribution is sharply peaked along the target normal at low fluences but rapidly broadens with increasing fluence. The total ionization fraction increases monotonically with fluence to a 5-6% maximum, which is substantially lower than the typical ionization fractions obtained with nanosecond-pulse ablation. The angular distribution of the ions does not depend on the laser pulse length within the measurement uncertainty. These results are of particular interest for the possible utilization of fs-ps laser systems in plasma sources of extreme ultraviolet light for nanolithography.Comment: 8 pages, 7 figure

The Effect of Grassland Management on Bovine Nitrogen Efficiency

Nitrogen (N) losses through grazing bovines are at the heart of the current debate on environment and agriculture. N utilisation of grazing bovines is predominantly determined by the form and amount of energy and protein in their diet, which in Ireland consists mainly of grazed grass. The two main problems of grazed grass with respect to animal N utilisation are 1) the imbalance between total N content and energy content, and 2) the lack of synchronisation between the release of N and carbohydrates in the rumen. It was hypothesised that both the balance and synchronisation of N and energy in herbage could be improved through grassland management. The objective of this study was to study the effect of grassland management on herbage carbohydrate and protein fractionation