Sub-milliarcsec-scale structure of the gravitational lens B1600+434

In the gravitational lens system B1600+434 the brighter image, A, is known to show rapid variability which is not detected in the weaker image, B (Koopmans & de Bruyn 2000). Since correlated variability is one of the fundamental properties of gravitational lensing, it has been proposed that image A is microlensed by stars in the halo of the lensing galaxy (Koopmans & de Bruyn 2000). We present VLBA observations of B1600+434 at 15 GHz with a resolution of 0.5 milliarcsec to determine the source structure at high spatial resolution. The surface brightness of the images are significantly different, with image A being more compact. This is in apparent contradiction with the required property of gravitational lensing that surface brightness be preserved. Our results suggest that both the lensed images may show two-sided elongation at this resolution, a morphology which does not necessarily favour superluminal motion. Instead these data may suggest that image B is scatter-broadened at the lens so that its size is larger than that of A, and hence scintillates less than image A.Comment: 4 pages, 2 figures, accepted in AA Letter

Organic Soil Management: Impacts on Yields, Soil Quality and Economics

Understanding organic management practices is a key in developing sustainable organic farming systems. We report the results of four different organic fertilization strategies in a field trial on yields, soil quality and economic performance. We found highest yields and economic performance in two direct plant feeding strategies. One of these strategies, a newly developed strategy based on biowaste compost (GFT) and an additional fertilizer performed well in terms of yields but looks also very promising in terms of soil quality and biodiversity. The economic perspective of this strategy renders it promising in regions with little animal manures

Concepts of Optimality and Their Uses

Lecture to the memory of Alfred Nobel, December 11, 1975allocation of resources;

Organic fertilisers of the mac trial and their impact on soil quality, environment and climate change

After 8 years, the MAC field trial in Lelystad, the Netherlands, shows the effects of different fertiliser strategies, ranging from animal manure to plant compost to mineral fertiliser. The impact on yield, soil quality, soil health, environment and climate change is discussed. The trial is unique in monitoring the effect of so many types of fertilisers over so many year

The inner mass power spectrum of galaxies using strong gravitational lensing: beyond linear approximation

In the last decade the detection of individual massive dark matter sub-halos has been possible using potential correction formalism in strong gravitational lens imaging. Here we propose a statistical formalism to relate strong gravitational lens surface brightness anomalies to the lens potential fluctuations arising from dark matter distribution in the lens galaxy. We consider these fluctuations as a Gaussian random field in addition to the unperturbed smooth lens model. This is very similar to weak lensing formalism and we show that in this way we can measure the power spectrum of these perturbations to the potential. We test the method by applying it to simulated mock lenses of different geometries and by performing an MCMC analysis of the theoretical power spectra. This method can measure density fluctuations in early type galaxies on scales of 1-10 kpc at typical rms-levels of a percent, using a single lens system observed with the Hubble Space Telescope with typical signal-to-noise ratios obtained in a single orbit

Electrocatalytic phenomena in gas phase reactions in solid electrolyte electrochemical cells

The recent literature on electrocatalysis and electrocatalytic phenomena occurring in gas phase reactions on solid, oxygen conducting electrolytes is reviewed. In this field there are a number of different subjects which are treated separately. These are: the use of electrochemical methods to study catalytic phenomena, electrocatalysis proper, the transfer of oxygen at the electrodes or electrolyte, and the (electro)catalytic properties of mixed, electronic and ionic, conducting materials

Balancing fertilization strategy with crop requirements in organic greenhouse cultivation of sweet pepper

An on-farm field trial was set up in an organic greenhouse in order to balance the N-uptake by a sweet pepper crop and the mineralization of the organic fertilizers was applied. The effects of six fertilizer treatments were compared regarding yield, nutrient availability and mineral balance. Application of high levels of compost turned out to be favourable in order to reduce surplusses of available-N on the short term. On the long term, such high levels of compost are unfavourable as a high pool of mineralizable-N in the soil organic matter restricts the possiblities for precise fertilization adapted to plant uptake. Application of lower levels of farm yard manure in combination with additional fertilization with feathermeal turned out to be a good fertilization strategy both on the short and the long term unless there is a need for minimizing salt levels in the applied fertilizers