Thomson scattering in a low-pressure neon mercury positive column

The electron density and the electron temperature in a low-pressure neon mercury positive column are determined using Thomson scattering. Special attention has been given to the stray light reduction in the Thomson scattering setup. The results are obtained in a discharge tube with a 26 mm diam, 10 mbar of neon, a mercury pressure inbetween 0.14 and 0.85 Pa, and an electric current ranging from 100 to 400 mA. The systematic error in the electron density is 15%–45%, the statistical error is 25%–35%. The total error in the electron temperature is 15%–35%. ©2001 American Institute of Physics

Smooth Blended Subdivision Shading

The concept known as subdivision shading aims at improving the shading of subdivision surfaces. It is based on the subdivision of normal vectors associated with the control net of the surface. By either using the resulting subdivided normal field directly, or blending it with the normal field of the limit surface, renderings of higher visual smoothness can be obtained. In this work we propose a different and more versatile approach to blend the two normal fields, yielding not only better results, but also a proof that our blended normal field is C

An Outlook on the Localisation and Structure-Function Relationships of R Proteins in Solanum

The co-evolution of plants and plant-pathogens shaped a multi-layered defence system in plants, in which Resistance proteins (R proteins) play a significant role. A fundamental understanding of the functioning of these R proteins and their position in the broader defence system of the plant is essential. Sub-project 3 of the BIOEXPLOIT programme studies how R proteins are activated upon effector recognition and how recognition is conveyed in resistance signalling pathways, using the solanaceous R proteins Rx1 (from S. tuberosum spp. andigena; conferring extreme resistance against Potato Virus X), I-2 (from S. lycopersicon; mediating resistance to Fusarium oxysporum) and Mi-1.2 (from S. lycopersicon; conferring resistance to Meloidogyne incognita) as model systems. The results obtained in this project will serve as a model for other R proteins and will be translated to potential applications or alternative strategies for disease resistance. These include the modification of the recognition specificity of R proteins with the aim to obtain broad spectrum resistance to major pathogens in potato

Model wine solutions: Effect of sulphur dioxide on colour and composition during ageing

The effect of sulphur dioxide and acetaldehyde on the interaction between malvidin 3-glucoside, the main anthocyanin in red wine made from Vitis vinifera grapes, and (+)-catechin was examined. In all model wines the molar losses of malvidin 3-glucoside were significantly greater than the losses of catechin. The concentration of malvidin 3-glucoside decreased fastest in the presence of acetaldehyde while the most rapid loss of catechin occurred in the model containing malvidin 3-glucoside and catechin only. In the presence of sulphur dioxide, these losses still occurred, but much more slowly, indicating that condensation reactions may take place even in the presence of sulphur dioxide. Polymerisation was most prominent in the model containing malvidin 3-glucoside, catechin and acetaldehyde. Concurrent with the losses in anthocyanin and catechin, qualitative and quantitative changes in visible colour were also observed. Changes in colour monitored by measuring hue angle and chroma are also reported

Model wine solutions: Colour and composition changes during ageing

The interaction between malvidin 3-glucoside, the main anthocyanin in red wine made from Vitis vinifera grapes, and (+)-catechin and the effect on this interaction of ferric ions and acetaldehyde was examined. In the models not containing acetaldehyde losses of malvidin 3-glucoside were observed, but there were only negligible losses of catechin; no new compounds were observed. In the presence of acetaldehyde the formation of new compounds was determined by high performance liquid chromatography; this formation coincided with rapid losses in the concentrations of malvidin 3-glucoside and catechin. A molecular ion at m/z 809 was determined by FAB MS, corresponding to a dimer consisting of malvidin 3-glucoside linked to catechin by an acetaldehyde bridge, according to a mechanism previously suggested by TIMBER-LAKE and BRIDLE (1976). Concurrent with the losses in anthocyanins, qualitative and quantitative changes in visible colour were also observed, consisting of changes in the wavelength of maximum absorbance (λmax) and in maximum absorbance intensity (Amax). Models containing malvidin 3-glucoside plus catechin or catechin plus ferric ions showed a marked decrease in their λmax from 525 nm to 440 nm; there was little net effect of the ferric ions on these changes. The model containing acetaldehyde showed a large increase in Amax while the λmax showed a bathochromic shift from 524 nm to 557 nm; colour decreased after achieving a maximum and the λmax decreased slightly. Changes in colour monitored by measuring hue angle, chroma and L* value are also reported

The effect of pH on the formation of coloured compounds in model solutions containing anthocyanins, catechin and acetaldehyde

The qualitative and quantitative effect of pH on the formation of new coloured compounds from the interaction between malvidin 3-glucoside, (+) catechin and acetaldehyde was studied. Five different solutions were prepared at pH 2, 3, 3.7, 4 and 5, and the concentration of the reactants and newly formed compounds was monitored by HPLC. In all mixtures there was a decrease in the concentration of malvidin 3-glucoside and catechin, coupled with the formation of two principal new compounds thought to be dimers (labelled A and B), linked at different positions, and several minor compounds. The rate of loss of the reactants and the longevity and concentrations of A and B varied according to pH, with the greatest amounts and most rapid formation of these compounds occurring at pH 2. The catechin concentration still decreased when there was no malvidin 3-glucoside remaining. This observation indicated that further polymerisation reactions were occurring, involving catechin molecules only, or catechin and coloured polymers