Trichodorideaaltjes en bodemschimmels lijken veroorzakers onbekend wortelrot

Onderzoek van PPO en BAB naar de mogelijke oorzaken en maatregelen om problemen met onbekend wortelrot in leli

Naar een oplossing voor onbekend wortelrot in lelie : praktijkproef

In lelies komt er al jaren een vorm van wortelrot voor waarvan de veroorzaker onbekend is. Net als bij een aantasting door wortellesie-aaltjes leidt een aantasting door het onbekende wortelrot tot opbrengstderving en kwaliteitsverlies. De symptomen van onbekend wortelrot ontstaan op de bolwortels en zien eruit als insnoeringen en ingezonken bruine plekjes. Soms lijkt het alsof er hapjes uit de wortels zijn genomen. De wortels rotten op dergelijke plaatsen geheel door waarna bruine wortelpunten ontstaan en de wortels zich sterk gaan vertakken. In dit project werd onderzocht of grondstructuur (verdichting) en het gebruik van GFT al dan niet in combinatie met grondgebonden pathogene schimmels een rol spelen in het optreden van onbekend wortelrot in lelie. Ook werd onderzocht of het vochtig of juist droog houden van de grond na planten van invloed is op de mate van onbekend wortelrot. Ten slotte werd de werking van de middelen Amistar en Monam tegen onbekend wortelrot onderzocht. In dit onderzoek werd 15 l/ha Amistar gebruikt i.p.v. de 6 l/ha die is toegestaan, terwijl voor Monam de gebruikelijke concentratie van 500 l/ha werd toegepast. Het onderzoek werd uitgevoerd op een praktijkperceel waar in 2007 lelies werden geteeld waarin volop onbekend wortelrot was waargenomen. Onder praktijkomstandigheden werd onderzocht of combinaties van genoemde factoren mogelijk een rol spelen bij het ontstaan van onbekend wortelrot

Gravity waves over topographical bottoms: Comparison with the experiment

In this paper, the propagation of water surface waves over one-dimensional periodic and random bottoms is investigated by the transfer matrix method. For the periodic bottoms, the band structure is calculated, and the results are compared to the transmission results. When the bottoms are randomized, the Anderson localization phenomenon is observed. The theory has been applied to an existing experiment (Belzons, et al., J. Fluid Mech. {\bf 186}, 530 (1988)). In general, the results are compared favorably with the experimental observation.Comment: 15 pages, 7 figure

Frozen water waves over rough topographical bottoms

The propagation of surface water waves over rough topographical bottoms is investigated by the multiple scattering theory. It is shown that the waves can be localized spatially through the process of multiple scattering and wave interference, a peculiar wave phenomenon which has been previously discussed for frozen light in optical systems (S. John, Nature {\bf 390}, 661, (1997)). We demonstrate that when frozen, the transmission of the waves falls off exponentially, and a cooperative behavior appears, fully supporting previous predictions. A phase diagram method is used to illustrate this distinct phase states in the wave propagation.Comment: 4 pages and 5 figure

Probing a non-biaxial behavior of infinitely thin hard platelets

We give a criterion to test a non-biaxial behavior of infinitely thin hard platelets of $D_{2h}$ symmetry based upon the components of three order parameter tensors. We investigated the nematic behavior of monodisperse infinitely thin rectangular hard platelet systems by using the criterion. Starting with a square platelet system, and we compared it with rectangular platelet systems of various aspect ratios. For each system, we performed equilibration runs by using isobaric Monte Carlo simulations. Each system did not show a biaxial nematic behavior but a uniaxial nematic one, despite of the shape anisotropy of those platelets. The relationship between effective diameters by simulations and theoretical effective diameters of the above systems was also determined.Comment: Submitted to JPS

Phase Behavior of Bent-Core Molecules

Recently, a new class of smectic liquid crystal phases (SmCP phases) characterized by the spontaneous formation of macroscopic chiral domains from achiral bent-core molecules has been discovered. We have carried out Monte Carlo simulations of a minimal hard spherocylinder dimer model to investigate the role of excluded volume interations in determining the phase behavior of bent-core materials and to probe the molecular origins of polar and chiral symmetry breaking. We present the phase diagram as a function of pressure or density and dimer opening angle $\psi$. With decreasing $\psi$, a transition from a nonpolar to a polar smectic phase is observed near $\psi = 167^{\circ}$, and the nematic phase becomes thermodynamically unstable for $\psi < 135^{\circ}$. No chiral smectic or biaxial nematic phases were found.Comment: 4 pages Revtex, 3 eps figures (included

The Basics of Water Waves Theory for Analogue Gravity

This chapter gives an introduction to the connection between the physics of water waves and analogue gravity. Only a basic knowledge of fluid mechanics is assumed as a prerequisite.Comment: 36 pages. Lecture Notes for the IX SIGRAV School on "Analogue Gravity", Como (Italy), May 201

Bandgaps in the propagation and scattering of surface water waves over cylindrical steps

Here we investigate the propagation and scattering of surface water waves by arrays of bottom-mounted cylindrical steps. Both periodic and random arrangements of the steps are considered. The wave transmission through the arrays is computed using the multiple scattering method based upon a recently derived formulation. For the periodic case, the results are compared to the band structure calculation. We demonstrate that complete band gaps can be obtained in such a system. Furthermore, we show that the randomization of the location of the steps can significantly reduce the transmission of water waves. Comparison with other systems is also discussed.Comment: 4 pages, 3 figure

Solar cell

A solar cell comprising a semiconductor layer (1), a collecting layer (6) for collecting free charge carriers from the semiconductor layer (1) and a buffer layer (3) which is arranged between the semiconductor layer (1) and the collecting layer (6), which buffer layer (3) is designed as a tunnel contact (31) between the semiconductor layer (1) and the collecting layer (6) is characterised in that the buffer layer (3) essentially comprises a material with a surface charge density of at least 1012 cm-2, preferably of at least 5x1012 cm- 2