A study on bacterial softrot in witloof chicory

The production process of witloof chicory, which consists of the root production stage, the storage of the roots and the forcing of the chicory heads, was monitored for the presence of softrot bacteria. In the Netherlands, bacterial softrot in chicory is caused by Erwinia carotovora subsp . carotovora ( Ecc ) and Pseudomonas marginalis .Populations of these species colonised the chicory leaves during the root production stage causing softrot only in the forcing stage. The colonisation incidence, the number of populations of both pathogens present on the chicory leaves, increased during the root production. Ecc was inhibited by high radiation levels during the first months of the growing season of the plants. The colonisation incidence of the chicory leaves was influenced by the average temperature throughout the growing season but not by nitrogen fertilisation of the crop or rainfall. The colonisation incidence of the stored roots decreased from harvest time in September until December but increased thereafter. High colonisation incidences during storage coincided with high disease incidence during the subsequent forcing period of the roots.Bacterial softrot occurred during forcing of the roots in all three forcing seasons. Nitrogen fertilisation of the plants, root immersion with calciumchloride and the sampling year had significant effects on disease incidence. Aggregation of diseased chicory heads in forcing trays could be described by an aggregation parameter of the beta-binomial distribution. Studies on the enzyme activity of the softrot bacteria showed that nitrogen and calcium effects on disease severity could be explained by the influence of these treatments on the activity of two pectolytic enzymes of the bacteria. Reduction of bacterial softrot is possible by reduced nitrogen fertilisation during root production and by application of calciumchloride to harvested roots.</p

Twee weten meer dan een : Eindrapportage

Het AKK project Twee Weten Meer Dan Een wil de belangrijkste kennisthema’s en bijbehorende doelgroepen in biologische afzetketens identificeren en nagaan welke kennisverspreidingsactiviteiten, zowel binnen de projecten als binnen de biologische keten het meeste effect hebben. Behoefte en interesse vanuit de biologische sector voor de onderwerpen moet hierin centraal staan. In een eerste behoeftepeiling is met deskresearch en bij projectparticipanten, belangenbehartigers en bedrijven uit de biologische keten de kennisbehoefte geïnventariseerd. Welke kennis is anno 2003/2004 interessant en belangrijk, welke thema’s achten zij actueel voor de biologische keten en hoe vergaren ze bij voorkeur deze kennis? Deze behoeftepeiling heeft drie centrale thema’s geïdentificeerd: 1. Thema Consument: Meerwaarde biologisch en consumentenbehoeften (hoe aansluiting te vinden bij de behoeften van consumenten en aan te spreken op het moment van aankoop): communicatie in de keten! 2. Thema Kwaliteit: Ketenbeheersing van Kwaliteit 3. Thema Samenwerking: Proceskennis voor samenwerking in de kete

Optical properties of MgH2 measured in situ in a novel gas cell for ellipsometry/spectrophotometry

The dielectric properties of alpha-MgH2 are investigated in the photon energy range between 1 and 6.5 eV. For this purpose, a novel sample configuration and experimental setup are developed that allow both optical transmission and ellipsometric measurements of a transparent thin film in equilibrium with hydrogen. We show that alpha-MgH2 is a transparent, colour neutral insulator with a band gap of 5.6 +/- 0.1 eV. It has an intrinsic transparency of about 80% over the whole visible spectrum. The dielectric function found in this work confirms very recent band structure calculations using the GW approximation by Alford and Chou [J.A. Alford and M.Y. Chou (unpublished)]. As Pd is used as a cap layer we report also the optical properties of PdHx thin films.Comment: REVTeX4, 15 pages, 12 figures, 5 table

Magnetic Field Amplification in Galaxy Clusters and its Simulation

We review the present theoretical and numerical understanding of magnetic field amplification in cosmic large-scale structure, on length scales of galaxy clusters and beyond. Structure formation drives compression and turbulence, which amplify tiny magnetic seed fields to the microGauss values that are observed in the intracluster medium. This process is intimately connected to the properties of turbulence and the microphysics of the intra-cluster medium. Additional roles are played by merger induced shocks that sweep through the intra-cluster medium and motions induced by sloshing cool cores. The accurate simulation of magnetic field amplification in clusters still poses a serious challenge for simulations of cosmological structure formation. We review the current literature on cosmological simulations that include magnetic fields and outline theoretical as well as numerical challenges.Comment: 60 pages, 19 Figure

Natrot in witlof beheersbaar

In een onderzoek is een aantal beheersmaatregelen ter beperking ter berperking van natrot nader uitgewerkt. Verder is gewerkt aan een toets om het risico op natrot bij gerooide wortels in te kunnen schatte