Voorstel aanpassing bemestingsadvies voor stikstof van rozen

Op 1 januari 2006 is de nieuwe mestwetgeving van kracht geworden met daarin o.a. stikstof (N)9gebruiksnormen. De N9gebruiksnormen zijn gebaseerd op de bestaande bemestingsadviezen. In de boomkwekerij sector hebben de kwekers van rozen aangegeven dat de normen voor stikstof te laag zijn. Een belangrijke reden hiervoor is dat sinds de totstandkoming van het bestaande bemestingsadvies de teelt is geïntensiveerd. Op basis van gegevens uit de literatuur, praktijk en eigen onderzoek is volgens de richtlijnen van het hiervoor beschikbare protocol een verzoek voor een voorlopig nieuw bemestingsadvies voor stikstof voor de rozen opgestel

THE COMET MINE: AN ENGENDERED STUDY OF VICTORIAN CONSUMPTION PRACTICES AND MATERIAL CULTURE ON A SMALL MINING LANDSCAPE

The Comet mine is an early 20th-century, largely undocumented mining community that existed along the periphery of the Coloma Mining District in the Garnet Range of western Montana. During the summer of 2010, archaeological excavations occurred at multiple features at the site. Through an analysis of cultural material found in deposits at the Comet, this study interprets the way in which patterns of refuse can reveal information about consumption behavior and evolving gender roles in mining communities in Montana, during late Victorian era

Développement de nouveaux catalyseurs appliqués à l'alpha-tosyloxylation catalytique énantiosélective des cétones basée sur l'iode(III)

Les travaux de recherche présentés dans ce mémoire ont été effectués dans le but de développer de nouveaux catalyseurs chiraux base d'iode afin de les utiliser dans différentes méthodes de synthèse catalytiques énantiosélectives. Pour ce faire, l'optimisation d'une réaction étalon, soit l' alpha-tosyloxylation de la propiophénone, a principalement été étudiée afin d'évaluer l'efficacité des catalyseurs. Le premier chapitre abordera la synthèse d'une première génération d'iodooxazolines et de bisiodooxazolines chirales. L'efficacité de cette nouvelle gamme de catalyseurs sera discutée au niveau de l'activité et de la sélectivité. Suite aux résultats obtenus avec cette première génération d'iodooxazolines chirales, une étude plus approfondie de l'activité et de la sélectivité a été effectuée à l'aide de composés modèles plus accessibles. Le second chapitre présentera l'étude de l'activité de différents composés iodoamides et iodoéthers sur le système catalytique. Cette étude plus approfondie permettra d'évaluer l'effet stérique et électronique du noyau aromatique sur le système catalytique. Finalement, au dernier chapitre sera étudiée plus en détail l'induction asymétrique du système à l'aide de différentes iodooxazolines chirales de deuxième génération. Celles-ci étant synthétisées suite aux résultats obtenus au chapitre précédent possèdent un noyau aromatique permettant une bonne activité. Une optimisation des paramètres de la réaction sera effectuée afin d'obtenir une meilleure activité et sélectivité lors de la catalyse

Advanced chemical and structural Characterization of Nuclear Waste Materials related to the Nuclear Fuel Cycle

This dissertation reports structural and speciation investigations of simulated and genuine nuclear wastes. Chapters 4 and 5 emphasize on the very first application of the bulk U, Np and Pu M4,5 absorption edge high-energy resolution X-ray absorption near edge structure (HR XANES) method for characterization of U, Np and Pu oxidation states in model and genuine nuclear waste glasses and spent nuclear fuel (SNF). Chapters 6 and 7 address volatilization and precipitation challenges occurring during vitrification of fission products (FP) like Cs, Tc, Ru and Pd. Various approaches are discussed and potential solutions are proposed. Chapter 4.1 describes the results from the studies of Pu doped borosilicate glasses. Pu(III), Pu(IV) and Pu(VI) are for the first time characterized simultaneously present in a borosilicate glass using Pu M5 edge HR-XANES. It is illustrated that the method can be very efficiently used to determine Pu oxidation states which control the solubility limit of Pu in a glass matrix. HR XANES results show that the addition of excess Si3N4 is not sufficient for complete reduction of Pu to Pu(III) which has a relatively high solubility limit (10-25 wt% PuO2) due to its network-modifying behavior in glasses. It is provided evidences that the initially added Pu(VI) is partly preserved during vitrification at 1200/1400 °C in Ar atmosphere. Pu(VI) could be very advantageous for immobilization of Pu rich wastes since from U(VI) vitrification a possible glass solubility limit of up to 40 wt% can be deduced. Chapter 4.2 reports the characterization and the structural differences between U, Np and Pu doped model and genuine nuclear waste glasses. The U, Np and Pu M4,5 edge HR-XANES reveals predominant U(VI) and Pu(IV) species in all glasses. But ordered structures involving U, O and likely Si are found only in the genuine waste glass by U L3 EXAFS analyses. Strong synchrotron X-ray induced radiation damage leading to reduction of U(VI) to U(IV) is detected also only for the genuine waste glass by U M4 HR-XANES. This effect might be related to differences in the radioactivity and/or the local atomic U environments in the model and the waste glasses. It might be explained with transfer of electronic charge to U from binding ligands and/or free charges as well as possible U reactions with radicals or charged species. Such reduction of U and potentially other An elements might be inducible by α, β and/or γ irradiation processes on a long-time scale and are hence of relevance for the An speciation in HLW glasses stored in an underground repository. Chapter 5 discusses the speciation of U and Pu in commercial and special irradiated high burn up SNF samples as well as of unirradiated UO2 reference materials. The bulk sensitivity of the An M4,5 edge HR-XANES technique is unambiguously demonstrated, whereas X-ray photoelectron spectroscopy (XPS) is sensitive only to species formed on the surface. The U M4,5 HR-XANES method can clearly distinguish between U(IV) and U(V) as well as Pu(IV) and Pu(V)/Pu(VI), which is not always possible with the conventional U and Pu L3 XANES. U(IV) and U(V) likely in the form of U4O9 are found in the two commercial SNF samples. It is shown that the U oxidation continues in ambient conditions as a function of time due to the small particle size of the samples. No phase transformation from UO2 to U3O8 or UO3 is observed for any of the studied SNF samples. The special irradiated high burn-up sample stored in atmosphere with ca. 1% O2 for 20 years has only very minor amount of U(V) which illustrates its high stability against oxidation being advantageous in case of a potential cladding failure scenario for example in extended interim storage. For the first time it is demonstrated that along Pu(IV) also Pu(VI) is present in the bulk of presumably all SNF samples. This Pu(VI) is unlikely formed by oxidation in air but rather is a result of the neutron absorption and subsequent nuclear reactions. Chapter 6 reports studies of HLW residual materials from a reprocessing and a vitrification plant. They are simulated and the formed compounds are characterized as well as possible host matrices for their immobilization are reviewed. The challenge of Cs and Tc volatilization loss is addressed by careful selection of immobilization processes, i.e., addition of reducing agent and application of host matrices with low melting temperature. A selection of suitable immobilization materials is made with regard to minimized FP volatilization behavior. Potential leaching performance is discussed considering composition and macroscopic appearance of the synthesized samples. Chapter 7 presents insights obtained from the X-ray CT in-situ study of a vitrification process with emphasize on the precipitation of noble metal particles (NMP) which are known to cause severe problems in industrial vitrification processes in form of drain plugging and short circuits. Results indicate the formation of the particles at 600 700 °C in the lower part of the cold-cap. An exceptional large precipitated specie is observed and described. Its formation might have an impact on the NMPs sedimentation behavior. For the first time, in-situ tracking of their movement in a glass melt is reported. The designed setup has the potential to unambiguously reveal the highly debated NMP sedimentation mechanism. Two counter measures on the particles formation are tested. The use of glass powder instead of glass beads and the addition of 1 wt% Si as reducing agent decreased the NMP precipitation by 40% and 30%, respectively, and simultaneously retain Re used as a surrogate of Tc by a factor of 2-3

Aspects of the composition, pigments and carbon fixation of marine phytoplankton

The seasonal variation of phytoplankton biomass in terms of total number of algal cells, chlorophyll a levels and phytoplankton productivity was investigated in the years 1984, 1985, 1986 and 1987 for samples collected from the photic zone (surface and 5 metres depth) at stations 11 and 9, at the Fairlie Channel in relation to the changes in nutrient levels and weather conditions. The seasonal variation in the phytoplankton composition was assessed using microscopic examination of the samples and the qualitative analysis of the different algal pigments. Also investigated was the contribution of the different phytoplankton size fractions to the total photosynthetic activity, including that of net -, nano - and picophytoplankton. Although there is a year to year slight variability in weather conditions and nutrient concentrations during the course of this investigation, certain features recurred annually: 1) The spring diatom increase (spring bloom) occurred in March or early April. 2) The phytoplankton biomass during the summer fluctuated about intermediate levels, althoughon certain occasions they were comparable or higher than those observed during the spring diatom increase and during this period the minimum nutrient levels were recorded. The maximum photosynthetic activities were found during the summer period (1986) in reflection of the favourable weather conditions marking this period. 3) Small to relatively high standing crop levels were recorded during the autumn period with photosynthetic activities comparable to those found during the summer. Relatively high nutrient levels were recorded during the autumn. 4) Low phytoplankton biomass (representing the year minimum) and high nutrient concentrations (representing the year maximum) were found during winter. There was no regular recurring autumnal bloom. With the exception of the findings on 25 May and 6 June, 1984 when the benthic organisms represented a large part of the total population, these organisms were found to be most numerous during autumn and winter months, coinciding with the prevailing conditions. Diatoms were the most dominant fraction of the population mainly during the spring diatom increase of which Skeletonema costatum and Thalassiosira nordenskioldii were the most dominant species; also observed in considerable numbers was Navicula spp. The largest levels of contribution by dinoflagellates to the total phytoplankton biomass were recorded during the autumn months; the dinoflagellate fraction was predominantly composed of the genus Ceratium. Green flagellates were found in considerable numbers during the summer months although they were common in the autumn and winter months of 1986. The seasonal variations of the total phytoplankton biomass and nutrient levels were similar to those observed in the past in the Fairlie Channel. (Abstract shortened by ProQuest.)