Preservation of panorama mesdag, the Haque

This paper deals with the preservation of the Panorama Mesdag, a cylindrical painting, more than 14 meters high and 120 meters in circumference. The vista of the sea, the dunes and Scheveningen village was painted by one of the most famous painters of the Hague School, Hendrik Willem Mesdag. It is the oldest 19th century panorama in the world in its original site and a unique cultural heritage. About three years ago the building, which is a uniquely complex structure, was damaged by a nearby excavation. In the years to follow a series of measures have been taken of which the compensation grouting of the foundation is the most extensive from a geotechnical point of view.\ud This paper outlines the history of the damage, the construction of the building and most importantly the extents of the compensation grouting and the result of the grouting and the extensive monitoring. The effectiveness of the grouting is determined and conclusions have been drawn for the still to be performed excavations and construction activities

Specificity, pathogenicity and population dynamics of the endoparasitic nematode Heterodera arenaria in coastal foredune

Key words : Heterodera , plant-parasitic nematodes, soil pathogens, Ammophila arenaria , occurrence, abundance, specificity, population dynamics, life history, pathogenicity, PCR-SSCP, molecular method, escape, sand burial, dispersal, migration, fitness, development time, survival, reproductive success, bottom-up, top-down. In natural ecosystems hardly any attention has been given to the population dynamics of plant-parasitic nematodes. In coastal foredunes, plant-parasitic nematodes are supposed to be involved in the degeneration and succession of the dominant sand-fixing grass Ammophila arenaria (Marram grass). The specificity, pathogenicity and population dynamics of the sedentary endoparasitic nematode Heterodera arenaria have been studied to determine if this species might be a key component of the soil pathogen complex of A. arenaria.H. arenaria was found to be specific to Elymus farctus and A. arenaria in the mobile area of the coastal foredunes. Colonisation of the newly deposited sand layer by H. arenaria corresponded well with the development of pathogenicity in a series of bioassays. However, direct addition of the nematode to A. arenaria did not result in growth reduction of the plant. So, H. arenaria behaves like a biotrophic parasite, which has a high specificity but is not aggressive. Therefore, H. arenaria did not seem to be directly involved in the degeneration of A. arenaria .Each year, the majority of the population of new H. arenaria cysts develops in the newly deposited sand layers. These layers are colonised by A. arenaria roots throughout the growing season. Migration to the new root layer may offer an individual nematode the benefit of early development and a larger potential offspring. The continuous release of juveniles in the field and their development in experiments indicate that release of juveniles from cysts is an ultimately determined process. Juveniles were found to emerge in November and many eggs or juveniles did not survive the winter period. The strategy of release, however, seems effective; the distance of migration could be too large to detect specific cues from the plant and the start of root formation in the field is highly variable. The emergence of juveniles late in the growing season could result in a second generation within the same year. The constant number of cysts per gram of roots suggests that the population density of H. arenaria is most likely a bottom-up directed process.</p

Thermal and photochemical reactions of dihydrodiazines

This thesis describes the results of an investigation into the thermal and photochemical reactivity of dihydrodiazines.In order to prepare the title compounds the diazines and some phenyldiazines are treated with phenyllithium in ether, yielding adducts resulting from attack of phenyllithium on the various positions of the heteroaromatic ring. With pyrimidine addition takes place mainly at C(4), with pyridazine at C(3). By using TMEDA, addition at C(2) in 4-phenylpyrimidine and at C(4) in pyridazine is strongly promoted. The structure of the adducts is studied by n.m.r. spectroscopy. The charge distribution pattern in the C(4)-adduct of pyrimidine and in both the C(3)-adduct and the C(4)-adduct of pyridazine is determined by comparing the carbon chemical shifts of these compounds with those of the corresponding dihydrodiazines obtained by hydrolysis of the adducts. C(5) in the phenyllithium-pyrimidine adduct carries little negative charge, C(4) in the phenyllithium-pyridazine adduct has a considerable amount of charge while the charge density at C(6) in the 3-adduct and both C(3) and C(5) in the 4-adduct of pyridazine is moderate.Some organolithium-diazine adducts and some dihydropyrimidines are treated with electrophilic reagents. Both 4,6-diphenyl-1(3)-lithio-1,4(3,4)-dihydropyrimidine and 4,6-diphenyl-1,4(3.4)-dihydropyrimidine are attacked by the electrophilic reagent (methyliodide, methyl chloroformate) at N(3), yielding 4,6-dipheny]-3-methyl(methoxycarbonyl)-3,4-dihydropyrimidine. 4,4,6-Triphenyl-1,4(3,4)-dihydropyrimidine gives upon treatment with methyliodide mainly 3-methyl-4,4,6-triphenyl-3,4-dihydropyrimidine. The 3,4-dihydro structure of the products is established both spectroscopically and chemically. Reaction of 2-lithio-3-methyl-2,3-dihydropyridazine with methyliodide (methyl chloroformate, tosylchloride) gives the corresponding 2,3-dimethyl-(2-methoxycarbonyl-3-methyl-, 2-tosyl-3-methyl-)2,3-dihydropyridazine. 1-Lithio-2-phenyl-1,2-dihydropyrazine yields upon treatment with methyliodide 5-methyl-2-phenylpyrazine. Reaction with carbonyl compounds only yields high molecular material.Photolysis of 4-R-1,4(3,4)-dihydropyrimidines causes rearrangement to 5-R-1,2(2,3)-dihydropyrimidines, provided that the substituent R contains a π-bond in αposition to the heterocyclic ring (R=phenyl,isobutenyl,phenylethynyl). 4-Methyl-1,4(3,4)-dihydropyrimidine does not show this rearrangement. Chemical evidence is presented that the rearrangement occurs via the di-π-methane mechanism leading to 6-R-2,4-diazabicyclo [3.1.0] hex-2(3)-ene. This latter intermediate undergoes a thermal homo [1,5] hydrogen shift into 5-R-2,5-dihydropyrimidine which on tautomerization gives the final product. The reaction can be sensitized by acetone. 4,5-Diphenyl-, 5-methyl-4-phenyl and 5-bromo-4-phenyl-1,4(3,4)-dihydropyrimidine do not rearrange under photochemical conditions.Several 4-R-1,4(3,4)-dihydropyrimidines (R=2- or 3-thienyl,2-furyl, 1-methyl-2-pyrrolyl and 3-pyridyl) containing heteroaryl vinyl methane moieties undergo photochemical rearrangement into 5-R-1,2(2,3)-dihydropyrimidines. Oxidation of these compounds yield 5-heteroarylpyrimidines. The chemical yields are strongly dependent of the nature of the heteroaryl group.The existence of a 6-R-2,4-diazabicyclo [3.1.0] hex-2(3)-ene as an intermediate in the photoisomerization of 4-R-1,4(3,4)- dihydropyrimidines into 5-R-1,2(2,3)-dihydropyrimidines is confirmed spectroscopically in case R= p -trifluoromethylphenyl. It is established that the p -trifluoromethylphenyl group is in exo position in the bicyclic compound. 6- Exo -( p -trifluoromethylphenyl)-2,4-diazabicyclo [3.1.0] hex- 2(3)-ene immediately gives 5-( p -trifluoromethylphenyl)-1,2(2,3)- dihydropyrimidine upon addition of potassium hydroxide in methanol.Photolysis of 4-R-1,4(3,4)-dihydropyrimidines causes ring contraction into imidazoles, provided that the substituent R is sufficiently capable of stabilizing an anionic centre (R=2-thiazolyl and 2- or 4-pyridyl). Chemical evidence is presented that the ring contraction of 6-phenyl-4-(2-pyridyl)-1,4(3,4)-dihydropyrimidine occurs via heterolytic fission of the C(1)-C(6) bond of intermediate 1-phenyl-6-(2-pyridyl)-2,4-diazabicyclo [3.1.0] hex-2(3)-ene. The anion stabilizing effect of R is correlated with the acid strength (pKa) of R-CH 3 . A pKa value around 30 determines the border-line between ring contraction into an imidazole and formation of an isomeric 5-R-1,2(2,3)-dihydropyrimidine

‘Hij die de harten van allen vormt’ : de betekenis van het begrip omvorming in de spiritualiteit van studenten theologie

Masterthesis Gemeentepredikan

Minderheden en Conflictvoorkoming

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