3,666 research outputs found
Yellowing viruses in sugarbeet : epidemiology and damage
No full textThe epidemiology and damage effects of beet yellows virus (BYV) and beet mild yellowing virus (BMYV) were studied.Chapter 2 . The incubation period (time between infection and symptom expression) was determined so that progress curves of the disease (symptoms) could be translated into progress curves of the infection. The incubation period increased during the season from 3 (BYV) or 4 to 5 weeks (BMYV) in June to two months when plants were infected with either virus in August. The incubation period increased with plant development stage and lower temperature.Chapter 3. Symptoms of systemic virus infection developed on the leaves that appeared after the inoculation. Older leaves (except those inoculated) remained healthy and green. In field experiments the infection date was retrospectively determined by calculating the appearance date of the oldest systemically-infected leaf.Chapter 4. Theoretical analyses show that high infection percentages must be avoided in bait plant test for the determination of infection pressure. Otherwise the number of viruliferous vectors cannot be estimated accurately. Confidence intervals for the number of vectors are given as well as lower bounds when all plants have become infected.Chapter 5. The extent of secondary spread of yellowing viruses was strongly affected by the date of primary infection. Inoculations before 15 June resulted in extensive secondary spread while negligible spread occurred in plots inoculated after this date. In early-inoculated plots spread started around 15 June when adjacent plants made leaf contact, so that the vector, Myzus persicae , could disperse more readily. Little spread occurred in plots in which the number of M. persicae was reduced by coccinellids.Chapter 6. Inoculations at the end of June in late-sown crops resulted in more extensive spread than inoculations in early-sown crops. The higher rate of spread in young crops was correlated with (1) a higher multiplication rate of M. persicae on young plants, (2) a better acceptance of young plants by M.persicae, promoting virus transmission and (3) a shorter latency period (time between infection and possibility of virus acquisition).Chapter 7. Damage by BYV resulted from (1) a smaller size of infected leaves. (2) reduced light absorption by yellow leaves, (3) reduced photosynthesis in yellow leaves and (4) increased respiration in infected leaves. Reduced photosynthesis was the most important damage component. Photosynthesis was almost completely inhibited in bright yellow, infected leaves while healthy leaves on infected plants or infected leaves without symptoms photosynthesized at normal rates. Yield loss decreases with later infection as the proportion of yellow leaves on the plants decreases.The results demonstrate that plant development stage plays a key role in vector population dynamics, virus spread, symptom development and damage. Thus, the benefit from pesticide applications for the control of virus spread depends on crop development stage. Therefore the development stage of the crop should be considered before control measures are taken
Aanpassing van een partieel vernet copolymeer voor tonergebruik
No full textDit afstudeerwerk bestaat uit twee delen. Deel 1 is het scriptie-gedeelte waar nader wordt ingegaan op de theoretische aspecten van het copieerproces; in het bijzonder de fixatie, de dynamische reologie en de copiekwaliteit. Deel 1 geeft theoretische ondersteuning aan het verslag. Deel 2 betreft het experimentele verslag van het afstudeerwerk…Applied SciencesScheikundige Technologie en der MateriaalkundeTechnologie van Macromoleculaire Stoffe
Implementation and Effects of European and International Orientation at Secondary Schools in the Netherlands
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Implementation and effects of EIO across countries: current knowledge base and directions for future research
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Endotoxemia-induced inflammation and the effect on the human brain
Get PDFIntroduction: Effects of systemic inflammation on cerebral function are not clear, as both inflammation-induced encephalopathy as well as stress-hormone mediated alertness have been described.Methods: Experimental endotoxemia (2 ng/kg Escherichia coli lipopolysaccharide [LPS]) was induced in 15 subjects, whereas 10 served as controls. Cytokines (TNF-?, IL-6, IL1-RA and IL-10), cortisol, brain specific proteins (BSP), electroencephalography (EEG) and cognitive function tests (CFTs) were determined.Results: Following LPS infusion, circulating pro- and anti inflammatory cytokines, and cortisol increased (P < 0.0001). BSP changes stayed within the normal range, in which neuron specific enolase (NSE) and S100-? changed significantly. Except in one subject with a mild encephalopathic episode, without cognitive dysfunction, endotoxemia induced no clinically relevant EEG changes. Quantitative EEG analysis showed a higher state of alertness detected by changes in the central region, and peak frequency in the occipital region. Improved CFTs during endotoxemia was found to be due to a practice effect as CFTs improved to the same extent in the reference group. Cortisol significantly correlated with a higher state of alertness detected on the EEG. Increased IL-10 and the decreased NSE both correlated with improvement of working memory and with psychomotor speed capacity. No other significant correlations between cytokines, cortisol, EEG, CFT and BSP were found.Conclusions: Short-term systemic inflammation does not provoke or explain the occurrence of septic encephalopathy, but primarily results in an inflammation-mediated increase in cortisol and alertness
Karakterisering van een styreen-butylacrylaat-acrylonitrilterpolymeer
No full textIn samenwerking met Rank Xerox is onderzoek gedaan naar de microstruktuur en de morf ologie van een styreen-butylacrylaat-acrylonitrilterpolymeer met de mechanische eigenschappen van een vernet polymeer (S103C). Er is getracht de hypothese te verifieren dat de vernetting veroorzaakt wordt door paarsgewijze intermoleculaire associatie van nitrilgroepen. Daarnaast is er getracht terpolymeren te synthetiseren met lang acrylonitrilsequenties om daarin netwerkvorming door intermoleculaire dipoolinteracties van acrylonitrilsequenties aan te tonen. De in dit onderzoek gesynthetiseerde polymeren lijken in samenstelling en microstruktuur overeen te komen met in voorgaand onderzoek gesynthetiseerde polymeren. De dynamische mechanische eigenschappen zijn identiek en er is dus geen sprake van vernetting. Analyse van S103C met infraroodspectroscopie duidt op de aanwezigheid van paarsgewijs geassocieerde nitrilgroepen. Deze interactie wordt opgeheven door langdurig zwellen in dimethylformamide. Interactie van nitrilgroepen is in veel kleinere mate ook aanwezig in de in voorgaand onderzoek gesynthetiseerde terpolymeren. Er zijn met behulp van sequentieanalyse aan de hand van 13C-NMR geen sequentielengteverdelingen in S103C bepaald die specifiek geschikt kunnen zijn voor netwerkvorming. Sequentie-analyse kan verder worden uitgevoerd aan de hand van de pyrolyseprodukten van het polymeer, waarvan de identiteiten grotendeels zijn bepaald in dit onderzoek. Het rontgendiffractogram van S103C vertoont geen aanwezigheid van voor kristallijne polyacrilonitrilgebieden representatieve diffracties. Het is mogelijk dat geassocieerde nitrilgroepen verantwoordelijk ziJn voor de netwerkvorming in S103C maar het is niet aangetoond dat deze nitrilgroepen zich in homogene sequenties bevinden. Er dient te worden onderzocht of netwerkvorming ook mogelijk is door intermoleculair geassocieerde geïsoleerd ingebouwde acrylonitrileenheden. Andere mogelijke oorzaken van netwerkvorming worden voorgesteld, waarnaar verder onderzoek zou kunnen worden gedaan.Applied SciencesScheikundige Technologie en der MateriaalkundeTechnologie van Macromoleculaire stoffe
Simplivariate Models: Ideas and First Examples
Get PDFOne of the new expanding areas in functional genomics is metabolomics: measuring the metabolome of an organism. Data being generated in metabolomics studies are very diverse in nature depending on the design underlying the experiment. Traditionally, variation in measurements is conceptually broken down in systematic variation and noise where the latter contains, e.g. technical variation. There is increasing evidence that this distinction does not hold (or is too simple) for metabolomics data. A more useful distinction is in terms of informative and non-informative variation where informative relates to the problem being studied. In most common methods for analyzing metabolomics (or any other high-dimensional x-omics) data this distinction is ignored thereby severely hampering the results of the analysis. This leads to poorly interpretable models and may even obscure the relevant biological information. We developed a framework from first data analysis principles by explicitly formulating the problem of analyzing metabolomics data in terms of informative and non-informative parts. This framework allows for flexible interactions with the biologists involved in formulating prior knowledge of underlying structures. The basic idea is that the informative parts of the complex metabolomics data are approximated by simple components with a biological meaning, e.g. in terms of metabolic pathways or their regulation. Hence, we termed the framework ‘simplivariate models’ which constitutes a new way of looking at metabolomics data. The framework is given in its full generality and exemplified with two methods, IDR analysis and plaid modeling, that fit into the framework. Using this strategy of ‘divide and conquer’, we show that meaningful simplivariate models can be obtained using a real-life microbial metabolomics data set. For instance, one of the simple components contained all the measured intermediates of the Krebs cycle of E. coli. Moreover, these simplivariate models were able to uncover regulatory mechanisms present in the phenylalanine biosynthesis route of E. col
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