39 research outputs found
Ischaemic preconditioning in exercise and disease: One size fits all?
No full textContains fulltext :
150174.pdf (Publisher’s version ) (Open Access)Radboud Universiteit Nijmegen, 25 januari 2016Promotores : Hopman, M.T.E., Cable, N.T. Co-promotores : Thijssen, D.H.J., Timmers, S
Ban Bedcentricity: Stimulating patients’ physical activity during hospital stay by cultural change. Beter uit bed: Stimuleren van fysieke activiteit bij patiënten tijdens een ziekenhuisopname door middel van cultuurverandering.
No full textTelematica met landmobiele satellietcommunicatie voor transport: mogelijkheden en wensen
No full textNa een inleiding over het beroepsgoederenvervoer over de weg worden systemen voor landmobiele satellietcommunicatie en -plaatsbepaling beschreven en vergeleken. Regelgeving en andere introductievoorwaarden komen aan de orde. Enige planningsprogrammatuur wordt beschouwd. Een alternatief wordt geïntroduceerd: het elektronisch planbord. Geïntegreerd met satellietcommunicatie en -plaatsbepaling wordt dat als realiseerbaar modelsysteem getoetst bij transportbedrijven.Electrical Engineering, Mathematics and Computer ScienceTelecommunicatie- en Verkeersbegeleidingssysteme
1,2-dichloorethaan via directe chlorering van ethyleen
No full textDocument(en) uit de collectie Chemische Procestechnologie.DelftChemTechApplied Science
A combination of SWASH and Harberth to compute wave forces on moored ships
No full textMoored vessels are subject to wave forces and moments at different frequencies, which induce motions of the body and can be transferred to the mooring lines and fenders. Under extreme forcing and vessel motions, dangerous line breaking accidents can occur or the ship movements can be simply too large to continue the on/off-loading process, causing downtime of the port. An accurate modelling of the waves in the harbour and the response of moored ships is of prime importance to determine the safety and workability of the berths. In this project the combination of the wave model SWASH and the 3D diffraction model Harberth to compute waves forces acting on moored ships is investigated. The proposed approach using the SWASH wave model come as a possible alternative to the current practice of Royal HaskoningDHV, who experienced a sequence of numerical issues while simulating extreme incident waves with an operational Boussinesq-type model. The objectives of the study lead to the following research question: To which extent can the SWASH wave model and the Harberth model be combined in order to accurately compute wave forces acting on moored ships? Each computational tool considered in the proposed approach (the wave model SWASH, the coupling procedure, and the diffraction model Harberth) can contribute to the (in)accuracy of the computed wave forces acting on a moored ship. A series of systematic tests with SWASH indicates that the dispersion errors are generally negligible, while amplitude errors remain small provided that: i) the number of vertical layers is sufficient (especially in relatively deep waters); ii) the horizontal resolution of the computational grid is sufficient; iii) important terms of the momentum equation are modelled with higher-order numerical schemes (especially for non-linear waves in relatively deep waters). The possible wave amplitude errors impact directly the predicted wave forces acting on the ship. The coupling tool developed to combine the SWASH and Harberth models proved to be consistent for the simplified tested conditions. The first-order forces computed using SWASH and Harberth are generally well predicted, while larger deviations can occur for the second-order forces. These are partially related to the simplification of motions made by Harberth in the computation of second-order forces. The proposed approach using the SWASH and Harberth models, combined with the developed coupling tool, is validated using model test data of waves and forces acting on a restrained ship. In general the performance is satisfactory, even for very energetic conditions, implying that the investigated modelling approach is a potential alternative for future applications. Finally, a list of recommendations is provided, including possible improvements in the SWASH model and Harberth model, and additional tests to consolidate the proposed modelling approach.Coastal EngineeringHydraulic EngineeringCivil Engineering and Geoscience
Onderzoek Loran-C bij de Meetkundige Dienst van Rijkswaterstaat
No full textCivil Engineering and GeosciencesMathematische en fysische geodesi
Textuur, inwendige spanningen, kristalietgrootte en hardheid van elektrolytisch neergeslagen chroomlagen
No full textFysische en Chemische MetaalkundeTechnische MateriaalwetenschappenApplied Science
A nonlinear Schrödinger equation in L² with multiplicative white noise
No full textIn this thesis existence and uniqueness of the solution of a nonlinear Schrödinger equation in L² with multiplicative white noise is proven under some assumptions. Furthermore, pathwise L²-norm conservation of the solution is studied.AnalysisApplied mathematicsElectrical Engineering, Mathematics and Computer Scienc
Optimization of the operational use of entrance channels based on channel depth requirements
No full textLarge capital and maintenance dredging operations are required to ensure the accessibility of many ports. The expenses associated with the dredging operations can have a significant impact on the finances of these ports. Therefore, considerable attention to the design of the width and depth aspects of access channels is justifiable. This study considered this topic within the framework of an Additional Master Thesis (3-month internship). The objectives of the study are: i) to verify the influence of different processes and sources of uncertainties in the evaluation of minimum depth requirements; and ii) to investigate the advantages and drawbacks of different methods of depth requirement evaluation. The Port of Tubarão (Southeast Brazil) is used as a case study to verify processes and methods. Four different approaches were considered to evaluate depth requirements for the access channel of the Port. These methods are based on either deterministic and/or probabilistic methods, and on approaches without or including wave influences. The results for the case study indicate that ship motions due to waves have a minor influence on the required channel depth at that location during most of the time. However, in certain wave conditions (not only in terms of wave height, but also wave period and wave direction relative to the manoeuvring ship) vertical ship motions become the dominant issue regarding depth requirements; consequently waves should be included in a practical evaluation over time. In probabilistic approaches more knowledge can be incorporated in the analysis, however, this requires detailed information. The deterministic approach, on the other hand, is simpler to use and gives good insight about the main driving variables. Although, the main drawback of deterministic methods is that the reliability of the evaluation cannot be accessed, or that conservative assumptions need to be made. This may be uneconomical. The use of a probabilistic method for the case study led to a more optimized use of the channel in terms of accessibility in comparison to the results obtained with the deterministic method. Nevertheless, those results depend largely on the safety factors assumed in the deterministic computations relative to the probability distributions considered in the deterministic approach. Alternatively, the safety margins can be computed or calibrated for specific cases based on probabilistic calculations. In that case the results of deterministic and probabilistic methods can be similar, ensuring the required reliability of the practical deterministic approach, but not being excessively restrictive.Ports and WaterwaysHydraulic EngineeringCivil Engineering and Geoscience
Localization of viral antigens in leaf protoplasts and plants by immunogold labelling
No full textThis thesis describes the application of an immunocytochemical technique, immunogold labelling, new in the light and electron microscopic study of the plant viral infection. In Chapter 1 the present state of knowledge of the plant viral infection process, as revealed by insitu studies of infected cells, is briefly reviewed. Until now, light and electron microscopic studies have merely described morphological changes in cells and tissue as a result of viral infection, but have failed to provide information on the functional role of these structures in the viral infection process and their association with viral components. A common cytopathological feature of many different plant viruses seems to be the induction of membranous vesicles or membranous bodies, which have been implicated in viral replication. However, only in a few cases some evidence was obtained with regard to the Intracellular location of viral replication and the association of replication and membranes. Available cytochemical techniques have apparently failed to provide a tool for the identification of virus particles and virus-encoded proteins within cellular structures. The Impact of a suitable detection techniques to elucidate the molecular processes of viral replication and transport insitu is obvious, as it would link findings obtained by invitro experiments to the events observed in the cell.Immunogold labelling seems to provide such a tool for the tracing of antigens in light and electron microscopic preparations of biological specimens. Gold particles are excellent markers for electron microscopy, because of their high electron density which makes them appear as black dots In EM preparations. Furthermore, by a simple silver staining following gold labelling, viral antigens can be dete cted in semi-thin sections with the light microscope. The application of immunogold labelling for the light and electron microscopic localization of antigens is described in Chapters 2, 3, 4, 5, 6 and 7.In Chapter 2 the preparation of homodisperse suspensions of colloidal gold particles is described. By adsorption of protein A to the surface of the gold particles, a marker (protein A-gold, pAg) is obtained which can be used for labelling antigen-antibody complexes. The specificity of the technique was demonstrated by gold labelling of antibodies bound to plant viruses in mixed suspensions of two viruses. Each virus was labelled using its homologous antiserum and pAg, and no significant cross-reaction with the other virus occurred. Simultaneous identification of two different viruses (CCMV and SBMV) with similar morphological appearance was achieved by double labelling with pAg-complexes containing gold particles of 7 and 16 nm, respectively. Immunogold labelling of viral antigens in suspension has been applied to distinguish between different serologically related viruses like strains of TMV (Pares and Whitecross, 1982), and the potyvirus sugarcane mosaic virus and maize dwarf mosaic virus (Alexander and Toler, 1986; 1985). A clear advantage of the immunogold labelling over conventional decoration of antigens is that the discrete gold particles allow quantification of the results.The immunogold labelling of viral antigen in ultrathin sections of infected protoplasts is described in Chapter 3. Best results were obtained when the protoplasts were only mildly fixed with aldehydes, dehydrated and finally embedded in Lowicryl K4M at -30°C. The antigenicity of viral coat protein was well preserved. A disadvantage of the method is the limited preservation of cell structures, especially membranes due to extraction of lipids. Weibull etal. (1983) reported that approximately 50% of the lipid content of cells may be extracted, despite the low temperatures used in the Lowicryl K4M embedding procedure. Ashford etal. (1986) questioned the low temperature character of Lowicryl embedding, and found that during polymerization of the resin, temperature rises due to the exothermic nature of the reaction. With plant tissue (not protoplasts), low temperature dehydration and infiltration of the embedding resin must be prolonged, to allow sufficient penetration of the chemicals through the thick walls surrounding the plant cells, and this may result in even more extraction than reported by Weibull and colleagues. Rapid dehydration in ethanol and infiltration of plant tissue with a polar resin like LR White at ambient temperatures, therefore, seems to be a good alternative (Newman etal. , 1983; Causton, 1984; Newman and Jasani, 1984).Light microscopic localization of viral antigen in semi-thin sections of LR White embedded plant tissue is described in Chapter 6. CCMV was successfully localized in petiolules of systemically inoculated cowpea plants by immunogold labelling and subsequent silver staining (immunogold/silver staining: IGSS). The silver stain could be observed in the light microscope by brightfield, darkfield and phase-contrast illumination. Most sensitive detection, however, was obtained with epi- illumination using polarized light (epipolarization microscopy). Combining epipolarization illumination with brightfield illumination allowed the simultaneous observation of silver stain and cell morphology.Immunogold labelling and IGSS in combination with appropriate fixation and embedding of biological specimens, appear to be efficient and simple techniques for the insitu identification and localization of antigens, with many advantages over other immunochemical and cytochemical techniques, like ferritin- labelling, peroxidase-anti-peroxidase, immunofluorescence and autoradiography, which have only incidentally been used in plant virus research. Recently, Patterson and Verduin (1987) have reviewed the literature on the use of immunogold labelling in animal and plant virology, showing numerous fields of applications and discussing progress made in virus research. With respect to the technique the authors rightly concluded that immunogold labelling is a flexible technique with little limitation for the improvement of existing assays and the development of new ones.Using immunogold labelling to identify and localize virus particles and coat protein, CCMV- infection in cowpea protoplasts was studied as function of the infection time. Observations with regard to virus entry into protoplasts are reported in Chapter 3. Upon inoculation aggregates of virus particles were observed attached to the plasmamembrane, or sometimes penetrating the plasmamembrane at places where the membrane appeared to be damaged. Virus was also found inside vesicles formed by invagination of the plasmamembrane. These vesicles with inoculum-virus particles were stable over long periods of time. Large vesicles (vacuoles) containing viral antigen were also detected at 24 h post-inoculation in protoplasts which were not infected by CCMV.The mechanism by which plant viruses enter their host cells is still disputed (Shaw, 1986). Passage of the plasmalemma by endocytosis was suggested by Takebe (1975), and through pores or lesions by Burgess etal. (1973) and Watts etal. (1981). Our observations do not favour endocytosis to be the mechanism of virus entry leading to infection of the protoplasts as virus containing vesicles are stable. Recently, Roenhorst etal. (1988) presented data supporting a mechanism of virus entry by initial physical association of virus particles with the protoplast membrane and subsequent invasion of virus particles through membrane lesions. Such a mechanism may be also applicable to the cytoplasmic extrusions observed by Laidlaw (1987) after puncturing plant epidermal cells. The author suggested that virus particles may adsorb to the plasmalemma covering the extrusions, which are then withdrawn into the cell. Invasion of whole particles through membrane lesions may then be followed by a uncoating and initial translation (cotranslational disassembly) at the cytoplasmic ribosomes as suggested by Wilson (1985).Ultrastructure of RNA-inoculated protoplasts was studied in sections of aldehyde- and osmium-fixed protoplasts (Chapter 4). Cytological alterations attributed to virus infection consisted of dilation of the endoplasmic reticulum (ER) and the formation of vesicles early in infection. Distended ER and vesicles seemed to form a kind of membranous area in the cytoplasm. In protoplasts fixed and embedded in Lowicryl K4M newly synthesized virus particles or coat protein were first localized in restricted areas of the cytoplasm at 6-9 h post-inoculation. The rough appearance of the cytoplasm in these areas suggested the presence of membranous structures like observed in osmium-fixed protoplasts. However, due to poor membrane preservation in Lowicryl embedded material this could not be proven. Within one protoplast several of these labelled areas were identified. At later stages of infection viral antigen was located throughout the cytoplasm, but also in the nucleus and in particular the nucleolus. No viral antigen was detected in or specifically associated with chloroplasts, mitochondria, microbodies and vacuoles. The specificity of gold labelling was demonstrated by quantification of the labelling density on sections of infected and non-infected protoplasts. These results indicate that CCMV coat protein synthesis and virus assembly take place in the cytoplasm of plant cells, but the involvement of cellular structures, in particular membranes, remains to be established. Protein synthesis and virus assembly may occur in certain restricted sites (compartments) in the cytoplasm possibly formed by the membranous bodies. Compartmentalization of the cytoplasm, creating different environments in the cell, may explain the occurrence of both disassembly and assembly in the same cell, and furthermore account for the phenomenon of specific assembly of viral RUA and homologous coat protein in cells infected with two related viruses like CCMV and BMV (Sakai etal. , 1983 ; Zaitlin and Hull, 1987). Whether RNA-replication also occurs in the same location as coat protein synthesis and virus assembly could be established by localization of non-structural virus encoded proteins involved in viral replication. However, antisera against these products of the CCMV-genome were not available. The function of CCMV coat protein or virus in the nucleus and especially the nucleolus is not known. Coat protein may have an affinity for ribosomal proteins and/or fulfill some functional role in the viral replication. Kim 1977 described the occurrence of filamentous inclusions (FI) in the nucleus often associated with the nucleolus. These FI were not found in the nuclei of cowpea protoplasts (this study) or tobacco protoplasts (Burgess etal. , 1974), but may be formed later in the infection by excess coat protein. Bancroft etal. (1969) showed the ability of CCMV-coat protein to form narrow tubules under specific conditions. The (FI) described by Kim (1977) may represent this type of coat protein aggregation, although the chemical composition of the (FI) is not yet known.In Chapter 5 preliminary observations are reported on the localization of sites of CPMV replication in cowpea protoplasts, by in situ detection of coat proteins and non-structural proteins involved in viral replication and proteolytic processing. With regard to virus entry and subsequent locations of inoculum virus inside vesicles, similar phenomena were observed as in infection with CCMV. Infection of CPMV generates large inclusion bodies in the cytoplasm, consisting of membranous vesicles with fibrillary material and adjoining amorphous electron-dense material which have been observed as early as 12 h post- inoculation. Virus particles and/or coat protein were first detected 24 h after inoculation throughout the entire cytoplasm and in between the membranous vesicles and electron dense material. The 24K, 170K and their precursor proteins were exclusively localized in the electron dense material and not in association with the membranous vesicles or any other location in the cell. These results show that the electron-dense material consists at least in part of CPMV-encoded non-structural proteins and may represent a site for accumulation of non-functional proteins. The membranous vesicles have been implicated in viral RNA synthesis (Goldbach and Van Kammen, 1985). The failure to detect non- structural proteins in association with these membranes may be explained by either a low concentration of these proteins at the site of replication or by extraction of these proteins during the fixation and embedding procedure, despite the low temperature.With IGSS the distribution of CCMV in cowpea plants was monitored at different times after systemic inoculation according to Dawson and Sehlegel (1976) (Chapters 6 and 7). No virus was detected at the time of temperature shift (t=0) in petiolule and leaves of plants subjected to 3 days of differential temperature treatment. Virus was first localized in phloem parenchyma cells of petiolule and veins at t=3 h and from there it spread to neighbouring tissues. Twenty four hours after systemic inoculation virus was located in the phloem, bundle sheath, cortex, but also in the cambium and some xylem cells. These results show that CCMV is transported from the inoculated primary leaves to the secondary leaves through the phloem, apparently following the route of metabolites. This finding is in agreement and further supports the generally accepted concept of plant virus long-distance transport through phloem. tissue (Matthews, 1982; Atabekov and Dorokhov, 1984). The failure to detect CCMV in differentiated sieve elements may indicate that the form in which the infectious entity is transported is another than virus particles (Atabekov and Dorokhov, 1984), or that the amount of virus transported through the sieve elements is below detectable levels. The true character of the synchrony of infection of leaf mesophyll cells obtained by differential temperature treatment is disputed. Infection of mesophyll tells may have been accomplished after shifting the plants to higher temperature by fast transport of infectious particles from the vascular tissue, as was also suggested by Dorokhov etal. (1981).For the first time a suitable method for localization of antigens is available, which can be routinely applied for both light and electron microscopic study of the plant viral infection process. The application of the gold labelling technique in the localization of viral structural and non-structural proteins has been demonstrated, using CCMV- and CPMV-infections of plant cells as model system.With regard to the technique, future work must be done on the improvement of the preservation of cellular structures, especially membranes, as these appear only poorly in Lowicryl embedded plant tissue even with dehydration, infiltration and polymerization at low temperatures. Alternatives, may be found in cryofixation and cryosectioning or freeze-substitution techniques.With regard to the study of the plant viral infection process, the localization of virus-encoded proteins involved in replication and transport, but also the localization of plant viral nucleic acids by insitu hybridization, will contribute to the understanding of the mechanisms underlying these events. New biochemical techniques like the production of infectious transcripts from cloned viral cDNA (Ahlquist etal. 1984) enabling genetic manipulation of the viral genome, and integration of plant viral genes into the plant genome (Gardner etal. , 1984; Abel etal. , 1986) will supply future model systems for the study of virus-host interactions
