847 research outputs found
Intra-operative bacterial contamination : control and consequences
Get PDFEen combinatie van gedragsmaatregelen en een beter luchtinblaassysteem in de operatiekamer leidt tot een afname van het aantal bacteriën bij plaatsing van een knie- of heupprothese. Hierdoor neemt de kans af op infectie van de prothese en op problemen met wondgenezing na de operatie. Dit blijkt uit onderzoek van Bas Knobben, uitgevoerd bij de afdeling Orthopedie en de vakgroep Biomedical Engineering van het Universitair Medisch Centrum Groningen. Deze bevindingen kunnen ertoe bijdragen dat gewrichtsprothesen minder vaak infecteren en vervangen moeten worden. Hij promoveert op 26 april 2006 op zijn onderzoek aan de Rijksuniversiteit Groningen.
In elke operatiekamer kunnen ondanks strenge hygiënische maatregelen bacteriën voorkomen die een mogelijk risico vormen voor infectie van prothesen en problemen met wondgenezing na de operatie. Tot nu toe was de omvang hiervan onduidelijk. Uit het onderzoek van Knobben blijkt dat bij 36 procent van de plaatsingen van heupprothesen bacteriën aanwezig waren op het instrumentarium en op verwijderde botsnippers bij het inbrengen van de prothesen. Ook bleek er een verband te zijn tussen het vóórkomen van deze bacteriën en het optreden van verstoorde wondgenezing en infectie van de prothesen.
Gedragsmaatregelen
Knobben onderzocht of gedrags- en technische maatregelen, aanvullend op de gebruikelijke hygiënerichtlijnen, de kans op bacteriële besmetting tijdens de operatie verkleinen. Uit zijn onderzoek blijkt dat de combinatie van deze maatregelen in een operatiekamer de kans op aanwezigheid van bacteriën deed afnemen van 34 procent naar 8 procent. Tegelijk nam de kans op infectie van prothesen, verstoorde wondgenezing en wondinfectie beduidend af.
De gedragsmaatregelen die onder andere werden genomen, zijn het beperken van het spreken en het in- en uitlopen van de operatiekamer door het operatiekamerpersoneel, het gecontroleerd bewegen, het juiste gebruik van het neus-/mondkapje en een beter gebruik van het gebied onder de luchtstroom. Een van de technische maatregelen betrof het gebruik van een beter luchtinblaassysteem (laminaire airflow). Hierbij vindt een constante aanvoer van schone lucht plaats boven het operatiegebied en worden bacteriën via verticale luchtstromen afgevoerd.
Kosteneffectief
Met dit onderzoek toont Knobben aan dat gedragsmaatregelen en een beter luchtinblaassysteem in de operatiekamer infecties van prothesen en problemen met wondgenezing kunnen voorkomen. De maatregelen zijn bovendien kosteneffectief: de gemiddelde totale kosten per patiënt met een eerste (primaire) prothese zonder infectie zijn ongeveer € 15.000, zo’n 3,5 keer lager dan die van een patiënt met een geïnfecteerde prothese (ongeveer € 52.000). De resultaten van dit proefschrift hebben ertoe geleid dat het Universitair Medisch Centrum Groningen de aanvullende gedrags- en technische maatregelen toepast bij het plaatsen van prothesen.
Verdubbeling
In Nederland zijn in 2004 ongeveer 25.000 heup- en 20.000 knieprothesen geplaatst. De belangrijkste indicatie voor het plaatsen hiervan is gewrichtsslijtage. De verwachting is dat door vergrijzing het aantal mensen dat in aanmerking komt voor deze operaties de komende twintig jaar zal verdubbelen. Bij ongeveer één tot vier procent van de patiënten treedt na plaatsing een bacteriële infectie op.
Biogeochemical redox proxies in sediments from Schandelah during the Toarcian (Early Jurassic)
No full textAuthor contributions:
The sampling was led by Bas van de Schootbrugge and measurements performed by Nina Papadomanolaki, with supervision of Niels A. G. M. van Helmond and Caroline P. Slomp. Measurements were gathered, processed and analysed by Itzel Ruvalcaba Baroni
Multiplexed proteomics mapping of yeast RNA polymerase II and III allows near-complete sequence coverage and reveals several novel phosphorylation sites.
Get PDFThe multisubunit RNA polymerases (Pols) II and III synthesize mainly eukaryotic mRNAs and tRNAs, respectively. Pol II and Pol III are protein complexes consisting of 12 and 17 subunits. Here we analyzed both yeast Pol II and Pol III by multiplexed mass spectrometric analysis using various proteases and both collision induced and electron transfer dissociation. The cumulative data obtained from using the various proteases (trypsin, chymotrypsin, Glu-C and Lys-C) and the two peptide fragmentation approaches allowed us to map nearly the complete sequences of all constituents of both Pol II and III. Notably, chymotrypsin behaved equally well as and in certain circumstances better than trypsin in the context of protein coverage. Although the available high resolution structures have exposed extensive mechanistic insights into transcription, the role of post-translational modification in these processes has been addressed to a lesser extent. In our analysis of Pol II and III we detected 19 phosphorylation sites, of which 12 have not been previously reported. Identified phosphosites were mapped on the Pol II structure which provided indications that they might play a role in regulating the conformation of the clamp region and, as a consequence, interaction of Pol II with nucleic acids. The described multiplexed proteomics approach is generic and reveals that it is possible to map a protein complex to near completion while applying less than 5 mug (approximately 10 pmol) of total starting material
Hoe centrale groepsuitbreidingen ontstaan uit oppervlaktes van driehoeken
No full textIn deze scriptie volgen we de lijn die in W. van Est in “A group theoretic interpretation of area in the elementary geometries” heeft uitgezet, maar we gaan grondiger in op de stof en bewijzen de meeste claims die door Van Est worden gedaan. We kijken naar wat triviale en nontriviale centrale groepsuitbreidingen zijn, wat die te maken hebben met cocykels en coranden en cohomologieklassen. We zien dat iedere cocykel een corresponderende homogene cocykel heeft. Aan de hand van het oppervlaktebegrip in een tweedimensionale ruimte kunnen we een homogene cocykel definiëren en daarmee kunnen we dan een centrale groepsuitbreiding construeren van de symmetriegroepen op het tweedimensionale hyperbolische, euclidische en elliptische vlak. We zien dat die uitbreidingen niet triviaal zijn, maar dat wanneer we ieder van deze uitbreidingen verheffen naar hun universele overdekking, de uitbreiding op de symmetriegroep van het hyperbolische vlak triviaal wordt, in tegenstelling tot die van het euclidische vlak
Computational proteomics: from numbers to biology
No full textThe field of biological research is increasingly trying to understand the complex processes that are too small to observe by eye, even when using a microscope. The real action is taking place at the molecular level; therefore, the only way to investigate this is to use molecular tools. Modern techniques allow studying all proteins in a sample, and the prevailing tool is mass spectrometry based proteomics. As a high-throughput technique, computational analysis is indispensable. In this thesis, we describe several aspects of the treatment of proteomics data using in-house developed tools, and the analysis of several biological experiments. In a first example to illustrate how we used mass spectrometry to investigate biological problems, we investigated the evolution of tyrosine phosphorylation, which possibly arose simultaneously with multicellularity. To investigate this, the placozoan Trichoplax adhaerens was analysed, which is arguably the most primitive animal. We observed several tyrosine kinases in the genome sequence, and phosphoproteomics analysis revealed an extraordinary amount of tyrosine phosphorylation events compared to modern animals. In a second example, we simultaneously analysed RNA, DNA and proteins in a study of a single organ, the rat liver. We compared two different rat strains, the Brown Norwegian (BN) rat, and a variant exhibiting spontaneous hypertension (SHR). Through these measurements we found a differentially regulated rat homolog of a gene that is linked to hypertension in human, CYP17A1, both at the RNA and at the proteome level. The DNA sequence showed a polymorphism in the gene promoter, indicating that a single point mutation may be responsible for the mis-regulation of this gene and protein
De herimplementatie van de automatisering van stichting 'De Delftse Bedrijvendagen'
No full textDit verslag beschrijft het bachelor project van Bas Schaafsma, Ronald Evers en Ste?an Karger. Het doel van dit project is de website en alle achterliggende systemen van stichting ‘De Delftse Bedrijvendagen’ opnieuw te implementeren in één systeem. Dit in tegenstelling tot het huidige systeem waarin vele losse systemen en scripts op een chaotische en niet onderhoudbare manier met elkaar samenwerken.Computer ScienceElectrical Engineering, Mathematics and Computer Scienc
Stability of rock on mild slopes
No full textUntil now, an extensive design method for mild slopes has not been available. The aim of this thesis is to understand the stability of rock on mild slopes under wave attack for impermeable cores in order to optimize designs. Physical model tests have been executed to study this stability for a 1:8 slope. Mossinkoff (2019) executed physical model tests for a 1:10 slope and a re-analysis of these tests is included in this thesis as well. Damage caused by entrained rocks is quantified by damage parameters using stereophotogrammetry and coloured rocks in strips. In this study, the influence of several hydraulic and structural parameters on damage parameters has been investigated for mild slopes. A positive correlation has been found between the significant wave height and the damage parameters. Besides this, based on the analysis it can be concluded that the wave steepness and damage parameters are negatively correlated. An increase in layer thickness of the rocks does not seem to increase the stability of rock on mild slopes. However, the slope angle does have an effect on the stability as a milder slope is associated with less damage. Another conclusion is that more damage continues to be observed even after 15 000 waves. Based on the results of the physical model tests, a design formula is developed for mild slopes to be able to increase efficiency in designs of coastal structures for these mild slopes. This study also provides evidence that rocks on mild slopes have different characteristics of damage and damage development compared to steep slopes. The largest share of entrained rocks transport in upward direction and rocks on mild slopes seem to be more mobile compared to steep slopes. This suggested that it might be more efficient to study the moment when the filter layer or the core becomes visible instead of the static stability of rock within the armour layer itself.Civil Engineering | Hydraulic Engineerin
Computational proteomics: from numbers to biology
No full textThe field of biological research is increasingly trying to understand the complex processes that are too small to observe by eye, even when using a microscope. The real action is taking place at the molecular level; therefore, the only way to investigate this is to use molecular tools. Modern techniques allow studying all proteins in a sample, and the prevailing tool is mass spectrometry based proteomics. As a high-throughput technique, computational analysis is indispensable. In this thesis, we describe several aspects of the treatment of proteomics data using in-house developed tools, and the analysis of several biological experiments. In a first example to illustrate how we used mass spectrometry to investigate biological problems, we investigated the evolution of tyrosine phosphorylation, which possibly arose simultaneously with multicellularity. To investigate this, the placozoan Trichoplax adhaerens was analysed, which is arguably the most primitive animal. We observed several tyrosine kinases in the genome sequence, and phosphoproteomics analysis revealed an extraordinary amount of tyrosine phosphorylation events compared to modern animals. In a second example, we simultaneously analysed RNA, DNA and proteins in a study of a single organ, the rat liver. We compared two different rat strains, the Brown Norwegian (BN) rat, and a variant exhibiting spontaneous hypertension (SHR). Through these measurements we found a differentially regulated rat homolog of a gene that is linked to hypertension in human, CYP17A1, both at the RNA and at the proteome level. The DNA sequence showed a polymorphism in the gene promoter, indicating that a single point mutation may be responsible for the mis-regulation of this gene and protein
Lubricated friction on pipeline pigs
No full textPigs are devices that are transported from time to time through a pipeline, mainly to either clean the pipeline or to inspect the integrity of the pipeline wall. Conventional models for the friction between the pig and the pipe wall, as used in the oil and gas industry, are often criticized for their inaccuracies. To obtain a more accurate model, this thesis investigates the detailed physics behind the frictional forces. The effect of the sliding conditions on the wall-normal force and on the friction force was investigated by conducting 1D lubricated sliding experiments for a rubber lip moving along a metal surface and by performing model simulations, including a parameter sensitivity study. The experiments were conducted for dry water, dodecane and castor oil under varying sliding velocities and loads. The loads were measured with a dual axis transducer and the lubrication film was observed during the experiments with a microscope set-up. The experimental results consist of friction forces for various configurations, which show that the frictional behaviour depends strongly on the lubrication regime in which the rubber lip is operating. The friction coefficients for the boundary lubrication regime and the mixed lubrication regime were measured and compared with results from the model. Among the tested fluids, castor oil showed a non-proportional decrease in friction force when the sliding velocity was increased. This decrease in friction force was interpreted as a transition from the boundary lubrication regime to the mixed lubrication regime. The other tested fluids remained in the boundary lubrication regime in the experimental runs. A validation study was performed by fitting the friction model to the experimental results. Only the dry friction coefficients are in good agreement with the model. Both the water and dodecane experiments show a slight increase for the friction coefficient with increasing lubrication factor and are in mediocre agreement with the friction model. The castor oil experiments are in the mixed lubrication regime of the Stribeck curve and are in reasonable agreement with the model. The results can be linked to the oil and gas industry as pigs can operate in different regimes of the Stribeck curve. Stalled pigs can be the result of transitions from the mixed lubrication regime to the boundary lubrication regime. This can happen when a pig is momentarily slowed down in the pipeline. Recommendations for future experimental work are: performing experiments at higher sliding velocities, using an emulsion as lubricant and finding suitable methods to calibrate models that have a range of input parameters. This work was carried out by the author at the Shell Technology Centre in Amsterdam. The supervision by the Shell staff and the support obtained in carrying out the experiments in the Shell lab are greatly acknowledged.Aerospace Engineerin
Understanding the influence of beach morphology on the alongshore variance in wave run-up on an intermediate reflective beach, considering bars and cusps
No full textThe topic which is considered in this thesis is: understanding the influence of beach morphology on the alongshore variance in wave run-up on an intermediate reflective beach, considering bars and cusps. The focus of this thesis is laid inside the swash zone, in which the water motion is present of waves that run up and run down on a beach. Energy from wave run-up could deliver erosion to the beach. It is relevant to know what the magnitude is of run-up during extreme events, in order to protect the beach. Several studies are done to wave run-up. There are relations which specify run-up, however, the alongshore variability is not studied in detail and less knowledge is available about this topic. At Anmok beach in South-Korea an intermediate reflective beach is present containing beach cusps and crescentic sandbars. A rhythmic bar and beach state contains the most complex morphology, furthermore the morphology changes a lot within intermediate beaches (Wright and Short [1]). The characteristics of this beach are used to perform an analysis to the influence of cusp and bar morphology on alongshore variation in wave run-up. Run-up is composed of setup and swash. Setup is the super elevation of the mean water level, swash is ‘’a time-varying location of the intersection between the ocean and the beach’’ according to Stockdon, Holman [2]. Swash can be decomposed into two parts, incident band swash and infragravity band swash. Swash and setup depend on beach slope, deep-water wave height and the deep water period[2]. To analyse the alongshore variability multiple bathymetries have been generated on which 500 waves are modelled for 60 different wave condition. First of all a reference case is modelled with a uniform bathymetry. Secondly beach cusps are used as input with different length scales and at last a beach cusp with crescentic sandbar is used. The length scales of the cusps are 452, 300 and 100 metres. The bathymetries are idealized bathymetries with the characteristics of Anmok beach. The run-up and components are calculated and an analysis is done to the magnitude of run-up and the standard deviation along the beach. The magnitude of run-up is lower for a cusp system compared with the reference situation and even lower for the cusp bar system. Furthermore there are no large differences in magnitude of run-up between different cusp lengths. A larger alongshore variance is observed when a cusp (bar) system is present. A cusp system of 452 metres contains larger run-up at the horn compared with the embayment, this holds for large and small wave heights. The difference is 18% and 8.4% respectively. However, when a cusp bar system is present less alongshore variability is visible and an opposite behaviour is visible for small wave heights. In this case the same pattern can be seen for large wave heights. A difference of 3.68% is seen when the horn is compared with the embayment. However, for small wave heights the run-up is 10.5% smaller at a horn compared with an embayment. A cusp length of 100 metres shows different behaviour compared with a cusp length of 452 metres. Run-up is larger at an embayment compared to the horn. This holds for large wave heights. The alongshore variance is in this case larger compared to larger cusp lengths. A cusp of 452 metres and 300 metres leads to similar results, whereas a 100 metres cusp shows deviations. It could be edge waves which could have an influence on a cusp with a length of 100 metres.<br/
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