106 research outputs found
Out-of-hours primary care and the quality of telephone triage
No full textContains fulltext :
mmubn000001_575475080.pdf (Publisher’s version ) (Open Access)Radboud Universiteit Nijmegen, 26 januari 2012Promotores : Wensing, M.J.P., Grol, R.P.T.M. Co-promotor : Giesen, P.H.J
HIV Treatment Monitoring in Resource-Limited Settings: Current Paradigms and Future Strategies
No full textThe human immunodeficiency virus (HIV) has a profound impact on global health and severely affects many low- and middle-income countries in sub-Saharan Africa. Antiretroviral therapy (ART) has transformed HIV infection from a deadly disease into a treatable chronic condition. However, ART is not always successful.
This thesis aims to contribute to the durable effectiveness of ART through the development of novel strategies for laboratory monitoring during treatment for sub-Saharan African countries. Most of this research was performed in South Africa, where approximately 12.8% of inhabitants are currently living with HIV.
This thesis shows that while ART is usually effective, success is not attained in all cases for a variety of reasons. It confirms that the risk of therapy failure is not solely determined by patient-related factors such as gender and income, but equally by characteristics of the virus, in particular viral resistance to ART. It also shows that there is a considerable delay between the detection of therapy failure and clinical action to address this problem in routine clinical care in South Africa.
The thesis subsequently explores novel strategies for HIV treatment monitoring in sub-Saharan Africa. A more stringent definition of treatment success, that is currently already in use in high-income countries, should also be used in low- and middle-income countries, as this definition allows for earlier identification of therapy failure. Furthermore, innovative tools for drug exposure testing may be used to detect suboptimal adherence to treatment and to identify persons who are at risk of harbouring drug resistant HIV
INVESTIGATION OF THE CENTRAL NERVOUS SYSTEM AS A VIRAL RESERVOIR FOR HIV
No full textAntiretroviral therapy (ART) has substantially improved treatment outcomes for people with HIV (PWH) by effectively suppressing viral replication. However, HIV hides in resting cells and achievement of HIV cure therefore relies on the eradication or permanent silencing of these infected resting cells.
We investigated whether the central nervous system (CNS) can serve as an anatomical reservoir for HIV and in which brain cells HIV might be hiding. Therefore, we used a unique collection of samples, obtained from blood, cerebrospinal fluid (CSF) and brain biopsies from untreated and treated PWH. Importantly, we detected intact proviral DNA in the CNS despite long-term effective treatment. Furthermore, we found that some individuals had significant differences between the virus population in the blood and the CSF, indicating that HIV can infect and replicate within cells in the CNS. Using microglial culture models, we demonstrated that microglia support productive HIV infection and based upon our newly developed cerebral organoid culture model, also known as “mini-brains”, we demonstrated microglia to be the only HIV target cell in the CNS.
Overall, we demonstrated that the CNS, particularly microglial cells, can support HIV infection and replication and also harbor intact HIV DNA despite long-term ART and viral suppression, suggesting that the CNS can function as a viral reservoir. With this knowledge, we advocate for the inclusion of the CNS in future HIV eradication strategies
Het stedelijke mozaïek: Een vertaling van de voorkeuren van stedelijke bevolkingscategorieën naar ruimtelijke milieus
No full textArchitectur
Verifying the BR-DTS method with hand measurements executed with the PT-100 and the Eddy Covariance method
No full textWithin hydrology evaporation is one of the most important terms in the water- and land surface energy balance. However evaporation is difficult to estimate accurately. Conventional techniques to measure actual evaporation have their drawbacks. One of the main drawbacks is that multiple sensors need to be used, with all their own bias. One of these techniques, the Eddy Covariance (EC) system has the drawback that it is dependent on weather conditions and is known for its problems with closure of the energy balance (Foken, 2008). A new method called the Bowen Ratio- Distributed Temperature Sensing (BR-DTS) method is introduced by Euser et al. (2014). This method determines the Bowen ratio which is the ratio between the sensible heat flux and the latent heat flux. The BR-DTS method measures temperature using a fiber optic cable. This cable is placed vertically along a tower, the cable going up is dry and the cable going down is wrapped in cotton and kept wet. With the dry and wet temperature of the DTS-cable the air temperature and vapour pressure can be determined. By having a large amount of measurements over the height and measuring it with a single sensor the BR-DTS method does not have the problem of varying biases of sensors (Euser et al. 2014). The aim of this study is at first to verify if the temperature data of the dry and wet cable are correct and second to compare the outcome with the EC data. The temperature of the dry and wet cable measured with the BR-DTS method are really close to the temperatures measured with the relative humidity sensors with a maximum R2 of 0.998 at 4 and 16 meter height for the dry cable and a maximum R2 of 0.988 at 16 meter height for the wet cable. The energy gap found is relatively small, see figure 11, and the latent heat flux measured with the BR-DTS setup is just as in the results from B. Schilperoort (2015) greater than the latent heat flux measured with the EC setup. On the other hand the sensible heat flux measured with the BR-DTS setup is smaller than the sensible heat flux measured with the EC setup which is in contradiction with the results from B. Schilperoort (2015).Civil Engineering and GeosciencesWater Managemen
The role of interception in the hydrological cycle
No full textInterception is the part of the rainfall that is intercepted by the earth’s surface and which subsequently evaporates. In this definition the earth’s surface includes everything that becomes wet after a rainfall event and that dries out soon after. It includes: vegetation, soil surface, litter, build-up surface, etc. How much of the precipitation evaporates depends on land cover characteristics, rainfall characteristics, and on the evaporative demand. Interception can amount up to 15-50% of precipitation, which is a significant part of the water balance. One can distinguish many types of interception, which can also interplay with each other. For example canopy, forest floor, fog, snow, and urban interception. This study we focus on canopy and forest floor interception. We measured interception of three dominant European vegetation types at three locations. In the Huewelerbach (Luxembourg) a beech forest has been investigated, in Westerbork (the Netherlands) grasses and mosses, and in the Botanical Garden (Delft, the Netherlands) a Cedar tree. Canopy interception is determined by the difference between gross precipitation and the sum of throughfall and stemflow. To measure forest floor interception a special device has been developed. It consists of two aluminium basins which are mounted above each other. The upper basin is permeable and contains the forest floor. By weighing both basins simultaneously, evaporation from interception can be calculated. For the beech forest we found that canopy interception has a clear seasonal trend ranging from 15% of rainfall in summer to 7% in winter. On the other hand, forest floor interception appears to be constant over the year and evaporates on average 22% of precipitation. Evaporation from the Cedar needle floor is only a bit lower: 18%, although the storage capacity is significantly lower: 1.0 mm for the needle floor compared to 1.8 mm for beech leaves. Both interception thesholds have a coefficient of variation as high as ±100%. However, the interception process is not sensitive to this variability, resulting only in 11% variation of evaporation estimates for the beech forest. Hence the number of raindays and the potential evaporation are stronger drivers of interception. Furthermore, the spatial correlation of the throughfall and infiltration has been investigated with semi-variograms and time stability plots. Within 6-7 m distance throughfall and infiltration are correlated and the general persistence is weak. The effect of spatial variability of interception on subsurface storm flow has also been investigated with a virtual experiment. A virtual experiment is a numerical experiment driven by collective field intelligence. It provides a learning tool to investigate the effect of separated processes in a complex system. We used this approach to better understand the generation and behaviour of subsurface stormflow (SSF) at the hillslope scale, because this is still poorly understood. Interactions between the permeable soil and the less permeable bedrock may cause non-linearity in subsurface flow depending on several hillslope attributes such as soil depth, slope angle, and bedrock permeability. It is known that the size of storm events also controls subsurface flow generation. The objectives of this study were three-fold: 1) to investigate if and how different configurations of throughfall patterns change the SSF behaviour; 2) to investigate the interplay between the spatially variable input and the hillslope attributes (slope angle and soil depth) on the generation of SSF; and 3) to investigate a geo-statistical tool that uses semi-variogram characteristics to analyse if soil moisture patterns during an event are dominated by throughfall patterns or by bedrock topography patterns. In our virtual experiment we combined spatial throughfall data from the Huewelerbach catchment in Luxembourg with the topography characteristics of the Panola hillslope in Georgia, USA. We used HYDRUS-3D as a modeling platform. The effect of the spatial throughfall pattern appears to be large on both SSF generation and the spatial variability of SSF along the hillslope, but only marginal on total SSF amounts. The spatial variability of SSF along the hillslope appears to be closely related to the drainage pattern of the bedrock. The geo-statistical analysis indicates that during the event soil moisture distribution reflects throughfall patterns, whereas after the event, during the drainage of the hillslope, the bedrock topography increasingly dominates soil moisture patterns. Furthermore, we found that on a daily time scale, interception is a typical threshold process. We used this characteristic to upscale daily interception to an annual evaporation model and found similarities with the Budyko curve. The Budyko curve is often used to estimate the actual evaporation as a function of the aridity index in a catchment. Different empirical equations exist to describe this relationship; however, these equations have very limited physical background. Our model concept is physically based and uses only measurable parameters. It makes use of two types of evaporation: interception and transpiration. Interception is modeled as a threshold process at a daily time scale. If multiplied with the rainfall distribution function, integrated, and multiplied with the expected number of rain days per month, the monthly interception is obtained. In a similar way, the monthly interception can be upscaled to annual interception. This results in a Budyko-type equation. Analogous to the interception process, transpiration can be modeled as a threshold process at a monthly time scale and can be upscaled by integration and multiplication with the expected number of rain months. The expected rain days per month are modeled in two ways: as a fixed proportion of the monthly rainfall and as a power function based on Markov properties of rainfall. The latter is solved numerically. It appears that on an annual basis the analytical model does not differ much from the numerical solution. Hence, the analytical model is used and applied on 10 locations in different climates. We show that the empirical Budyko curve can be constructed on the basis of measurable parameters representing evaporation threshold values and the expected number of rain days and rain months and, in addition, a monthly moisture carry-over amount for semi-arid zones. Overall, we can conclude that interception has different roles in the hydrological cycle. The most important role is as a rainfall reducer, causing a significant amount of rainfall to be directly fed back to the atmosphere which is not available for infiltration. Second, interception influences the spatial distribution of infiltration. This has large influences on the soil moisture pattern and on subsurface flow paths. Finally, interception redistributes the water flows in time. Due to the filling of the spatial variable storage capacity and rainfall, the delay time is not homogeneous in space. This thesis shows that interception is a key process in the hydrological cycle. It involves significant fluxes in the water balance and influences the subsequent processes both in quantity and timing. It is an important cause for non-linear behaviour of catchments. The role of interception in the hydrological cycle is crucial.WatermanagementCivil Engineering and Geoscience
Partitioning of evaporation fluxes in summer and winter using stable isotope approach
No full textIrrigation is the largest user of fresh water in the world. Unfortunately a large part of irrigation is unsustainable and inefficiently causing water scarcity with sometimes terrible effects on the water cycle, ecology, economy and food production. The key in determining the efficiency of irrigation is to investigate how much irrigation water is indeed used by crops for transpiration. Only this part of the total evaporation is used by crops to produce biomass and can be seen as productive evaporation. To separate evaporation into the productive (transpiration) and non-productive (interception and soil evaporation) terms we use stable isotopes 2-H and 18-O. This research investigates the changes of isotopic composition of stable isotopes 2-H and 18-O in the soil over the year in a lysimeter setup in the Netherlands. When the water balance is combined with isotopic values, an isotope mass balance can be made. This is used to separate evaporation fluxes and makes it possible to determine the transpiration flux of vegetation. During a six month period (November 2010 to June 2011) values of stable isotopes 2-H and 18-O in a lysimeter covered with grass were monitored. Furthermore, during a two month period (May and June 2011) a second lysimeter without vegetation was monitored to find out what the effect is of vegetation on isotope composition. When comparing the lysimeter with and without grass cover, it was found that transpiration plays no role in the non-covered lysimeter. In the latter, higher enrichment of soil water was observed and the isotope regression line had a lower slope. Isotope composition changes during the year. In winter (November to February) soil evaporation and isotopic enrichment were low. In summer (April to June) soil evaporation and isotopic enrichment were high. This research shows that it is possible to separate evaporation into soil evaporation and transpiration. During the cold period (December to February) the amount of transpiration was relatively high (75.0 % - 90.5 %) , since only limited soil evaporation could take place. When less water was available during warm periods (April and May), the share of transpiration in the total evaporation term decreased (47.3% - 53.4 %).Water ManagementCivil Engineering and Geoscience
The effect of the imperviousness on the hydrological response time of sewer districts in Rotterdam: Study based on new monitoring system by municipality of Rotterdam
No full textAdditional thesis - Due to an expected increase in rainfall intensity in the future because of climate change for the area of Rotterdam, the amount of storm water runoff will increase as well, resulting in higher stress on the sewer system. But until now we don’t fully understand the behavior of a sewer system. This additional thesis should help in a better understanding of the system, as it investigates the hydrological response time of the urban drainage system of Rotterdam and focuses on the effect of imperviousness. This research is based on data which are collected during the first seven months of operation of the monitoring system at 21 combined sewer overflow (CSO) weirs which was implemented in June 2016. As the hydrological response time gives information about the behavior of a sewage system, it’s an important parameter to investigate and the question is how it’s being influenced by parameters such as the imperviousness and to what extent the behavior of the sewer districts in Rotterdam is different from what we would expect from theory. From the results, we see that there is no single hydrological response time for both Time-to-Peak and Peak-to-Peak responses. The response times are highly variable with large standard deviations. There seems to be no clear linear relationship with the imperviousness or the connected surface area for the sewer system of Rotterdam. Furthermore, no significant relationship was found for several rainfall characteristics like intensity, rain event duration and cumulative rain volumes in the previous period with the hydrological response time. Finally, it was shown that the large variability in response times is mainly associated with assumptions on starting time of a rain event, which can produce large Time-to-Peak responses. However, Peak-to-Peak responses found in the research are also significantly larger than the responses found in theory. All in all, the results have shown that the response times are larger than we expected from theory and that variability cannot be explained by variability in rainfall characteristics nor by relations with catchment size or imperviousness for the urban drainage system of Rotterdam. For future research, it is recommended to have a further look into the system responses by doing a signal analysis for individual events in order to understand the high variability in responses. Furthermore, the rain radar, which will be implemented in Rotterdam in the summer of 2017, might help in a better understanding of the influence of local rainfall variability on the response time.Civil Engineering and GeosciencesWater Managemen
Sapogenol is a major microbial metabolite in human plasma associated with high protein soy-based diets : the relevance for functional food formulations
No full textFunding: This work was supported by The Scottish Government's Rural and Environment Science and Analytical Services Division (RESAS). Acknowledgments: The authors are grateful to the ALPRO™ Foundation for supporting this work. Author Contributions: Conceptualization, A.M.J. and W.R.R.; methodology, M.N., Y.B., S.H.D., G.J.D., J.S.C.; data curation, M.N.; V.R.; writing—original draft preparation, M.N.; writing—review and editing, M.N.; V.R., W.R.R. All authors have read and agreed to the published version of the manuscript.Peer reviewe
Bouwakoestische aspecten van IFD-bouwen: Onderzoek naar de huidige kwaliteit en verbetermogelijkheden
No full textOnderzoek naar de bouwakoestische aspecten van IFD-constructies: - Binnenwanden - Vloerconstructies - GevelconstructiesSteel and Timber structuresStructural EngineeringCivil Engineering and Geoscience
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