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The object of this thesis is to use travel-time tomography to focus and enhance the existing global image of the Earth's mantle and crust. This image is still rather blurred with respect to the considerably sharper pictures commonly obtained in regional studies. The improvement is basically obtained in two steps: In the first step a more or less conventional tomography method is applied to a reprocessed and sensibly averaged data set for a more sophisticated, irregular discretization of the study volume, and in the second step the (global) method itself is refined by introducing 3-D ray tracing to calculate accurate seismic ray paths through heterogeneous velocity models (nonlinear tomography)

Quality assurance of radiodiagnostic equipment -Overview of literature since 2004

Het Britse handboek voor de kwaliteitsborging (Quality Assurance) van CT-scanners en andere rontgentoestellen, kan met enkele aanpassingen ook in Nederland gebruikt worden. Dit blijkt uit een literatuurstudie van het RIVM naar de kwaliteitsborging van deze apparaten. Beelden van CT-scanners en andere rontgentoestellen moeten goed genoeg zijn om een juiste diagnose te kunnen stellen. Ze worden gemaakt met rontgenstraling en die is schadelijk voor de gezondheid. De beelden worden echter vaak beter als er meer straling wordt gebruikt. Om goede beelden te krijgen met een zo laag mogelijke stralingsdosis is er veel aandacht nodig voor het optimaal laten functioneren van de apparatuur. Het geheel van maatregelen die hieraan bijdragen wordt kwaliteitsborging genoemd. Er is in Nederland geen algemeen handboek voor de kwaliteitsborging van CT-scanners en andere rontgenapparaten. Uit het onderzoek van het RIVM blijkt dat het Britse handboek, aangevuld met enkele andere documenten, vrij eenvoudig naar de Nederlandse praktijk vertaald kan worden. Wel is er nog een enkele toevoeging nodig en moeten grenswaarden worden aangepast aan de Nederlandse regelgeving.The British handbook on quality assurance of CT and other x-ray equipment may, with some adaptations, also be used in the Netherlands. This is the main conclusion of a literature study by RIVM on quality assurance of such equipment. Images from CT scanners and other x-ray equipment must have sufficient quality to enable a correct diagnosis. They are obtained using x-rays, which have adverse health effects. However, in diagnostic imaging, higher x-ray doses often lead to better image quality. To obtain good images while keeping the radiation dose as low as reasonably achievable, much attention is needed for the optimal performance of the equipment. Quality assurance is the complex of all measures needed to achieve this. A general handbook on quality assurance of CT and other x-ray equipment adapted to the Dutch practice does not exist. The literature study by RIVM shows that it should be relatively straightforward to adapt, with some additions, the British handbook to the Dutch practice and legislation.Inspectie voor de Gezondheidszor

Quality assurance for the optimization of patient dose in interventional radiology

Drie maatregelen kunnen de dosis straling optimaliseren die patienten ontvangen tijdens radiologische interventies. Ten eerste moderne apparatuur gebruiken die speciaal geschikt is voor interventies. Ten tweede extra aandacht schenken aan stralingsbescherming tijdens opleidingen op het gebied van de interventieradiologie. En tot slot complicaties van straling opnemen in het complicatieregister van de sectie Interventieradiologie van de Nederlandse Vereniging voor Radiologie. Dit blijkt uit onderzoek dat het RIVM in opdracht van de Inspectie voor de Gezondheidszorg heeft uitgevoerd naar de kwaliteitsborging van de interventieradiologie in Nederland. De opdracht is ingegeven door de relatief hoge stralingsdosis waaraan patienten kunnen worden blootgesteld tijdens radiologische interventies. Bij interventieradiologie worden medische behandelingen uitgevoerd via een kleine opening in de huid, terwijl die ingreep in beeld wordt gebracht met behulp van rontgen, CT, MRI of echografie. Bij gebruik van rontgen of CT kan de stralingsdosis leiden tot nadelige effecten voor de gezondheid, zoals roodheid, verbranding van de huid, (tijdelijke) ontharing of op de lange termijn kanker.Three measures may optimize the radiation dose that patients receive during interventional radiology procedures. The first is by using modern equipment that is appropriate for interventional radiology procedures, while the second involves paying extra attention to radiation protection in courses in the field of interventional radiology. A final measure is to incorporate radiation-related complications into the complication register of the Interventional Radiology section of the Dutch Association for Radiology. This was found in an investigation of quality assurance in interventional radiology in the Netherlands that was assigned to RIVM by the Dutch Health Inspectorate. The investigation was motivated by the relatively high radiation dose that patients undergoing an interventional radiology procedure may be exposed to. In interventional radiology, medical treatment is applied through a small opening in the skin, while the procedure is monitored using medical imaging such as X-ray, CT, MRI or ultrasound. In the case of X-ray or CT, the radiation dose may cause adverse health effects such as erythema, burnt skin, (temporary) epilation or, in the long term, cancer.Inspectie voor de Gezondheidszor

Physical and psychological health at adolescence and home care use later in life

OBJECTIVES: To examine the relation between physical and psychological health indicators at adolescence (age 18) and household, personal, and nursing home care use later in life at ages 57–69 years. METHODS: Using medical examinations on men born in 1944–1947 who were evaluated for military service at age 18 in the Netherlands, we link physical and psychological health assessments to national administrative microdata on the use of home care services at ages 57–69 years. We postulate a panel probit model for home care use over these years. In the analyses, we account for selective survival through correlated panel probit models. RESULTS: Poor mental health and being overweight at age 18 are important predictors of later life home care use. Home care use at ages 57–69 years is also highly related to and interacts with father’s socioeconomic status and recruits’ education at age 18. DISCUSSION: Specific health characteristics identified at age 18 are highly related to the later utilization of home-care at age 57–69 years. Some characteristics may be amenable to early life health interventions to decrease the future costs of long-term home care

Gains in Life Expectancy Associated with Higher Education in Men

Background: Many studies show large differences in life expectancy across the range of education, intelligence, and socio-economic status. As educational attainment, intelligence, and socio-economic status are highly interrelated, appropriate methods are required to disentangle their separate effects. The aim of this paper is to present a novel method to estimate gains in life expectancy specifically associated with increased education. Our analysis is based on a structural model in which education level, IQ at age 18 and mortality all depend on (latent) intelligence. The model allows for (selective) educational choices based on observed factors and on an unobserved factor capturing intelligence. Our estimates are based on information from health examinations of military conscripts born in 1944–1947 in The Netherlands and their vital status through age 66 (n = 39,798). Results: Our empirical results show that men with higher education have lower mortality. Using structural models to account for education choice, the estimated gain in life expectancy for men moving up one educational level ranges from 0.3 to 2 years. The estimated gain in months alive over the observational period ranges from -1.2 to 5.7 months. The selection effect is positive and amounts to a gain of one to two months. Decomposition of the selection effect shows that the gain from selection on (latent) intelligence is larger than the gain from selection on observed factors and amounts to 1.0 to 1.7 additional months alive. Conclusion: Our findings confirm the strong selection into education based on socio-economic status and intelligence. They also show significant higher life expectancy among individuals with higher education after the selectivity of education choice has been taken into account. Based on these estimates, it is plausible therefore that increases in education could lead to increases in life expectancy

War- and famine-related excess mortality among civilians in the Netherlands, 1944-1945

National estimates exist for war- and famine-related deaths in the Netherlands during the last stages of World War II, but no such estimates are available at the local level. To fill this information gap, this article aims at mapping and visualizing the timing of war- and famine-related excess mortality by municipality among the civilian population within the Netherlands. We use mortality statistics at the level of municipalities because these are the smallest administrative units for which this information is available. We use a seasonally adjusted mortality model combined with a difference-in-difference approach to estimate the number of excess deaths in the period between January 1944 and July 1945 separately for each Dutch municipality

Mesozoic subducted slabs under Siberia

Recent results from seismic tomography demonstrate that subducted oceanic lithosphere can be observed globally as slabs of relatively high seismic velocity in the upper as well as lower mantle(1,2). The Asian mantle is no exception, with high-velocity slabs being observed downwards from the west Pacific subduction zones under the Kurile Islands, Japan and farther south(3-5), as well as under Asia's ancient Tethyan margin. Here we present evidence for the presence of slab remnants of Jurassic age that were subducted when the Mongol-Okhotsk and Kular-Nera oceans closed between Siberia, the combined Mongolia-North China blocks and the Omolon block(6-8). We identify these proposed slab remnants in the lower mantle west of Lake Baikal down to depths of at least 2,500 km, where they join what has been interpreted as a 'graveyard'(9) of subducted lithosphere at the bottom of the mantle. Our interpretation implies that slab remnants in the mantle can still be recognized some 150 million years or more after they have been subducted and that such structures may be useful in associating geodynamic to surface-tectonic processes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62524/1/397246a0.pd