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Coming dissertations at Uppsala university

  • Water–fat separation in magnetic resonance imaging and its application in studies of brown adipose tissue Author: Jonathan Andersson Link: Publication date: 2019-08-23 13:12

    Virtually all the magnetic resonance imaging (MRI) signal of a human originates from water and fat molecules. By utilizing the property chemical shift the signal can be separated, creating water- and fat-only images. From these images it is possible to calculate quantitative fat fraction (FF) images, where the value of each voxel is equal to the percentage of its signal originating from fat. In papers I and II methods for water–fat signal separation are presented and evaluated.

    The method in paper I utilizes a graph-cut to separate the signal and was designed to perform well even for a low signal-to-noise ratio (SNR). The method was shown to perform as well as previous methods at high SNRs, and better at low SNRs.

    The method presented in paper II uses convolutional neural networks to perform the signal separation. The method was shown to perform similarly to a previous method using a graph-cut when provided non-undersampled input data. Furthermore, the method was shown to be able to separate the signal using undersampled data. This may allow for accelerated MRI scans in the future.

    Brown adipose tissue (BAT) is a thermogenic organ with the main purpose of expending chemical energy to prevent the body temperature from falling too low. Its energy expending capability makes it a potential target for treating overweight/obesity and metabolic dysfunctions, such as type 2 diabetes. The most well-established way of estimating the metabolic potential of BAT is through measuring glucose uptake using 18F-fludeoxyglucose (18F-FDG) positron emission tomography (PET) during cooling. This technique exposes subjects to potentially harmful ionizing radiation, and alternative methods are desired. One alternative method is measuring the BAT FF using MRI.

    In paper III the BAT FF in 7-year olds was shown to be negatively associated with blood serum levels of the bone-specific protein osteocalcin and, after correction for adiposity, thigh muscle volume. This may have implications for how BAT interacts with both bone and muscle tissue.

    In paper IV the glucose uptake of BAT during cooling of adult humans was measured using 18F-FDG PET. Additionally, their BAT FF was measured using MRI, and their skin temperature during cooling near a major BAT depot was measured using infrared thermography (IRT). It was found that both the BAT FF and the temperature measured using IRT correlated with the BAT glucose uptake, meaning these measurements could be potential alternatives to 18F-FDG PET in future studies of BAT.

  • Immigration: Policies, Mobility, and Integration Author: Cristina Bratu Link: Publication date: 2019-08-23 11:46

    Essay I: Labor immigration is an important tool that countries can use to address labor shortages. The design of labor immigration policies may affect flows and the composition of immigrant workers, which can, in turn, have an effect on firms and workers in the host country. I quantify such effects by studying a major Swedish reform that made it significantly easier for firms to recruit non-Europeans. Using a difference-in-differences setup, I exploit variation in the strictness of immigration rules which affected industries differentially before and after the reform. Treated industries are predominantly lower-skilled, and concentrated in sectors like hotels and restaurants and retail trade sectors. Using linked employer-employee data, I study the effect of the reform on both firm-level and individual-level outcomes. I find that the mean earnings at firms in treated industries unambiguously increase. Firms also seem to take advantage of skill complementarities between natives and immigrants and intensify their overall hiring of high-skilled workers. Moreover, I follow native incumbents' employment and earnings over time and find heterogeneous effects along the skill and age dimensions.

    Essay II (with Matz Dahlberg, Mattias Engdahl and Till Nikolka): We evaluate the importance of spillover effects of national migration policies by estimating the effect of stricter rules on family reunification in Denmark in 2002 on migration to neighboring countries. We reach two main conclusions. First, we show that stricter rules for reunification lead to a clear and significant increase in emigration of Danish citizens with immigrant background. Most of the emigrants left Denmark for Sweden, a neighboring country in which reunification was possible. Second, we demonstrate that a significant fraction of the individuals that came to Sweden to reunite with a partner left the country again; within two (eight) years around 20% (50%) had left, with the absolute majority leaving for Denmark. Our results indicate that potential spillover effects from national migration policies should be taken into account when forming migration policy.

    Essay III (with Valentin Bolotnyy): We use administrative Swedish data to show that, conditional on parent income, immigrant children have similar incomes and higher educational attainment in adulthood than native-born Swedes. This result, however, masks the fact that immigrant children born into poor families are more likely than similar natives to both reach the top of the income distribution and to stay at the bottom. Immigrant children from high-income families are also more likely than natives to regress to the economic bottom. Notably, however, children from predominantly-refugee sending countries like Bosnia, Syria, and Iran have higher intergenerational mobility than the average immigrant child in Sweden.

    Essay IV (with Valentin Bolotnyy): Home ownership is an important indicator of socio-economic status and a good proxy for wealth. We show that on average, children of immigrants are less likely to own their homes than children of natives at age thirty. The difference remains even after we control for socio-economic characteristics, parental background, and municipality of residence. We find that parental background - both in terms of parents' income and education, but also their own home ownership status - is the most important determinant of home ownership in adulthood. We additionally investigate the role of age at arrival on outcomes in adulthood and find a significant negative effect of age at arrival on income and education, which also translates into a lower probability of owning a home in adulthood. However, growing up in a highly-educated family may partly mitigate this negative effect.

  • Aspects of Coherency in Luke’s Composite Christology Author: Daniel Gustafsson Link: Publication date: 2019-08-23 11:37

    In presenting the life and teachings of Jesus and his function in salvation history, the authors of the New Testament Gospels employ a variety of motifs and titles drawn from earlier biblical literature as well as various strands of second temple Jewish literature. This study of Luke’s Christology investigates how such motifs merge and intertwine in ways that invite the reader to perceive a measure of coherency among those motifs. 

    Luke’s presentation of Jesus is studied, above all, with tools from narrative criticism. In addition, complementary insights are drawn from Luke’s rewriting of Mark. Previous scholarship has often concluded that Luke employs a variety of christological motifs without having reflected on them or how they may function in relation to each other. Such estimations may, in part, be due to the fact that a narrative approach has not come into focus. The present investigation shows that a narrative approach to Luke’s Christology reveals much in regard to how several christological motifs are integrated with Luke’s overarching narrative. 

    The study first surveys previous scholarly approaches to Luke’s Christology, and thereafter considers second temple Jewish conceptions of eschatological prophets and messiahs. The core of the investigation analyzes four sections in Luke’s Gospel: the infancy narrative (1:26–2:52); Jesus’s proclamation in Nazareth (4:16–30); the end of the travel narrative and Jesus’s triumphal entry into Jerusalem (18:31–19:48), and the passion narrative (22:1–23:49). 

    A central conclusion of the investigation is that detailed attention to features in the narrative – including which characters use a particular christological title, and how it is used – shed new light on how, and to what extent, different motifs merge within Luke. Observations are also made of when different motifs overlap with each other and form clusters with similar meanings. The investigation further identifies some features that are distinct to Luke’s presentation of Jesus. An example of such a feature is that the Holy Spirit is described as a defining factor for the presentation of Jesus as Son of God and Messiah.