A Comparative Study of Population-Graph Construction Methods and Graph Neural Networks for Brain Age Regression

The difference between the chronological and biological brain age of a subject can be an important biomarker for neurodegenerative diseases, thus brain age estimation can be crucial in clinical settings. One way to incorporate multimodal information into this estimation is through population graphs, which combine various types of imaging data and capture the associations among individuals within a population. In medical imaging, population graphs have demonstrated promising results, mostly for classification tasks. In most cases, the graph structure is pre-defined and remains static during training. However, extracting population graphs is a non-trivial task and can significantly impact the performance of Graph Neural Networks (GNNs), which are sensitive to the graph structure. In this work, we highlight the importance of a meaningful graph construction and experiment with different population-graph construction methods and their effect on GNN performance on brain age estimation. We use the homophily metric and graph visualizations to gain valuable quantitative and qualitative insights on the extracted graph structures. For the experimental evaluation, we leverage the UK Biobank dataset, which offers many imaging and non-imaging phenotypes. Our results indicate that architectures highly sensitive to the graph structure, such as Graph Convolutional Network (GCN) and Graph Attention Network (GAT), struggle with low homophily graphs, while other architectures, such as GraphSage and Chebyshev, are more robust across different homophily ratios. We conclude that static graph construction approaches are potentially insufficient for the task of brain age estimation and make recommendations for alternative research directions.Comment: Accepted at GRAIL, MICCAI 202

The Challenge of Identifying the Importance of Drivers and Barriers for Implementation of Technology Enhanced Learning

The potential of technology enhanced learning (TEL) can have both pedagogical and administrative benefits. In a previous study, we investigated the drivers and barriers for TEL in higher education using Force Field Analysis (FFA). In this follow-up study, we collected new data through a questionnaire to a group of pedagogical developers and at a presentation at a university internal conference for teachers. A Kruskal Wallis test was carried out to test if the groups filling out questionnaire deviated from each other in their ranking. A comparison was also done to the scores in the previous study. As a result of this triangulation, deviations were found between ratings for seven of the 20 identified forces. While the assessments of strengths in FFA is debated, we argue that each group’s view is an important component to understand the situation, and triangulation of data is helpful in understanding the different views.QCR 20190211</p

The Challenge of Identifying the Importance of Drivers and Barriers for Implementation of Technology Enhanced Learning

The potential of technology enhanced learning (TEL) can have both pedagogical and administrative benefits. In a previous study, we investigated the drivers and barriers for TEL in higher education using Force Field Analysis (FFA). In this follow-up study, we collected new data through a questionnaire to a group of pedagogical developers and at a presentation at a university internal conference for teachers. A Kruskal Wallis test was carried out to test if the groups filling out questionnaire deviated from each other in their ranking. A comparison was also done to the scores in the previous study. As a result of this triangulation, deviations were found between ratings for seven of the 20 identified forces. While the assessments of strengths in FFA is debated, we argue that each group’s view is an important component to understand the situation, and triangulation of data is helpful in understanding the different views.QCR 20190211</p

The Challenge of Identifying the Importance of Drivers and Barriers for Implementation of Technology Enhanced Learning

The potential of technology enhanced learning (TEL) can have both pedagogical and administrative benefits. In a previous study, we investigated the drivers and barriers for TEL in higher education using Force Field Analysis (FFA). In this follow-up study, we collected new data through a questionnaire to a group of pedagogical developers and at a presentation at a university internal conference for teachers. A Kruskal Wallis test was carried out to test if the groups filling out questionnaire deviated from each other in their ranking. A comparison was also done to the scores in the previous study. As a result of this triangulation, deviations were found between ratings for seven of the 20 identified forces. While the assessments of strengths in FFA is debated, we argue that each group’s view is an important component to understand the situation, and triangulation of data is helpful in understanding the different views.QCR 20190211</p

The geochemistry of fluids from an active shallow submarine hydrothermal system: Milos island, Hellenic Volcanic Arc

Geothermal activity in the Aegean island of Milos (Greece), associated with island-arc volcanism, is abundant both on-and off-shore. Hydrothermal fluids venting from several sites, mainly shallow submarine (up to 10 m), but also just above seawater level in one locality, were sampled over four summer field seasons. Some of the discharging fluids are associated with the formation of hydrothermal edifices. Overall, the main characteristics of the hydrothermal fluids are low pH and variable chlorinity. The lowest recorded pH was 1.7, and chlorinity ranged from 0.1 to 2.5 times that of seawater. The highest fluid temperatures recorded on site were 115 °C. Two main types of fluids were identified: low-chlorinity fluids containing low concentrations of alkalis (potassium, lithium, sodium) and calcium, and high concentrations of silica and sulphate; and high-chlorinity fluids containing high concentrations of alkalis and calcium, and lower concentrations of silica and sulphate. The type locality of the high-chlorinity fluids is shallow submarine in Palaeochori, near the east end of the south coast of the island, whereas the type locality of the low-chlorinity fluids is a cave to the west of Palaeochori. The two fluid types are therefore often referred to as "submarine" and "cave" fluids respectively. Both fluid types had low magnesium and high metal concentrations but were otherwise consistently different from each other. The low-chlorinity fluids had the highest cobalt, nickel, aluminium, iron and chromium (up to 1.6 μM, 3.6 μM, 1586 μM, 936 μM and 3.0 μM, respectively) and the high-chlorinity fluids had the highest zinc, cadmium, manganese and lead (up to 4.1 μM, 1.0 μM, 230 μM and 32 μM, respectively). Geochemical modelling suggests that metals in the former are likely to have been transported as sulphate species or free ions and in the latter as chloride species or free ions. Isotopic values for both water types range between δD -12 to 33% and δ18O 1.2 to 4.6%. The range of fluid compositions and isotopic contents indicates a complex history of evolution for the system. Both types of fluids appear to be derived from seawater and thus are likely to represent end members of a single fluid phase that underwent phase separation at depth. © 2005 Published by Elsevier B.V

The geochemistry of fluids from an active shallow submarine hydrothermal system: Milos island, Hellenic Volcanic Arc

Geothermal activity in the Aegean island of Milos (Greece), associated with island-arc volcanism, is abundant both on-and off-shore. Hydrothermal fluids venting from several sites, mainly shallow submarine (up to 10 m), but also just above seawater level in one locality, were sampled over four summer field seasons. Some of the discharging fluids are associated with the formation of hydrothermal edifices. Overall, the main characteristics of the hydrothermal fluids are low pH and variable chlorinity. The lowest recorded pH was 1.7, and chlorinity ranged from 0.1 to 2.5 times that of seawater. The highest fluid temperatures recorded on site were 115 °C. Two main types of fluids were identified: low-chlorinity fluids containing low concentrations of alkalis (potassium, lithium, sodium) and calcium, and high concentrations of silica and sulphate; and high-chlorinity fluids containing high concentrations of alkalis and calcium, and lower concentrations of silica and sulphate. The type locality of the high-chlorinity fluids is shallow submarine in Palaeochori, near the east end of the south coast of the island, whereas the type locality of the low-chlorinity fluids is a cave to the west of Palaeochori. The two fluid types are therefore often referred to as &quot;submarine&quot; and &quot;cave&quot; fluids respectively. Both fluid types had low magnesium and high metal concentrations but were otherwise consistently different from each other. The low-chlorinity fluids had the highest cobalt, nickel, aluminium, iron and chromium (up to 1.6 μM, 3.6 μM, 1586 μM, 936 μM and 3.0 μM, respectively) and the high-chlorinity fluids had the highest zinc, cadmium, manganese and lead (up to 4.1 μM, 1.0 μM, 230 μM and 32 μM, respectively). Geochemical modelling suggests that metals in the former are likely to have been transported as sulphate species or free ions and in the latter as chloride species or free ions. Isotopic values for both water types range between δD -12 to 33% and δ18O 1.2 to 4.6%. The range of fluid compositions and isotopic contents indicates a complex history of evolution for the system. Both types of fluids appear to be derived from seawater and thus are likely to represent end members of a single fluid phase that underwent phase separation at depth. © 2005 Published by Elsevier B.V