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On seismic behavior and vulnerability of building structures: Dynamic identification, condition assessment, and fragility modeling
(University of Iceland, School of Engineering and Natural Sciences, Faculty of Civil and Environmental Engineering, 2026-06-10) Gautam, Dipendra; Rajesh Rupakhety, Bjarni Bessason, Hugo Rodrigues; Faculty of Civil and Environmental Engineering (UI); Umhverfis- og byggingarverkfræðideild (HÍ); School of Engineering and Natural Sciences (UI); Verkfræði- og náttúruvísindasvið (HÍ)
Structures undergo various changes during their service life due to deterioration or external loading. These changes are the keys to design, assess, and predict structural behavior. The three pillars of structural engineering are the most governing factors to justify safety, serviceability, functionality, and operability of structures, considering forms and functions. Although independently extensively studied, coordinated efforts have not been widely practiced in structural engineering, starting from characterization to condition assessment and finally probabilistic response depiction. Aiming at coordinated dissemination of the three pillars, the present study performs system identification based modal characterization to develop period-height relationships and condition assessment under no external loading, structure undergoing deterioration, changed state of structure due to extreme loading, changed state of structure due to construction progression, and strengthened structures following various states of damage. Furthermore, many sets of seismic fragility functions have been developed for low-rise RC buildings, considering global and component level performance using empirical data. This study covers RC and stone and brick masonry buildings for dynamic identification, condition assessment, and seismic vulnerability modeling. Experimental and empirical approaches have been deployed to estimate dynamic characteristics as structural performance signatures, evolution of dynamic characteristics as signatures of changed state of the structures, and probabilistic models as signatures to quantify the exceedance probability of particular damage level in buildings and components under seismic excitation. Bayesian modeling based formulation is adopted through MCMC using Metropolis-Hastings sampling to derive period-height relationships and fragility functions. Subsequently, posterior parameter uncertainties have also been characterized.
Verk
Computational reconstruction of non-crossover recombination
(2026-05) Harðarson, Marteinn Þór; Halldórsson, Bjarni Vilhjálmur; Department of Engineering
As a diploid organism, humans inherit two copies of each autosomal chromosome, one from the father and one from the mother. The copy of a chromosome transmitted by a parent is reshuffle, via meiotic recombination, of the two parental copies through meiotic recombination. Most apparent are large chromosome parts of alternating chromosomal origin separated by crossover recombination. The other type of meiotic recombination is gene conversion, small segment of one of the parental homologous chromosomes on the background of the other. Gene conversions arise through process called non-crossover recombination (NCO). Recombinations can only be detected indirectly in offspring, at heterozygous markers, sites where the two homologous chromosomes differ. Sequencing errors, genotyping errors, phasing errors and structural variations can all mimic the signature of gene conversions making them difficult to be detected reliably. Not all NCOs create gene conversions, due to their short span and limit number of heterozygous markers. Large NCOs have a better chance to generate gene conversion than short NCO, due to higher likelihood of overlapping heterozygous markers. This makes it difficult to infer information about NCOs from gene conversions. This thesis makes three main contributions. First, three-generation families are used to find and verify gene conversions showing age and sex dependent patterns for these events. Second, a statistical framework modelling the underlying NCO processes generating these gene conversions is developed in order to obtain the underlying length distribution and their quantity. Finally, combining crossovers and non-crossover recombinations to construct a complete human recombination map revealing their contribution to de novo mutagenesis.
Verk
Bleeding following cardiac surgery: Incidence, risk factors, complications and outcomes
(University of Iceland, School of Health Sciences, Faculty of Medicine, 2026-06) Heimisdóttir, Alexandra; Tómas Guðbjartsson; Faculty of Medicine (UI); Læknadeild (HÍ); School of Health Sciences (UI); Heilbrigðisvísindasvið (HÍ)
Aims: Bleeding is a common and inevitable complication of cardiac surgery, and excessive bleeding is associated with increased morbidity, mortality, and healthcare costs. Various complications related to excessive bleeding and re-exploration have been identified, including prolonged hospital stay, increased incidence of infections, and a higher risk of 30-day mortality. Less is known, however, regarding the long-term prognosis of these patients, and results of previous studies on certain proposed risk factors have been conflicting. The aim of this thesis was to gain a better understanding of bleeding complications after cardiac surgery, especially coronary artery bypass grafting (CABG) and valve replacement surgery. The specific aims were to identify risk factors (Studies III and IV) and analyse short- and long-term outcomes (Studies I, II, and V), in order to help prevent excessive bleeding and improve patient prognosis. Methods: The project consisted of five retrospective, nationwide cohort studies. Study I was based on data from over 48,000 patients from the SWEDEHEART registry who underwent CABG and/or valve replacement surgery in Sweden between 2006 and 2015. Studies II–V included all patients who underwent CABG in Iceland between 2001 and 2022. Risk factors for excessive bleeding were assessed, as well as the relationship between excessive bleeding and preoperative use of antidepressants (SSRI/SNRI), red cell distribution width (RDW), and perioperative complications. Short- and long-term outcomes of patients re-explored for bleeding were also examined, and perioperative transfusion trends over an 18-year period in Iceland were analysed. Multivariable logistic regression was used to identify independent factors associated with excessive bleeding, re-exploration, and transfusions, while Cox proportional hazards regression analysis was used to assess long-term outcomes. Results: Re-exploration for bleeding was associated with significantly increased 30- and 90-day mortality and higher rates of perioperative complications, including stroke, acute kidney injury, and prolonged hospital stay, but was not associated with increased long-term mortality among patients who survived the initial postoperative period. Preoperative use of SSRI/SNRIs was not associated with an increased risk of bleeding, perioperative complications, or 30-day mortality. Elevated preoperative RDW was independently associated with increased 24-hour chest tube output, higher rates of red blood cell transfusion, re-exploration for bleeding, and other perioperative complications, but not with 30-day mortality. Over an 18-year study period, a significant decline was observed in the proportion of patients receiving perioperative transfusion of any blood product. This decline may have been attributed to increased awareness, improved surgical techniques, and the implementation of international transfusion guidelines and strategies such as cell salvage and point-of-care coagulation testing. The main factors associated with excessive bleeding were female sex, low body mass index, preoperative use of antiplatelet medication, and impaired renal function. Conclusions: This project provided in-depth insight into bleeding as a complication of cardiac surgery and highlighted important risk factors and predictors of severe bleeding, as well as the short- and long-term outcomes of affected patients. The findings underscored the importance of preoperative risk stratification, timely intervention, and the implementation of strategies to reduce bleeding during and after surgery. The decline in transfusion rates in Iceland over the past two decades likely reflected the positive impact of system-level improvements in bleeding and transfusion management.
Verk
Can a novel imagery-competing task intervention reduce intrusive memories of trauma? A study among Icelandic women
(University of Iceland, School of Health Sciences, Faculty of Psychology, 2026) Thorarinsdottir, Kristjana; Andri Steinþór Björnsson; Faculty of Psychology (UI); Sálfræðideild (HÍ); School of Health Sciences (UI); Heilbrigðisvísindasvið (HÍ)
Objective: Intrusive memories of trauma, experienced as vivid and distressing involuntary sensory memories, are the core clinical symptom of posttraumatic stress disorder (PTSD) and contribute to the enduring distress and functional impairment associated with the disorder. Although existing PTSD treatments are effective, they often require a detailed description of the trauma on the patient’s behalf, causing additional distress. They also depend on specialist clinical delivery, making therapists too few to deliver therapy to all those in need. These factors limit accessibility and scalability of the interventions. There is a pressing need for brief, simple and scalable interventions that minimize treatment barriers and that can be delivered remotely. The overarching aim of this thesis was to adapt to the Icelandic population and then evaluate a brief cognitive intervention designed to reduce the frequency of established intrusive trauma memories using an imagery-competing task after a memory retrieval, drawing from theories of memory reconsolidation. This is known as a novel imagery-competing task intervention (ICTI). Specifically, the intervention combines a memory reminder cue with a visuospatial task (playing Tetris with mental rotation) to disrupt sensory-perceptual features of intrusive memories. The objectives were to test the efficacy of the intervention in an Icelandic context. Further objectives were to evaluate whether the intervention would be a feasible way to reduce the frequency of intrusive memories and whether such reduction in frequency would have an impact on PTSD symptoms, depression and anxiety symptoms and functional impairment. Methods: Three studies were conducted using repeated single-case AB designs in which each intrusive memory “hotspot” was targeted individually. Study I was a single-case design with a woman with subthreshold PTSD. She monitored four intrusive memories across a four-week baseline, an eight week intervention period, and one- and three-month follow-ups. Study II was a case series of three women (two with PTSD, one with subthreshold PTSD). Each participant monitored their intrusive memories for one week at baseline, up to six weeks during the intervention phase, and again for one week at the one- and three-month follow-ups. Study III was a case series with eight trauma-exposed women, three with PTSD and three with subthreshold PTSD. The intervention was delivered face-to-face in Study I, partly remotely in Study II and entirely remotely in Study III, with guidance provided by either clinical psychologists or psychology students without specialist mental health training. Participants completed baseline, intervention, and follow-up diaries at one- and threemonths. Across all studies, the primary outcome was frequency of intrusive memories recorded in daily diaries. Secondary outcomes were PTSD symptoms, depression symptoms, anxiety symptoms, functional impairment, and acceptability and feasibility of the intervention. Results: Across the three studies, the intervention was found to be feasible, acceptable, and consistently associated with substantial reductions in intrusive memories. Results in Study I showed a 52% reduction in the frequency of total intrusive memories during the intervention compared to baseline, increasing to a 76% reduction at the one-month follow-up and a 92% reduction at the three-month followup. Improvements were also observed in PTSD symptoms, depression and anxiety symptoms, sleep, concentration, and functioning. The participant rated the intervention as an acceptable way to reduce the frequency of intrusive memories. Study II also found reductions across all three participants. One participant reported 38.8 intrusions per week at baseline, which reduced to 18.0 per week during the intervention period (54% reduction). The number of intrusive memories further reduced to 8 per week at the one-month follow-up (80% reduction) and increased to 13 (67% reduction) at the three-month follow-up. The second participant reported 10.8 intrusions per week at baseline, which reduced to 4.7 per week during the intervention period (57% reduction) with a further reduction to 1 per week at the onemonth follow-up (91% reduction) and to zero at the three-month follow-up. The third participant reported 33.7 intrusions per week at baseline, which reduced to 20.7 per week during the intervention period (39% reduction) and to 5 per week at the onemonth follow-up (85% reduction) and increased to 8 per week (76% reduction) at the three-month follow-up. All participants reported reductions in PTSD symptoms postintervention, with two also showing reductions in depression and anxiety symptoms. Participants rated the intervention as being acceptable. Study III extended these findings to remote delivery and non-specialist guidance. All eight participants showed reductions in intrusive memories from baseline to the intervention period, although reductions were minimal for two participants, overall, 6.3% to 93% reduction. At the one-month follow-up, six out of eight participants showed further reductions, 58% to 100%, and by the three-month follow-up reductions were 72% to 100%. Most participants experienced improvements in PTSD, depression, and anxiety symptoms, and functioning improved for seven out of eight participants. Participants rated the digital delivery and non-specialist guidance as highly acceptable. Conclusions: The research presented in this thesis provides evidence in support of a brief imagery-competing task intervention which can substantially reduce the frequency of long-standing intrusive memories of trauma. Furthermore, it can improve associated psychological symptoms and functioning. The intervention targeting the core clinical symptom of PTSD is low-cost, scalable and acceptable. It does not require patients to describe their trauma in detail, and it can be delivered by nonspecialists after training, thereby addressing key barriers in traditional effective PTSD treatments. The studies further demonstrate the feasibility of remote digital delivery, indicating scalability and public mental health relevance. The findings support progression to a randomized controlled trial. Overall, the thesis highlights the promise of this simple and brief intervention for reducing intrusive memories and related distress, improving access to care for trauma-exposed populations. Keywords: Intrusive memories of trauma, trauma, post-traumatic stress disorder, visuospatial task intervention
Verk
Daily dynamics of pro-environmental behaviors and eudaimonic well-being among adolescents
(2026-06) Caldaroni, Silvia; Gerbino, Maria; Schmiedek, Florian; Neubauer, Andreas; Beolchini, Elisabetta; Virzì, Alessia Teresa; Lundie, David; Jónsson, Ólafur Páll; Luengo Kanacri, Bernadette Paula; Camps, Diana; Guttesen, Kristian; Barrero Toncel, Virginia Isabel; Gregori, Fulvio; Quilodrán Fuentes, Valentina Paz; Pastorelli, Concetta; Zuffianò, Antonio; Faculty of Education
Research shows that engaging in pro-environmental behaviors (PEBs) might enhance individuals' eudaimonic well-being, including meaning in life (ML) and closeness to others (CO). Despite adolescents' potential role in shaping sustainable societies and their vulnerability to environmental issues, existing literature has not adequately addressed this age group. Additionally, most of the extant research is built on cross-sectional studies, which target between-person differences and fail to capture within-person fluctuations occurring in everyday life. To address these gaps, this study explored the association of daily PEB with adolescents' daily ML and CO, and whether variations in habitual PEB levels are positively associated with variations in habitual levels of these two dimensions. Additionally, we examined the moderating role of self-transcendence values in the PEB-ML and PEB-CO relations. The study included 78 Italian adolescents (MAge = 14.8, SD = .73, 29.5% females) from a larger cross-cultural research project. Participants completed a daily diary study, reporting their PEB, ML and CO once a day over 28 days. Using Dynamic Structural Equation Modeling, the results revealed a significant positive spillover effect from PEB to ML (B = .258; 95% CI: [.121, .402]), indicating that when individuals engaged in more PEB than usual, they experienced higher-than-usual ML the following day. On the other hand, the spillover from PEB to CO was non-significant (B = .099; 95% CI: [-.034, .226]). Moreover, no link was found between self-transcendence values and these spillover effects. These findings provide insights into possible short-term benefits of PEB for adolescents’ ML and contribute to understanding the role of PEB in promoting youth well-being.

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