A new general family of mixed graphs

A new general family of mixed graphs is presented, which generalizes both the pancake graphs and the cycle prefix digraphs. The obtained graphs are vertex transitive and, for some values of the parameters, they constitute the best infinite families with asymptotically optimal (or quasi-optimal) diameter for their number of verticesPeer ReviewedPostprint (author's final draft

Does Tool Use in Virtual Reality Change the Visual Perception of Extrapersonal and Peripersonal Space?

People often try to reach out and interact with space in VR when they experience it for the first time. In the real world the space where people are able to physically manipulate objects is referred to as peripersonal space whereas extrapersonal space is beyond our arms reach. Gamberini, Carlesso, Seraglia, and Craighero (2013) examined how people perform a line bisection task in VR and suggested that a tools-action-consequence affects how people perceive space. Researchers reported that when a tool was perceived as a “cutter” and a to-be-bisected line broke, the tool brought extrapersonal space into peripersonal space due to its line breaking action. Two experiments are reported in which the tool by distance interaction reported by Gamberini et al. was examined. In contrast to Gamberini et al., it is concluded that line length and distance have more of an effect on how people perceive space than the tool type

IPOs of Restaurant Companies after the pandemic

openThis thesis analyses the IPOs of restaurant companies after the pandemic, using both quantitative and qualitative methods to better understand the process through which these companies obtain funds and visibility, it is also analyzed the bookbuilding of the issued securities and the underpricing phenomenon. The study also focuses on how these funds will be spent to support the long-term growth of these companies.This thesis analyses the IPOs of restaurant companies after the pandemic, using both quantitative and qualitative methods to better understand the process through which these companies obtain funds and visibility, it is also analyzed the bookbuilding of the issued securities and the underpricing phenomenon. The study also focuses on how these funds will be spent to support the long-term growth of these companies

Exploring the association between self-reported alcohol consumption and intake of micronutrients. An analysis based on data from a general population study: The seventh survey of the Tromsø Study (Tromsø7) in 2015-2016

Background: Alcohol consumption may affect dietary patterns and nutrient intake, but the association between alcohol use and micronutrient could be investigated further. Understanding how alcohol consumption relates to the intake of micronutrients is important for public health, also in populations with moderate to high alcohol use. Materials and methods: This cross-sectional study used self-reported data from the seventh survey of the Tromsø Study (Tromsø7, 2015–2016). A total of 21,069 adults aged 40 years and older were included. Alcohol intake, measured in grams per day, was estimated from a validated food frequency questionnaire (FFQ). In addition, participants were categorized into low-, moderate-, or high/severe-risk groups based on their scores on the Alcohol Use Disorders Identification Test (AUDIT). Micronutrient intake was also derived from the FFQ and calculated using standardized food composition tables. Statistical analyses were conducted using IBM SPSS Statistics version 29.0. Descriptive statistics, Pearson’s correlation coefficients, and linear regression models (both unadjusted and adjusted for total energy intake) were used to examine associations between alcohol consumption and micronutrient intake also taking total energy intake into consideration. Results: Participants with higher self-reported alcohol intake also reported greater total energy intake and higher unadjusted intake of several micronutrients. However, after adjusting for total energy intake, alcohol consumption was negatively associated with key nutrients including folate, calcium, phosphorus, vitamin A, and zinc. Iron and magnesium were not significantly associated with alcohol intake in adjusted models. These findings suggest that alcohol may displace nutrient-dense foods when total energy intake is accounted for. Conclusion: Greater alcohol intake was linked to higher energy intake and slightly increased unadjusted micronutrient intake. After adjusting for total energy intake, alcohol showed inverse associations with several key micronutrients. This may have implications for dietary quality among frequent drinkers. Further studies are needed to explore potential health outcomes linked to these dietary patterns and whether similar associations are observed in other populations.Background: Alcohol consumption may affect dietary patterns and nutrient intake, but the association between alcohol use and micronutrient could be investigated further. Understanding how alcohol consumption relates to the intake of micronutrients is important for public health, also in populations with moderate to high alcohol use. Materials and methods: This cross-sectional study used self-reported data from the seventh survey of the Tromsø Study (Tromsø7, 2015–2016). A total of 21,069 adults aged 40 years and older were included. Alcohol intake, measured in grams per day, was estimated from a validated food frequency questionnaire (FFQ). In addition, participants were categorized into low-, moderate-, or high/severe-risk groups based on their scores on the Alcohol Use Disorders Identification Test (AUDIT). Micronutrient intake was also derived from the FFQ and calculated using standardized food composition tables. Statistical analyses were conducted using IBM SPSS Statistics version 29.0. Descriptive statistics, Pearson’s correlation coefficients, and linear regression models (both unadjusted and adjusted for total energy intake) were used to examine associations between alcohol consumption and micronutrient intake also taking total energy intake into consideration. Results: Participants with higher self-reported alcohol intake also reported greater total energy intake and higher unadjusted intake of several micronutrients. However, after adjusting for total energy intake, alcohol consumption was negatively associated with key nutrients including folate, calcium, phosphorus, vitamin A, and zinc. Iron and magnesium were not significantly associated with alcohol intake in adjusted models. These findings suggest that alcohol may displace nutrient-dense foods when total energy intake is accounted for. Conclusion: Greater alcohol intake was linked to higher energy intake and slightly increased unadjusted micronutrient intake. After adjusting for total energy intake, alcohol showed inverse associations with several key micronutrients. This may have implications for dietary quality among frequent drinkers. Further studies are needed to explore potential health outcomes linked to these dietary patterns and whether similar associations are observed in other populations

Near-shore target tracking with clutter maps

Target tracking is of vital importance for autonomous vehicles moving in areas with unpredictable traffic. The radar is an important sensor in target tracking for autonomous vessels, though, it suffers from occasional false alarms, which may be particularly troublesome near land. Track initiation methods have different approaches to filtering the clutter and detecting true targets among the measurements. Integrated Probabilistic Data Association (IPDA) is a method suitable for both data association and track initiation, though its assumption of uniform clutter is not fully adaptable to many real world situations. Near-shore environments tend to have an uneven clutter distribution at the same time as they are the subject to targets leaving shore, making efficient track initiation a difficult task. Clutter maps attempt to estimate clutter density to assist in the process of selecting or weighting measurements associated with a target. Three clutter estimators were thoroughly tested and compared, which given some initialization time, improved the efficiency and accuracy of the IPDA in simulations. The Spatial estimator shows the best results for a shorter initialization length of 20 scans, while the Classic and Temporal estimators are able to achieve higher true detection rates when given longer initialization time. The Spatial estimator performs the best in simulated uniform clutter which correlates with its theoretical bias and quick convergence. The tests from real data sets recorded in Trondheimsfjorden suggest that the Classic estimator is most suitable for tracking scenarios where the radar is on board the ownship. For a stationary radar setup, which is more comparable to the simulations in this thesis, the Temporal estimator is a logical choice due to no theoretical bias when given sufficient estimation time. Excluding estimated target measurements from clutter estimation shows a positive effect on track initiation time, and should be tested and explored in further testing of clutter maps

Stress, social support and parental behavior

The present study investigated the relationship between stress, social support and parenting behavior. Eighty-six mothers who had a child enrolled in a daycare center in the Kitchener-Waterloo region volunteered for this study. Participants completed four questionnaires: A Demographic Sheet, the Perceived Stress Scale (Cohen, Kamarck & Mermelstein, 1983), the Interpersonal Support Evaluation List (Cohen and Hoberman, 1983), and the Parent Behavior Scale (which was specifically constructed for this study). The overall support scale and the four subscales (tangible, belonging, appraisal, and self-esteem support) were used to determine whether the perceived availability of social support is directly related to parenting behavior (main effect) or whether it moderates the effects of stress on parenting behavior (buffering effect). The results showed that social support was strongly positively related to Positive Parental Behavior. In addition, stress was strongly associated with Negative Parental Behavior. No stress by support interactions were found; hence, the buffering hypothesis was not supported. However, evidence supporting a two-factor model was found, in that social support correlated with Positive Parental Behavior, but not Negative; and Perceived Stress correlated positively with Negative Parental Behavior but not Positive. Limitations of the study, future recommendations and suggestions and for interventions utilizing social support with parents in overcoming stress are discussed

Parameter selection methods for variational image restoration

Vi undersøker diskrepansprinsippet og ein L-hyperflate-metode som automatiserte parametervalmetodar i støyfjerningsproblem for bilete. Å velje optimale regulariseringsparametrar er alltid utfordrande, og utfordringa er enda større for regulariseringsfunksjonar med fleire parametrar. Vi eksperimenterer med total generalisert variasjon, ei fleirparameterval-metode, og med einparametervalmetoden total variasjon. Total generalisert variasjon er kjent som ein god støyfjerningsmetode for bilete, sidan rekonstruksjonar med denne metoden ikkje har den stykkvis konstante eigenskapen kjent som "trappeeffekta", som er vanleg i rekonstruksjonar basert på total variasjon. Dei numeriske løysarane som er testa er basert på konveks optimeringsteori og ein Chambolle-Pock primal-dual-løysar. Eksperiment med einparametermetodar viser at diskrepansprinsippet presterer betre enn L-kurvemetoden for eit støyfjerningsproblem for eit RGB-bilete, når ein bruker total varisjon som regulariseringsfunksjon. For høge støynivå gjer ein ved bruk av diskrepansprinsippet nær optimale parameterval for total variasjon. Dei numeriske resultata viser at ein automatisert versjon av det balanserte diskrepansprinsippet med Broyden si metode som numerisk løysar presterer betre enn eksisterande parametervalalgortimar for einparametermetodar. For bilete med færre detaljar og overflater med nesten konstante intensitetar, forblir total variasjon ein betre metode. Testar av L-hyperoverflate-metoden antyder at det er vanskeleg å velje gode parametrar for total generalisert variasjon med denne metoden.We investigate the discrepancy principle and the L-hypersurface method as automated parameter selection methods for image denoising problems. Choosing optimal regularization parameters is always challenging, and the challenge is even bigger for multi-parameter regularization. We experiment with total generalized variation, a multi-parameter regularization functional, and the single-parameter regularization functional total variation. Total generalized variation is known to be a good multi-parameter regularization functional for image denoising, as its reconstructions avoids the piecewise constant property known as 'staircasing', which is commonly observed in total variation reconstructions. The numerical solvers we test are based on convex optimization theory and use a Chambolle-Pock primal-dual solver. Single-parameter choice experiments show that the discrepancy principle performs better than the L-curve method for a RGB-image denoising problem, using a total variation regularization functional. For high noise levels, the discrepancy principle makes an almost optimal parameter choice for total variation. The numerical results show that an automated balanced discrepancy principle with Broyden's method as numerical solver performs better than the existing parameter choice algorithms for single-parameter methods. For images with fewer details and surfaces with almost constant intensities, total variation remains a better method. Tests of the L-hypersurface method suggest difficulties with choosing good parameters for total generalized variation by the means of this method

Triangulated Categories and Matrix Factorizations

In this thesis we study triangulated categories and look at one specific example, the homotopy category of matrix factorizations. First we define categories and functors. Then we introduce additive and triangulated categories and see that the octahedral axiom can be replaced by Neeman's mapping cone axiom. After this we look at matrix factorizations and the homotopy category of matrix factorizations, HMF(S,x) which leads us to one of our main results, i.e. that HMF(S,x) is triangulated. We prove this with both the octahedral axiom and Neeman's mapping cone theorem. Lastly we look at the homotopy category of totally acyclic complexes over a local, regular ring and see that this is equivalent to HMF(S,x)