In this thesis the relative spectral energy density of stochastic primordial gravitational waves is investigated. Decoupling of Standard Model particles and neutrino free-streaming affect the...Show moreIn this thesis the relative spectral energy density of stochastic primordial gravitational waves is investigated. Decoupling of Standard Model particles and neutrino free-streaming affect the expansion history of the universe and thus leave characteristic signatures on the amplitude of the gravitational wave spectrum. Adding extra light or heavy particles damps the spectrum at frequencies before the particle decouples. Including an extra neutrino species amplifies the spectrum at larger wave numbers, but damps it at shorter wave numbers. Measuring these primordial gravitational waves reveals the thermal history of the universe. One possible non-standard thermal history is early matter domination due to the inflaton. It is shown that, in this cosmology, the end of early matter domination and beginning of the radiation era depend linearly on the reheating temperature.Show less
Earlier research suggests that some exercise intensities are more beneficial to enhance creativity than others. However, if and why specific exercise intensities are related to better creativity is...Show moreEarlier research suggests that some exercise intensities are more beneficial to enhance creativity than others. However, if and why specific exercise intensities are related to better creativity is not exactly clear yet. This study aimed to gain insight into which exercise intensity is best for improving creativity and to explore the possible role of physical fitness in the relationship between exercise intensity and creativity. This is the first study in which participants were given a more objective individually-tailored instruction with regard to exercise intensity and in which four conditions (low intensity exercise, moderate-intensity exercise, high-intensity exercise and a control condition) were compared with respect to the enhancement of divergent creativity (including fluency and originality). First, it was expected that moderate-intensity is best to enhance creativity compared to low intensity exercise, highintensity exercise and no exercise. Second, it was expected that creativity is enhanced more after someone exercises at an intensity level that matches his/her level of physical fitness compared to someone exercising at an intensity level that does not match his/her physical fitness. A total of N = 73 students were studied. A between-subjects design was used in which participants were randomly assigned to one of the four conditions. The participants had to visit the lab of Leiden University twice. First they had to perform a physical fitness test and then they were randomly assigned to one of the four conditions and they had to do a task that measured divergent creativity. For the first hypothesis, the Two-Way ANOVA indicated that neither the fluency (η² = .009, p = .88) nor the originality scores (η² = .006, p = .94) differed between conditions. For the second hypothesis, the Two-Way ANOVA indicated that neither the fluency (η² = .024, p = .19) nor the originality scores (η² = .008, p = .45) differed between participants who had a match or non-match between their physical fitness level and the assigned exercise intensity. The results suggest that changing exercise intensity and matching exercise intensity to physical fitness level do not make a difference in the improvement of creativity.Show less
Aggressive behaviour is one of the most common behavioural issues in children and adolescents. Given its negative effects on social, emotional and academic development, early intervention is deemed...Show moreAggressive behaviour is one of the most common behavioural issues in children and adolescents. Given its negative effects on social, emotional and academic development, early intervention is deemed necessary. This study investigated the predictive role of emotion regulation and executive functioning, along with the mediating role of emotion regulation in the relationship between executive functioning and aggression problems. This current correlational study is part of the TRIXY project. The sample consisted of 47 children between the ages of three and seven year old. Aggression was measured using the Child Behaviour Checklist, emotion regulation was measured using the Child Behaviour Questionnaire – Very short form and the executive functions inhibition, planning ability, working memory and cognitive flexibility were measured using the Behavior Rating Inventory of Executive Functions (BRIEF) and the BRIEF-P. The findings indicated that children who experienced more difficulties in executive functioning exhibited heightened levels of aggressive behaviour. Additionally, research showed that emotion regulation is a mediating factor in the relation between executive functioning and aggression. However, the relation between these three constructs differ when splitting the sample in a group consisting of children aged three to four years of age and a group consisting of children who are five to seven years of age, indicating that the relation between these three constructs changes during development. Furthermore, research showed that inhibition, working memory, and cognitive flexibility were predictors of emotion regulation problems and aggression, with inhibition being the most significant predictor of aggression in all ages. Results showed no relation between planning ability, emotion regulation and aggression. This research contributes to the development of effective interventions and the understanding of the development of aggression.Show less
Job Burnout (JB) is a demanding syndrome that leaves employees exhausted and dealing with cognitive and emotional problems, with symptoms lasting up to 10 years. To understand why JB symptoms...Show moreJob Burnout (JB) is a demanding syndrome that leaves employees exhausted and dealing with cognitive and emotional problems, with symptoms lasting up to 10 years. To understand why JB symptoms pertain for so long, different resource theories were integrated to investigate the impact of JB on an individual gain process between job resources, personal resources, and recovery gained through physical exercise. It was predicted that skill discretion (SD), a common job resource, increases the personal resource self-efficacy (SE) which, in turn, enhances the recovery gained from physical exercise. This gain process was proposed to be dampened by JB, leaving employees with higher JB symptoms in a less advantageous position for resource gain as compared to those with lower symptoms. Using longitudinal data across three workweeks, self-report questionnaires were administered among full-time employees (N = 163). Although correlations revealed that the proposed relationships were found at specific weeks, hierarchical regression analyses revealed no across-time relationships, meaning no weekly gain process could be identified between SD, SE, and recovery gained through exercise. In addition, against expectations, no negative impact of JB on the gain process was found. Thus, the exact relationships between job resources, personal resources, recovery gained through exercise, and JB remain unclear. Future research is needed to further investigate these relationships preferably by using a different time lag than one week and by applying different roles of personal resources within the Job Demands-Resources framework.Show less
The aim of this study was to investigate the relation between parental mental well-being and parenting skills and whether this relationship differs based on the child's temperament. Parenting...Show moreThe aim of this study was to investigate the relation between parental mental well-being and parenting skills and whether this relationship differs based on the child's temperament. Parenting skills are crucial factors in a child's emotional, cognitive, social, and behavioral development. Data were collected from 20 parents of young children (3 - 5 years old). Parenting skills were assessed using self-report questionnaires regarding confidence in parenting, reflective capacity, and parental sensitivity. The child's temperament was also assessed through questionnaires filled out by the parents. All multiple regressions were non-significant, and the relationships between parental mental well-being and parenting skills were not moderated by the child's temperament. This means that parental mental well-being and the child's temperament were not sufficiently predictive of parental self-confidence, reflective capacity, and parental sensitivity in parenting. By examining the correlations, a moderate positive relationship was found between parental mental well-being and their confidence in parenting. Parents with higher mental well-being had more confidence in their parenting. Parental mental well-being was negatively associated with their reflective capacity, indicating that parents with lower mental well-being displayed higher levels of reflective capacity. A moderate positive relationship was found between the child's temperament and parental sensitivity, suggesting that parents of children with a more challenging temperament were generally more sensitive in their parenting.Show less
The intergalactic medium (IGM) contains most of the baryonic matter of the Universe and serves as a suitable environment for probing the thermal history of the Universe. The crucial moment in IGM...Show moreThe intergalactic medium (IGM) contains most of the baryonic matter of the Universe and serves as a suitable environment for probing the thermal history of the Universe. The crucial moment in IGM evolution is the Epoch of Reionization, corresponding to the transition from neutral to ionized IGM. However, due to the observational limitations, this period is still not well understood. In this thesis, we focus on constraining IGM thermal history by using Lyman-alpha forests data. This method is applicable in a wide range of temperatures, densities, and ionization fractions of cosmic gas at z about 2 − 5. Observations show that the longitudinal flux power spectrum of the Lyman-α forest exhibits a cut-off at small scales. This phenomenon is caused by thermal Doppler broadening, peculiar velocities along the line of sight (LOS), Hydrogen pressure smoothing, and warm dark matter. The first two effects act only along LOS, while the last two affect all spatial directions. To separate the one-dimensional and three-dimensional effects, we used the method of close quasar pairs, which is based on studying the correlations between Lyman-alpha forests of close quasar pairs. We used the Kolmogorov-Smirnov test to analyze the differences between distributions of phase difference, which characterizes correlations between Lyman-alpha forests. The calculations were performed for various thermal histories, parameters characterizing IGM, LOS separations, and wavenumbers, and accounting for different effects (Doppler broadening and peculiar velocities). Our results indicate that this method can distinguish various thermal histories regardless of the IGM thermal state and one-dimensional effects. Moreover, at separations of the order of pressure broadening, there is a prominent feature caused by different influences of pressure smoothing at large and small scales. In addition, this simple and powerful approach has the potential to distinguish scenarios with warm dark matter.Show less
Objective. To determine the effectiveness of a rehabilitation program including physical exercise, in improving cognition, participation, and coping in patients with a subarachnoid hemorrhage (SAH)...Show moreObjective. To determine the effectiveness of a rehabilitation program including physical exercise, in improving cognition, participation, and coping in patients with a subarachnoid hemorrhage (SAH). Secondary, it was aimed to identify the role of clinical characteristics in the effectiveness of the rehabilitation program. Methods. A longitudinal pilot intervention study was performed, with measurements before the start (T0), after three months (T1), and after six months (T2). Cognition was measured with the Montreal Cognitive Assessment, participation with the Impact on Participation and Autonomy questionnaire, and coping with the Utrecht Proactive Coping Competence Scale. Generalized Estimating Equation analyses were performed. Results. A total of 19 patients with SAH participated; 13 in the intervention group and 6 in the control group. For the intervention group, cognition improved between T0 and T2 and between T1 and T2. Participation declined between T0 and T1, but improved between T1 and T2. Proactive coping declined between T0 and T2 and between T1 and T2. Cognition of the control group did not change, but participation improved between T0 and T1 and proactive coping declined between T0 and T1. There was no significant difference between the control and intervention groups in improvements in cognition between T0 and T1 (p = 0.090). However, there was a significant difference between the control and intervention groups in changes in participation between T0 and T1 (p = 0.001) and in changes in coping between T0 and T1 (p < 0.001). The location of SAH played a role in the differences in participation, but not in cognition and coping. For treatment type and time since SAH, no significant effects were found. Conclusion. There was no effect of the rehabilitation program on cognition. The control group had a better participation level after three months and the intervention group worsened. The intervention group had a stable coping style after three months, whereas the control group declined in the use of proactive coping. Only the characteristic location of the aneurysm played a role in the participation level after three months, but not in cognition or coping. The other characteristics did not play a role in the changes. This study indicates that some long-term complaints can improve after the rehabilitation program, but more research is needed.Show less
In this thesis we present an experimental realisation of a double loop type Magnetic Paul Trap. We show that a microgram heavy NdFeB permanent magnet can stably be levitated for hours at room...Show moreIn this thesis we present an experimental realisation of a double loop type Magnetic Paul Trap. We show that a microgram heavy NdFeB permanent magnet can stably be levitated for hours at room temperature in this trap. Magnetic levitation of a magnetized particle is theoretically possible with this trap by generating opposed alternating magnetic fields. We show the fabrication of a printed circuit structure capable of producing these fields, as well as the engineering behind the realisation of the trap. Both by optical and magnetic readout we characterize the motion of the trapped magnet and show that its center of mass motion frequencies $\omega_z = 2\omega_{x,y} \approx 20Hz$. We characterize the damping on these modes and find that at low pressure the quality factor is strongly limited (to $Q \approx 90$) by coupling to the environment through generation of Eddy currents.Show less
It has been demonstrated that exploring a new environment promotes memory in young adults. Animal studies propose that the enhancement of memory in novel settings is linked to hippocampal dopamine....Show moreIt has been demonstrated that exploring a new environment promotes memory in young adults. Animal studies propose that the enhancement of memory in novel settings is linked to hippocampal dopamine. While the dopaminergic system undergoes changes across the lifespan, little is known about the effects of novelty on memory throughout different life stages. This research contributes to the understanding of the effects of novelty in older adults. The participants (n=14) explored both novel and previously familiarised virtual environments to assess the influence of spatial novelty on declarative memory. Subsequently, participants were presented with a word list to memorise, and their memory performance was evaluated through both immediate and delayed recall. Our results indicate superior immediate recall compared to delayed recall, with no evidence for an effect of novelty. We found no difference in spontaneous eye blinking rate following exposure to a novel or familiar environment. Furthermore, a negative correlation was found between spontaneous eye blinking rate and memory recall. Finally, this sample showed that participants had a slightly better performance on day two compared to day three, especially when they had lower expectations. This suggests that there is an extra novelty effect that is noticeable on the second day, which is suggestive of a decreasing novelty effect over the course of subsequent days. Our findings could potentially be explained by the fact that the advantageous effects of novelty decrease as individuals age, likely due to deterioration in the neural pathways associated with novelty processing. In today's society, where the active contribution of older adults is increasingly valued, it is crucial to address age-related cognitive decline. In order to develop intervention for age-related memory decline, further research is necessary for the specific role of novelty-induced memory in older adults.Show less
Individuals diagnosed with a personality disorder (PD) are often confronted with a low quality of life (QoL) and high health costs, both important outcome variables among cost-effectiveness studies...Show moreIndividuals diagnosed with a personality disorder (PD) are often confronted with a low quality of life (QoL) and high health costs, both important outcome variables among cost-effectiveness studies. Several factors have been identified that are associated with a low QoL and high health costs in individuals diagnosed with a PD. The influence of trauma is unknown. It has been found that PDs are associated with both past trauma experiences and symptoms of posttraumatic stress disorder (PTSD) in their daily life. While several studies suggested that individuals with a Borderline PD (BPD) and comorbid PTSD suffer from a more impaired QoL compared to individuals with a single disorder, less is known about the effect of PTSD on PDs other than BPD and the relation between trauma severity and health costs. The current study investigates the effect of both childhood trauma and current PTSD symptoms on QoL and health costs in individuals diagnosed with a PD and the possible mediating role of QoL on the relationship between trauma and health costs. The sample consisted of 65 individuals, with a mean age of 38 (SD = 12.3), diagnosed with one or more PDs. Data was collected with several questionnaires (Childhood Trauma Questionnaire-Short Form, Posttraumatic Stress Disorder Checklist for DSM-5, Treatment Inventory of Costs in Patients with psychiatric disorders, and the Mental Health Quality of Life questionnaire). The results show that severity of current PTSD symptoms (t(58) = -4.19, p < .001) but not childhood trauma was related to a decreased QoL in individuals diagnosed with a PD. Both current PTSD symptoms and childhood trauma were not significantly related to health costs. QoL did not perform a mediating role on the relationship between trauma and health costs. To conclude, severe PTSD symptoms represent an additional deprivation for QoL among personality-disordered individuals in this sample. This conclusion is based on a relatively small sample, thus should be further investigated with a larger sample.Show less
Research on suicidal ideation indicates the significant role of adverse childhood experiences (ACEs) and early parental attachment but fails to investigate risk potential in student populations....Show moreResearch on suicidal ideation indicates the significant role of adverse childhood experiences (ACEs) and early parental attachment but fails to investigate risk potential in student populations. This study aimed to research how adverse childhood experiences in a population of university students who report mood and stress problems are related to suicidal ideation and whether the relationship between adverse childhood experiences and suicidal ideation is moderated by attachment style. To target students at risk for suicidal ideation, purposive sampling was employed. An independent samples t-test with consecutive multiple regression (n= 234) showed that adverse childhood experiences, measured with the ACE questionnaire, predicted the presence and severity of suicidal ideation, measured by the BSSI. Consecutive ANCOVA showed that disorganized attachment to the mother and father, measured with the PBI, were found to predict suicidal ideation. Secure attachment was negatively associated with suicidal ideation, whereas for avoidant and anxious attachment there was no association found. A logistic regression analysis showed no moderation effect of insecure attachment styles in the relation between adverse childhood experiences and suicidal ideation. Gender, academic pressure, and nationality were controlled. Findings may be limited due to methodological and performance flaws. The results highlight the importance of early identification of adverse childhood experiences and disorganized attachment for intervention and prevention of later suicidal ideation amongst students.Show less
