Utrecht University
  • Utrecht, Netherlands, Netherlands
Recent publications
Spiral Galaxies is a pencil-and-paper puzzle played on a grid of unit squares: given a set of points called centers, the goal is to partition the grid into polyominoes such that each polyomino contains exactly one center and is 180∘ rotationally symmetric about its center. We show that this puzzle is NP-complete, ASP-complete, and #P-complete even if (a) all solutions to the puzzle have rectangles for polyominoes; or (b) the polyominoes are required to be rectangles and all solutions to the puzzle have just 1×1, 1×3, and 3×1 rectangles. The proof for the latter variant also implies NP/ASP/#P-completeness of finding a noncrossing perfect matching in distance-2 grid graphs where edges connect vertices of Euclidean distance 2. Moreover, we prove NP-completeness of the design problem of minimizing the number of centers such that there exists a set of galaxies that exactly cover a given shape.
Background and objectives This study compared the effect of imagery rescripting focusing on self-compassion, imagery rescripting focusing on mastery, and a positive memory control condition on (1) emotional responses towards the memory (one day after), (2) changes in the believability of negative core beliefs, and dysfunctional eating behaviors (one week after) in individual at risk for developing an eating disorder. Methods Female participants (N = 69) were allocated to one of three conditions: ImRs focusing on self-compassion (N = 24), ImRs focusing on self-mastery (N = 23), and positive memory control condition (N = 22). Participants in the ImRs conditions received a 20-min self-guided ImRs intervention, whereas participants in the control condition received a 20-min self-guided task focusing on an unrelated positive memory. Results The experimental manipulation successfully induced the use of self-compassion and mastery strategies in the respective imagery rescripting condition. However, our data show that a single 20-min session of self-guided imagery rescripting focusing on compassion and/or mastery has no effect on the emotional response towards the aversive memory or in the change of core beliefs and eating behaviors at follow up. Limitations We discuss potential reasons for the null findings, including the use of a single imagery rescripting session, the sample size and the measurement of manipulation checks. Conclusion Future studies are needed to rule out methodological explanations for the null results. These findings may be of value for the development of future experimental lab paradigms which aim to evaluate the causal effects and working mechanisms of imagery rescripting.
Young children are generally overconfident in their abilities and performances, but the reasons that underlie such self-overestimation are unclear. The current cross-cultural experiment aimed to address this issue, testing the possibility that young children’s overconfidence in task performance is, at least in part, motivated. We tested 89 Chinese children (49 % girls) and 104 Dutch children (50 % girls) aged 4 and 5 years and asked them to estimate how well they would perform on both a motor test and a memory task. They were randomly assigned to either an experimental condition (in which they were promised a reward for providing accurate performance estimates) or a no-incentive control condition, and then they performed the task. The incentive lowered Chinese (but not Dutch) children’s performance overestimation on the motor task. Unexpectedly, children did not overestimate their performance on the memory task. Thus, this study supports the view that young children’s self-overestimation can be motivated (rather than due to cognitive immaturity alone) but also reveals task contingencies and cultural differences.
Purpose: This study reports on survival and health related quality of life (HRQOL) after extracorporeal membrane oxygenation (ECMO) treatment and the associated costs in the first year. Materials and Methods: Prospective observational cohort study patients receiving ECMO in the intensive care unit during August 2017 and July 2019. We analyzed all healthcare costs in the first year after index admission. Follow-up included a HRQOL analysis using the EQ-5D-5L at 6 and 12 months. Results: The study enrolled 428 patients with an ECMO run during their critical care admission. The one-year mortality was 50%. Follow up was available for 124 patients at 12 months. Survivors reported a favorable mean HRQOL (utility) of 0.71 (scale 0–1) at 12 months of 0.77. The overall health status (VAS, scale 0–100) was reported as 73.6 at 12 months. Mean total costs during the first year were $204,513 ± 211,590 with hospital costs as the major factor contributing to the total costs. Follow up costs were $53,752 ± 65,051 and costs of absenteeism were $7317 ± 17,036. Conclusions: At one year after hospital admission requiring ECMO the health-related quality of life is favorable with substantial costs but considering the survival might be acceptable. However, our results are limited by loss of follow up. So it may be possible that only the best-recovered patients returned their questionnaires. This potential bias might lead to higher costs and worse HRQOL in a real-life scenario.
Periodontitis is a chronic inflammatory condition that often causes serious damage to tooth-supporting tissues. The limited successful outcomes of clinically available approaches underscore the need for therapeutics that cannot only provide structural guidance to cells but can also modulate the local immune response. Here, three-dimensional melt electrowritten (i.e., poly(ε-caprolactone)) scaffolds with tissue-specific attributes were engineered to guide differentiation of human-derived periodontal ligament stem cells (hPDLSCs) and mediate macrophage polarization. The investigated tissue-specific scaffold attributes comprised fiber morphology (aligned vs. random) and highly-ordered architectures with distinct strand spacings (small 250 μm and large 500 μm). Macrophages exhibited an elongated morphology in aligned and highly-ordered scaffolds, while maintaining their round-shape on randomly-oriented fibrous scaffolds. Expressions of periostin and IL-10 were more pronounced on the aligned and highly-ordered scaffolds. While hPDLSCs on the scaffolds with 500 μm strand spacing show higher expression of osteogenic marker (Runx2) over 21 days, cells on randomly-oriented fibrous scaffolds showed upregulation of M1 markers. In an orthotopic mandibular fenestration defect model, findings revealed that the tissue-specific scaffolds (i.e., aligned fibers for periodontal ligament and highly-ordered 500 μm strand spacing fluorinated calcium phosphate [F/CaP]-coated fibers for bone) could enhance the mimicking of regeneration of natural periodontal tissues.
With increasing immigration, it is increasingly important to understand whether and when children consider immigrant peers as co-nationals. Using an experimental design, we examined among native-born preadolescents (8–13 years of age) in the Netherlands whether and when they perceive immigrant peers as co-nationals. First, and in agreement with the social categorization account, we expected that the use of dual identity (vs single ethnic identity) labels for immigrant peers leads to stronger co-nationality perceptions and a related stronger desire for close social contact. Second, and in line with the acculturation account, we expected that an early age of arrival in the country (vs a later age of arrival) leads to stronger perceived co-nationality and related contact desire. The findings support the acculturation account, especially among native-born children with higher national identification. There was no evidence for the social categorization account.
The cooperative eye hypothesis posits that human eye morphology evolved to facilitate cooperation. Although it is known that young children prefer stimuli with eyes that contain white sclera, it is unknown whether white sclera influences children’s perception of a partner’s cooperativeness specifically. In the current studies, we used an online methodology to present 5-year-old children with moving three-dimensional face models in which facial morphology was manipulated. Children found “alien” faces with human eyes more cooperative than faces with dark sclera (Study 2) but not faces with enlarged irises (Study 1). For more human-like faces (Study 3), children found human eyes more cooperative than either enlarged irises or dark sclera and found faces with enlarged irises cuter (but not more cooperative) than eyes with dark sclera. Together, these results provide strong support for the cooperative eye hypothesis.
The current research examined the similarities and differences in parenting behaviors between 1090 Dutch and 2339 urban Chinese mothers with 1- to 4-year olds and investigated to what extent group differences in parenting stress, proportions of only children, and maternal working hours explain cultural variations in parenting behaviors. Thirteen parenting behaviors were assessed using the Comprehensive Early Childhood Parenting Questionnaire. Parenting stress was measured by 10 items selected from the Parenting Stress Index-Short Form. Mothers also reported whether the child was an only child and how many hours they worked per week. Results showed that Dutch mothers and urban Chinese mothers had similar levels of sensitivity, affection, using toys, verbal punishment, and positive discipline. For the other 8 parenting behaviors on which cultural variations were found, a mediational model, examining whether parenting stress, the only-child status, and maternal working time could explain cultural differences in parenting behaviors, was investigated. Compared to Dutch mothers, urban Chinese mothers had higher parenting stress, worked longer hours, and were more likely to have an only child. The group differences in involvement in activities, exposure, over-reactivity, and physical punishment were fully explained by cultural differences in parenting stress and proportions of only children. These mediators, however, only explained a part of the cultural differences in responsiveness, psychological control, consistency, and laxness, showing that Dutch mothers were still more consistent in enforcing rules and less lax in parenting, whereas urban Chinese mothers were still slightly more responsive to children's signals, but also more psychologically controlling.
Social contexts can affect how people respond to feedback from others. We investigated how context information modulates the cognitive processing of feedback messages (i.e., external evaluations of one's character). We manipulated two aspects of (positive and negative) feedback messages: The identity of the sender (ingroup vs. outgroup member), and the dimension (one's competence vs. morality) as focal concern addressed in the feedback. We measured affective and behavioral responses after participants received such feedback (Study 1, N = 194), and additionally recorded an EEG in Study 2 (N = 49). In both studies, participants reported being more emotionally affected by negative feedback from ingroup compared to outgroup senders. Participants in Study 1 also reported to perceive feedback on their morality (vs. competence) as more negative. Complementing these findings, ERP results of Study 2 revealed greater preferential processing (i.e., increased P200) of feedback messages delivered by ingroup rather than outgroup members. Additionally, participants paid less sustained attention to feedback on their morality (vs. competence, as indicated by decreased P300- and LPP-amplitudes), and afterward recalled less morality- (vs. competence-) related feedback messages. The ERP findings were more pronounced for negative compared to positive feedback. These results suggest that subtle cues such as the social group-membership of a sender or the dimension addressed in a feedback message can modulate the cognitive processing of that message. Furthermore, our findings may explain why people are inclined to disregard negative feedback from outgroup senders and on their moral character.
We study the effect of having a female top manager (FTM) on firm performance using World Bank Enterprise Survey data that cover 130,000 firms in 130 mostly developing countries from 2008 to 2017. We show that firms with FTMs underperform their male-led counterparts. FTMs’ underperformance is largely driven by small and medium-sized enterprises and varies widely across world regions. FTMs influence firm performance through affecting firms’ three critical factors of production, which are finance, technology, and labor. Our mediation analyses indicate that the negative FTM–performance relation can be partially mediated by firms’ access to finance, technology usage, and labor selection, which are proxied by lines of credit, internet purchases, and labor cost, correspondingly. This study synthesizes the leadership literature, extends upper echelon and social role theories, and brings clarity to the equivocal findings in the literature on the relation between female leadership and firm performance.
Background Cartilage regenerative mechanisms initiated by knee joint distraction (KJD) remain elusive. Animal experiments that are representative for the human osteoarthritic situation and investigate the effects of KJD at consecutive time points could be helpful in this respect but are lacking. This study investigated the effects of KJD on the osteoarthritic joint of dogs on two consecutive timepoints. Methods Osteoarthritis was bilaterally induced for 10 weeks in 12 dogs using the groove model. Subsequently, KJD was applied to the right hindlimb for 8 weeks. The cartilage, subchondral bone and synovial membrane were investigated directly after KJD treatment, and after 10 weeks of follow-up after KJD treatment. Macroscopic and microscopic joint tissue alterations were investigated using the OARSI grading system. Additionally, proteoglycan content and synthesis of the cartilage were assessed biochemically. RT-qPCR analysis was used to explore involved signaling pathways. Results Directly after KJD proteoglycan and collagen type II content were reduced accompanied by decreased proteoglycan synthesis. After 10 weeks of follow-up, proteoglycan and collagen type II content were partly restored and proteoglycan synthesis increased. RT-qPCR analysis of the cartilage suggests involvement of the TGF-β and Notch signalling pathways. Additionally, increased subchondral bone remodelling was found at 10 weeks of follow-up. Conclusion While the catabolic environment in the cartilage is still present directly after KJD, at 10 weeks of follow-up a switch towards a more anabolic joint environment was observed. Further investigation of this timepoint and the pathways involved might elucidate the regenerative mechanisms behind KJD. The Translational Potential of this Article Further elucidation of the regenerative mechanisms behind KJD could improve the existing KJD treatment. Furthermore, these findings could provide input for the discovery or improvement of other joint regenerative treatment strategies.
Nature-based solutions (NBS) are multifunctional and cost-effective innovations delivering urban sustainability, but they are not yet mainstream in urban development. This can be explained by persistent structural conditions in the urban infrastructure regime, resulting in barriers such as lack of collaborative governance, inadequate knowledge and limited funding availability. In this paper we argue that (supra)national governments could play an important role in breaking down these barriers by employing policy instruments and strategically combining these into policy mixes targeting multiple regime structures. By means of an empirical analysis across six European countries and the European Union (EU), we provide an overview of regulatory, financial and soft (supra)national policy instruments supporting urban NBS mainstreaming and how these are combined in policy mixes across cases. In addition, we investigate policy mix comprehensiveness by mapping the extent to which these target each of the relevant urban infrastructure regime structures underpinning barriers to urban NBS mainstreaming. We demonstrate that, with the exception of the EU, none of the studied cases employs a fully comprehensive policy mix. We conclude that by strategically adopting policy instruments with the aim of crafting a comprehensive policy mix, obstacles in pathways to urban NBS mainstreaming could be overcome.
Most Remaining Useful Life (RUL) prognostics are obtained using supervised learning models trained with many labelled data samples (i.e., the true RUL is known). In aviation, however, aircraft systems are often preventively replaced before failure. There are thus very few labelled data samples available. We therefore propose a Long Short-Term Memory (LSTM) autoencoder with attention to develop health indicators for an aircraft system instead. This autoencoder is trained with unlabelled data samples (i.e., the true RUL is unknown). Since aircraft fly under various operating conditions (varying altitude, speed, etc.), these conditions are also integrated in the autoencoder. We show that the consideration of the operating conditions leads to robust health indicators and improves significantly the monotonicity, trendability and prognosability of these indicators. These health indicators are further used to predict the RUL of the aircraft system using a similarity-based matching approach. We illustrate our approach for turbofan engines. We show that the consideration of the operating conditions improves the monotonicity of the health indicators by 97%. Also, our approach leads to accurate RUL estimates with a Root Mean Square Error (RMSE) of 2.67 flights only. Moreover, a 19% reduction in the RMSE is obtained using our approach in comparison to existing supervised learning models.
The empirical relationship between educational attainment and pay levels has been widely acknowledged in the labour-economic and labour-sociology literatures. While the causalities underlying this relationship are not conclusively established, researchers broadly agree that higher educational attainment leads to higher income levels in dependent employment, temporary hiring, and freelancing alike. The ‘gig economy’, where workers complete jobs mediated by online platforms, challenges this paradigm as gig workers can access jobs without any educational certificates. Building a theoretical framework based on agency-driven accounts, we investigate whether we can empirically observe a relationship between educational attainment and wage levels in the gig economy. Our OLS regression analyses of 1607 gig workers in 14 Western economies illustrate no statistically significant correlation. Instead, the platform's review system as well as the gig workers' level of previous job experience serve as the major signalling mechanisms that help to reduce information asymmetry. Qualitative insights gained from in-depth interviews explain this finding by revealing how gig workers gain the necessary qualifications for their jobs, most importantly, through self-study, learning-by-doing, and trial-and-error processes. Our findings therefore point out that advanced educational credentials are only of limited use for gig workers.
Background Cycling for transportation and recreation is gaining in popularity, especially in older age groups. The rise in electric assisted cycles (EAC) may also have a role to play in this. With an increase in the number of cyclists comes an increase in the prevalence of cycle crashes. However, there is a lack of knowledge on EAC crashes and crash studies including cycle use data. An important question is also whether the high number of serious road injuries among older cyclists, is due to increased risk or more serious consequences in the event of a crash. Study aim To compare the odds of reporting a cycle crash on a conventional (CC) against electrically assisted cycle (EAC), while controlling for age, gender, BMI, impairments while cycling, cycling frequency and region of residence. Methods A 12-month retrospective cross-sectional survey-based study, including male and female cyclists aged 40+ years, was conducted in Belgium and the Netherlands. Socio-demographics, physical and mental impairments while cycling (such as lower reaction time), crash details and cycling frequency data were collected. Cyclists were grouped into CC, EAC or both (CC + EAC) based on the type of cycle they used during the study period. Logistic regression models were used to calculate the odds of reporting a cycle crash. Main and interaction effects were studied. Results 1,919 cyclists were included in the data analysis (63.2 ± 11.1 years; 50% women). 319 (17% of the total sample) cyclists reported a crash in the previous 12 months, of which 36% were EAC crashes. Those reporting a crash were significantly younger compared to those not reporting a crash. The following significant main effects were observed: those cycling on an EAC had a higher odds of reporting a cycle crash compared to those cycling on a CC (OR = 1.41, 95% CI = 1.01–1.97); cyclists in the category average and high on mental impairments while cycling had a higher odds of reporting a cycle crash compared to those in the category low (OR = 1.72, 95% CI = 1.23–2.40 and OR = 3.49, 95% CI = 2.51–4.90, respectively); higher cycling frequency is related to higher odds of reporting a cycle crash (OR = 3.25, 95% CI = 2.25–4.90). A significant interaction effect was observed between age category and gender (OR = 1.93, 95% CI = 1.15–3.26). Post-hoc tests revealed that men in the younger age category (40–64 years) had the highest probability (18.95%) of reporting a cycle crash, whereas men in the oldest age category (65+ years) had the lowest probability (9.99%) of reporting a cycle crash. No significant difference between age categories in women was observed. Conclusion This study indicates that within a cohort of middle aged and older adults living in regions with high to low cycling modal shares, cycle type, mental impairments while cycling, cycling frequency and region of residence play a significant role in the odds of reporting a (minor) cycle crash. Men in the age category 40–64 years have a significantly higher probability of reporting a cycle crash compared to men of 65+ years. Safety campaigns and instructions should pay particular attention to men in the age category 40–64 years and those with a mental impairment while cycling.
The aggressiveness of melanoma and lack of effective therapies incite the discovery of novel strategies. Recently, a new dual acting hybrid molecule (HM), combining a triazene and a ʟ-tyrosine analogue, was synthesized. HM was designed to specifically be activated by tyrosinase, the enzyme involved in melanin biosynthesis and overexpressed in melanoma. HM displayed remarkable superior antiproliferative activity towards various cancer cell lines compared with temozolomide (TMZ), a triazene drug in clinical use, that acts through DNA alkylation. In B16-F10 cells, HM induced a cell cycle arrest at phase G0/G1 with a 2.8-fold decrease in cell proliferation index. Also, compared to control cells, HM led to a concentration-dependent reduction in tyrosinase activity and increase in caspase 3/7 activity. To maximize the therapeutic performance of HM in vivo, its incorporation in long blood circulating liposomes, containing poly(ethylene glycol) (PEG) at their surface, was performed for passively targeting tumour sites. HM liposomes (LIP HM) exhibited high stability in biological fluids. Preclinical studies demonstrated its safety for systemic administration and in a subcutaneous murine melanoma model, significantly reduced tumour progression. In a metastatic murine melanoma model, a superior antitumour effect was also observed for mice receiving LIP HM, with markedly reduction of lung metastases compared to positive control group (TMZ). Biodistribution studies using ¹¹¹In-labelled LIP HM demonstrated its ability for passively targeting tumour sites, thus correlating with the high therapeutic effect observed in the two experimental murine melanoma models. Overall, our proposed nanotherapeutic strategy was validated as an effective and safe alternative against melanoma.
Lumbar interbody fusion (IF) is a common procedure to obtain fusion of the spine by replacement of the intervertebral disc with a cage. Optimization of spinal cages is ongoing to reduce complications such as a pseudoarthrosis and subsidence of the cage. IF animal models (primate, dog, pig, goat and sheep) remain important to assess implant effectivity. But currently the available literature is dispersed and not IF model specific. Therefore unwanted inconsistencies between studies occur that limit generalizability. Based on our experience, anatomical preparation and literature research, we present a rationale for species selection and a practical guide for the surgical procedure in the goat animal model. The translational Potential of this Article Rigorous methodologic design is an important means to improve translational value and generalizability of large animal IF efficacy studies. This paper provides a rationale and practical guide for animal selection and surgical decision making that can help reduce unnecessary variation between models and improve methodologic rigor and documentation for future experiments.
Featuring the most direct and closest social relationships, the household plays a crucial role in influencing an individual's wants, needs, and behavior. However, the role of intra-household decisions in the connection between the built environment and activity-travel behavior has not been systematically analyzed. This paper adds to the literature by: (1) proposing a conceptual framework explaining how intra-household decisions are related to activity-travel behavior, the built environment, and attitudes; (2) synthesizing the current literature on this topic; and (3) identifying gaps in the literature and suggesting avenues for future research. In particular, we focus on the relationships between intra-household decisions and (changes in) travel attitudes, residential self-selection, and residential dissonance. Based on the results of the literature review, we found that very few studies have explored the extent to which the residential built environment meets and satisfies the travel needs and preferences of different household members, and how these contribute to different activity-travel behaviors. As attitudes may vary over time, capturing changes in attitudes and activity-travel behavior of different members of a household during and after residential relocation is recommended for future research to understand the role of intra-household decisions in the relationship between attitudes, built environment, and activity-travel behavior.
Commonly, parenting behaviors are assessed in an explicit way, usually by means of self-reports. Yet under suboptimal conditions, it is expected that parents act more automatically. The aim of the present longitudinal empirical study was to investigate the influence of automatic and explicit parenting cognitions on alcohol use in adolescents and whether this relationship is dependent on adolescents’ age and gender and parent gender. A sample of 111 parent-child dyads (71.9% mothers; M age = 47.4, SD = 5.3) with children between 12 and 18 years old (55.2% boys; M age = 14.8 years, SD = 1.6) completed the Relational Responding Task (RRT) at T1 (September 2015) and T2 (April 2016) to assess automatic parenting prior to an online questionnaire that assessed explicit alcohol-specific parenting. For lifetime prevalence of drinking, stricter explicit parenting cognitions predicted a lower likelihood of children ever having consumed alcohol at T2. This effect was particularly relevant for older adolescents. Automatic parenting cognitions were not predictive of the lifetime prevalence of alcohol use. For weekly drinking, a significant protective effect of stricter automatic parenting cognitions was found only for older adolescents. This study is the first to demonstrate longitudinally that automatic parenting cognitions as measured by the RRT can be used as a predictor of the level of drinking among older adolescents, even after controlling for explicit parenting behaviors. We argue that the influence of parents is subject to change as a function of adolescents’ age, with the prevailing role of automatic parenting over explicit parenting.
Objective: Using data from a randomized controlled trial on psychotherapy for posttraumatic stress disorder (PTSD) in older adults (aged >55), this study aimed at analysing the efficacy of two psychological interventions in terms of self-reported symptoms, comorbid psychopathology and resilience outcomes. Method: Thirty-three outpatients (age 55-81) with PTSD were randomly assigned to eleven sessions of narrative exposure therapy or present-centered therapy. Self-reported symptom severity of PTSD, depression and general psychopathology, along with measures of resilience (self-efficacy, quality of life and posttraumatic growth cognitions), were target outcomes. Harvard Trauma Questionnaire, Beck Depression Inventory, Brief Symptom Inventory, General Efficacy Scale, World Health Organization Quality of Life Assessment and Meaning of War Scale (personal growth) were assessed pre-treatment, post-treatment and at four months follow-up. Because of variable inter-assessment intervals, a piecewise mixed effects growth model was used to investigate treatment effects. Results: Neither post-treatment, nor at mean follow-up, between-group effects were found. At follow-up, significant medium to large within-group effect sizes were found in the NET-group for psychopathology (self-reported PTSD: Cohen's d = 0.54, p < .01; depression: Cohen's d = 0.51, p = .03; general psychopathology: Cohen's d = 0.74, p = .001), but not so in the PCT-group. Resilience (self-efficacy, quality of life and personal growth cognitions) did not significantly change in either group. Conclusions: In older adults with PTSD, the efficacy of NET extended beyond PTSD, reducing not only self-reported symptoms of PTSD but also comorbid depression and general psychopathology.
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25,229 members
Michael Volk
  • Department of Earth Sciences
Lech Grzelak
  • Mathematical Institute of Utrecht University
Egon Peter Köster
  • Department of Psychology
Saskia van Wees
  • Department of Biology
Heidelberglaan 2, 3508TC, Utrecht, Netherlands, Netherlands
Head of institution
Henk Kummeling