University of Groningen
  • Groningen, Netherlands
Recent publications
Unlike the case with identical neighboring agents whose actions are mirrored, the problem of distributed formation control design with heterogeneous sensing is not straightforward. This paper considers the problem of distributed formation control where each agent can only control distances or bearings with its neighbors. We firstly develop a rigidity theory with heterogeneous sensing to ensure that the desired shape is well-posed. Secondly, we propose an iterative method that allows us to scale up the number of agents with heterogeneous sensing. Finally, we show the effectiveness of our method by numerical simulation.
In this article, we consider a dc microgrid composed of distributed generation units (DGUs) trading energy among each other, where the energy price depends on the total current generated by all the DGUs. We then use a Cournot aggregative game to describe the self-interested interaction among the DGUs, where each DGU aims at minimizing the deviation with respect to the given reference signals and maximizing the revenue from the sale of the generated power. Thus, we design a fully distributed continuous-time equilibrium-seeking algorithm to compute the generalized Nash equilibrium (GNE) of the game. We interconnect the designed decision-making algorithm with the dynamics of the microgrid in a passive way, and, by leveraging passivity theory, we prove the convergence of the closed-loop system trajectory to a feasible operating point that is also a Nash equilibrium of the collective aggregative game. Finally, we present extensive simulation results that validate the proposed distributed optimal control scheme, showing excellent performance.
Purpose. Positron emission tomography (PET) image quality can be affected by artifacts emanating from PET, computed tomography (CT), or artifacts due to misalignment between PET and CT images. Automated detection of misalignment artifacts can be helpful both in data curation and in facilitating clinical workflow. This study aimed to develop an explainable machine learning approach to detect misalignment artifacts in PET/CT imaging. Approach. This study included 1216 PET/CT images. All images were visualized and images with respiratory misalignment artifact (RMA) detected. Using previously trained models, four organs including the lungs, liver, spleen, and heart were delineated on PET and CT images separately. Data were randomly split into cross-validation (80%) and test set (20%), then two segmentations performed on PET and CT images were compared and the comparison metrics used as predictors for a random forest framework in a 10-fold scheme on cross-validation data. The trained models were tested on 20% test set data. The model’s performance was calculated in terms of specificity, sensitivity, F1-Score and area under the curve (AUC). Main results. Sensitivity, specificity, and AUC of 0.82, 0.85, and 0.91 were achieved in ten-fold data split. F1_score, sensitivity, specificity, and AUC of 84.5 vs 82.3, 83.9 vs 83.8, 87.7 vs 83.5, and 93.2 vs 90.1 were achieved for cross-validation vs test set, respectively. The liver and lung were the most important organs selected after feature selection. Significance. We developed an automated pipeline to segment four organs from PET and CT images separately and used the match between these segmentations to decide about the presence of misalignment artifact. This methodology may follow the same logic as a reader detecting misalignment through comparing the contours of organs on PET and CT images. The proposed method can be used to clean large datasets or integrated into a clinical scanner to indicate artifactual cases.
As a sociotechnical practice at the nexus of humans, machines, and visual culture, text-to-image generation relies on verbal prompts as the primary technique to guide generative models. To align desired aesthetic outcomes with computer vision, human prompters engage in extensive experimentation, leveraging the model’s affordances through prompting for style. Focusing on the interplay between machine originality and repetition, this study addresses the dynamics of human-model interaction on Midjourney, a popular generative model (version 6) hosted on Discord. It examines style modifiers that users of visual generative media add to their prompts and addresses the aesthetic quality of AI images as a multilayered construct resulting from affordance actualization. I argue that while visual generative media holds promise for expanding the boundaries of creative expression, prompting for style is implicated in the practice of generating a visual aesthetic that mimics paradigms of existing cultural phenomena, which are never fully reduced to the optimized target output.
Extracellular vesicles (EVs) play a crucial role in mediating communication between cells across species and kingdoms. The intercellular communication facilitated by EVs through autocrine and paracrine signalling mechanisms is essential for cell survival, maintaining normal metabolic functions and ensuring overall bodily homeostasis and health. Extracellular vesicles are present in various bodily fluids, such as pleural effusions, plasma, breast milk, amniotic fluid, semen and saliva. Additionally, the generation and release of EVs contribute to the removal of cellular waste. Patients with obesity exhibit a higher release and amount of circulating EVs than individuals with normal weight. This increased EV release in obesity might contribute to the inflammatory state characteristic of this metabolic condition, because higher levels of pro‐inflammatory molecules are found within their cargo. However, interpreting results related to EV abundance, cargo and biological actions can be complicated by several factors; these include variations in cell sources, a wide age range (from children to the elderly), a mix of females and males, medication use and health status, a range of body weights (from normal weight to morbid obesity) and differences between in vitro assays using cell lines versus primary cultures. This article addresses the shortcomings, limitations and gaps in knowledge, providing a framework for enhancing our understanding of the physiological effects of EVs on obesity. image
Background Coronary artery disease (CAD) has one of the highest mortality rates in humans worldwide. Single‐photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) provides clinicians with myocardial metabolic information non‐invasively. However, there are some limitations to interpreting SPECT images performed by physicians or automatic quantitative approaches. Radiomics analyzes images objectively by extracting quantitative features and can potentially reveal biological characteristics that the human eye cannot detect. However, the reproducibility and repeatability of some radiomic features can be highly susceptible to segmentation and imaging conditions. Purpose We aimed to assess the reproducibility of radiomic features extracted from uncorrected MPI‐SPECT images reconstructed with 15 different settings before and after ComBat harmonization, along with evaluating the effectiveness of ComBat in realigning feature distributions. Materials and methods A total of 200 patients (50% normal and 50% abnormal) including rest and stress (without attenuation and scatter corrections) MPI‐SPECT images were included. Images were reconstructed using 15 combinations of filter cut‐off frequencies, filter orders, filter types, reconstruction algorithms, number of iterations and subsets resulting in 6000 images. Image segmentation was performed on the left ventricle in the first reconstruction for each patient and applied to 14 others. A total of 93 radiomic features were extracted from the segmented area, and ComBat was used to harmonize them. The intraclass correlation coefficient (ICC) and overall concordance correlation coefficient (OCCC) tests were performed before and after ComBat to examine the impact of each parameter on feature robustness and to assess harmonization efficiency. The ANOVA and the Kruskal–Wallis tests were performed to evaluate the effectiveness of ComBat in correcting feature distributions. In addition, the Student's t‐test, Wilcoxon rank‐sum, and signed‐rank tests were implemented to assess the significance level of the impacts made by each parameter of different batches and patient groups (normal vs. abnormal) on radiomic features. Results Before applying ComBat, the majority of features (ICC: 82, OCCC: 61) achieved high reproducibility (ICC/OCCC ≥ 0.900) under every batch except Reconstruction. The largest and smallest number of poor features (ICC/OCCC < 0.500) were obtained by IterationSubset and Order batches, respectively. The most reliable features were from the first‐order (FO) and gray‐level co‐occurrence matrix (GLCM) families. Following harmonization, the minimum number of robust features increased (ICC: 84, OCCC: 78). Applying ComBat showed that Order and Reconstruction were the least and the most responsive batches, respectively. The most robust families, in a descending order, were found to be FO, neighborhood gray‐tone difference matrix (NGTDM), GLCM, gray‐level run length matrix (GLRLM), gray‐level size zone matrix (GLSZM), and gray‐level dependence matrix (GLDM) under Cut‐off, Filter, and Order batches. The Wilcoxon rank‐sum test showed that the number of robust features significantly differed under most batches in the Normal and Abnormal groups. Conclusion The majority of radiomic features show high levels of robustness across different OSEM reconstruction parameters in uncorrected MPI‐SPECT. ComBat is effective in realigning feature distributions and enhancing radiomic features reproducibility.
The European Quality In Preclinical Data (EQIPD) consortium was born from the fact that publications report challenges with the robustness, rigor, and/or validity of research data, which may impact decisions about whether to proceed with further preclinical testing or to advance to clinical testing, as well as draw conclusions on the predictability of preclinical models. To address this, a consortium including multiple research laboratories from academia and industry participated in a series of electroencephalography (EEG) experiments in mice aimed to detect sources of variance and to gauge how protocol harmonisation and data analytics impact such variance. Ultimately, the goal of this first ever between-laboratory comparison of EEG recordings and analyses was to validate the principles that supposedly increase data quality, robustness, and comparability. Experiments consisted of a Localisation phase, which aimed to identify the factors that influence between-laboratory variability, a Harmonisation phase to evaluate whether harmonisation of standardized protocols and centralised processing and data analysis reduced variance, and a Ring-Testing phase to verify the ability of the harmonised protocol to generate consistent findings. Indeed, between-laboratory variability reduced from Localisation to Harmonisation and this reduction remained during the Ring-Testing phase. Results obtained in this multicentre preclinical qEEG study also confirmed the complex nature of EEG experiments starting from the surgery and data collection through data pre-processing to data analysis that ultimately influenced the results and contributed to variance in findings across laboratories. Overall, harmonisation of protocols and centralized data analysis were crucial in reducing laboratory-to-laboratory variability. To this end, it is recommended that standardized guidelines be updated and followed for collection and analysis of preclinical EEG data.
Brain health is a pressing global concern. Poor diet quality is a recognized major environmental risk factor for brain disorders and one of the few that is modifiable. There is substantial evidence that nutrition impacts brain development and brain health across the life course. So why then is the full potential of nutrition not utilized to improve brain function? This commentary, which is based on discussions of the European Brain Research Area BRAINFOOD cluster, aims to highlight the most urgent research priorities concerning the evidence base in the area of nutrition and brain health and identifies 3 major issues that need to be addressed: (1) increase causal and mechanistic evidence on the link between nutrition and brain health, (2) produce effective messages/education concerning the role of food for brain health, and (3) provide funding to support collaborative working across diverse stakeholders.
Seemingly simple bacteria mount intricate adaptive responses when exposed to physical stress or nutrient limitation, and the activation of these responses is governed by complex signal transduction networks. Upon entry into the stationary growth phase, the soil bacterium Bacillus subtilis may develop natural competence, form biofilms or stress-resistant cells, or ultimately trigger a cellular differentiation program leading to spore formation. Master regulators, such as Spo0A, ComK, SinR, and SigB, constantly monitor the bacterium’s environment and then determine appropriate adaptive responses. Here, we show that exposure of B. subtilis to visible light and other stresses triggers a general stress response-dependent block in competence development. SigB serves as an “emergency system” to silence inappropriate expression of an alternative developmental program in the face of unfavorable conditions. In particular, we document a stress-dependent molecular mechanism that prevents accumulation of the central competence regulator ComK via expression of a SigB-driven antisense RNA ( as-comK , S365) which is part of a noncontiguous operon. IMPORTANCE Bacillus subtilis exhibits a large number of different specific and general adaptation reactions, which need to be well balanced to sustain survival under largely unfavorable conditions. Under specific conditions, natural competence develops, which enables B. subtilis to actively take up exogenous DNA to integrate it into its own genome. In contrast to this specific adaptation, the general stress response is induced by a variety of exogenous stress and starvation stimuli, providing comprehensive protection and enabling survival of vegetative B. subtilis cells. In the present work, we reveal the molecular basis for the interconnection of these two important responses in the regulatory network. We describe that the master regulator of the general stress response SigB is activated by physiological stress stimuli, including daylight and ethanol stress, leading to the inactivation of the competence master regulator ComK by transcriptional anti-sense regulation, showing a strict hierarchy of adaptational responses under severe stress.
This study investigates the potential of energy‐coupling factor (ECF) transporters as promising anti‐infective targets to combat antimicrobial resistance (AMR). ECF transporters, a subclass of ATP‐binding cassette (ABC) transporters, facilitate the uptake of B‐vitamins across bacterial membranes by utilizing ATP as an energy source. Vitamins are essential cofactors for bacterial metabolism and growth, and they can either be synthesized de novo or absorbed from the environment. These transporters are considered promising drug targets, underscoring the need for further research to harness their medicinal potential and develop selective inhibitors that block vitamin uptake in bacteria. Herein, we focused on the ECF transporter for pantothenate (vitamin B5) from Streptococcus pneumoniae and the ECF transporter for folate (vitamin B9) from Lactobacillus delbrueckii as a reference protein. We also included the energizing module for pantothenate along with both full transporter complexes. Initially, we transformed and purified the transporters, followed by an assessment of their thermal stability under various buffer composition, pH, and salt concentrations. Additionally, we monitored the melting temperature over six days to confirm their stability for further assays. We then measured the binding affinities of six ECF inhibitors using surface plasmon resonance (SPR) and evaluated their inhibitory effects through in vitro assays, including bacterial growth assay, whole‐cell uptake, and transport‐activity assays. After determining cytotoxicity in two human cell lines, we established an in vivo infection model using Galleria mellonella larvae to further validate our findings.
Humans become more selective with whom they spend their time, and as a result, the social networks of older humans are smaller than those of younger ones. In non-human animals, processes such as competition and opportunity can result in patterns of declining sociality with age. While there is support for declining sociality with age in mammals, evidence from wild bird populations is lacking. Here, we test whether sociality declines with age in a wild, insular bird population, where we know the exact ages of individuals. Using 6 years of sociality data, we find that as birds aged, their degree and betweenness decreased. The number of same-age birds still alive also decreased with age. Our results suggest that a longitudinal change in sociality with age may be, in part, an emergent effect of natural changes in demography. This highlights the need to investigate the changing costs and benefits of sociality across a lifetime. This article is part of the discussion meeting issue ‘Understanding age and society using natural populations’.
Ground‐nesting shorebirds must balance the need for acoustic communication at the nest with the constant threat posed by predators. Although it may seem likely that their calls are adapted to minimize detection by predators, little is known about how these birds communicate at the nest or whether they employ cryptic strategies to avoid predation. Using passive acoustic devices and software to analyse extensive acoustic data, we quantified and categorised the calls of black‐tailed godwits Limosa limosa limosa recorded throughout the whole incubation at eight nests at a dairy farm in the Netherlands in March–June 2021. While incubating, godwits frequently use five main call types, with distinct diurnal patterns and high variation in the number of calls between breeding pairs. Birds used two quiet calls, one for communication at the nest and a second without an easily suggested meaning. Three loud calls were presumably used for predator alert, territory establishment, and long‐range communication. Interestingly, although nests were close to each other and exposed to the same aerial predators, the involvement of incubating birds in predator alert calling consistently differed. Furthermore, we described the relationship between the number of predator alert calls and the probability of a godwit flying off the nest. Our findings show that incubating godwits predominantly use loud vocalizations during the day, with only a few calls at night, which were more frequent on nights with a full moon. These descriptive findings for a single godwit community should now be expanded to other contexts, experimental situations, and shorebird species.
Racecar drivers use left-foot braking, i.e., simultaneously engaging brake and throttle, to carefully balance acceleration and traction when navigating chicanes. In this issue, Lara-Gonzalez et al. (https://doi.org/10.1083/jcb.202308034) show that C. elegans embryos employ the molecular equivalent of left-foot braking to faithfully speed through mitosis.
Alzheimer's disease (AD) affects millions of people worldwide and represents the most prevalent form of dementia. Treatment strategies aiming to interfere with the formation of amyloid β (Aβ) plaques and neurofibrillary tangles (NFTs), the two major AD hallmarks, have shown modest or no effect. Recent evidence suggests that ferroptosis, a type of programmed cell death caused by iron accumulation and lipid peroxidation, contributes to AD pathogenesis. The existing link between ferroptosis and AD has been largely based on cell culture and animal studies, while evidence from human brain tissue is limited. Here we evaluate if Aβ is associated with ferroptosis pathways in post-mortem human brain tissue and whether ferroptosis inhibition could attenuate Aβ-related effects in human brain organoids. Performing positive pixel density scoring on immunohistochemically stained post-mortem Brodmann Area 17 sections revealed that the progression of AD pathology was accompanied by decreased expression of nuclear receptor co-activator 4 and glutathione peroxidase 4 in the grey matter. Differentiating between white and grey matter, allowed for a more precise understanding of the disease's impact on different brain regions. In addition, ferroptosis inhibition prevented Aβ pathology, decreased lipid peroxidation and restored iron storage in human AD iPSCs-derived brain cortical organoids at day 50 of differentiation. Differential gene expression analysis of RNAseq of AD organoids compared to isogenic controls indicated activation of the ferroptotic pathway. This was also supported by results from untargeted proteomic analysis revealing significant changes between AD and isogenic brain organoids. Determining the causality between the development of Aβ plaques and the deregulation of molecular pathways involved in ferroptosis is crucial for developing potential therapeutic interventions. Cell Death and Disease (2024) 15:782 ; https://doi.
The need to develop 21st-century skills requires lecturers to apply appropriate learning to develop skills. This study aims to describe how the implementation of case-method learning for physics lectures on the topic of hydrostatic pressure by integrating the maritime context. This research is a descriptive study. The approach used in this study is a qualitative approach. Data collection was carried out through observation and documentation. Data were analyzed descriptively and presented based on the stages of case- method learning. The implementation of the case method in physics learning on the topic of hydrostatic pressure by linking the maritime context can be done by providing problems that are in accordance with the conditions or events that students often encounter. For instance, we present a problem related to the sinking of the KRI Nanggala 402 ship, a real-life maritime incident involving a steel ship that split into 3 parts. Students discuss in groups to find solutions to problems using appropriate physics concepts and strategies. After going through a series of problem-solving processes, students can understand the essence of the concept of hydrostatic pressure, what events are related to this concept, and how to apply it in solving problems.
Physics and biology are two branches of science that have many connections. In marine biology courses, students must have a good basic concept of physics. The purpose of this study was to determine whether students’ physics knowledge is sufficient to follow marine biology lectures. This study is a quantitative descriptive study. The study was conducted in May 2024 in the Biology Education study program at Raja Ali Haji Maritime University involving 27 students in their third year of study. Data collection was carried out by testing and analyzing descriptively. The results of the study showed that students did not have sufficient knowledge of physics to be able to follow marine biology courses. This is indicated by the problems found by students in solving questions related to the Effect of the position of the earth, moon, and sun on sea tides, the relationship between salinity and density of seawater, the specific heat of seawater, and the impact of global warming on increasing temperature and rising sea levels. Therefore, action is needed to strengthen the basic concepts of physics of biology students so that when taking biology lectures related to physics, students will be able to understand them well.
The limited existing literature studying the effects of childhood residential mobility suggests that it influences a range of life outcomes, at least in young adulthood. Little is known about how the frequency of moving in childhood is related to later-life demographic behaviour in Europe. Drawing on residential and partnership histories from the Survey of Health, Ageing and Retirement in Europe (SHARE), this paper examines whether moving in childhood relates to union dissolution in adulthood. It empirically addresses two theoretical explanations underlying the potential association: First, according to the confounding hypothesis, effects of childhood residential mobility differ by family background and resources. Second, the family stress model suggests that the accumulated stress and conflicts associated with frequent residential mobility disrupt the family and child’s social ties, resulting in worse relationship skills in later life (mediation hypothesis). Applying discrete-time event history analysis to individuals born between 1945 and 1965 in Sweden, Denmark, and Finland, we find a significant association between childhood moves (prior to age 17) and adult union dissolution. The effect’s strength varies based on the number of childhood moves, demonstrating a clear gradient. Notably, adults with three or more childhood moves exhibit a 55% higher likelihood of union dissolution compared to non-movers. These associations persist even after accounting for childhood background factors, while family stress mediates the link partially. Our findings shed light on the role of spatial mobility in shaping demographic outcomes and underscore its potential contribution to the accumulation and reproduction of life disadvantages.
The trend towards evidence-based health care challenges chaplains to work with structured—predefined and standardized—interventions that lead to measurable outcomes. However, chaplaincy literature raises various objections against using a structured approach. These include compromising the chaplain-client relationship, standardizing and limiting chaplaincy content, and the instrumentalization of the spiritual dimension. Based on a thematic analysis of 20 interviews and 33 workbooks, the current study investigates the experiences of chaplains in the Netherlands who participated in a structured intervention provided in palliative clients’ homes. The results show that most chaplains did indeed struggle with developing a healing relationship with their clients in which they are attuned to their specific needs. At the same time, the participating chaplains reported that a structured approach enriches and broadens the content of their care, improves the impact on clients, and grasps the spiritual dimension of their work. We found that the chaplains’ experiences differed depending on the professional role they emphasized. When they integrate and balance the roles of companion, counselor, and spiritual guide evenly, a structured approach can complement chaplains’ professional identity.
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Roelof A. Hut
  • Groningen Institute of Evolutionary Life Sciences (GELIFES)
Cristina Paulino
  • Groningen Biomolecular Sciences and Biotechnology Institute (GBB)
Michel MRF Struys
  • Department of Anaesthesiology
Roos Nieweg
  • Department of History
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