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Leaking Outside the Box: Kinetic Turbulence with Cosmic-Ray Escape
No full textsponsorship: E. A. G. acknowledges useful discussions with M. Lemoine, A. Philippov, and V. Zhdankin during the development of this work. D. G. thanks L. Comisso and L. Sironi for stimulating discussions, which motivated this study. F. B. acknowledges support from the FED-tWIN Programme (Profile No. Prf-2020-004, Project "ENERGY") issued by BELSPO, and from the FWO Junior Research Project No. G020224N granted by the Research Foundation - Flanders (FWO). D. G. is supported by the Research Foundation - Flanders (FWO) Senior Postdoctoral Fellowship Grant No. 12B1424N. The resources and services used in this work were provided by the VSC (Flemish Supercomputer Center), funded by the Research Foundation - Flanders (FWO) and the Flemish Government. (FWO - Research Foundation - Flanders (FWO)|G020224N, Research Foundation - Flanders (FWO) Senior Postdoctoral Fellowship|12B1424N, Research Foundation - Flanders (FWO), Flemish Government)status: Publishe
Vesalius komt thuis. Zijn persoonlijk exemplaar van de tweede editie van De humani corporis fabrica verworven voor KU Leuven
No full textstatus: Publishe
Thermische aggregatie en gelering van plantaardige eiwitten in modelsystemen relevant voor geëmulgeerde vleesanalogen
No full textPlant-based meat analogues (PBMA) offer a sustainable alternative to meat products and subsequently support the dietary shift from animal to plant proteins. While they have been commercialized for over a decade, many still fail to mimic meat products nutritionally and sensorially. This is partly caused by their inferior texture and physical stability due to sub-par techno-functional properties of plant proteins. Overcoming these shortcomings is essential to stimulate PBMA integration into Western diets.
Most literature in this respect focuses on texturized plant proteins, as high-shear, high-temperature processing yields a fibrous, meat-like structure. In contrast, emulsified PBMA, analogues of emulsified meat products (e.g. cooked sausages) with an anisotropic gel structure, remain underexplored. Mechanistic insight into how ingredients affect their texture and physical stability is limited, and therefore the focus of this doctoral study.
A market survey revealed that proteins and lipids are key structure-related ingredients in commercial emulsified PBMA, alongside starches and dietary fibres. Therefore, this study explored how these affect physical stability and texture of emulsified PBMA. The research was divided into three parts: (1) four commercial plant proteins and two plant-based lipids were tested for their impact on the viscoelasticity, physical stability, and texture of an emulsified PBMA model system; (2) three lab-extracted native plant proteins were evaluated towards their thermal aggregation and gelation in function of temperature under a salt- and pH-condition relevant to emulsified PBMA; (3) the same three proteins were evaluated in the same system towards thermal unfolding and changes in viscoelastic properties under both dynamic and isothermal heating processes.
In the first part, based on the market survey and the literature, commercial sunflower oil and coconut fat, and commercial soybean, potato, mung bean, and pea protein powders were selected to evaluate their effects on gelation, physical stability and texture of emulsified PBMA model systems. Overall, protein source had an equal or greater impact than lipid source or lipid content, with systems of potato protein powder excelling in several aspects.
Gelation of proteins in these systems was monitored via viscoelastic properties (storage modulus G´ and loss modulus G´´) during heating. Unheated, systems with soybean protein powder showed highest G´, which slightly increased upon heating, whereas those with potato protein powder showed low G´ that strongly increased upon heating. Emulsified PBMA model systems with sunflower oil showed mostly lower G´ than those with coconut fat, which is attributed to coconut fat's higher solid fat content at 5 °C.
Model systems with pea, potato, and soybean protein powder showed very high stability, with impact of lipids being smaller and protein powder-dependent. Upon long-term chilled storage no differences between proteins nor between lipid additions were observed, but upon freeze-thawing systems with soybean protein powder showed higher stability and those with potato protein powder lower stability than the other protein powders.
Model systems with potato protein powder showed much higher peak forces than those made from soybean, pea and mung bean protein powder, regardless of lipid source. Sunflower oil consistently yielded systems with lower peak force, while coconut fat yielded systems with higher peak force, especially at higher lipid content, which was attributed to their different solid fat content at 5 °C.
In the second part, three proteins were selected and extracted from plant raw materials: potato (POP), mung bean (MBP), and pea protein extract (PEP). PEP was isolated from yellow peas via salt extraction and dialysis. POP was isolated from potato tubers and MBP from mung beans, both using an ethanol-isoelectric precipitation (ethanol-IEP), a novel method for mung bean protein. All protein extracts were isolated with minimal protein unfolding, allowing evaluation of their full techno-functional potential.
Thermal aggregation, gelation, and gel properties of these protein extracts were examined at pH 6.8 and 250 mM NaCl, conditions relevant to emulsified PBMA. To assess the impact of isothermal heating temperature, these dispersions were heated at 50, 60 (except MBP), 70, 90 and 100 °C (only MBP) for 30 min followed by cooling at 5 °C.
At 0.50 wt%, POP aggregation increased from 50 °C to 70 °C, corresponding to patatin unfolding (50-60 °C) and protease inhibitor unfolding (60-70 °C). The aggregation was likely hydrophobically driven, since only 8 M urea prevented it. At 17.5 wt%, higher temperatures improved physical stability and gel properties, as water-holding capacity increased from 50 °C to 70 °C, and least gelation concentration decreased, while gels became tougher between 60 °C and 90 °C.
At 0.50 wt%, MBP aggregation increased from 20 °C to 90 °C, hence even below the onset denaturation temperature (85.2 °C). This aggregation was likely driven by hydrophobic interactions. Similarly, gelation of 17.5 wt% MBP was driven by hydrophobic interactions, as the gels only dissolved in 8 M urea. Gels heated at 50 °C and 60 °C were weak and dissolved after overnight shaking, unlike gels heated at 90 °C or 100 °C. Higher temperature improved MBP gel properties, as between 70-90 °C water-holding capacity rose from 69% to 97% and least gelation concentration dropped from 12% to 7%. Further heating to 100 °C increased fracture stress and strain, yielding tougher gels.
At 0.50 wt%, PEP aggregation increased from 50 °C to 90 °C, hence even below the onset denaturation temperature (77.8 °C), with a marked jump at 90 °C. This aggregation coincided with increased surface hydrophobicity and decreased free sulfhydryl groups, especially at 90 °C. Gelation of 17.5 wt% PEP was probably driven by hydrophobic interactions, although some albumin fractions were also involved in disulfide bond formation. Gels heated at 50 °C and 60 °C were weak and dissolved after overnight shaking, unlike gels heated at 90 °C. With higher heating temperatures, water-holding increased and least gelation concentration decreased, but only gels heated at 70 °C and 90 °C were self-supporting.
Cooling improved physical stability of systems across all extracts, with POP and PEP gels heated at 50 °C holding already near maximal amounts of water, despite being not self-supporting.
The third part compared 5 wt% MBP, PEP, and POP dispersions in pH 6.8 and 250 M NaCl under both dynamic and isothermal heating. POP showed lower thermal stability and lower gelation temperature than MBP and PEP. All extracts formed weak physical gels, but POP gels had the highest G´ and were strongest. Across all extracts, higher heating temperature led to higher G´, enhanced gel stiffening upon cooling, and increased yield stress (highest in POP). All extracts gelled at temperatures below the onset of protein denaturation, suggesting that irreversible protein unfolding is not a prerequisite for thermal gelation under the food matrix conditions found in emulsified PBMA.
Ethanol-IEP isolation of proteins from mung beans and potato tubers yielded protein extracts with good and excellent gelation properties, respectively. Therefore, this method can extract functional potato protein from starch industry side streams. The method showed promising protein recovery and purity, but also an increased energy consumption, which adds about € 8/kg protein powder to the cost of acid/heat-coagulated potato protein (€ 1.5/kg protein powder). However, expanded bed adsorption chromatography, an industrial method yielding functional potato protein, is priced much higher at a total cost of € 25-30/kg protein powder. Therefore, the potato starch industry could evaluate the feasibility of the proposed ethanol-IEP method in more detail.status: Publishe
High-temperature dissolutive wetting: Role of solutal Marangoni convection in multiphase transport
No full textsponsorship: Youqing Sun thanks the support from Major Project of Technological Innovation and Application Development in Chongqing (2024TIAD-STX0069) . The authors gratefully acknowledge support for this research by the European Union's Horizon 2020-Research and Innovation Framework Programme under grant agreement No 958307. (Major Project of Technological Innovation and Application Development in Chongqing|2024TIAD-STX0069, European Union|958307)status: Accepte
Tunable noise and vibration reduction on a piezoelectric metamaterial panel: modelling and validation
No full textstatus: Published onlin
Opgroeien in een digitale wereld: Inzichten in de gepercipieerde positieve ervaringen van digitaal mediagebruik bij (kwetsbare) adolescenten
No full textThe impact of adolescents' ubiquitous digital media use on their development has drawn considerable attention from the public and scientific community. Public discourse tends to adopt a predominantly negative stance on this matter. However, research has demonstrated a complex relationship between digital media use and areas important for adolescents' development. Quantitative studies have primarily investigated associations between digital media use (measured by screen time or, less frequently, content) and developmental outcomes. In contrast, qualitative studies have explored adolescents' perceived effects of digital media use. While quantitative findings often show non-significant or small negative and positive effects, qualitative research suggests that adolescents subjectively perceive strong struggles or benefits of digital media use. Although some quantitative research has examined perceived negative experiences, such as digital stress, considerably less attention has been paid to perceived positive digital experiences, particularly among developmentally vulnerable adolescents. Yet, such research is necessary to bridge and understand the differential conclusions drawn from quantitative and qualitative research. This gap is partly due to the absence of a robust conceptual framework and limited measurement instruments to assess such experiences.
The first objective (O1) of this dissertation was to address this conceptual and methodological gap by developing frameworks and validated measures that move beyond screen time to capture adolescents' positive digital experiences. Therefore, Chapter 1 focused on adolescents' exclusively positive digital experiences by conceptualizing and developing a measure of digital flourishing in adolescence. This construct was adapted from adult digital flourishing literature, grounded in positive media psychology, specifically self-determination theory. Additionally, drawing on digital inequality theory, this chapter provided preliminary insights into how digital inequality determinants (i.e., gender, age, educational track, and parental education) relate to digital flourishing. Chapter 1 used a pilot cognitive interview and two cross-sectional online surveys with Slovenian adolescents (n1 = 147; n2 = 1,046).
To further address O1, Chapter 3 introduced the concept of perceived digital well-being, considering the balance between simultaneous positive and negative self-perceived effects of smartphone use in the social, emotional, and cognitive domains. The developed measure was informed by uses and gratifications theory, media effects literature, digital well-being literature, and social constructivism theory. This chapter also preliminarily explored the relationships between digital inequality determinants (e.g., gender, age, educational track) and perceived digital well-being. It used a pilot cognitive interview study (n = 5) and two cross-sectional online surveys among Slovenian adolescents (n1 = 161; n2 = 1,040).
The second objective of this dissertation was to apply these concepts and instruments in (intensive) longitudinal designs to examine predictors of adolescents' digital flourishing (O2a) and the long-term and short-term effects of perceived digital well-being (O2b).
Chapter 2 addressed O2a by applying the newly developed digital flourishing measure in a one-year, three-wave panel study with 1,081 Slovenian adolescents. Two distinct, equally distributed developmental trajectories emerged. The first group exhibited consistently high levels of digital flourishing dimensions over time, while the second reported lower levels, with a decline in self-control over time. The predictive role of developmental changes (i.e., age) and digital inequality determinants (i.e., parental education, ethnicity, parental mediation style, and parental digital skills) was studied to understand which adolescents flourish digitally over time. Adolescents whose parents were more digitally skilled and used more active and autonomy-supportive mediation styles were more likely to belong to the first, flourishing group.
Chapter 4 addressed O2b by exploring the between-person and longitudinal reciprocal within-person cross-lagged relationships between adolescents' perceived digital well-being and offline identity and resilience for well-being (i.e., self-esteem). Using the same three-wave panel dataset (n = 1,081), between-person correlations revealed that high perceived digital well-being in the emotional domain (but not in the social and cognitive domains) was associated with high self-esteem. However, long-term within-person cross-lagged relationships were inconsistent. Digital inequality determinants (i.e., gender and parental education) and objectively measured smartphone screen time were considered as moderators of the explored relationships. Unstable differences were observed in the relationships between gender and the social domain, as well as between smartphone screen time and the cognitive domain. Parental education did not moderate the relationships.
Given that digital media use effects can vary across the time spans of the study, Chapter 5 used a 14-day daily diary study data among 303 Slovenian adolescents to examine the between-person and short-term, within-person relationships between adolescents' perceived digital well-being and offline well-being (i.e., affective well-being) and its resilience factors (i.e., state self-esteem) (O2b). Daily increase in perceived digital well-being was significantly associated with an increase in both outcomes. Digital inequality determinants (i.e., gender and maternal education) were again tested as moderators. Girls had a stronger positive relationship between perceived digital well-being in the emotional domain and state self-esteem/affective well-being than boys. No (consistent) moderation was observed for maternal education or other (negative) perceptions about smartphone use (i.e., adolescents' perceived smartphone addiction).
The findings revealed that adolescents generally report high digital flourishing. Short-term but not long-term perceptions of digital well-being were positively linked to offline well-being and resilience. However, results underscored the complexity of perceived positive and balanced digital experiences, which varied based on social, cognitive, and emotional components of digital use, temporal frame (i.e., short-term versus long-term), analytical level (i.e., between-person versus within-person), and digital inequalities determinants (i.e., gender and parental behavior). Boys appeared to benefit less emotionally and socially from digital media uses, whereas girls reported stronger social and emotional benefits, albeit with greater vulnerability to emotion regulation challenges posed by digital media uses. Adolescents with digitally skilled parents and parents using autonomy-supportive parents who communicate with their children about digital media uses reported higher digital flourishing.
Theoretically, the findings call for an expansion of digital media use theoretical frameworks to incorporate adolescents' perceptions of positive digital experiences. Practically, they highlight the need for digital platforms to take measures toward adolescent uses, policy initiatives and educational interventions to go beyond a one-size-fits-all, risk-prevention approach and recognize the nuanced, potentially beneficial aspects of adolescents' digital uses. Interventions should also aim to diminish digital inequalities based on gender and enhance parents' digital literacy and promote autonomy-supportive, active parental mediation strategies to empower adolescents in their digital lives.status: Publishe
Ontwerp van een adsorptie gebaseerde elektrochemische sensor
No full textThe development of reliable, low-cost electrochemical sensors depends critically on the properties of the electrode materials used. This thesis explores how the interplay between surface area, adsorption behavior, and conductivity in carbon and zeolite-based materials affects electrochemical performance—particularly for applications in small-molecule sensing.
Special emphasis was placed on understanding how hybrid coatings, consisting of conductive carbon black (Vulcan XC-72R) combined with microporous zeolites (all-silica zeolite β and ZSM-5), influence the electrochemically active surface area (EC-ASA) and analyte interaction. By employing both capacitive and redox-probe-based methods, the work demonstrates that these hybrid materials enhance surface accessibility and sensitivity, despite the zeolites being non-conductive themselves. This highlights the need for context-dependent surface area characterization when designing sensor interfaces.
A central theme in the thesis is the role of adsorption in shaping electrochemical signals. It is shown that strongly adsorbing analytes can significantly distort EC-ASA measurements, depending on the probe used. This behavior is especially pronounced in porous materials and can lead to considerable overestimations if not properly accounted for. The combination of adsorption studies with electrochemical analysis offers a more nuanced understanding of how molecules interact with electrode surfaces.
Based on these insights, a disposable electrochemical sensor was designed for the detection of paracetamol (PAR). The sensor achieved a detection limit as low as 150 nM and demonstrated selective response even in the presence of interfering substances like glucose. This selectivity was directly linked to the tailored adsorption properties of the coating materials, emphasizing the practical value of surface chemistry control in real-world sensing applications.
Finally, the work evaluates surface modifications intended to further improve analyte capture. While increased adsorption was achieved in some cases, this came at the cost of reduced conductivity and accessible surface area. The findings offer clear guidance for future material design, suggesting that in situ modification on already-structured electrodes or using flat model systems could overcome current limitations.
Overall, this research provides a materials-based framework for improving both the sensitivity and selectivity of electrochemical sensors, with potential applications in diagnostics, environmental monitoring, and beyond.status: Publishe
Katalytische fosforylatie van alcoholen voor de synthese van fosfaatesters
No full textAlongside key elements like hydrogen, carbon, oxygen and nitrogen, phosphorus is vital in nature through phosphate ester (PE) structures, found in DNA and ATP. Nature's use of phosphorylations to form P(O)-O bonds inspires the development of phosphorus-based APIs like pronucleotides and prodrugs to combat diseases. While APIs support life, PE based pesticides target harmful organisms to protect crops and ensure food security. PEs are also used industrially, such as in flame retardants and surfactants. In this way, the application of phosphate esters are widespread into our lives, rendering them an important synthetic target with ongoing advances in their production.
Chapter 1 outlines various synthetic pathways towards phosphate esters, placing this PhD work within the broader field of alcohol phosphorylation. The transformation of phosphate rock into white phosphorus (P₄), though energy-intensive, remains key for producing P-precursors. Current methods rely mainly on nucleophilic substitution of P₄-derived phosphoryl chlorides, but newer phosphorylating reagents aim to offer more selective and sustainable alternatives. H-phosphonates, as P(III) reagents, enable mild Atherton-Todd-type reactions, although oxidative conditions can limit their use. This has led to growing interest in P(V) reagents like phosphoanhydrides, dialkyl phosphates or leaving group activated phosphates, which show high reactivity under suitable conditions. Despite progress, there's a strong demand for milder, more atom-efficient phosphorylation strategies and the application of heterogeneous catalysis.
In Chapter 2, the use of isopropenyl phosphate was studied as phosphorylating reagent of alcohols enabling an atom efficient method that produces acetone as the only by-product. The reaction proceeds at room temperature using catalytic potassium tert‑butoxide avoiding commonly applied equimolar base amounts. A catalytic cycle is sustained by the enolate anion regenerating the nucleophile, achieving full conversion of the enolphosphate. This reaction mechanism was further elucidated by composing experimental kinetic plots through in operando 31P NMR spectroscopy with high resolution. Furthermore, with an extensive alcohol reaction scope including a nucleotide, the reaction potential for the selective phosphorylation of primary alcohols was illustrated.
Subsequently, the atom efficiency of alcohol phosphorylations could be improved further in Chapter 3 by the direct esterification of phosphoric acid with water as the only by-product, catalyzed by Brønsted acids. With H3PO4 produced directly from phosphate rocks, P4 is circumvented completely in the synthetic pathway towards PEs. Initially, a Dean-Stark set-up using NBP:o‑xylene was optimized to move the equilibrium towards the product side. To address separation issues with homogeneous acids and PEs, heterogeneous niobium oxides were experimentally evaluated as catalyst with decent alcohol conversions observed. To increase the alcohol conversion, the niobium oxide catalyst was pretreated with phosphoric acid to increase its acidity resulting in high mono-ester yields. The increased acidity and H3PO4 adsorption were characterized by Hammett titrations and 31P solid state NMR respectively, whereas the selectivity was further studied by kinetic experiments to determine relative reactivities. Finally, the reaction potential was shown with a scope of high boiling alcohols, including the synthesis of an oleyl phosphate surfactant.
Chapter 4 explored creatine phosphate as a P4-independent phosphorylating agent to selectively produce phosphate mono-esters under mild reaction conditions, inspired by its biochemical functionality. By applying Brønsted acidic catalysis, the P-N bond could be activated allowing creatine to act as leaving group in a room temperature nucleophilic substitution. Although strong homogeneous Brønsted acids were effective with excess alcohol, heterogeneous aluminum-rich zeolites were evaluated as well. A clear correlation of the zeolites Si/Al ratio and the creatine phosphate conversion were observed, with a faujasite and Si/Al=5.2 performing best. By conducting recycling experiments, intermittent calcination was shown to be essential to prevent acid site neutralization by adsorbed creatine. With an extensive alcohol scope, a high functional group tolerance was observed.
In conclusion, in this PhD manuscript, innovative phosphorylating agents were studied as well as the application of heterogeneous catalysis for the synthesis of phosphate esters to increase the overall sustainability of these reactions.status: Publishe
The gendered dynamics between religiosity and gender equality attitudes in adolescence. A study among Belgian youth
No full textstatus: Published onlin
The Shadow of the Soldier: Men, Kinship and the Urban Landscape in Contemporary Namibia
No full textsponsorship: The author disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Deutsche Forschungsgemeinschaft (503940884) (Deutsche Forschungsgemeinschaft|503940884)status: Published onlin