In our globalised food system, farmers meet domestic and transboundary food needs. As a result, the contribution of farmers to domestic food production is a poor proxy for their role in national... Show moreIn our globalised food system, farmers meet domestic and transboundary food needs. As a result, the contribution of farmers to domestic food production is a poor proxy for their role in national food security. This study offers the first global assessment of how small-, medium-, and large-scale farmers contribute to global food security. We find that the role of small-scale farmers in national and global food security has been significantly underestimated due to the localised focus of previous studies, particularly in high-income nations. Future research must account for the differentiated roles, impacts, and vulnerabilities of farmers within a global context. Show less
The circular economy has become a useful concept in sustainable resource management and an area of research that influences business and policy. The successful application of the circular economy... Show moreThe circular economy has become a useful concept in sustainable resource management and an area of research that influences business and policy. The successful application of the circular economy benefits from extensive engagement with the body of scientific knowledge that brought it about, and which offers many relevant methods and findings. This white paper promotes such engagement by presenting 10 insights from the field of industrial ecology; each insight presents critical concepts, challenges, or opportunities for the circular economy stakeholders. Show less
Thakur, M.; Sloot, M. van der; Wilschut, R.; Hannula, S.E; Hooven, F. ten; Geisen, S.; ... ; Putten, W. van der 2023
The human intestinal microbiome starts to form immediately after birth, and can greatly influence the health of the infant. During the first days facultative anaerobic species generally dominate,... Show moreThe human intestinal microbiome starts to form immediately after birth, and can greatly influence the health of the infant. During the first days facultative anaerobic species generally dominate, followed by a dominance of strictly anaerobic species, particularly Bifidobacterium species. An early transition to Bifidobacterium is associated with health benefits. To study the mechanisms of this transition and its hypothesised relation to oxygen, we introduce a multiscale mathematical model that considers metabolism, spatial bacterial population dynamics and resource sharing. Based on publicly available metabolic network data, the model predicts that differences in oxygen availability explain some of the observed individual variation in succession to anaerobic species. The model also predicts that anaerobic Bifidobacterium species become dominant through metabolizing lactose with a suboptimal yield, but a higher anaerobic growth rate than its competitors. The current work is the first step towards a more comprehensive understanding of the formation of a steady state adult colonic microbiota. Show less
Jong, T.A. de; Chen, X.; Jobst, J.; Krasovskii, E.E.; Tromp, R.M.; Molen, S.J. van der 2022
Stacking domain boundaries occur in Van der Waals heterostacks whenever there is a twist angle or lattice mismatch between subsequent layers. Not only can these domain boundaries host topological... Show moreStacking domain boundaries occur in Van der Waals heterostacks whenever there is a twist angle or lattice mismatch between subsequent layers. Not only can these domain boundaries host topological edge states, imaging them has been instrumental to determine local variations in twisted bilayer graphene. Here, we analyse the mechanisms causing stacking domain boundary contrast in Bright Field Low-Energy Electron Microscopy (BF-LEEM) for both graphene on SiC, where domain boundaries are caused by strain and for twisted few layer graphene. We show that when domain boundaries are between the top two graphene layers, BF-LEEM contrast is observed due to amplitude contrast and corresponds well to calculations of the contrast based purely on the local stacking in the domain boundary. Conversely, for deeper-lying domain boundaries, amplitude contrast only provides a weak distinction between the inequivalent stackings in the domains themselves. However, for small domains phase contrast, where electrons from different parts of the unit cell interfere causes a very strong contrast. We derive a general rule-of-thumb of expected BF-LEEM contrast for domain boundaries in Van der Waals materials. Show less
Jong, T.A. de; Visser, L.; Jobst, J.; Tromp, R.M.; Molen, S.J. van der 2022
Terrace-sized, single-orientation graphene can be grown on top of a carbon buffer layer on silicon carbide by thermal decomposition. Despite its homogeneous appearance, a surprisingly large... Show moreTerrace-sized, single-orientation graphene can be grown on top of a carbon buffer layer on silicon carbide by thermal decomposition. Despite its homogeneous appearance, a surprisingly large variation in electron transport properties is observed.Here, we employ Aberration-Corrected Low-Energy Electron Microscopy (AC-LEEM) to study a possible cause of this variability. We characterize the morphology of stacking domains between the graphene and the buffer layer of high-quality samples. Similar to the case of twisted bilayer graphene, the lattice mismatch between the graphene layer and the buffer layer at the growth temperature causes a moiré pattern with domain boundaries between AB and BA stackings.We analyze this moiré pattern to characterize the relative strain and to count the number of edge dislocations. Furthermore, we show that epitaxial graphene on silicon carbide is close to a phase transition, causing intrinsic disorder in the form of co-existence of anisotropic stripe domains and isotropic trigonal domains. Using adaptive geometric phase analysis, we determine the precise relative strain variation caused by these domains. We observe that the step edges of the SiC substrate influence the orientation of the domains and we discuss which aspects of the growth process influence these effects by comparing samples from different sources. Show less
Bronkhorst, P.; Winter, R. de; Velner, T.; Kana, A.A. 2022
Measures in the SARS-CoV-2 pandemic were based on rough ideas regarding transmission routes of pathogens. Quantified models of physical transmission routes are mostly lacking, a gap to be filled.... Show moreMeasures in the SARS-CoV-2 pandemic were based on rough ideas regarding transmission routes of pathogens. Quantified models of physical transmission routes are mostly lacking, a gap to be filled. Vaccines and medicines, important, are not studied here. We first survey main routes, from primary production in the alveoli and intestines to emissions, environmental routes, to exposure and alveolar infection. Next, specific routes are modelled, mostly at a preliminary state, open to systematic improvement. Starting from a standardized emitter, modelling results show extreme differences in potential exposure, in a range covering up to 4 orders of magnitude. The outcomes are pathogen-specific, already different between SARS-CoV-2 and influenza. Extreme exposures may result in smaller spaces; with lower ventilation rates; with a high density of emitting persons per m3; who stay there for several hours; and visitors staying more than a few minutes. In spaces where a build-up of concentrations is low, exposures are low, lowest in open air situations. A main conclusion for the next pandemic is that a quantified model can give strong guidance on where measures are primarily due. For SARS-CoV-2, ventilation can be improved short-term. Longer-term, effective ventilation rules and adaptation of buildings may reduce high exposures substantially. Show less
