Vlakwa

Lignin, a naturally abundant and renewable aromatic polymer, remains vastly underexploited, despite its immense potential for sustainable materials development. Reductive catalytic fractionation of lignocellulosic biomass results in low-molecular-weight lignin oils. A large fraction of these oils consists of 4-n-propanolguaiacol (PohG) and 4-n-propanolsyringol (PohS) and is unexplored as polyester building blocks. In this study, 4-n-propanolphenol (PohP), PohG, and PohS were modified in AB monomers by reaction with bromoalkanoates with different alkyl chain lengths. The AB monomers were subsequently polymerized into poly(ether ester)s. The resulting polymers were characterized in-depth by size exclusion chromatography, nuclear magnetic resonance, (modulated) differential scanning calorimetry, wide-angle X-ray scattering, thermogravimetric analysis, and dynamic mechanical analysis and were subsequently successfully depolymerized by base catalysis to prove the recycling potential. The produced poly(ether ester)s have high molecular weights, and clear trends in the glass transition, melting temperature, and viscoelastic properties of the resulting polymers were observed in relation to the AB monomers. The poly(ether ester)s showed comparable thermal and viscoelastic properties to poly(butylene adipate-co-terephthalate) and poly(butylene adipate-co-furanoate) and represent a novel class of semiaromatic polyesters derived from lignin.

An injective colouring of a graph is a colouring in which every two vertices sharing a common neighbour receive a different colour. Chen, Hahn, Raspaud, and Wang conjectured that every planar graph of maximum degree Δ ≥ 3 admits an injective colouring with at most ⌊3Δ/2⌋ colours. This was later disproved by Lužar and Škrekovski for certain small and even values of Δ and they proposed a new refined conjecture. Using an algorithm for determining the injective chromatic number of a graph, i.e. the smallest number of colours for which the graph admits an injective colouring, we give computational evidence for Lužar and Škrekovski’s conjecture and extend their results by presenting an infinite family of 3-connected planar graphs for each Δ (except for 4) attaining their bound, whereas they only gave finitely many examples for each Δ. Hence, together with another infinite family of maximum degree 4, we provide infinitely many counterexamples to the conjecture by Chen et al. for each Δ if 4 ≤ Δ ≤ 7 and every even Δ ≥ 8. We provide similar evidence for analogous conjectures by La and Štorgel and Lužar, Škrekovski, and Tancer when the girth is restricted as well. Also in these cases we provide infinite families of 3-connected planar graphs attaining the bounds of these conjectures for certain maximum degrees Δ ≥ 3.

ABSTRACT The COVID-19 pandemic triggered unprecedented challenges to the clinical education of healthcare students. Although alternative clinical placements were developed and introduced, it is unclear whether students successfully acquired interprofessional competencies required to be collaborative practice-ready healthcare workers. We examined interprofessional collaboration competency acquisition from adapted and alternative clinical placements that were made available to pre-qualification healthcare students during the COVID-19 pandemic. Information searches from online databases and supplementary sources identified 20 articles that met criteria. Student perceptions indicate that these alternative placements supported the learning of interprofessional collaboration competencies. Outcomes mapped against the updated Canadian Interprofessional Health Collaborative Competency Framework indicate that the most frequently reported interprofessional collaboration competency was team communication and the least reported were collaborative leadership and team differences/disagreements processing. Although gains in interprofessional collaboration competencies were reported across the studies, their methodological shortcomings make it difficult to determine whether alternative placements (e.g. online and telephone-based) were better or comparable to traditional placements (i.e. with face-to-face interactions), for interprofessional collaboration competency development. These findings suggest the need for further research assessing the effectiveness and sustainability of alternative placement models. A greater understanding of clinical placement alternatives could inform educational practices in future pandemics or other unprecedented events.

Knowledge graph embeddings can be trained to infer which missing facts are likely to be true. For this, false training examples need to be derived from the available set of positive facts, so that the embedding models can learn to recognize the boundary between fact and fiction. Various negative sampling strategies have been proposed to tackle this issue, some of which have tried to make use of axiomatic knowledge claims to minimize the number of nonsensical negative samples being generated. By putting constraints on the construction of each candidate sample, these techniques have tried to maximize the number of true negatives outputted by the procedure. However, such strategies rely exclusively on binary interpretations of constraint-based reasoning and have so far also failed to incorporate literal-valued entities into the negative sampling procedure. To alleviate these shortcomings, we propose a negative sampling strategy based on a combination of fuzzy set theory and strict axiomatic semantics, which allow for the incorporation of literal-awareness when determining domain or range membership values. When evaluated on benchmark datasets AIFB and MUTAG, we found that these improvements offered significant performance gains across multiple metrics with respect to state of the art negative sampling techniques, suggesting that fuzzy semantics and literal-awareness can help to improve the quality of generated negative samples. On AIFB, our fuzzy negative sampling approach outperforms baselines on four metrics, with performance gains up to 17.14%. On MUTAG, our fuzzy negative sampling approach outperforms baselines on eight metrics, with performance gains up to 55.49%.

We define the Wiener-entropy, which is together with the eccentricity-entropy one of the most natural distance-based graph entropies. By deriving the (asymptotic) extremal behaviour, we conclude that the Wiener-entropy of graphs of a given order is more spread than is the case for the eccentricity-entropy. We solve 3 conjectures on the eccentricity-entropy and give a conjecture on the Wiener-entropy related to some surprising behaviour on the graph minimizing it.

The safety and efficacy of proton therapy is currently hampered by range uncertainties. The combination of ultrasound imaging with injectable radiation-sensitive superheated nanodroplets was recently proposed for in vivo range verification. The proton range can be estimated from the distribution of nanodroplet vaporization events, which is stochastically related to the stopping distribution of protons, as nanodroplets are vaporized by protons reaching their maximal LET at the end of their range. Here, we aim to estimate the range estimation precision of this technique. As for any stochastic measurement, the precision will increase with the sample size, that is, the number of detected vaporizations. Thus, we first develop and validate a model to predict the number of vaporizations, which is then applied to estimate the range verification precision for a set of conditions (droplet size, droplet concentration, and proton beam parameters). Starting from the thermal spike theory, we derived a model that predicts the expected number of droplet vaporizations in an irradiated sample as a function of the droplet size, concentration, and number of protons. The model was validated by irradiating phantoms consisting of size-sorted perfluorobutane droplets dispersed in an aqueous matrix. The number of protons was counted with an ionization chamber, and the droplet vaporizations were recorded and counted individually using high frame rate ultrasound imaging. After validation, the range estimate precision was determined for different conditions using a Monte Carlo algorithm. A good agreement between theory and experiments was observed for the number of vaporizations, especially for large (5.8±2.2µm) and medium (3.5±1.1µm) sized droplets. The number of events was lower than expected in phantoms with small droplets (2.0±0.7µm), but still within the same order of magnitude. The inter-phantom variability was considerably larger (up to 30x) than predicted by the model. The validated model was then combined with Monte Carlo simulations, which predicted a theoretical range retrieval precision improving with the square-root of the number of vaporizations, and degrading at high beam energies due to range straggling. For single pencil beams with energies between 70 and 240 MeV, a range verification precision below 1% of the range required perfluorocarbon concentrations in the order of 0.3-2.4µM. We proposed and experimentally validated a model to provide a quick estimate of the number of vaporizations for a given set of conditions (droplet size, droplet concentration, and proton beam parameters). From this model, promising range verification performances were predicted for realistic perfluorocarbon concentrations. These findings are an incentive to move towards preclinical studies, which are critical to assess the achievable droplet distribution in and around the tumor, and hence the in vivo range verification precision.

Abstract Although ENCs (maritime) and IENCs (inland) are based on the same model, many differences have arisen over the years. An important issue with both chart systems is the lack of interoperability. In mixed zones as sea ports or estuary zones, the ECDIS viewer can’t be used to visualize both chart types. This means that a vessel should be equipped with two different viewers.IHO started with the development of a universal hydrographic framework that would be the base for all the ‘S-products’ which are in development. The framework makes it possible to interact between these different products in such a way that the visualisation of features and attributes is handled automatically. E.g. Notices to Marines (S-124) or Aids to Navigation Information (S-201) will be displayed correctly on the S-100 viewer). In other words, the S-100 framework will handle the interoperability between the different products without any interaction of the skipper.The Inland ENC Harmonization Group (IEHG) decided to develop their own S-401 product. This new standard had to be in line with the maritime S-101 to make the use of inland and maritime charts possible on the same viewer onboard. The development of this new standard in replacement of the S-57, is mainly done within the European RIS COMEX project.During this presentation, the status of all elements will be given together with the decisions the IEHG had to take.

Abstract In the homogeneous case, the only curvature behavior which is still far from being understood is Ricci negative. In this paper, we study which nilpotent Lie algebras admit a Ricci negative solvable extension. Different unexpected behaviors were found. On the other hand, given a nilpotent Lie algebra, we consider the space of all the derivations such that the corresponding solvable extension has a metric with negative Ricci curvature. Using the nice convexity properties of the moment map for the variety of nilpotent Lie algebras, we obtain a useful characterization of such derivations and some applications.

Abstract In this paper, we introduce a new variant of the travelling salesman problem, namely the intermittent travelling salesman problem (ITSP), which is inspired by real‐world drilling/texturing applications. In this problem, each vertex can be visited more than once and there is a temperature constraint enforcing a time lapse between two consecutive visits. A branch‐and‐bound approach is proposed to solve small instances to optimality. We furthermore develop four variable neighbourhood search metaheuristics which produce high‐quality solutions for large instances. An instance library is built and made publicly available.