Zoogdieren, bossen en wederzijdse invloeden

Met het doel nu eens niet de 'schade'-aspecten van zoogdieren te belichten, wat al zo vaak gebeurd is, maar de overige aspecten, gezien binnen het hele ecosysteem, te onderzoeken, is deze literatuurstudie oorspronkelijk opgezet. Door de bij wetenschappers en particuliere organisaties toegenomen belangstelling voor een natuurlijker bosontwikkeling is bovendien getracht antwoord te vinden op vragen omtrent een aantal natuurprocessen, die van groot belang zijn bij plant-dierrelaties. Hoe liggen precies de betrekkingen tussen zoogdieren en de bossuccessies. Wat is de invloed van zoogdieren op het bos, en omgekeerd, wat is de invloed van bossuccessie op zoogdieren? In hoeverre is houtteelt te combineren met de eisen die zoogdieren aan hun biotoop stellen? Hoe zou een zo natuurlijk mogelijk bos er uit moeten zien om optimaal te kunnen functioneren voor een verscheidenheid van zoogdieren? Hoe is de oorspronkelijke zoogdierfauna te herstellen? Kortom wat kan gedaan worden om de natuurwaarden van onze bossen te vergrote

Physics of multi-GEM structures

We show that physics of multi-GEM structures is rather complex, regarding the number of phenomena affecting detector performance. The high-pressure operation in noble gases and the ion feedback are considered in more detail. It is proposed that the dominant avalanche mechanism in He and Ne, at high pressures, is the associative ionization. Ion feedback effects related to the dependence on gas, pressure and gain and to possible avalanche extension outside the GEM holes are discussed.Comment: Presented at the 8th International Conference on Instrumentation for Colliding Beam Physics, Novosibirsk, Febuary 28 - March 6, 2002. To be published in Nucl. Instr. and Meth.

Non-dried flax fibre reinforced thermoplastic composites in wet environments

The long-term performance of natural fibre reinforced thermoplastic (NFRP) composites is critical for developing more sustainable structures. The defects developed in NFRP due to fibre swelling and shrinkage in wet service conditions constitute a significant issue. Here, a method for restricting the in-service swelling and shrinkage of NFRP is proposed. The NFRP composites were processed with swollen fibres stored in moist conditions before thermoplastic resin infusion. The swelling of water-saturated NFRP was decreased up to 56% by non-dry fibres. The similar in-plane shear strength and transverse tensile strength of NFRP composites processed with oven-dried and preconditioned fibres (at 50% RH) showed the in-situ polymerisation of poly (methyl-methacrylate) (PMMA) to be insensitive to moisture. Processing composites with preconditioned fibres (at 90% RH) decreased the water immersion ageing sensitivity for in-plane shear properties of NFRP from 30% to nearly zero.publishedVersionNon peer reviewe

In-depth study of the microstructure of bamboo fibres and their relation to the mechanical properties

The mechanical properties of bamboo technical fibre, from the species Guadua angustifolia, have been studied showing values of strength up to 800 MPa and E-modulus up to 43 GPa, proving their adequate tensile properties that make this natural fibre suitable as reinforcement in composite materials. To fully explore the good mechanical properties and to make an adequate use of this new reinforcement, it is indispensable to comprehensively understand the fibre behaviour as a function of the microstructure. Microscopic observations have provided us with an extensive knowledge of the complex microstructure of this natural fibre from the macroscale down to the microscale level where different features like the distribution of the elementary fibres within the fibre bundle, dimensions and layering pattern of the elementary fibres and the main microfibrillar angles could be measured. The Young’s modulus of the elementary fibre is analysed based on the micromechanics of composite materials, commonly used for unidirectional short fibre composites, and the fibre microstructure. The predicted results are in reasonable agreement with experimental data, showing the appropriateness of the model for describing the elementary fibre stiffness. Also, the failure modes of single fibres after tensile testing are analysed by microscopic observations, to have an indication of the stress development in the elementary fibres and the different failure mechanisms.  NaturalisPlant science

Y-SNPs Do Not Indicate Hybridisation between European Aurochs and Domestic Cattle

Background: Previous genetic studies of modern and ancient mitochondrial DNA have confirmed the Near Eastern origin of early European domestic cattle. However, these studies were not able to test whether hybridisation with male aurochs occurred post-domestication. To address this issue, Götherström and colleagues (2005) investigated the frequencies of two Y-chromosomal haplotypes in extant bulls. They found a significant influence of wild aurochs males on domestic populations thus challenging the common view on early domestication and Neolithic stock-rearing. To test their hypothesis, we applied these Y-markers on Neolithic bone specimens from various European archaeological sites. Methods and Findings: Here, we have analysed the ancient DNA of 59 Neolithic skeletal samples. After initial molecular sexing, two segregating Y-SNPs were identified in 13 bulls. Strikingly, our results do not support the hypothesis that these markers distinguish European aurochs from domesticated cattle. Conclusions: The model of a rapid introduction of domestic cattle into Central Europe without significant crossbreeding with local wild cattle remains unchallenged

The emerging era of visionary composites by plant-grown matrix and reinforcing fibres: the cellular adhesion

The truly sustainable future with engineering materials will require completely new ways of creating materials. A significant part of emissions and energy consumption originates due to the processing of materials for various products, especially in the case of advanced composites. The more circular economy and recycling is to be applied, the more emphasis must be put on the processing of materials. In nature, the ‘processes’ of synthesis and material circulation are completely sustainable. This work includes actual field trials that were started during the year 2018 – aiming to the studies about the generation of fibre-reinforced visionary composites with the help of natural adhesion and cellular growth in pine trees.publishedVersionNon peer reviewe

Impact and fatigue tolerant natural fibre reinforced thermoplastic composites by using non-dry fibres

This article introduces stiff and tough biocomposites with in-situ polymerisation of poly (methyl methacrylate) and ductile non-dry flax fibres. According to the results, composites processed with non-dry fibres (preconditioned at 50% RH) had comparable quasi-static in-plane shear strength but 42% higher elongation at failure and toughness than composites processed with oven-dried fibres. Interestingly, the perforation energy of flax–PMMA cross-ply composites subjected to low-velocity impact increased up to 100% with non-dry flax fibres. The in-situ impact damage progression on the rear surface of composites was evaluated based on strain and thermal field maps acquired by synchronised high-speed optical and thermal cameras. Impact-induced delamination lengths were investigated with tomography. Non-dry fibres also decreased the tension–tension fatigue life degradation rate of composites up to 21% and altered the brittle failure mode of flax–PMMA to ductile failure dominated by fibre pull-out.publishedVersionPeer reviewe