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For the assessment of the barrier function of the geosphere around a nuclear waste repository information about the nature of the accessible rock pore space and internal surfaces is needed. Intact samples of various types of fresh and altered crystalline rocks have been studied by means of mercury intrusion porosimetry and gas adsorption methods using various adsorbates. Furthermore, fluorescence microscopy and scanning electron microscopy was applied and the results were compared with those of impregnation with carbon-l4-polymethylmethacrylate (PMMA). Additional structural information was derived from hydraulic conductivity determinations using helium gas.
The investigations were focussed on the reliability of these measurements of intact core samples, the influence of rock composition, structure and geological evolution on the microstructure of the matrices and the consequences regarding the retardation properties of the bedrock.
The application of two sets of methods for the characterization of rock pore systems is reported. Both are discussed in the context of other techniques described in the literature. (i) Impregnation with labelled polymethylmethacrylate (PMMA) and autoradiography or direct measurement of the tracer activity allows the investigation of the pattern of the spatial porosity distribution and quantitative measurement of mineral-specific, local porosities, porosity gradients as well as an assessment of hydraulic and diffusive transport properties. (ii) Quantitative information on surface areas within certain pore size ranges can be achieved by combination of mercury intrusion porosimetry with X-ray absorption computertomography. As examples of applications of these techniques, the effects of weathering, alteration, mechanical stress and large diameter coring on the pore network of rocks have been studied.
Hydrogen is present in anhydrous materials as a result of their synthesis and of their environment during conservation. IBA provides techniques to measure H concentration depth profiles allowing to identify various aspects of the materials including the history of objects such as gemstones used in cultural heritage.
A newly established ERDA set-up, using an external microbeam of alpha particles, has been developed to study hydrated near-surface layers in quartz and sapphire by non-destructive H depth profiling in different atmospheres. The samples were also analysed using resonant NRA and SIMS.
This document deals with the characterization of porous materials having pore widths in the macropore range of 50 nm to 500 µm. In recent years, the development of advanced adsorbents and catalysts (e.g., monoliths having hierarchical pore networks) has brought about a renewed interest in macropore structures. Mercury intrusionextrusion porosimetry is a well-established method, which is at present the most widely used for determining the macropore size distribution. However, because of the reservations raised by the use of mercury, it is now evident that the principles involved in the application of mercury porosimetry require reappraisal and that alternative methods are worth being listed and evaluated. The reliability of mercury porosimetry is discussed in the first part of the report along with the conditions required for its safe use. Other procedures for macropore size analysis, which are critically examined, include the intrusion of other non-wetting liquids and certain wetting liquids, capillary condensation, liquid permeation, imaging, and image analysis. The statistical reconstruction of porous materials and the use of macroporous reference materials (RMs) are also examined. Finally, the future of macropore analysis is discussed.
Evolution relies on the availability of genetic diversity for fitness-based selection. However, most deoxyribonucleic acid (DNA) viruses employ DNA polymerases (Pol) capable of exonucleolytic proofreading to limit mutation rates during DNA replication. The relative genetic stability produced by high-fidelity genome replication can make studying DNA virus adaptation and evolution an intensive endeavor, especially in slowly replicating viruses. Here, we present a proofreading-impaired Pol mutant (Y547S) of Marek’s disease virus that exhibits a hypermutator phenotype while maintaining unimpaired growth in vitro and wild-type (WT)-like pathogenicity in vivo. At the same time, mutation frequencies observed in Y547S virus populations are 2–5-fold higher compared to the parental WT virus. We find that Y547S adapts faster to growth in originally non-permissive cells, evades pressure conferred by antiviral inhibitors more efficiently, and is more easily attenuated by serial passage in cultured cells compared to WT. Our results suggest that hypermutator viruses can serve as a tool to accelerate evolutionary processes and help identify key genetic changes required for adaptation to novel host cells and resistance to antiviral therapy. Similarly, the rapid attenuation achieved through adaptation of hypermutators to growth in cell culture enables identification of genetic changes underlying attenuation and virulence, knowledge that could practically exploited, e.g. in the rational design of vaccines.
While sociality is present in a taxonomically diverse number of species, most animals remain solitary (Bourke, 2011). Over the last centuries, this apparent imbalance in social and non-social animals has led to a great deal of research aimed at shedding light on the biotic and abiotic factors explaining the emergence and maintenance of sociality in nature (West et al., 2015).
Among them, microbes were quickly identified as a major problem for the evolution of social life, because frequent contact between group members typically facilitates the transmission of pathogens, high nest fidelity favours the establishment of microbial pathogens close to their social hosts and, finally, because social groups often exhibit limited genetic diversity and thus limited genetic resistance against certain pathogen strains (Schmid-Hempel, 1998; Cremer et al., 2007). However, this long-standing view has changed considerably over the last few years. Recent research indeed revealed that group living may be more effective than solitary living to Limit the risk of infection by pathogenic microbes because group living also allows the development of an additional layer of defence against pathogens in the form of social immunity (Cremer et al., 2007; Cotter and Kilner, 2010). Under strong pressure from pathogens, microbes could therefore promote, rather than hinder, the evolutionary transition from solitary to group Living (Meunier, 2015; Biedermann and Rohlfs, 2017). Moreover, we are increasingly aware that many microbes provide essential benefits to their hosts by performing critical digestive, physiological, and reproductive functions (Engel and Moran, 2013; McFall-Ngai et al., 2013). The need to Access beneficial microbes may thus have played a role in the expression of frequent and tight interactions between conspecifics and ultimately promoted social evolution (Wilson, 1971; Onchuru et al., 2018). Finally, a growing number of studies suggest that microbes could enforce the Aggregation and expression of cooperative behaviours of the hosts to increase their chance of reaching new hosts and may therefore be involved in the evolution of host sociality (Lewin-Epstein et al., 2017) (but see Johnson and Foster, 2018).
Honeybee symbionts, predominantly bacteria, play important roles in honeybee health, nutrition, and pathogen protection, thereby supporting colony health. On the other hand, fungi are often considered indicators of poor bee health, and honeybee microbiome studies generally exclude fungi and yeasts. We hypothesized that yeasts may be an important aspect of early honeybee biology, and if yeasts provide a mutual benefit to their hosts, then honeybees could provide a refuge during metamorphosis to ensure the presence of yeasts at emergence. We surveyed for yeast and fungi during pupal development and metamorphosis in worker bees using fungal-specific quantitative polymerase chain reaction (qPCR), next-generation sequencing, and standard microbiological culturing. On the basis of yeast presence in three distinct apiaries and multiple developmental stages, we conclude that yeasts can survive through metamorphosis and in naïve worker bees, albeit at relatively low levels. In comparison, known bacterial mutualists, like Gilliamella and Snodgrassella, were generally not found in pre-eclosed adult bees. Whether yeasts are actively retained as an important part of the bee microbiota or are passively propagating in the colony remains unknown. Our demonstration of the constancy of yeasts throughout development provides a framework to further understand the honeybee microbiota.
Im Rahmen eines gemeinschaftlichen Projektes der Stahl- und Automobilindustrie wurden für 17 Stahlfeinbleche des Automobilbaus in verschiedenen Anlieferungs- und Verformungszuständen unter -40°C, Raumtemperatur und +100°C mit 37 Versuchsreihen Anrisswöhlerlinien und zügige bzw. zyklische Spannung-Dehnung-Kurven bestimmt. Sämtliche Versuchspunkte, Hysteresen und ermittelte zyklische Kennwerte liegen in einer Datenbank vor. Eine Korrelationen zwischen den Kennwerten aus dem Zugversuch und den Kennwerten aus den zyklischen, dehnungsgeregelten Versuchen ist grundsätzlich möglich.
Im Rahmen der Lebensdauerverlängerung oder der Umnutzung von Bauwerken (z. B. Brücken, Bürogebäude oder Maste) müssen diese zum Teil neu bewertet werden. Dafür ist eine Nachrechnung für statische und dynamische Lastfälle erforderlich. Dies betrifft zum einen die Struktur selbst, die gegebenenfalls verstärkt werden muss. Aber auch die Gründung (oft Pfähle verschiedenster Typen) muss neu beurteilt werden. Nach mehreren Jahrzehnten sind jedoch für einige Bauwerke keine zuverlässigen Bestandsunterlagen verfügbar.
Eine vollständige Freilegung der Pfähle verbietet sich aus Kostengründen sowie Verlust an Widerstand gegen Zug. Lediglich der Pfahlanschluss kann visuell begutachtet werden, um Pfahlzahl, -typ und Durchmesser zu bestimmen. Für die Bestimmung der Pfahllänge müssen zerstörungsfreie Verfahren eingesetzt werden. In einer Machbarkeitsstudie wurden von den Autoren teils im Blindversuch drei Verfahren evaluiert: die klassische Pfahlintegritätsprüfung nach der Hammerschlagmethode, eine mehrkanalige Variante hierzu und das Parallel-Seismik-Verfahren. Die ersten beiden Methoden lieferten an den untersuchten Pfählen nur in Einzelfällen verwertbare Ergebnisse. Die Parallel-Seismik-Methode lieferte auch im Blindversuch an Fundamenten, bei denen die Pfahllänge dem Eigentümer bekannt war, Ergebnisse mit einer Abweichung von max. 0,5 m. Diese Toleranz lässt sich bei der Standfestigkeitsbeurteilung berücksichtigen. Die Mehrkosten des Verfahrens (anders als bei den anderen Verfahren wird ein verrohrtes Bohrloch im Boden nahe dem Pfahl benötigt) halten sich in Grenzen, wenn man es in die geotechnische Untersuchung integriert. Daher wurde es inzwischen auch in der Praxis eingesetzt. Auch liegen die Gesamtkosten für die Untersuchung deutlich unter denen für eventuell notwendigen Ersatz – oder Verstärkungsmaßnahmen, die notwendig werden, wenn keine Daten zur Pfahllänge verfügbar sind.
Der Vortrag erläutert die Ergebnisse der Machbarkeitsstudie, zeigt erste Praxisfälle und weist auf Möglichkeiten hin, das Parallel-Seismik Verfahren in Zukunft noch genauer und effizienter einzusetzen.
Emerging infectious diseases (EIDs) pose a risk to human welfare, both directly1 and indirectly, by affecting managed livestock and wildlife that provide valuable resources and ecosystem services, such as the pollination of crops2. Honeybees (Apis mellifera), the prevailing managed insect crop pollinator, suffer from a range of emerging and exotic high-impact pathogens3,4, and population maintenance requires active management by beekeepers to control them. Wild pollinators such as bumblebees (Bombus spp.) are in global decline5,6, one cause of which may be pathogen spillover from managed pollinators like honeybees7,8 or commercial colonies of bumblebees9. Here we use a combination of infection experiments and landscape-scale field data to show that honeybee EIDs are indeed widespread infectious agents within the pollinator assemblage. The prevalence of deformed wing virus (DWV) and the exotic parasite Nosema ceranae in honeybees and bumblebees is linked; as honeybees have higher DWV prevalence, and sympatric bumblebees and honeybees are infected by the same DWV strains, Apis is the likely source of at least one major EID in wild pollinators. Lessons learned from vertebrates10,11 highlight the need for increased pathogen control in managed bee species to maintain wild pollinators, as declines in native pollinators may be caused by interspecies pathogen transmission originating from managed pollinators.
A sting in the spit: widespread cross-infection of multiple RNA viruses across wild and managed bees
(2015)
1.Declining populations of bee pollinators are a cause of concern, with major repercussions for biodiversity loss and food security. RNA viruses associated with honeybees represent a potential threat to other insect pollinators, but the extent of this threat is poorly understood.
2.This study aims to attain a detailed understanding of the current and ongoing risk of emerging infectious disease (EID) transmission between managed and wild pollinator species across a wide range of RNA viruses.
3.Within a structured large-scale national survey across 26 independent sites, we quantify the prevalence and pathogen loads of multiple RNA viruses in co-occurring managed honeybee (Apis mellifera) and wild bumblebee (Bombus spp.) populations. We then construct models that compare virus prevalence between wild and managed pollinators.
4.Multiple RNA viruses associated with honeybees are widespread in sympatric wild bumblebee populations. Virus prevalence in honeybees is a significant predictor of virus prevalence in bumblebees, but we remain cautious in speculating over the principle direction of pathogen transmission. We demonstrate species-specific differences in prevalence, indicating significant variation in disease susceptibility or tolerance. Pathogen loads within individual bumblebees may be high and in the case of at least one RNA virus, prevalence is higher in wild bumblebees than in managed honeybee populations.
5.Our findings indicate widespread transmission of RNA viruses between managed and wild bee pollinators, pointing to an interconnected network of potential disease pressures within and among pollinator species. In the context of the biodiversity crisis, our study emphasizes the importance of targeting a wide range of pathogens and defining host associations when considering potential drivers of population decline.