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Le Vieux-Gallois
(2008)
Alexander I. Falilejevs Edition altwalisischer/altkymrischer Texte bietet eine erstmalige Zu-sammenstellung sämtlicher erhaltener Textzeugnisse dieser inselkeltischen Sprache. Sie datieren in die Zeit vor dem Jahr 1000 n.Chr. zurück. Jeder Text ist mit einem Glossar und einem ausführlichen linguistischen Kommentar versehen. Dieser Kommentar sowie die Einleitung liefern einen kompletten Überblick über den gegenwärtigen Wissensstand auf dem Gebiet des Altwalisischen. Der systematische Teil des Buches ordnet die linguistischen Formen (Phono-logie, Morphologie, Syntax) zu einem Abriß der altwalisischen Grammatik. Yves Le Berres Übersetzung der russischen Vorlage (Древневаллийский язык (Drevnevalliskiy yazyk), Moskau 2002) ins Französische ermöglicht der Forschung erstmalig einen Zugang zum Alt-walisischen in einer westeuropäischen Sprache. Das Altwalisische ist nicht nur für das Verständnis der anderen älteren inselkeltischen Spra-chen wichtig (Irisch, Bretonisch und Kornisch), sondern auch für die Entstehungsgeschichte des Englischen. Das Altwalisische war die erste Kontaktsprache der Sprecher des sich heraus-bildenden mittelalterlichen Englischen.
The need to reduce humankind reliance on fossil fuels by exploiting sustainably the planet renewable resources is a major driving force determining the focus of modern material research. For this reason great interest is nowadays focused on finding alternatives to fossil fuels derived products/materials. For the short term the most promising substitute is undoubtedly biomass, since it is the only renewable and sustainable alternative to fossil fuels as carbon source. As a consequence efforts, aimed at finding new synthetic approaches to convert biomass and its derivatives into carbon-based materials, are constantly increasing. In this regard, hydrothermal carbonisation (HTC) has shown to be an effective means of conversion of biomass-derived precursors into functional carbon materials. However the attempts to convert raw biomass, in particular lignocellulosic one, directly into such products have certainly been rarer. Unlocking the direct use of these raw materials as carbon precursors would definitely be beneficial in terms of HTC sustainability. For this reason, in this thesis the HTC of carbohydrate and protein-rich biomass was systematically investigated, in order to obtain more insights on the potentials of this thermochemical processing technique in relation to the production of functional carbon materials from crude biomass. First a detailed investigation on the HTC conversion mechanism of lignocellulosic biomass and its single components (i.e. cellulose, lignin) was developed based on a comparison with glucose HTC, which was adopted as a reference model. In the glucose case it was demonstrated that varying the HTC temperature allowed tuning the chemical structure of the synthesised carbon materials from a highly cross-linked furan-based structure (T = 180oC) to a carbon framework composed of polyaromatic arene-like domains. When cellulose or lignocellulosic biomass was used as carbon precursor, the furan rich structure could not be isolated at any of the investigated processing conditions. These evidences were indicative of a different HTC conversion mechanism for cellulose, involving reactions that are commonly observed during pyrolytic processes. The evolution of glucose-derived HTC carbon chemical structure upon pyrolysis was also investigated. These studies revealed that upon heat treatment (Investigated temperatures 350 – 900 oC) the furan-based structure was progressively converted into highly curved aromatic pre-graphenic domains. This thermal degradation process was observed to produce an increasingly more hydrophobic surface and considerable microporosity within the HTC carbon structure. In order to introduce porosity in the HTC carbons derived from lignocellulosic biomass, KOH chemical activation was investigated as an HTC post-synthesis functionalisation step. These studies demonstrated that HTC carbons are excellent precursors for the production of highly microporous activated carbons (ACs) and that the porosity development upon KOH chemical activation is dependent on the chemical structure of the HTC carbon, tuned by employing different HTC temperatures. Preliminary testing of the ACs for CO2 capture or high pressure CH4 storage yielded very promising results, since the measured uptakes of both adsorbates (i.e. CO2 and CH4) were comparable to top-performing and commercially available adsorbents, usually employed for these end-applications. The combined use of HTC and KOH chemical activation was also employed to produce highly microporous N-doped ACs from microalgae. The hydrothermal treatment of the microalgae substrate was observed to cause the depletion of the protein and carbohydrate fractions and the near complete loss (i.e. 90%) of the microalgae N-content, as liquid hydrolysis/degradation products. The obtained carbonaceous product showed a predominantly aliphatic character indicating the presence of alkyl chains presumably derived from the lipid fractions. Addition of glucose to the initial reaction mixture was found out to be extremely beneficial, because it allowed the fixation of a higher N amount, in the algae derived HTC carbons (i.e. 60%), and the attainment of higher product yields (50%). Both positive effects were attributed to Maillard type cascade reactions taking place between the monosaccharides and the microalgae derived liquid hydrolysis/degradation products, which were in this way recovered from the liquid phase. KOH chemical activation of the microalgae/glucose mixture derived HTC carbons produced highly microporous N-doped carbons. Although the activation process led to a major reduction of the N-content, the retained N-amount in the ACs was still considerable. These features render these materials ideal candidates for supercapacitors electrodes, since they provide extremely high surface areas, for the formation of electric double-layer, coupled to abundant heteroatom doping (i.e. N and O) necessary to obtain a pseudocapacitance contribution.
Magnetic fields, non-thermal radiation and particle acceleration in colliding winds of WR-O stars
(2015)
Non-thermal emission has been detected in WR-stars for many years at long wavelengths spectral range, in general attributed to synchrotron emission. Two key ingredients are needed to explain such emissions, namely magnetic fields and relativistic particles. Particles can be accelerated to relativistic speeds by Fermi processes at strong shocks. Therefore, strong synchrotron emission is usually attributed to WR binarity. The magnetic field may also be amplified at shocks, however the actual picture of the magnetic field geometry, intensity, and its role on the acceleration of particles at WR binary systems is still unclear. In this work we discuss the recent developments in MHD modelling of wind-wind collision regions by means of numerical simulations, and the coupled particle acceleration processes related.
In diesem Beitrag werden aus einer Metaperspektive vier verschiedene Reflexionsformate aus dem Bielefelder Projekt „BiProfessional“ der Qualitätsoffensive Lehrerbildung gegenübergestellt. Gemeinsamkeiten und Unterschiede werden mit Blick auf das Reflexionsverständnis, den Reflexionsgegenstand und den jeweiligen Zugang beschrieben. Am Ende des Beitrags werden Konsequenzen für eine multiparadigmatische Lehrkräftebildung aufgezeigt.
Biological materials have ever been used by humans because of their remarkable properties. This is surprising since the materials are formed under physiological conditions and with commonplace constituents. Nature thus not only provides us with inspiration for designing new materials but also teaches us how to use soft molecules to tune interparticle and external forces to structure and assemble simple building blocks into functional entities. Magnetotactic bacteria and their chain of magnetosomes represent a striking example of such an accomplishment where a very simple living organism controls the properties of inorganics via organics at the nanometer-scale to form a single magnetic dipole that orients the cell in the Earth magnetic field lines. My group has developed a biological and a bio-inspired research based on these bacteria. My research, at the interface between chemistry, materials science, physics, and biology focuses on how biological systems synthesize, organize and use minerals. We apply the design principles to sustainably form hierarchical materials with controlled properties that can be used e.g. as magnetically directed nanodevices towards applications in sensing, actuating, and transport. In this thesis, I thus first present how magnetotactic bacteria intracellularly form magnetosomes and assemble them in chains. I developed an assay, where cells can be switched from magnetic to non-magnetic states. This enabled to study the dynamics of magnetosome and magnetosome chain formation. We found that the magnetosomes nucleate within minutes whereas chains assembles within hours. Magnetosome formation necessitates iron uptake as ferrous or ferric ions. The transport of the ions within the cell leads to the formation of a ferritin-like intermediate, which subsequently is transported and transformed within the magnetosome organelle in a ferrihydrite-like precursor. Finally, magnetite crystals nucleate and grow toward their mature dimension. In addition, I show that the magnetosome assembly displays hierarchically ordered nano- and microstructures over several levels, enabling the coordinated alignment and motility of entire populations of cells. The magnetosomes are indeed composed of structurally pure magnetite. The organelles are partly composed of proteins, which role is crucial for the properties of the magnetosomes. As an example, we showed how the protein MmsF is involved in the control of magnetosome size and morphology. We have further shown by 2D X-ray diffraction that the magnetosome particles are aligned along the same direction in the magnetosome chain. We then show how magnetic properties of the nascent magnetosome influence the alignment of the particles, and how the proteins MamJ and MamK coordinate this assembly. We propose a theoretical approach, which suggests that biological forces are more important than physical ones for the chain formation. All these studies thus show how magnetosome formation and organization are under strict biological control, which is associated with unprecedented material properties. Finally, we show that the magnetosome chain enables the cells to find their preferred oxygen conditions if the magnetic field is present. The synthetic part of this work shows how the understanding of the design principles of magnetosome formation enabled me to perform biomimetic synthesis of magnetite particles within the highly desired size range of 25 to 100 nm. Nucleation and growth of such particles are based on aggregation of iron colloids termed primary particles as imaged by cryo-high resolution TEM. I show how additives influence magnetite formation and properties. In particular, MamP, a so-called magnetochrome proteins involved in the magnetosome formation in vivo, enables the in vitro formation of magnetite nanoparticles exclusively from ferrous iron by controlling the redox state of the process. Negatively charged additives, such as MamJ, retard magnetite nucleation in vitro, probably by interacting with the iron ions. Other additives such as e.g. polyarginine can be used to control the colloidal stability of stable-single domain sized nanoparticles. Finally, I show how we can “glue” magnetic nanoparticles to form propellers that can be actuated and swim with the help of external magnetic fields. We propose a simple theory to explain the observed movement. We can use the theoretical framework to design experimental conditions to sort out the propellers depending on their size and effectively confirm this prediction experimentally. Thereby, we could image propellers with size down to 290 nm in their longer dimension, much smaller than what perform so far.
The Postmasburg Manganese Field (PMF), Northern Cape Province, South Africa, once represented one of the largest sources of manganese ore worldwide. Two belts of manganese ore deposits have been distinguished in the PMF, namely the Western Belt of ferruginous manganese ores and the Eastern Belt of siliceous manganese ores. Prevailing models of ore formation in these two belts invoke karstification of manganese-rich dolomites and residual accumulation of manganese wad which later underwent diagenetic and low-grade metamorphic processes. For the most part, the role of hydrothermal processes and metasomatic alteration towards ore formation has not been adequately discussed. Here we report an abundance of common and some rare Al-, Na-, K- and Ba-bearing minerals, particularly aegirine, albite, microcline, banalsite, sérandite-pectolite, paragonite and natrolite in Mn ores of the PMF, indicative of hydrothermal influence. Enrichments in Na, K and/or Ba in the ores are generally on a percentage level for most samples analysed through bulk-rock techniques. The presence of As-rich tokyoite also suggests the presence of As and V in the hydrothermal fluid. The fluid was likely oxidized and alkaline in nature, akin to a mature basinal brine. Various replacement textures, particularly of Na- and K- rich minerals by Ba-bearing phases, suggest sequential deposition of gangue as well as ore-minerals from the hydrothermal fluid, with Ba phases being deposited at a later stage. The stratigraphic variability of the studied ores and their deviation from the strict classification of ferruginous and siliceous ores in the literature, suggests that a re-evaluation of genetic models is warranted. New Ar-Ar ages for K-feldspars suggest a late Neoproterozoic timing for hydrothermal activity. This corroborates previous geochronological evidence for regional hydrothermal activity that affected Mn ores at the PMF but also, possibly, the high-grade Mn ores of the Kalahari Manganese Field to the north. A revised, all-encompassing model for the development of the manganese deposits of the PMF is then proposed, whereby the source of metals is attributed to underlying carbonate rocks beyond the Reivilo Formation of the Campbellrand Subgroup. The main process by which metals are primarily accumulated is attributed to karstification of the dolomitic substrate. The overlying Asbestos Hills Subgroup banded iron formation (BIF) is suggested as a potential source of alkali metals, which also provides a mechanism for leaching of these BIFs to form high-grade residual iron ore deposits.
Rabbi Jacob ben Isaac of Yanova (d. 1623) is best known as the author of the Ze’enah U-Re’enah; the Melits Yosher (“Intercessor before God”) is one of his lesser known works. It was first published in Lublin in 1622 and reprinted once in Amsterdam in 1688. Like the Ze’enah U-Re’enah, it was a Torah commentary, but composed for men who had some yeshivah education, but who could not continue their studies. The commentary on the Song of Songs by Isaac Sulkes is another Yiddish work that addresses the same audience as the Melits Yosher. The purpose of this article is to bring to scholarly attention an audience that has not been noticed or studied in the previous scholarship on early modern Yiddish literature.
Die Erweiterung des natürlichen Zahlbereichs um die positiven Bruchzahlen und die negativen ganzen Zahlen geht für Schülerinnen und Schüler mit großen gedanklichen Hürden und einem Umbruch bis dahin aufgebauter Grundvorstellungen einher. Diese Masterarbeit trägt wesentliche Veränderungen auf der Vorstellungs- und Darstellungsebene für beide Zahlbereiche zusammen und setzt sich mit den kognitiven Herausforderungen für Lernende auseinander. Auf der Grundlage einer Diskussion traditioneller sowie alternativer Lehrgänge der Zahlbereichserweiterung wird eine Unterrichtskonzeption für den Mathematikunterricht entwickelt, die eine parallele Einführung der Bruchzahlen und der negativen Zahlen vorschlägt. Die Empfehlungen der Unterrichtkonzeption erstrecken sich über den Zeitraum von der ersten bis zur siebten Klassenstufe, was der behutsamen Weiterentwicklung und Modifikation des Zahlbegriffs viel Zeit einräumt, und enthalten auch didaktische Überlegungen sowie konkrete Hinweise zu möglichen Aufgabenformaten.
In aquatic ecosystems, light availability can significantly influence microbial turnover of terrestrial organic matter through associated metabolic interactions between phototrophic and heterotrophic communities. However, particularly in streams, microbial functions vary significantly with the structure of the streambed, that is the distribution and spatial arrangement of sediment grains in the streambed. It is therefore essential to elucidate how environmental factors synergistically define the microbial turnover of terrestrial organic matter in order to better understand the ecological role of photo-heterotrophic interactions in stream ecosystem processes. In outdoor experimental streams, we examined how the structure of streambeds modifies the influence of light availability on microbial turnover of leaf carbon (C). Furthermore, we investigated whether the studied relationships of microbial leaf C turnover to environmental conditions are affected by flow intermittency commonly occurring in streams. We applied leaves enriched with a 13C-stable isotope tracer and combined quantitative and isotope analyses. We thereby elucidated whether treatment induced changes in C turnover were associated with altered use of leaf C within the microbial food web. Moreover, isotope analyses were combined with measurements of microbial community composition to determine whether changes in community function were associated with a change in community composition. In this study, we present evidence, that environmental factors interactively determine how phototrophs and heterotrophs contribute to leaf C turnover. Light availability promoted the utilization of leaf C within the microbial food web, which was likely associated with a promoted availability of highly bioavailable metabolites of phototrophic origin. However, our results additionally confirm that the structure of the streambed modifies light-related changes in microbial C turnover. From our observations, we conclude that the streambed structure influences the strength of photo-heterotrophic interactions by defining the spatial availability of algal metabolites in the streambed and the composition of microbial communities. Collectively, our multifactorial approach provides valuable insights into environmental controls on the functioning of stream ecosystems.
Microbial processing of organic matter (OM) in the freshwater biosphere is a key component of global biogeochemical cycles. Freshwaters receive and process valuable amounts of leaf OM from their terrestrial landscape. These terrestrial subsidies provide an essential source of energy and nutrients to the aquatic environment as a function of heterotrophic processing by fungi and bacteria. Particularly in freshwaters with low in-situ primary production from algae (microalgae, cyanobacteria), microbial turnover of leaf OM significantly contributes to the productivity and functioning of freshwater ecosystems and not least their contribution to global carbon cycling.
Based on differences in their chemical composition, it is believed that leaf OM is less bioavailable to microbial heterotrophs than OM photosynthetically produced by algae. Especially particulate leaf OM, consisting predominantly of structurally complex and aromatic polymers, is assumed highly resistant to enzymatic breakdown by microbial heterotrophs. However, recent research has demonstrated that OM produced by algae promotes the heterotrophic breakdown of leaf OM in aquatic ecosystems, with profound consequences for the metabolism of leaf carbon (C) within microbial food webs. In my thesis, I aimed at investigating the underlying mechanisms of this so called priming effect of algal OM on the use of leaf C in natural microbial communities, focusing on fungi and bacteria.
The works of my thesis underline that algal OM provides highly bioavailable compounds to the microbial community that are quickly assimilated by bacteria (Paper II). The substrate composition of OM pools determines the proportion of fungi and bacteria within the microbial community (Paper I). Thereby, the fraction of algae OM in the aquatic OM pool stimulates the activity and hence contribution of bacterial communities to leaf C turnover by providing an essential energy and nutrient source for the assimilation of the structural complex leaf OM substrate. On the contrary, the assimilation of algal OM remains limited for fungal communities as a function of nutrient competition between fungi and bacteria (Paper I, II). In addition, results provide evidence that environmental conditions determine the strength of interactions between microalgae and heterotrophic bacteria during leaf OM decomposition (Paper I, III). However, the stimulatory effect of algal photoautotrophic activities on leaf C turnover remained significant even under highly dynamic environmental conditions, highlighting their functional role for ecosystem processes (Paper III).
The results of my thesis provide insights into the mechanisms by which algae affect the microbial turnover of leaf C in freshwaters. This in turn contributes to a better understanding of the function of algae in freshwater biogeochemical cycles, especially with regard to their interaction with the heterotrophic community.
This paper presents in the first section a methodological introduction concerning statistics of consumer prices in Georgia. The second section gives a general idea of the development of consumer prices from January 1994 till September 1999. A detailed regional analysis is added in section 3. The fourth section analyses the development of consumer prices for the eight main groups included in the total CPI. Section 5 compares the changes in Georgian CPI with the movements of foreign exchange rates in Georgian Lari. This paper ends with a summary including a short outlook to the next years.