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We isolated and characterized 16 new di- and tetranudeotide microsatellite markers for the critically endangered Asian box turtle genus Cuora, focusing on the "Cuora trifasciata" species complex. The new markers were then used to analyse genetic variability and divergence amongst five described species within this complex, namely C. aurocapitata (n = 18), C. cyclornata (n = 31), C. pani (n = 6), C. trifasciata (n = 58), and C. zhoui (n = 7). Our results support the view that all five species represent valid taxa. Within two species (C. trifasciata and C. cyclornata), two distinct morphotypes were corroborated by microsatellite divergence. For three individuals, morphologically identified as being of hybrid origin, the hybrid status was confirmed by our genetic analysis. Our results confirm the controversial species (Cuora aurocapitata, C. cyclornata) and subspecies/morphotypes (C. cyclornata meieri, C. trifasciata cf. trifasciata) to be genetically distinct, which has critical implications for conservation strategies.
The AlpArray seismic network
(2018)
The AlpArray programme is a multinational, European consortium to advance our understanding of orogenesis and its relationship to mantle dynamics, plate reorganizations, surface processes and seismic hazard in the Alps-Apennines-Carpathians-Dinarides orogenic system. The AlpArray Seismic Network has been deployed with contributions from 36 institutions from 11 countries to map physical properties of the lithosphere and asthenosphere in 3D and thus to obtain new, high-resolution geophysical images of structures from the surface down to the base of the mantle transition zone. With over 600 broadband stations operated for 2 years, this seismic experiment is one of the largest simultaneously operated seismological networks in the academic domain, employing hexagonal coverage with station spacing at less than 52 km. This dense and regularly spaced experiment is made possible by the coordinated coeval deployment of temporary stations from numerous national pools, including ocean-bottom seismometers, which were funded by different national agencies. They combine with permanent networks, which also required the cooperation of many different operators. Together these stations ultimately fill coverage gaps. Following a short overview of previous large-scale seismological experiments in the Alpine region, we here present the goals, construction, deployment, characteristics and data management of the AlpArray Seismic Network, which will provide data that is expected to be unprecedented in quality to image the complex Alpine mountains at depth.
Polymer libraries offer straightforward opportunities for the investigation of structure property relationships and for a more thorough understanding of certain research problems. Furthermore, if combined with high-throughput methods for their preparation as well as screening, they offer the additional advantage of time savings and/or the reduction of experimental efforts. Thus, the herein discussed methods of polymer library preparation and selected literature examples of polymer libraries describe efficient and state-of-the-art methods to tackle difficult research challenges in polymer and materials science.
Thiol-ene additions of methyl 10-undecenoate, a castor oil derived renewable platform chemical, were studied with the goal of preparing a set of renewable monomers. Good to excellent yields were obtained for these solvent and initiator free thiol-ene additions. The resulting monomers were then polymerized using TBD as a catalyst, to linear as well as hyperbranched polyesters that also contain thio-ether linkages. All thus prepared polymers were fully characterized (NMR, GPC, DSC, and TGA) and the results of these investigations will be discussed within this contribution. The thermal analysis of these polymers revealed melting points in the range from 50 to 71 degrees C. Moreover, no significant weight loss was observed below 300 degrees C.
The self-metathesis of methyl 10-undecenoate as well as its cross-metathesis with methyl acrylate was investigated in detail by a systematic variation of the reaction conditions. Unsaturated ;,;-diesters with a chain length of 20 and 12 carbon atoms were thus obtained, respectively. Four different metathesis catalysts were investigated under solvent-free conditions at catalyst loadings ranging from 0.05 mol% to 1 mol% and at temperatures ranging from 30 °C to 90 °C. In the case of the self-metathesis reactions quantitative conversions were obtained with all catalysts, but the second generation metathesis catalysts revealed high amounts of olefin isomerization side reactions at higher temperatures. Using a small quantity of the hydrogen acceptor 1,4-benzoquinone, the isomerization process was almost completely suppressed. Thus, the second generation catalysts allowed for high conversions at very low catalyst loadings. For the cross-metathesis reaction, an interesting temperature and catalyst loading dependent selectivity was observed with the second generation catalysts. Moreover, due to these optimizations, we were able to run these cross-metathesis reactions with a 1:1 ratio of the reactants and low catalysts loadings. This is an improvement over described literature procedures. Thus, we report on the detailed investigation of the described self- and cross- metathesis reactions leading to practical and optimized reaction conditions for the synthesis of unsaturated ;,;-diesters monomers from renewable raw materials in an efficient catalytic manner.
Due to depleting fossil resources, the ever increasing emission of greenhouse gases and toxic waste, as well as the inefficient utilization of our available resources, we have to implement the principles of green chemistry whenever and wherever possible. Plant oils are already the most important renewable resource for the chemical industry. Due to their inherent double-bond functionality, they offer the possibility of being transformed via several very efficient catalytic processes. Especially, new developments in olefin metathesis allow the chemist to directly polymerize or introduce a variety of functional groups to these renewable resources in an efficient manner. Therefore, olefin metathesis with plant-oil-derived fatty acids and their derivatives can contribute to a sustainable development of our future, since this approach has great potential for the substitution of currently used petrochemicals and a variety of value-added chemical intermediates, especially for the polymer industry, can be derived from these resources in a straightforward fashion. This contribution will address and discuss the most recent developments in this field of research.
Olefin isomerization side reactions that occur during ADMET polymerizations were studied by preparing polyesters via ADMET and subsequently degrading these polyesters via transesterification with methanol. The resulting diesters, representing the repeating units of the previously prepared polyesters, were then analyzed by GC-MS. This strategy allowed quantification of the amount of olefin isomerization that took place during ADMET polymerization with second generation ruthenium metathesis catalysts. In a second step, it was shown that the addition of benzoquinone to the polymerization mixture prevented the olefin isomerization. Therefore, second generation ruthenium metathesis catalysts may now be used for the preparation of well-defined polymers via ADMET with very little isomerization, which was not possible before.
An alpha,omega-diene containing hydroxyl groups was prepared from plant oil-derived platform chemicals. The acyclic diene metathesis copolymerization (ADMET) of this monomer with a phosphorus-containing alpha,omega-cliene (DOPO II), also plant oil derived, afforded a series of phosphorus containing linear polyesters, which have been fully characterized. The backbone hydroxyls of these polyesters have been acrylated and radically polymerized to produce crosslinked polymers. The thermomechanical and mechanical properties, the thermal stability, and the flame retardancy of these phosphorus-based thermosets have been studied. Moreover, methyl 10-undecenoate has been used as chain stopper in selected ADMET polymerizations to study the effect of the prepolymers' molecular weights on the different properties of the final materials.
High oleic sunflower oil, a renewable raw material consisting of triglycerides with internal C=C-double bonds, was polymerized via acyclic triene metathesis (ATMET) to highly branched and functionalized polyesters. If the Hoveyda- Grubbs second generation catalyst was used and methyl acrylate was introduced as a chain stopper, the molecular weight of the obtained polymers could be tuned by varying the ratio of the triglyceride and methyl acrylate. Using the first generation Grubbs catalyst for the polymerization of high oleic sunflower oil, no cross-linking was observed, even without the use of a chain stopper. The resulting branched materials were characterized by GPC, H-1 and C-13 NMR, and ESI-MS.
Structurally diverse polyamides obtained from monomers derived via the Ugi multicomponent reaction
(2012)
The combination of the Ugi four-component reaction (Ugi-4CR) with acyclic diene metathesis (ADMET) or thiolene polymerization led to the formation of poly-1-(alkylcarbamoyl) carboxamides, a new class of substituted polyamides with amide moieties in the polymer backbone, as well as its side chains. 10-Undecenoic acid, obtained by pyrolysis of ricinoleic acid, the main fatty acid of castor oil, was used as the key renewable building block. The use of different primary amines, as well as isonitriles (isocyanides) for the described Ugi reactions provided monomers with high structural diversity. Furthermore, the possibility of versatile post-modification of functional groups in the side chains of the corresponding polymers should be of considerable interest in materials science. The obtained monomers were polymerized by ADMET, as well as thiolene, chemistry and all polymers were fully characterized. Finally, ortho-nitrobenzylamide-containing polyamides obtained by this route were shown to be photoresponsive and exhibited a dramatic change of their properties upon irradiation with light.