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  • 1
    Language: English
    In: Journal of Hydrology, 2011, Vol.402(3), pp.274-289
    Description: ► Using multiple isotopes to study groundwater flow in active rifts. ► Hydrochemical and isotopic evolution from escarpments to Rift floor. ► Mantle CO influences groundwater hydrochemistry. ► Apparent C ages are similar in Rift floor groundwater. ► Groundwater flow paths occur both longitudinal and transversal to rift axis. This study aims to investigate groundwater recharge and flow patterns in tectonically active rift systems, exemplified by a case study in the Main Ethiopian Rift. The chosen approach includes the investigation of hydrochemical parameters and environmental isotopes ( H, δ H, δ O, δ C-DIC, C-DIC, Sr/ Sr). Apparent groundwater ages were determined by radiocarbon dating after correction of C-DIC using a modified δ C-mixing model and further validation using geochemical modelling with NETPATH. Hydrochemical and isotopic data indicate an evolutionary trend existing from the escarpments towards the Rift floor. Groundwater evolves from tritium-containing and hence recently recharged Ca–HCO -type water on the escarpments to tritium-free Na–HCO groundwater dominating deep Rift floor aquifers. Correspondingly, rising pH and values coupled with increasingly enriched δ C signatures point to hydrochemical evolution of DIC and beginning dilution of the carbon isotope signature by other carbon sources, related to a diffuse influx of mantle CO into the groundwater system. Especially thermal groundwater sampled near the most recent fault zones in the Fantale/Beseka region displays clear influence of mantle CO and increased water–rock interaction, indicated by a shift in δ C and Sr/ Sr signatures. The calculation of apparent groundwater ages revealed an age increase of deep groundwater from the escarpments to the Rift floor, complying with hydrochemical evolution. Within the Rift, samples show a relatively uniform distribution of apparent C ages of ∼1800 to ∼2800 years, with the expected down-gradient aging trend lacking, contradicting the predominant intra-rift groundwater flow described in existing transect-based models of groundwater flow. By combining hydrochemical and new isotopic data with knowledge of the structural geology of the Rift, we improve the existing groundwater flow model and propose a new conceptual model by identifying flow paths both transversal and longitudinal to the main Rift axis, the latter being strongly controlled by faulted and tilted blocks on the escarpment steps. The connection between groundwater flow and fault direction make this model applicable to other active rift systems with similar structural settings.
    Keywords: Rift Tectonics ; Hydrochemistry ; Isotope Hydrology ; Groundwater Cycle and Dating ; 87sr/ 86sr ; 14c ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 2
    Language: English
    In: Science of the Total Environment, 15 April 2017, Vol.584-585, pp.958-970
    Description: Arsenic contamination in groundwater from crystalline basement rocks in West Africa has only been documented in isolated areas and presents a serious health threat in a region already facing multiple challenges related to water quality and scarcity. We present a comprehensive dataset of arsenic concentrations from drinking water wells in rural Burkina Faso (n = 1498), of which 14.6% are above 10 μg/L. Included in this dataset are 269 new samples from regions where no published water quality data existed. We used multivariate logistic regression with arsenic measurements as calibration data and maps of geology and mineral deposits as independent predictor variables to create arsenic prediction models at concentration thresholds of 5, 10 and 50 μg/L. These hazard maps delineate areas vulnerable to groundwater arsenic contamination in Burkina Faso. Bedrock composed of schists and volcanic rocks of the Birimian formation, potentially harbouring arsenic-containing sulphide minerals, has the highest probability of yielding groundwater arsenic concentrations 〉 10 μg/L. Combined with population density estimates, the arsenic prediction models indicate that ~ 560,000 people are potentially exposed to arsenic-contaminated groundwater in Burkina Faso. The same arsenic-bearing geological formations that are positive predictors for elevated arsenic concentrations in Burkina Faso also exist in neighbouring countries such as Mali, Ghana and Ivory Coast. This study's results are thus of transboundary relevance and can act as a trigger for targeted water quality surveys and mitigation efforts.
    Keywords: Arsenic Contamination ; Drinking Water ; West Africa ; Sulphide Minerals ; Hazard Modelling ; Health Threat ; Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 3
    Language: English
    In: Science of the Total Environment, 15 November 2017, Vol.598, pp.562-562
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.scitotenv.2017.04.098 Byline: Anja Bretzler, Franck Lalanne, Julien Nikiema, Joel Podgorski, Numa Pfenninger, Michael Berg, Mario Schirmer
    Keywords: Environmental Sciences ; Biology ; Public Health
    ISSN: 0048-9697
    E-ISSN: 1879-1026
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  • 4
    Language: English
    In: Thin Solid Films, 31 December 2014, Vol.573, pp.164-175
    Description: Platinum, palladium and silver films with different microstructures have been prepared on differently orientated yttrium-stabilised zirconia (YSZ) substrates by pulsed laser deposition and then annealed at temperatures between 200 °C and 850 °C. Thereby, an influence of the type of metal, of the microstructure of the as-prepared film and of the orientation of the substrate on the annealing behaviour could be determined. The following annealing effects were observed for platinum, palladium and silver films: ) sharpening of the film boundary, ) smoothing of the film surfaces, ) sharpening of the texture [thereby: reduction of the fraction of small angle and twin grain boundaries], ) grain growth and accordingly reduction of the fraction of grains as well as ) grooving at grain boundaries, ) void formation at the metal|YSZ-interface, ) hole formation within the films and ) reduction of the fraction of droplets. In the case of palladium films also ) oxidation [between 300 °C ≤ 〈 750 °C] and stronger de-wetting phenomena than for platinum [with ) waving of the film and ) island formation at ≥ 750 °C] have been found. Silver films are not oxidised, but show stronger de-wetting phenomena than platinum and palladium, with ) island formation and ) evaporation of the silver at ≥ 550 °C. Interestingly, silver films on (111) orientated YSZ are thermally much more stable than silver films on the other orientated substrates up to 750 °C. The annealing effects were described by interface, grain boundary and surface energy minimization.
    Keywords: Platinum ; Palladium ; Silver ; Microstructure ; Annealing ; Engineering ; Physics
    ISSN: 0040-6090
    E-ISSN: 1879-2731
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  • 5
    Language: English
    In: Thin Solid Films, Dec 31, 2014, Vol.573, p.164(12)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.tsf.2014.11.035 Byline: Gesa Beck, Christoph Bachmann, Rita Bretzler, Ralf Kmeth Abstract: Platinum, palladium and silver films with different microstructures have been prepared on differently orientated yttrium-stabilised zirconia (YSZ) substrates by pulsed laser deposition and then annealed at temperatures between 200[degrees]C and 850[degrees]C. Thereby, an influence of the type of metal, of the microstructure of the as-prepared film and of the orientation of the substrate on the annealing behaviour could be determined. The following annealing effects were observed for platinum, palladium and silver films: i) sharpening of the film boundary, ii) smoothing of the film surfaces, iii) sharpening of the texture [thereby: reduction of the fraction of small angle and twin grain boundaries], iv) grain growth and accordingly reduction of the fraction of grains as well as v) grooving at grain boundaries, vi) void formation at the metal|YSZ-interface, vii) hole formation within the films and viii) reduction of the fraction of droplets. In the case of palladium films also ix) oxidation [between 300[degrees]C[less than or equal to] T 〈750[degrees]C] and stronger de-wetting phenomena than for platinum [with x) waving of the film and xi) island formation at T [greater than or equal to]750[degrees]C] have been found. Silver films are not oxidised, but show stronger de-wetting phenomena than platinum and palladium, with xi) island formation and xii) evaporation of the silver at T [greater than or equal to]550[degrees]C. Interestingly, silver films on (111) orientated YSZ are thermally much more stable than silver films on the other orientated substrates up to 750[degrees]C. The annealing effects were described by interface, grain boundary and surface energy minimization. Article History: Received 17 March 2014; Revised 7 November 2014; Accepted 10 November 2014
    Keywords: Rare Earth Metals ; Palladium ; Rare Earth Metal Compounds ; Zirconium Oxide ; Grain Boundaries ; Zirconium ; Annealing
    ISSN: 0040-6090
    Source: Cengage Learning, Inc.
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  • 6
    Language: English
    In: Chemistry – A European Journal, 18 May 2015, Vol.21(21), pp.7701-7704
    Description: We here report the construction of an expression system able to manufacture an unnatural amino acid by artificial biosynthesis. This can be orchestrated with incorporation into protein by amber stop codon suppression inside a living cell. In our case an alkyne‐bearing pyrrolysine amino acid was biosynthesized and incorporated site‐specifically allowing orthogonal double protein labeling. of pyrrolysine was utilized to convert the novel amino acid 3‐ethynyl‐‐ornithine to ethynylpyrrolysine (ePyl) and incorporate it into proteins. This new methodology based on amber suppression technology facilitates site‐specific protein labeling.
    Keywords: Amber Suppression ; Bioorganic Chemistry ; Pyrrolysine ; Synthetic Biology ; Unnatural Amino Acid
    ISSN: 0947-6539
    E-ISSN: 1521-3765
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  • 7
    Language: English
    In: Materials Chemistry and Physics, 2011, Vol.128(3), pp.383-387
    Description: ► Anodic alumina was formed on (1 1 1), (1 1 0) and (1 0 0) aluminium single crystals. ► The pore ordering of the nanopores was described on the basis of defect thermology and analyzed quantitatively by image evaluation. ► The best ordering was obtained in nanoporous alumina on (1 0 0) aluminium. ► We supposed that the minimisation of the interface energy is the reason for this. On aluminium single crystals with (1 1 1), (1 1 0) and (1 0 0) orientation, nanoporous alumina layers were formed in a two-step anodization process within sulphuric acid. The pore ordering within the hexagonal arrangement of the nanopores was documented by scanning electron microscopy (SEM), described on the basis of defect thermology and analyzed quantitatively by image evaluation. The best ordering was obtained in nanoporous alumina on (1 0 0) aluminium. We supposed that this is caused by the interface energy term within the driving force for the formation of the nanoporous alumina, since – in contrast to (1 1 1) and (1 1 0) aluminium as substrate – in the case of (1 0 0) aluminium the interface energy is minimised in the waved interface between aluminium and hexagonally arranged nanoporous alumina.
    Keywords: Nanostructure ; Microporous Material ; Interfaces ; Oxidation ; Engineering ; Chemistry
    ISSN: 0254-0584
    E-ISSN: 1879-3312
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  • 8
    Language: English
    In: Applied Geochemistry, December 2015, Vol.63, pp.642-646
    Description: In some groundwaters, arsenic and fluoride can reach concentrations that are hazardous to human health if geological and geochemical conditions favour the release of these contaminants. This can especially pose a problem in developing countries where water service providers already struggle with the provision of clean water. The Geogenic Contamination Handbook, released in January 2015, aims to provide concise guidelines for practitioners faced with the problem of geogenically contaminated drinking water in low- and middle-income countries. The handbook is a digital resource, with the reader benefitting from numerous weblinks and embedded documents giving additional information where relevant. The necessary steps needed for sustainable mitigation of arsenic or fluoride-contaminated drinking water are outlined. This includes information on water quality testing (e.g. how to plan a field survey), different water treatment options as well as practical guidelines on the integration of technical, institutional and sociological aspects of arsenic and fluoride mitigation.
    Keywords: Arsenic ; Fluoride ; Groundwater ; Geogenic Contamination ; Mitigation ; Guidelines ; Geology
    ISSN: 0883-2927
    E-ISSN: 1872-9134
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  • 9
    In: Macromolecular Chemistry and Physics, July 2014, Vol.215(14), pp.1396-1406
    Description: The copper(I)‐catalyzed alkine–azide cycloaddition (CuAAC) click polymerization is used for the synthesis of novel poly(dimethylsiloxane) (PDMS)‐containing alternating copolymers in a straightforward AA/BB polyaddition approach. The versatility of the CuAAC reaction allows incorporation of a series of different monomers varying in geometry, size, and functionality. A structure–property relation is revealed that shows that the polymer properties are dependent not only on the type of functionality incorporated but also on the size and geometry of the comonomer. The spectrum of properties that can be covered is highly interesting, ranging from viscous oils to brittle solids. Targeted application of monomers even gives access to properties that are typical for thermoplastic elastomers. Additional studies concerning the acceleration of the polymerization reaction support mechanistic considerations about a binuclear active species. by a copper(I)‐catalyzed alkine–azide cycloaddition (CuAAC) polyaddition. The respective combination of monomers has a strong effect on the individual properties. The rate of the CuAAC reaction can be controlled by addition of tris((1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)­methyl)amine (TBTA) as evidenced by in situ infrared (IR) spectroscopy.
    Keywords: Addition Polymerization ; Alternating Copolymers ; Elastomers ; Polysiloxanes ; Thermoplastics
    ISSN: 1022-1352
    E-ISSN: 1521-3935
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  • 10
    Language: German
    In: Arbeit und Recht, 1 October 2012, Vol.60(10), pp.407-412
    Keywords: Law;
    ISSN: 00037648
    Source: Archival Journals (JSTOR)
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