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In some cases difficult-to-read learning materials lead to better performance than easy to-read materials. This phenomenon is called the disfluency effect and is attributed to a subjective feeling of task difficulty resulting in a deeper learning approach. In two studies (n[subscript 1] = 67, n[subscript 2] = 73) we investigated the impact of three increasing disfluency levels compared to a fluent condition on learning outcomes, in the second study we additionally addressed effects on cognitive load and time on task. The first study revealed significant differences of the experimental groups and on a descriptive level a reversed u-shape pattern, i.e., learning performance increases with increasing disfluency but decreases when the text becomes too illegible. The same pattern could be found significantly in the second study for recall and transfer performance, engagement and time on task and the reversed pattern for extraneous load. Results indicate that there is in fact an optimal level of disfluency on performance that comes along with increased engagement and that there is a breaking point of disfluency where the extraneous load seems to be too high.

We report first results from a study on water and element exchange across the land-ocean boundary at the southern Baltic Sea. The focus is set on ferruginous fresh ground waters escaping at the shore line, flowing in air contact before entering a subterranean mixing zone with brackish Baltic Sea water. The present study combines the results from multiple sampling campaigns that investigated the composition of several springs as well as the surface and subsurface development of fresh waters on the way to the Baltic Sea. This is achieved by a combination of hydroand solid-phase geochemical and stable isotope measurements with ground water dating. Results are compared to the composition of groundwaters recovered from wells in the catchment area and the local isotope meteoric water line developed for Warnemünde. The spring water is shown to be impacted by the dissolution of biogenic carbon dioxide and marine carbonate as well as the oxidation of pyrite in glacial sediments. Dating yields a surprisingly high diversity between some closely associated springs with average ages of about 25 to 32 years, but different mixing proportions with older tritium-free ground-water.

In natural coastal wetlands, high supplies of marine sulfate suppress methanogenesis. Coastal wetlands are, however, often subject to disturbance by dyking and drainage for agricultural use and it has been shown that they can turn to potent methane sources when rewetted for remediation, suggesting that the sulfate-related methane suppressing mechanisms were suspended by the preceding land use measures. Here, we unravel the hydrological relocation and biogeochemical S and C transformation processes that induced high methane emissions in a disturbed and rewetted peatland despite former brackish impact. The underlying processes were investigated along a transect of increasing distance to the coastline using a combination of concentration patterns, stable isotope partitioning and analysis of the microbial community structure. We found that dyking and freshwater rewetting caused a distinct freshening and an efficient depletion of the brackish sulfate reservoir by dissimilatory sulfate reduction (DSR). Despite some legacy effects of brackish impact expressed as high amounts of sedimentary S and elevated electrical conductivities, contemporary metabolic processes operated mainly under sulfate-limited conditions. This opened up favorable conditions for the establishment of a prospering methanogenic community in the top 30-40 cm of peat, the structure and physiology of which resembles those of terrestrial organic-rich environments. Locally, high amounts of sulfate persisted in deeper peat layers through the suppression of DSR, probably by competitive electron acceptors of terrestrial origin, for example Fe(III), but did not interfere with high methane emissions on ecosystem scale. Our results indicate that the climate effect of disturbed and remediated coastal wetlands cannot simply be derived by analogy with their natural counterparts. From a greenhouse gas perspective, the re-exposure of dyked wetlands to natural coastal dynamics would literally open up the floodgates for a replenishment of the marine sulfate pool and constitute an efficient measure to reduce methane emissions. [ABSTRACT FROM AUTHOR]

The seminal synthesis of the sesquiterpene (±)-α-cedrene reported by Wender in 1981 offers a uniquely short and elegant access to the bridged-tricyclic target compound by exploiting an intramolecular arene-olefin photocycloaddition. However, the synthesis was performed only in the racemic series so far. This synthesis was now re-investigated and the catalytic methods for the enantioselective preparation of the chiral key intermediate were evaluated. It was found that Cu-catalyzed allylic substitution of a cinnamyl chloride with MeMgBr in the presence of a Taddol-derived chiral phosphine-phosphite ligand affords the corresponding (1-methylallyl)arene with high enantioselectivity (94% ee). Hydroboration and subsequent Suzuki coupling gave (R)-curcuphenol methyl ether from which (–)-α-cedrene was prepared along the route paved by Wender. [ABSTRACT FROM AUTHOR]

Land-ocean interactions in the coastal zone (LOICZ) are of particular interest regarding the exchange of elements, like nutrients, carbon and sulfur. An important pathway is submarine groundwater discharge (SGD) for this element exchange from the terrestrial to the marine environment and vice versa. On the pathway biogeochemical transformations may take place, that may lead to the accumulation of higher concentrations of nutrients, metals, carbon dioxide and methane.Beside fresh groundwater, SGD also consist of a considerable proportion of recirculated often brackish seawater. In the present study we followed the water and element exchange and associated biogeochemical transformation processes along a 2.5 km long coastal stretch in front of a rewetted peatland, the Hütelmoor area at the southern Baltic Sea.Drone-based thermal infrared images conducted during winter time allowed for the identification of several possible SGD sites. Highest temperature difference of about 1°C has been measured in the northern part of the study area created by a local plume near the coastline. Several vertical pore water profiles were retrieved via mobile push-pull and up to 5 m long permanent pore water samplers in the shallow water area on a seasonal base. Furthermore, Baltic Sea surface water samples were obtained during several ship cruises. A focus was set on the investigation of concentration gradients of major and redox-sensitive trace elements, nutrients and the stable isotope composition (H, C, S, O) of water, dissolved inorganic carbon (DIC) and sulfate to understand the mixing processes and superimposing biogeochemical transformation reactions. Ra isotope investigations in the water column and in the pore water complemented these measurements and are used for the detection of benthic-pelagic coupling via exchange of solutions on a local to regional scale. During different sampling campaigns, Rn, several Ra, and Ra isotopes were measured along transects with different lengths perpendicular to the coastline. Rn was found to be low in the water column. Both sampling campaigns reveal differences in dissolved Ra isotope concentrations indicating exchange between sediment and water column with higher contributions from SGD in the northern part of the study area. Nearshore water show higher Ra signals compared to the offshore stations and are positioned on a mixing line with the pore water end member. We found evidence for a strong control of the bottom-pore water exchange induced by exposed lithology and a high activity of dissimilatory sulfate-reducing microorganisms in the coastal sediments. Sedimentary sulfur fractions and their stable isotope signatures are controlled by the availability of dissolved organic matter or methane, reactive iron, and in the wetland particular dissolved sulfate. Following a recent flooding event with brackish Baltic Sea water, the sulfur isotope composition of sulfate in surface waters draining the peatland indicate the impact of solutions that were modified by net microbial sulfate reduction.Acknowledgement: This study is supported by the DFG research training group BALTIC TRANSCOAST and the Leibniz IOW. [ABSTRACT FROM AUTHOR]

Due to their pronounced bioactivity and limited availability from natural resources, metabolites of the soft coral Pseudopterogorgia elisabethae, such as erogorgiaene and the pseudopterosines, represent important target molecules for chemical synthesis. We have now developed a particularly short and efficient route towards these marine diterpenes exploiting an operationally convenient enantioselective cobalt-catalyzed hydrovinylation as the chirogenic step. Other noteworthy C-C bond forming transformations include diastereoselective Lewis acid-mediated cyclizations, a Suzuki coupling and a carbonyl ene reaction. Starting from 4-methyl-styrene the anti-tubercular agent (+)-erogorgiaene (>98 % ee) was prepared in only 7 steps with 46 % overall yield. In addition, the synthesis of the pseudopterosin A aglycone was achieved in 12 steps with 30 % overall yield and, surprisingly, was found to exhibit a similar anti-inflammatory activity (inhibition of LPS-induced NF-κB activation) as a natural mixture of pseudopterosins A-D or iso-pseudopterosin A, prepared by β-D-xylosylation of the synthetic aglycone., (© 2021 The Authors. Published by Wiley-VCH GmbH.)

An efficient and practical protocol for the enantioselective cobalt-catalyzed hydrovinylation of vinylarenes with ethylene at low (1.2 bar) pressure has been developed. As precatalysts, stable [L2 CoCl2 ] complexes are employed that are activated in situ with Et2 AlCl. A modular chiral TADDOL-derived phosphine-phosphite ligand was identified that allows the conversion of a broad spectrum of substrates, including heterocyclic vinylarenes and vinylferrocene, to smoothly afford the branched products with up to 99 % ee and virtually complete regioselectivity. Even polar functional groups, such as OH, NH2 , CN, and CO2 R, are tolerated., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)