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ABSTRACTRecently, the ‘method of tensile triangles’ has been introduced for optimizing the shape of notches by adding material at overloaded regions but also to remove unloaded material from an oversized design proposal.In this work, we apply the method to demonstrate that the unloaded region in the vicinity of a crack has the shape of spindle‐shaped hole, which looks like two dunce caps mirrored at the crack line. Also, these shapes can be predicted by the ‘method of tensile triangles’ without any FEM‐effort. Furthermore, we show a new way to stop cracks by deviating the crack tip into a shape‐optimized pattern leading to a compressive stress that closes the crack tip. This procedure is now used in chemical engineering.

AbstractSeveral nitrones and one nitroso compound have been evaluated for their ability to control the molecular weight of polystyrene via the recently introduced radical polymerization method of enhanced spin capturing polymerization (ESCP). In this technique, molecular weight control is achieved (at ambient or slightly elevated temperatures) via the reaction of a growing radical chain with a nitrone forming a macronitroxide. These nitroxides subsequently react rapidly and irreversibly with propagating macroradicals forming polymer of a certain chain length, which depends on the nitrone concentration in the system. Via evaluation of the resulting number‐average molecular weight, Mn, at low conversions, the addition rate coefficient of the growing radicals onto the different nitrones is determined and activation energies are obtained. For the nitrones N‐tert‐butyl‐α‐phenylnitrone (PBN), N‐methyl‐α‐phenylnitrone (PMN), and N‐methyl‐α‐(4‐bromo‐phenyl) nitrone (pB‐PMN), addition rate coefficients, kad,macro, in a similar magnitude to the styrene propagation rate coefficient, kp, are found with spin capturing constants CSC (with CSC = kad,macro/kp) ranging from 1 to 13 depending on the nitrone and on temperature. Activation energies between 23.6 and 27.7 kJ mol−1 were deduced for kad,macro, congruent with a decreasing CSC with increasing temperature. Almost constant Mn over up to high monomer to polymer conversions is found when CSC is close to unity, while increasing molecular weights can be observed when the CSC is large. From temperatures of 100 °C onward, reversible cleavage of the alkoxyamine group can occur, superimposing a reversible activation/deactivation mechanism onto the ESCP system. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1098–1107, 2009

AbstractAlthough canopy height has long been a focus of interest in ecology, it has remained difficult to study at large spatial scales. Recently, satellite‐borne LiDAR equipment produced the first systematic high resolution maps of vegetation height worldwide. Here we show that this new resource reveals three marked modes in tropical canopy height ~40, ~12, and ~2 m corresponding to forest, savanna, and treeless landscapes. The distribution of these modes is consistent with the often hypothesized forest‐savanna bistability and suggests that both states can be stable in areas with a mean annual precipitation between ~1,500 and ~2,000 mm. Although the canopy height states correspond largely to the much discussed tree cover states, there are differences, too. For instance, there are places with savanna‐like sparse tree cover that have a forest‐like high canopy, suggesting that rather than true savanna, those are thinned relicts of forest. This illustrates how complementary sets of remotely sensed indicators may provide increasingly sophisticated ways to study ecological phenomena at a global scale.

This study conducts a life-cycle assessment for the use of superconducting medium voltage cables based on the AmpaCity cable in Germany. The results are compared with the use of a conventional high voltage cable. For the conventional cable, additional transformer losses are included, while for the superconducting cable the operation of the necessary cooling system is considered. The annual transmitted energy represents the functional unit. The annual loss energy of the HTS cable system is lower than that of conventional cable from a load factor of ma= 0.43. This load factor also represents the ecological break-even point. For a load factor of ma≥ 0.43, the greenhouse gas emissions and cumulative energy demand of the superconducting cable system are lower than those of the conventional cable system. Thus, if the load is sufficiently high, a superconducting cable can thus be a more environmentally friendly alternative for a future energy system.

Addressing global sustainability challenges such as climate change in democratic societies requires thorough political and societal debates. Science and environmental communication is needed to inform these debates. However, not all parts of society are equally reached by traditional science communication. In particular young people, especially without academic background, are often left out. The cooperation of science communicators with influencers on the video platform YouTube can be a way to convey scientific information and raise awareness for environmental issues with new young audiences. This case study looks at three videos from the campaign #EarthOvershootDay on YouTube by the WWF (World Wide Fund for Nature) Germany and the educational initiative MESH Collective. The focus of the analysis lies on the established success factors of communication through influencers—specifically authenticity, comprehensibility and storytelling—and how they play out in detail in the three exemplary videos. Besides the analysis of the videos, the study is corroborated by interviews with the producers and a comment analysis in order to include the perspective of the viewers. Our analysis confirms previous findings on science communication with influencers and illustrates the practical implementation of these findings. It shows that authenticity is a central aspect which is not disturbed through the presentation of scientific content. The storytelling approaches are tailored to the respective influencer and their style. The language and structure of the videos are simple and comprehensible, scientific arguments focus on selected aspects and are tied to examples from everyday life. The comments by the users support these findings with the majority of comments addressing the three aspects of our analysis being positive. However, evidence for an in-depth engagement with the scientific contents could not be found in the comments. The stated goal of the campaign to reach educationally disadvantaged young people was only reached to a limited degree according to the assessment of the producers. Additionally, the views of two of the three videos remained below the average for the respective channel. Taken together this indicates that cooperation with influencers might not be an “all-purpose tool” guaranteeing success for science communication.

Applied Energy, 258 ISSN:0306-2619 ISSN:1872-9118