TY - JOUR A1 - Caliendo, Marco A1 - Goethner, Maximilian A1 - Weißenberger, Martin T1 - Entrepreneurial persistence beyond survival: Measurement and determinants JF - Journal of Small Business Management N2 - Entrepreneurial persistence is demonstrated by an entrepreneur’s continued positive maintenance of entrepreneurial motivation and constantly renewed active engagement in a new business venture despite counterforces or enticing alternatives. It thus is a crucial factor for entrepreneurs when pursuing and exploiting their business opportunities and in realizing potential economic gains and benefits. Using rich data on a representative sample of German business founders, we investigated the determinants of entrepreneurial persistence. Next to observed survival, we also constructed a hybrid persistence measure capturing the motivational dimension of persistence. We analyzed the influence of individual-level (human capital and personality) and business-related characteristics on both measures as well as their relative importance. We found that the two indicators emphasize different aspects of persistence. For the survival indicator, the predictive power was concentrated in business characteristics and human capital, while for hybrid persistence the dominant factors were business characteristics and personality. Finally, we showed that results were heterogeneous across subgroups. In particular, formerly unemployed founders did not differ in survival chances, but they were more likely to lack a high psychological commitment to their business ventures. KW - entrepreneurship KW - startups KW - persistence KW - survival Y1 - 2019 VL - 58 IS - 3 PB - Taylor & Francis CY - London ER - TY - JOUR A1 - Naliboff, John B. A1 - Glerum, Anne A1 - Brune, Sascha A1 - Péron-Pinvidic, G. A1 - Wrona, Thilo T1 - Development of 3-D rift heterogeneity through fault network evolution JF - Geophysical Research Letters N2 - Observations of rift and rifted margin architecture suggest that significant spatial and temporal structural heterogeneity develops during the multiphase evolution of continental rifting. Inheritance is often invoked to explain this heterogeneity, such as preexisting anisotropies in rock composition, rheology, and deformation. Here, we use high-resolution 3-D thermal-mechanical numerical models of continental extension to demonstrate that rift-parallel heterogeneity may develop solely through fault network evolution during the transition from distributed to localized deformation. In our models, the initial phase of distributed normal faulting is seeded through randomized initial strength perturbations in an otherwise laterally homogeneous lithosphere extending at a constant rate. Continued extension localizes deformation onto lithosphere-scale faults, which are laterally offset by tens of km and discontinuous along-strike. These results demonstrate that rift- and margin-parallel heterogeneity of large-scale fault patterns may in-part be a natural byproduct of fault network coalescence. KW - magma-poor KW - continental lithosphere KW - extension KW - insights KW - margins KW - architecture KW - systems KW - models KW - sea KW - reactivation Y1 - 2019 VL - 47 IS - 13 PB - John Wiley & Sons, Inc. CY - New Jersey ER - TY - JOUR A1 - Zimmermann, Malte A1 - De Veaugh-Geiss, Joseph P. A1 - Tönnis, Swantje A1 - Onea, Edgar T1 - (Non-)exhaustivity in focus partitioning across languages JF - Approaches to Hungarian N2 - We present novel experimental evidence on the availability and the status of exhaustivity inferences with focus partitioning in German, English, and Hungarian. Results suggest that German and English focus-background clefts and Hungarian focus share important properties, (É. Kiss 1998, 1999; Szabolcsi 1994; Percus 1997; Onea & Beaver 2009). Those constructions are anaphoric devices triggering an existence presupposition. EXH-inferences are not obligatory in such constructions in English, German, or Hungarian, against some previous literature (Percus 1997; Büring & Križ 2013; É. Kiss 1998), but in line with pragmatic analyses of EXH-inferences in clefts (Horn 1981, 2016; Pollard & Yasavul 2016). The cross-linguistic differences in the distribution of EXH-inferences are attributed to properties of the Hungarian number marking system. KW - clefts KW - definite pseudoclefts KW - Hungarian focus KW - exhaustivity KW - experimental evidence KW - semantics-pragmatics interface Y1 - 2020 VL - 16 PB - John Benjamins CY - Amsterdam ER - TY - JOUR A1 - Zwickel, Theresa A1 - Kahl, Sandra M. A1 - Rychlik, Michael A1 - Müller, Marina E. H. T1 - Chemotaxonomy of Mycotoxigenic Small-Spored Alternaria Fungi BT - Do Multitoxin Mixtures Act as an Indicator for Species Differentiation? JF - Frontiers in microbiology N2 - Necrotrophic as well as saprophytic small-spored Altemaria (A.) species are annually responsible for major losses of agricultural products, such as cereal crops, associated with the contamination of food and feedstuff with potential health-endangering Altemaria toxins. Knowledge of the metabolic capabilities of different species-groups to form mycotoxins is of importance for a reliable risk assessment. 93 Altemaria strains belonging to the four species groups Alternaria tenuissima, A. arborescens, A. altemata, and A. infectoria were isolated from winter wheat kernels harvested from fields in Germany and Russia and incubated under equal conditions. Chemical analysis by means of an HPLC-MS/MS multi-Alternaria-toxin-method showed that 95% of all strains were able to form at least one of the targeted 17 non-host specific Altemaria toxins. Simultaneous production of up to 15 (modified) Altemaria toxins by members of the A. tenuissima, A. arborescens, A. altemata species-groups and up to seven toxins by A. infectoria strains was demonstrated. Overall tenuazonic acid was the most extensively formed mycotoxin followed by alternariol and alternariol mono methylether, whereas altertoxin I was the most frequently detected toxin. Sulfoconjugated modifications of alternariol, alternariol mono methylether, altenuisol and altenuene were frequently determined. Unknown perylene quinone derivatives were additionally detected. Strains of the species-group A. infectoria could be segregated from strains of the other three species-groups due to significantly lower toxin levels and the specific production of infectopyrone. Apart from infectopyrone, alterperylenol was also frequently produced by 95% of the A. infectoria strains. Neither by the concentration nor by the composition of the targeted Altemaria toxins a differentiation between the species-groups A. altemata, A. tenuissima and A. arborescens was possible. KW - small-spored Alternaria fungi KW - Alternaria species-groups KW - Alternaria mycotoxins KW - chemotaxonomy KW - secondary metabolite profiling KW - LC-MS/MS KW - wheat KW - perylene quinone derivatives Y1 - 2018 U6 - https://doi.org/10.3389/fmicb.2018.01368 SN - 1664-302X VL - 9 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Heger, Tina A1 - Nikles, Gabriele A1 - Jacobs, Brooke S. T1 - Differentiation in native as well as introduced ranges BT - germination reflects mean and variance in cover of surrounding vegetation JF - AoB PLANTS N2 - Germination, a crucial phase in the life cycle of a plant, can be significantly influenced by competition and facilitation. The aim of this study was to test whether differences in cover of surrounding vegetation can lead to population differentiation in germination behaviour of an annual grassland species, and if so, whether such a differentiation can be found in the native as well as in the introduced range. We used maternal progeny of Erodium cicutarium previously propagated under uniform conditions that had been collected in multiple populations in the native and two introduced ranges, in populations representing extremes in terms of mean and variability of the cover of surrounding vegetation. In the first experiment, we tested the effect of germination temperature and mean cover at the source site on germination, and found interlinked effects of these factors. In seeds from one of the introduced ranges (California), we found indication for a 2-fold dormancy, hindering germination at high temperatures even if physical dormancy was broken and water was available. This behaviour was less strong in high cover populations, indicating cross-generational facilitating effects of dense vegetation. In the second experiment, we tested whether spatial variation in cover of surrounding vegetation has an effect on the proportion of dormant seeds. Contrary to our expectations, we found that across source regions, high variance in cover was associated with higher proportions of seeds germinating directly after storage. In all three regions, germination seemed to match the local environment in terms of climate and vegetation cover. We suggest that this is due to a combined effect of introduction of preadapted genotypes and local evolutionary processes. KW - Bet-hedging KW - competition KW - eco-evolutionary experience KW - facilitation KW - genetic adaptation KW - physical and physiological dormancy KW - preadaptation Y1 - 2018 U6 - https://doi.org/10.1093/aobpla/ply009 SN - 2041-2851 VL - 10 IS - 1 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Hesse, Julia A1 - Klier, Dennis Tobias A1 - Sgarzi, Massimo A1 - Nsubuga, Anne A1 - Bauer, Christoph A1 - Grenzer, Joerg A1 - Hübner, Rene A1 - Wislicenus, Marcus A1 - Joshi, Tanmaya A1 - Kumke, Michael Uwe A1 - Stephan, Holger T1 - Rapid Synthesis of Sub-10nm Hexagonal NaYF4-Based Upconverting Nanoparticles using Therminol((R))66 JF - ChemistryOpen : including thesis treasury N2 - We report a simple one-pot method for the rapid preparation of sub-10nm pure hexagonal (-phase) NaYF4-based upconverting nanoparticles (UCNPs). Using Therminol((R))66 as a co-solvent, monodisperse UCNPs could be obtained in unusually short reaction times. By varying the reaction time and reaction temperature, it was possible to control precisely the particle size and crystalline phase of the UCNPs. The upconversion (UC) luminescence properties of the nanocrystals were tuned by varying the concentrations of the dopants (Nd3+ and Yb3+ sensitizer ions and Er3+ activator ions). The size and phase-purity of the as-synthesized core and core-shell nanocrystals were assessed by using complementary transmission electron microscopy, dynamic light scattering, X-ray diffraction, and small-angle X-ray scattering studies. In-depth photophysical evaluation of the UCNPs was pursued by using steady-state and time-resolved luminescence spectroscopy. An enhancement in the UC intensity was observed if the nanocrystals, doped with optimized concentrations of lanthanide sensitizer/activator ions, were further coated with an inert/active shell. This was attributed to the suppression of surface-related luminescence quenching effects. KW - core-shell materials KW - lanthanides KW - nanostructures KW - photoluminescence KW - upconversion Y1 - 2018 U6 - https://doi.org/10.1002/open.201700186 SN - 2191-1363 VL - 7 IS - 2 SP - 159 EP - 168 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Käch, Heidi A1 - Mathe-Hubert, Hugo A1 - Dennis, Alice B. A1 - Vorburger, Christoph T1 - Rapid evolution of symbiont-mediated resistance compromises biological control of aphids by parasitoids JF - Evolutionary applications N2 - There is growing interest in biological control as a sustainable and environmentally friendly way to control pest insects. Aphids are among the most detrimental agricultural pests worldwide, and parasitoid wasps are frequently employed for their control. The use of asexual parasitoids may improve the effectiveness of biological control because only females kill hosts and because asexual populations have a higher growth rate than sexuals. However, asexuals may have a reduced capacity to track evolutionary change in their host populations. We used a factorial experiment to compare the ability of sexual and asexual populations of the parasitoid Lysiphlebus fabarum to control caged populations of black bean aphids (Aphis fabae) of high and low clonal diversity. The aphids came from a natural population, and one-third of the aphid clones harbored Hamiltonella defensa, a heritable bacterial endosymbiont that increases resistance to parasitoids. We followed aphid and parasitoid population dynamics for 3months but found no evidence that the reproductive mode of parasitoids affected their effectiveness as biocontrol agents, independent of host clonal diversity. Parasitoids failed to control aphids in most cases, because their introduction resulted in strong selection for clones protected by H.defensa. The increasingly resistant aphid populations escaped control by parasitoids, and we even observed parasitoid extinctions in many cages. The rapid evolution of symbiont-conferred resistance in turn imposed selection on parasitoids. In cages where asexual parasitoids persisted until the end of the experiment, they became dominated by a single genotype able to overcome the protection provided by H.defensa. Thus, there was evidence for parasitoid counteradaptation, but it was generally too slow for parasitoids to regain control over aphid populations. It appears that when pest aphids possess defensive symbionts, the presence of parasitoid genotypes able to overcome symbiont-conferred resistance is more important for biocontrol success than their reproductive mode. KW - aphids KW - Aphis fabae KW - biological control KW - defensive symbiosis KW - Hamiltonella defensa KW - Lysiphlebus fabarum KW - parasitoid KW - resistance Y1 - 2018 U6 - https://doi.org/10.1111/eva.12532 SN - 1752-4571 VL - 11 IS - 2 SP - 220 EP - 230 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Shi, Jun A1 - Joshi, Jasmin Radha A1 - Tielboerger, Katja A1 - Verhoeven, Koen J. F. A1 - Macel, Mirka T1 - Costs and benefits of admixture between foreign genotypes and local populations in the field JF - Ecology and evolution N2 - Admixture is the hybridization between populations within one species. It can increase plant fitness and population viability by alleviating inbreeding depression and increasing genetic diversity. However, populations are often adapted to their local environments and admixture with distant populations could break down local adaptation by diluting the locally adapted genomes. Thus, admixed genotypes might be selected against and be outcompeted by locally adapted genotypes in the local environments. To investigate the costs and benefits of admixture, we compared the performance of admixed and within-population F1 and F2 generations of the European plant Lythrum salicaria in a reciprocal transplant experiment at three European field sites over a 2-year period. Despite strong differences between site and plant populations for most of the measured traits, including herbivory, we found limited evidence for local adaptation. The effects of admixture depended on experimental site and plant population, and were positive for some traits. Plant growth and fruit production of some populations increased in admixed offspring and this was strongest with larger parental distances. These effects were only detected in two of our three sites. Our results show that, in the absence of local adaptation, admixture may boost plant performance, and that this is particularly apparent in stressful environments. We suggest that admixture between foreign and local genotypes can potentially be considered in nature conservation to restore populations and/or increase population viability, especially in small inbred or maladapted populations. KW - heterosis KW - inbreeding depression KW - local adaptation KW - Lythrum salicaria KW - outbreeding depression Y1 - 2018 U6 - https://doi.org/10.1002/ece3.3946 SN - 2045-7758 VL - 8 IS - 7 SP - 3675 EP - 3684 PB - Wiley CY - Hoboken ER - TY - GEN A1 - Frank, Mario A1 - Kreitz, Christoph T1 - A theorem prover for scientific and educational purposes T2 - Electronic proceedings in theoretical computer science N2 - We present a prototype of an integrated reasoning environment for educational purposes. The presented tool is a fragment of a proof assistant and automated theorem prover. We describe the existing and planned functionality of the theorem prover and especially the functionality of the educational fragment. This currently supports working with terms of the untyped lambda calculus and addresses both undergraduate students and researchers. We show how the tool can be used to support the students' understanding of functional programming and discuss general problems related to the process of building theorem proving software that aims at supporting both research and education. Y1 - 2018 U6 - https://doi.org/10.4204/EPTCS.267.4 SN - 2075-2180 IS - 267 SP - 59 EP - 69 PB - Open Publishing Association CY - Sydney ER - TY - JOUR A1 - Totz, Sonja Juliana A1 - Eliseev, Alexey V. A1 - Petri, Stefan A1 - Flechsig, Michael A1 - Caesar, Levke A1 - Petoukhov, Vladimir A1 - Coumou, Dim T1 - The dynamical core of the Aeolus 1.0 statistical-dynamical atmosphere model BT - validation and parameter optimization JF - Geoscientific model development : an interactive open access journal of the European Geosciences Union N2 - Here, we present novel equations for the large-scale zonal-mean wind as well as those for planetary waves. Together with synoptic parameterization (as presented by Coumou et al., 2011), these form the mathematical description of the dynamical core of Aeolus 1.0. The regions of high azonal wind velocities (planetary waves) are accurately captured for all validation experiments. The zonal-mean zonal wind and the integrated lower troposphere mass flux show good results in particular in the Northern Hemisphere. In the Southern Hemisphere, the model tends to produce too-weak zonal-mean zonal winds and a too-narrow Hadley circulation. We discuss possible reasons for these model biases as well as planned future model improvements and applications. Y1 - 2018 U6 - https://doi.org/10.5194/gmd-11-665-2018 SN - 1991-959X SN - 1991-9603 VL - 11 IS - 2 SP - 665 EP - 679 PB - Copernicus CY - Göttingen ER -