@article{AlbertiGonzalezPaijmansetal.2018, author = {Alberti, Federica and Gonzalez, Javier and Paijmans, Johanna L. A. and Basler, Nikolas and Preick, Michaela and Henneberger, Kirstin and Trinks, Alexandra and Rabeder, Gernot and Conard, Nicholas J. and Muenzel, Susanne C. and Joger, Ulrich and Fritsch, Guido and Hildebrandt, Thomas and Hofreiter, Michael and Barlow, Axel}, title = {Optimized DNA sampling of ancient bones using Computed Tomography scans}, series = {Molecular ecology resources}, volume = {18}, journal = {Molecular ecology resources}, number = {6}, publisher = {Wiley}, address = {Hoboken}, issn = {1755-098X}, doi = {10.1111/1755-0998.12911}, pages = {1196 -- 1208}, year = {2018}, abstract = {The prevalence of contaminant microbial DNA in ancient bone samples represents the principal limiting factor for palaeogenomic studies, as it may comprise more than 99\% of DNA molecules obtained. Efforts to exclude or reduce this contaminant fraction have been numerous but also variable in their success. Here, we present a simple but highly effective method to increase the relative proportion of endogenous molecules obtained from ancient bones. Using computed tomography (CT) scanning, we identify the densest region of a bone as optimal for sampling. This approach accurately identifies the densest internal regions of petrous bones, which are known to be a source of high-purity ancient DNA. For ancient long bones, CT scans reveal a high-density outermost layer, which has been routinely removed and discarded prior to DNA extraction. For almost all long bones investigated, we find that targeted sampling of this outermost layer provides an increase in endogenous DNA content over that obtained from softer, trabecular bone. This targeted sampling can produce as much as 50-fold increase in the proportion of endogenous DNA, providing a directly proportional reduction in sequencing costs for shotgun sequencing experiments. The observed increases in endogenous DNA proportion are not associated with any reduction in absolute endogenous molecule recovery. Although sampling the outermost layer can result in higher levels of human contamination, some bones were found to have more contamination associated with the internal bone structures. Our method is highly consistent, reproducible and applicable across a wide range of bone types, ages and species. We predict that this discovery will greatly extend the potential to study ancient populations and species in the genomics era.}, language = {en} } @article{SorgnerFritschKritikos2017, author = {Sorgner, Alina and Fritsch, Michael and Kritikos, Alexander}, title = {Do entrepreneurs really earn less?}, series = {Small business economics : an international journal}, volume = {49}, journal = {Small business economics : an international journal}, publisher = {Springer}, address = {Dordrecht}, issn = {0921-898X}, doi = {10.1007/s11187-017-9874-6}, pages = {251 -- 272}, year = {2017}, abstract = {Based on large representative German household survey data, we compare incomes of the self-employed with those of paid employees. We find that the entrepreneurial income gap is largest for those holding a tertiary degree, but in two directions: positive for employers (self-employed with further employees) and negative for solo entrepreneurs. Entrepreneurs holding a tertiary degree also face the greatest income variation. However, some solo self-employed earn more than their employed counterparts, in particular those with a university entrance degree as the highest level of education.}, language = {en} } @article{KononFritschKritikos2018, author = {Konon, Alexander and Fritsch, Michael and Kritikos, Alexander}, title = {Business cycles and start-ups across industries}, series = {Journal of Business Venturing Insights}, volume = {33}, journal = {Journal of Business Venturing Insights}, number = {6}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0883-9026}, doi = {10.1016/j.jbusvent.2018.04.006}, pages = {742 -- 761}, year = {2018}, abstract = {We analyze whether start-up rates in different industries systematically change with business cycle variables. Using a unique data set at the industry level, we mostly find correlations that are consistent with counter-cyclical influences of the business cycle on entries in both innovative and non-innovative industries. Entries into the large-scale industries, including the innovative part of manufacturing, are only influenced by changes in the cyclical component of unemployment, while entries into small-scale industries, like knowledge intensive services, are mostly influenced by changes in the cyclical component of GDP. Thus, our analysis suggests that favorable conditions in terms of high GDP might not be germane for start-ups. Given that both innovative and non-innovative businesses react counter-cyclically in 'regular' recessions, business formation may have a stabilizing effect on the economy.}, language = {en} } @article{FritschKritikosSorgner2015, author = {Fritsch, Michael and Kritikos, Alexander and Sorgner, Alina}, title = {Why did self-employment increase so strongly in Germany?}, series = {Entrepreneurship and regional development}, volume = {27}, journal = {Entrepreneurship and regional development}, number = {5-6}, publisher = {Routledge, Taylor \& Francis Group}, address = {Abingdon}, issn = {0898-5626}, doi = {10.1080/08985626.2015.1048310}, pages = {307 -- 333}, year = {2015}, abstract = {Germany experienced a unique rise in the level of self-employment in the first two decades following unification. Applying the nonlinear Blinder-Oaxaca decomposition technique, we find that the main factors driving these changes in the overall level of self-employment are demographic developments, the shift towards service sector employment and a larger share of population holding a tertiary degree. While these factors explain most of the development in self-employment with employees and the overall level of self-employment in West Germany, their explanatory power is much lower for the stronger increase in solo self-employment and in self-employment in former socialist East Germany.}, language = {en} } @article{FritschKritikosPijnenburg2015, author = {Fritsch, Michael and Kritikos, Alexander and Pijnenburg, Katharina}, title = {Business cycles, unemployment and entrepreneurial entry-evidence from Germany}, series = {International entrepreneurship and management journal}, volume = {11}, journal = {International entrepreneurship and management journal}, number = {2}, publisher = {Springer}, address = {New York}, issn = {1554-7191}, doi = {10.1007/s11365-014-0326-3}, pages = {267 -- 286}, year = {2015}, abstract = {We investigate whether people are more willing to become self-employed during boom periods or during recessions and to what extent business cycles and unemployment levels influence entries into entrepreneurship. Our analysis for Germany reveals that there is a positive relationship between unemployment rates and start-up activities. Moreover, new business formation is higher during recessions than in boom periods, implying that it is counter-cyclical. When disentangling periods of low and high unemployment we find that the effect of unemployment on new business formation is only statistically significant if the level of unemployment is below the trend, indicating a "low unemployment retain effect".}, language = {en} } @article{FritschSprengelEvansetal.2021, author = {Fritsch, Tobias and Sprengel, Maximilian and Evans, Alexander and Farahbod-Sternahl, Lena and Saliwan-Neumann, Romeo and Hofmann, Michael and Bruno, Giovanni}, title = {On the determination of residual stresses in additively manufactured lattice structures}, series = {Journal of applied crystallography / International Union of Crystallography}, volume = {54}, journal = {Journal of applied crystallography / International Union of Crystallography}, publisher = {Munksgaard}, address = {Copenhagen}, issn = {1600-5767}, doi = {10.1107/S1600576720015344}, pages = {228 -- 236}, year = {2021}, abstract = {The determination of residual stresses becomes more complicated with increasing complexity of the structures investigated. Additive manufacturing techniques generally allow the production of 'lattice structures' without any additional manufacturing step. These lattice structures consist of thin struts and are thus susceptible to internal stress-induced distortion and even cracks. In most cases, internal stresses remain locked in the structures as residual stress. The determination of the residual stress in lattice structures through nondestructive neutron diffraction is described in this work. It is shown how two difficulties can be overcome: (a) the correct alignment of the lattice structures within the neutron beam and (b) the correct determination of the residual stress field in a representative part of the structure. The magnitude and the direction of residual stress are discussed. The residual stress in the strut was found to be uniaxial and to follow the orientation of the strut, while the residual stress in the knots was more hydrostatic. Additionally, it is shown that strain measurements in at least seven independent directions are necessary for the estimation of the principal stress directions. The measurement directions should be chosen according to the sample geometry and an informed choice on the possible strain field. If the most prominent direction is not measured, the error in the calculated stress magnitude increases considerably.}, language = {en} }