Stability of Terrestrial Planets in the Habitable Zone of Gl 777 A, HD 72659, Gl 614, 47 Uma and HD 4208

We have undertaken a thorough dynamical investigation of five extrasolar planetary systems using extensive numerical experiments. The systems Gl 777 A, HD 72659, Gl 614, 47 Uma and HD 4208 were examined concerning the question of whether they could host terrestrial like planets in their habitable zones (=HZ). First we investigated the mean motion resonances between fictitious terrestrial planets and the existing gas giants in these five extrasolar systems. Then a fine grid of initial conditions for a potential terrestrial planet within the HZ was chosen for each system, from which the stability of orbits was then assessed by direct integrations over a time interval of 1 million years. The computations were carried out using a Lie-series integration method with an adaptive step size control. This integration method achieves machine precision accuracy in a highly efficient and robust way, requiring no special adjustments when the orbits have large eccentricities. The stability of orbits was examined with a determination of the Renyi entropy, estimated from recurrence plots, and with a more straight forward method based on the maximum eccentricity achieved by the planet over the 1 million year integration. Additionally, the eccentricity is an indication of the habitability of a terrestrial planet in the HZ; any value of e>0.2 produces a significant temperature difference on a planet's surface between apoapse and periapse. The results for possible stable orbits for terrestrial planets in habitable zones for the five systems are summarized as follows: for Gl 777 A nearly the entire HZ is stable, for 47 Uma, HD 72659 and HD 4208 terrestrial planets can survive for a sufficiently long time, while for Gl 614 our results exclude terrestrial planets moving in stable orbits within the HZ.Comment: 14 pages, 18 figures submitted to A&

Habitable Zones in the Universe

Habitability varies dramatically with location and time in the universe. This was recognized centuries ago, but it was only in the last few decades that astronomers began to systematize the study of habitability. The introduction of the concept of the habitable zone was key to progress in this area. The habitable zone concept was first applied to the space around a star, now called the Circumstellar Habitable Zone. Recently, other, vastly broader, habitable zones have been proposed. We review the historical development of the concept of habitable zones and the present state of the research. We also suggest ways to make progress on each of the habitable zones and to unify them into a single concept encompassing the entire universe.Comment: 71 pages, 3 figures, 1 table; to be published in Origins of Life and Evolution of Biospheres; table slightly revise

Global Entrepreneurship Monitor Unternehmensgründungen im weltweiten Vergleich: Länderbericht Deutschland 2018/19

Der Länderbericht Deutschland im Rahmen des Global Entrepreneurship Monitors gibt seit 1999 jährlich Auskunft über die Gründungsaktivitäten, -motive und -einstellungen in der deutschen Bevölkerung. Er wird vom deutschen Team des GEM unter Leitung von Prof. Rolf Sternberg herausgegeben.The country report of Germany of the Global Entrepreneurship Monitor (GEM) provides a yearly analysis of entrepreneurship activities, motives, and attitudes in the German population, since 1999. It is published by the German team of the GEM under the lead of Prof. Rolf Sternberg

Improving the selectivity of photocatalytic NOx abatement through improved O2 reduction pathways using Ti0.909W0.091O2Nx semiconductor nanoparticles : from characterisation to photocatalytic performance

Peer reviewedPostprin

Global Entrepreneurship Monitor Unternehmensgründungen im weltweiten Vergleich: Länderbericht Deutschland 2019/20

Der Länderbericht Deutschland im Rahmen des Global Entrepreneurship Monitors gibt seit 1999 jährlich Auskunft über die Gründungsaktivitäten, -motive und -einstellungen in der deutschen Bevölkerung. Er wird vom deutschen Team des GEM unter Leitung von Prof. Rolf Sternberg herausgegeben.The country report of Germany of the Global Entrepreneurship Monitor (GEM) provides a yearly analysis of entrepreneurship activities, motives, and attitudes in the German population, since 1999. It is published by the German team of the GEM under the lead of Prof. Rolf Sternberg

Global Entrepreneurship Monitor Unternehmensgründungen im weltweiten Vergleich: Länderbericht Deutschland 2017/18

Der Länderbericht Deutschland im Rahmen des Global Entrepreneurship Monitors gibt seit 1999 jährlich Auskunft über die Gründungsaktivitäten, -motive und -einstellungen in der deutschen Bevölkerung. Er wird vom deutschen Team des GEM unter Leitung von Prof. Rolf Sternberg herausgegeben.The country report of Germany of the Global Entrepreneurship Monitor (GEM) provides a yearly analysis of entrepreneurship activities, motives, and attitudes in the German population, since 1999. It is published by the German team of the GEM under the lead of Prof. Rolf Sternberg

Carbon dioxide and climate impulse response functions for the computation of greenhouse gas metrics: a multi-model analysis

The responses of carbon dioxide (CO2) and other climate variables to an emission pulse of CO2 into the atmosphere are often used to compute the Global Warming Potential (GWP) and Global Temperature change Potential (GTP), to characterize the response timescales of Earth System models, and to build reduced-form models. In this carbon cycle-climate model intercomparison project, which spans the full model hierarchy, we quantify responses to emission pulses of different magnitudes injected under different conditions. The CO2 response shows the known rapid decline in the first few decades followed by a millennium-scale tail. For a 100 Gt-C emission pulse added to a constant CO2 concentration of 389 ppm, 25 ± 9% is still found in the atmosphere after 1000 yr; the ocean has absorbed 59 ± 12% and the land the remainder (16 ± 14%). The response in global mean surface air temperature is an increase by 0.20 ± 0.12 °C within the first twenty years; thereafter and until year 1000, temperature decreases only slightly, whereas ocean heat content and sea level continue to rise. Our best estimate for the Absolute Global Warming Potential, given by the time-integrated response in CO2 at year 100 multiplied by its radiative efficiency, is 92.5 × 10−15 yr W m−2 per kg-CO2. This value very likely (5 to 95% confidence) lies within the range of (68 to 117) × 10−15 yr W m−2 per kg-CO2. Estimates for time-integrated response in CO2 published in the IPCC First, Second, and Fourth Assessment and our multi-model best estimate all agree within 15% during the first 100 yr. The integrated CO2 response, normalized by the pulse size, is lower for pre-industrial conditions, compared to present day, and lower for smaller pulses than larger pulses. In contrast, the response in temperature, sea level and ocean heat content is less sensitive to these choices. Although, choices in pulse size, background concentration, and model lead to uncertainties, the most important and subjective choice to determine AGWP of CO2 and GWP is the time horizon

Evolution and the regulation of environmental variables

The idea that the biota can regulate the abiotic components of their environment to levels suitable for life has attracted criticism from neo-Darwinian theorists but is still a viable hypothesis. Here we present a model, similar to Daisyworld [1] but more general, which allows for a more extensive study of the compatibility of biotic regulation with evolutionary theory. Results obtained highlight the importance of constraints on the evolutionary process for the emergence of regulation, and set the scene for more comprehensive future study

Photocatalytic NOx abatement: Why the selectivity matters

Titanium dioxide photocatalysis offers an excellent way to oxidise NOx to nitrate and thus reduce air pollution. However, unmodified titanium dioxide also releases a significant amount of the toxic intermediate nitrogen dioxide in the process, a problem that is rarely discussed in previous literature. Herein, we highlight this issue by presenting systematic data on the activity and selectivity of a number of commercial titania powders. The photocatalytic performance of a previously developed W/N-codoped titanium dioxide is also reported which, for the first time, offers a way to eliminate this problem as it exhibits an exceptionally high selectivity towards nitrate. The selectivity appears to be solely dependent on the tungsten content, a concentration of 4.8 at.% is sufficient to induce a very high selectivity. Furthermore, the high selectivity could also be replicated by a W/N-codoped sample derived from the industrial sulphate synthetic process. The increased selectivity comes at the expense of absolute activity, which is lower than in the reference titania samples. This raises the question of how to properly evaluate NOx abatement photocatalysts when there are two factors to consider, activity and selectivity. To resolve this, we propose to define a new figure of merit for the evaluation of NOx abatement photocatalysts by distilling total NOx removal and selectivity into one value, the DeNOx index. It is derived by assigning a toxicity value to both NO and NO2 and then expressing the change in total toxicity rather than the concentration change of the individual nitrogen oxides