Numerical studies on the link between radioisotopic signatures on Earth and the formation of the Local Bubble. I. 60Fe transport to the solar system by turbulent mixing of ejecta from nearby supernovae into a locally homogeneous ISM

The discovery of radionuclides like 60Fe with half-lives of million years in deep-sea crusts and sediments offers the unique possibility to date and locate nearby supernovae. We want to quantitatively establish that the 60Fe enhancement is the result of several supernovae which are also responsible for the formation of the Local Bubble, our Galactic habitat. We performed three-dimensional hydrodynamic adaptive mesh refinement simulations (with resolutions down to subparsec scale) of the Local Bubble and the neighbouring Loop I superbubble in different homogeneous, self-gravitating environments. For setting up the Local and Loop I superbubble, we took into account the time sequence and locations of the generating core-collapse supernova explosions, which were derived from the mass spectrum of the perished members of certain stellar moving groups. The release of 60Fe and its subsequent turbulent mixing process inside the superbubble cavities was followed via passive scalars, where the yields of the decaying radioisotope were adjusted according to recent stellar evolution calculations. The models are able to reproduce both the timing and the intensity of the 60Fe excess observed with rather high precision, provided that the external density does not exceed 0.3 cm-3 on average. Thus the two best-fit models presented here were obtained with background media mimicking the classical warm ionised and warm neutral medium. We also found that 60Fe (which is condensed onto dust grains) can be delivered to Earth via two physical mechanisms: either through individual fast-paced supernova blast waves, which cross the Earth's orbit sometimes even twice as a result of reflection from the Local Bubble's outer shell, or, alternatively, through the supershell of the Local Bubble itself, injecting the 60Fe content of all previous supernovae at once, but over a longer time range.Comment: 14 pages, 7 figures, accepted for publication in A&

The Internalisation of External Costs in Transport: From the Polluter Pays to the Cheapest Cost Avoider Principle

The European Commission mandated the consulting firm CE Delft to develop a framework for the internalisation of external costs and to devise a number of potential internalisation scenarios for further analysis. The results of their preliminary research are published in a CE discussion paper, and the Commission is now formulating draft legislative proposals which will be subjected to a consultation of stakeholders.The present report offers a critical assessment of the above mentioned CE study, provides a theoretical examination of the relative strengths and weaknesses of the polluter pays principle and the cheapest cost avoider principle in relation to the problems arising in the road transport sector, demonstrates how the cheapest cost avoider principle can be applied in practice by providing examples of external costs in road transport, and puts forward recommendations for the appropriate principles that should guide the Commission's further activities in this area.Cheapest Cost Avoider, Externalities, Transport,

Structural Stability: On the Prerequisites of Nonviolent Conflict Management

The concept of “structural stability” has been gaining prominence in development policy circles. In the EU’s and the OECD Development Assistance Committee’s (OECD DAC) understanding, it describes the ability of societies to handle intra-societal conflict without resorting to violence. This study investigates the preconditions of structural stability and tests their mutual interconnections. Seven dimensions are analyzed: (1) long-term economic growth, (2) environmental security, (3) social equality, (4) governmental effectiveness, (5) democracy, (6) rule of law, and (7) inclusion of identity groups. The postulated mutual enhancement of the seven dimensions is plausible but cannot be proven. The most significant positive relationship appears between “democracy” and “rule of law,” respectively, on the one hand and the dependent variable “violence/ human security” on the other hand. This points to the usefulness of the political concept of structural stability to promote development policy agendas in this area at least. Applications that reach beyond these initial findings will, however, require further research.Structural stability, violence, human security, development aid, conflict management, prerequisites of nonviolence

Pancreatic beta-cell failure in the pathogenesis of type 2 diabetes

Contains fulltext : 142146.pdf (publisher's version ) (Open Access)2 p

Development of iron catalysts for hydrogenation and polymerization

Im Rahmen der vorliegenden Arbeit wurden eine Reihe von neuen, einfach herzustellenden Eisenhydrierkatalysatoren eingeführt. Verschiedenste Aspekte dieser neuen Hydrierkatalysatoren wie Eisenquelle, Aktivierungsmittel, Substrate und Effizienz wurden untersucht. Ein ligandfreier Katalysator, hergestellt aus einer Eisen(II)chlorid-Suspension aktiviert mit Diisobutylaluminiumhydrid (DIBAH), weist die grösste Aktivität auf. Alle Arten von C-C-Doppelbindungen wie mono-, di- oder trisubstituierte, acyclische oder cyclische, isolierte oder konjugierte Doppelbindungen sowie Alkine werden von diesem Katalysator unter milden Bedingungen (3 bar Wasserstoffdruck, Raumtemperatur) in kurzer Zeit quantitativ hydriert. Sowohl TON wie auch TOF steigen mit zunehmender Menge Aktivierungsmittel, bis bei einem Verhältnis FeCl2/DIBAH 1:8 mit TON = 1900 und TOF = 125 h-1 der effizienteste Katalysator erhalten wird. Mit Ausnahme von Ethern und Aminen verhindert die Verwendung eines starken Reduktionsmittels zur Aktivierung die Hydrierung von funktionalisierten Olefinen. In Abwesenheit von Wasserstoff H2 konnte katalytische Aktivität für Alkinpolymerisierungs- und Alkincyclotrimerisierungsreaktionen nachgewiesen werden. Ferner kann dieser Katalysator zur Polymerisierung von Acetylen eingesetzt werden. Bei dem Versuch, die in diesen Fällen katalytisch aktive Spezies zu identifizieren fand man einen homogenen Präkatalysator, welcher erstaunliche Effizienz aufweist (TOF > 340 h-1). Abgeleitet von der angenommenen Struktur dieses Präkatalysators wurden eine Reihe von Allylbenzylether synthetisiert, welche als Liganden getestet wurden. Die entsprechenden Katalysatoren, erhalten durch Aktivierung mit Alkyllithiumreagenzien, weisen Alkenhydrier- und Ethylenoligomerisierungsaktivität auf.In the scope of this work, a series of new, easy to prepare iron hydrogenation catalysts have been introduced. Different aspects of this new hydrogenation catalysts such as iron source, activation reagent, substrates and efficiency were investigated. A ligand-free catalyst, prepared from an iron(II) chloride suspension activated with diisobutylaluminiumhydride (DIBAH), showed the highest activity. With this catalyst all kind of C-C double bonds like mono-, di- or trisubstituted, acyclic or cyclic, isolated or conjugated double bonds as well as alkynes were hydrogenated quantitatively under mild conditions (3 bar hydrogen pressure, room temperature) within short time. Both TON and TOF scale with the added amount of activation reagent up to a 1:8 FeCl2/DIBAH ratio furnishing the most active catalyst with TON = 1900 and TOF = 125 in this case. With the exception of ethers and amines, the use of strong reducing agents as activators prevents the hydrogenation of functionalized olefins. In absence of hydrogen H2, catalytic activity for alkyne polymerization and cyclotrimerization was observed. Furthermore, this catalyst is able to promote the polymerization of acetylene. Attempts to identify the catalytic active species led to the development of a homogeneous precatalyst showing an amazing efficiency (TOF > 340 h-1). Derived from the assumed structure of this precatalyst, a series of allylbenzylethers were synthesized and tested as ligands. The corresponding catalysts, obtained by activation with alkyllithium reagents, display alkene hydrogenation and ethylene oligomerization activity