Observations of extremely thin clouds in the tropical tropopause region by a ship based lidar.

During the cruises ANT XVII/4 (Punta Arenas Bremerhaven, 2000) and ANT XX1/1 (Bremerhaven - Cape Town, 2003) continuous measurements of clouds and aerosol have been performed by a Mobile Aerosol Raman Lidar (MARL). This system measures backscatter of light at 355 nm and 532 nm and is able to detect even extremely thin layers of particles in the atmosphere. Cloud base and top height, depolarisation optical depth and color index can be deduced from this data. During the Polarstern cruises very thin layers of ice particles have been observed frequently in the tropical tropopause layer (TTL). Cases of persistent cloud layers with an optical depth below 10^-3 are reported. Based on the data of radiosondes which were launched daily aboard the vessel, the conditions at which these type of clouds form are analysed. It is shown, that these clouds form in a layer below the cold point, but above the lapse rate tropopause. The relation between cloud occurrence and temperature and wind in the TTL as well as state of the QBO are discussed

On the Geographic and Cultural Determinants of Bankruptcy

This paper examines the role of geography and culture in explaining bankruptcy. We adopt survival analyses to model the bankruptcy risk of a firm, allowing for time-varying covariates. Based on a large sample from all major sectors of the Swiss economy, we find the following results: (i) The geographic location of a firm, which is characterized using a core-periphery approach, has a significant impact on its bankruptcy risk; (ii) Variables proxying for the cultural environment of a firm have significant explanatory power; (iii) The results of the previous literature on the standard determinants of bankruptcy are confirmed.bankruptcy, geography, culture, exit

Merge or Fail? The Determinants of Mergers and Bankruptcies in Switzerland, 1995-2000

This paper examines the determinants of mergers and bankruptcies, using firm level data from the Swiss Business Census and the Dun & Bradstreet exit database for Switzerland (1995-2000). Employing duration analysis, we find considerable differences in the determinants of mergers and bankruptcies, in particular with respect to firm size, location and the impact of macroeconomic conditions. Our results support the notion that mergers are often undertaken to seize growth opportunities.merger, bankruptcy, failure, survival, exit

Resilience of power grids and other supply networks: structural stability, cascading failures and optimal topologies

The consequences of the climate crisis are already present and can be expected to become more severe in the future. To mitigate long-term consequences, a major part of the world's countries has committed to limit the temperature rise via the Paris Agreement in the year 2015. To achieve this goal, the energy production needs to decarbonise, which results in fundamental changes in many societal aspects. In particular, the electrical power production is shifting from fossil fuels to renewable energy sources to limit greenhouse gas emissions. The electrical power transmission grid plays a crucial role in this transformation. Notably, the storage and long-distance transport of electrical power becomes increasingly important, since variable renewable energy sources (VRES) are subjected to external factors such as weather conditions and their power production is therefore regionally and temporally diverse. As a result, the transmission grid experiences higher loadings and bottlenecks appear. In a highly-loaded grid, a single transmission line or generator outage can trigger overloads on other components via flow rerouting. These may in turn trigger additional rerouting and overloads, until, finally, parts of the grid become disconnected. Such cascading failures can result in large-scale power blackouts, which bear enormous risks, as almost all infrastructures and economic activities depend on a reliable supply of electric power. Thus, it is essential to understand how networks react to local failures, how flow is rerouted after failures and how cascades emerge and spread in different power transmission grids to ensure a stable power grid operation. In this thesis, I examine how the network topology shapes the resilience of power grids and other supply networks. First, I analyse how flow is rerouted after the failure of a single or a few links and derive mathematically rigorous results on the decay of flow changes with different network-based distance measures. Furthermore, I demonstrate that the impact of single link failures follows a universal statistics throughout different topologies and introduce a stochastic model for cascading failures that incorporates crucial aspects of flow redistribution. Based on this improved understanding of link failures, I propose network modifications that attenuate or completely suppress the impact of link failures in parts of the network and thereby significantly reduce the risk of cascading failures. In a next step, I compare the topological characteristics of different kinds of supply networks to analyse how the trade-off between efficiency and resilience determines the structure of optimal supply networks. Finally, I examine what shapes the risk of incurring large scale cascading failures in a realistic power system model to assess the effects of the energy transition in Europe

Topological theory of resilience and failure spreading in flow networks

Link failures in supply networks can have catastrophic consequences that can lead to a complete collapse of the network. Strategies to prevent failure spreading are thus heavily sought after. Here, we make use of a spanning tree formulation of link failures in linear flow networks to analyse topological structures that prevent failures spreading. In particular, we exploit a result obtained for resistor networks based on the \textit{Matrix tree theorem} to analyse failure spreading after link failures in power grids. Using a spanning tree formulation of link failures, we analyse three strategies based on the network topology that allow to reduce the impact of single link failures. All our strategies do not reduce the grid's ability to transport flow or do in fact improve it - in contrast to traditional containment strategies based on lowering network connectivity. Our results also explain why certain connectivity features completely suppress any failure spreading as reported in recent publications.Comment: 9 pages, 5 figures

Energy transfer from retinal to amino acids — a time-resolved study of the ultraviolet emission of bacteriorhodopsin

Two-step excitation of retinal in bacteriorhodopsin by visible light is followed by an energy transfer to amino acids that is seen as fluorescent emission around 350 nm. The fluorescence spectrum obtained after two-step excitation (2 × 527 nm) differs from the fluorescence spectrum obtained after one-step ultraviolet excitation (263.5 nm) by a strongly quenched emission with a fluorescence lifetime of 10 ± 5 ps and a smaller spectral width. The two-step absorption process presumably selects tryptophan residues which strongly couple to the retinal chromophore

The geographic determinants of bankruptcy: evidence from Switzerland

This paper examines the geographic determinants of firm bankruptcy. We employ hazard rate models to study the bankruptcy risk of a firm, allowing for time-varying covariates. Based on a large sample from all geographic areas and the major sectors of the Swiss economy, we find the following main results: (1) Bankruptcy rates tend to be lower in the central municipalities of agglomerations; (2) bankruptcy rates are lower in regions with favorable business conditions (where corporate taxes and unemployment are low and public investment is high); (3) private taxes and public spending at the local level have little impact on bankruptcy rate

Integration ausländischer Jugendlicher durch MBSE : eine kritische Bestandsaufnahme zu Beginn der bundesweiten Evaluation der Maßnahmen zur Berufsvorbereitung und sozialen Eingliederung junger Ausländer

"Die Diskussion über die Zukunft von Maßnahmen zur Berufsvorbereitung und sozialen Eingliederung junger Ausländer (MBSE) wurde bislang erschwert durch das Fehlen umfassender Wirkungsuntersuchungen. Ausgangspunkt einer Evaluation von MBSE muß eine Bestandsaufnahme der bisher vorliegenden Daten, Erkenntnisse und Erfahrungen über diese Maßnahmen sein, die im folgenden Beitrag versucht wird. Zunächst wird durch die Diskussion des Integrationsbegriffs ein theoretischer Bezugsrahmen entwickelt, an dem Ziele, Inhalte und Erfolg von MBSE gemessen werden können. Auf eine detaillierte Darstellung der Konzeption von MBSE wurde an dieser Stelle verzichtet. Die Bestandsaufnahme führt im Ergebnis zu mehr offenen Fragen als Antworten. Sie beschreibt allerdings erstmals in detaillierter Form den STand der Erkenntnisse über MBSE, an dem Themen und Strategien der im Kursjahrgang 1982/83 laufenden MBSE-Wirkungsuntersuchung ansetzen können." (Autorenreferat)ausländische Jugendliche, MBSE, Berufsvorbereitung, soziale Integration, Wirkungsforschung

Early picosecond events in the photo cycle of Bacteriorhodopsin

The primary processes of the photochemical cycle of light-adapted bacteriorhodopsin (BR) were studied by various experimental techniques with a time resolution of 5 × 10-13 s. The following results were obtained. (a) After optical excitation the first excited singlet state S1 of bacteriorhodopsin is observed via its fluorescence and absorption properties. The population of the excited singlet state decays with a lifetime τ1 of ~0.7 ps (430 ± 50 fs) (52). (b) With the same time constant the first ground-state intermediate J builds up. Its absorption spectrum is red-shifted relative to the spectrum of BR by ~30 nm. (c) The second photoproduct K, which appears with a time constant of τ2 = 5 ps shows a red-shift of 20 nm, relative to the peak of BR. Its absorption remains constant for the observation time of 300 ps. (d) Upon suspending bacteriorhodopsin in D2O and deuterating the retinal Schiff base at its nitrogen (lysine 216), the same photoproducts J and K are observed. The relaxation time constants τ1 and τ2 remain unchanged upon deuteration within the experimental accuracy of 20%