When are static superhedging strategies optimal?

This paper deals with the superhedging of derivatives and with the corresponding price bounds. A static superhedge results in trivial and fully nonparametric price bounds, which can be tightened if there exists a cheaper superhedge in the class of dynamic trading strategies. We focus on European path-independent claims and show under which conditions such an improvement is possible. For a stochastic volatility model with unbounded volatility, we show that a static superhedge is always optimal, and that, additionally, there may be infinitely many dynamic superhedges with the same initial capital. The trivial price bounds are thus the tightest ones. In a model with stochastic jumps or non-negative stochastic interest rates either a static or a dynamic superhedge is optimal. Finally, in a model with unbounded short rates, only a static superhedge is possible

The response of foodborne pathogens to osmotic and desiccation stresses in the food chain

peer-reviewedIn combination with other strategies, hyperosmolarity and desiccation are frequently used by the food processing industry as a means to prevent bacterial proliferation, and particularly that of foodborne pathogens, in food products. However, it is increasingly observed that bacteria, including human pathogens, encode mechanisms to survive and withstand these stresses. This review provides an overview of the mechanisms employed by Salmonella spp., Shiga toxin producing E. coli, Cronobacter spp., Listeria monocytogenes and Campylobacter spp. to tolerate osmotic and desiccation stresses and identifies gaps in knowledge which need to be addressed to ensure the safety of low water activity and desiccated food products

TRY plant trait database – enhanced coverage and open access

Plant traits - the morphological, anatomical, physiological, biochemical and phenological characteristics of plants - determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits - almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives

Minority shareholders in close corporations : ways and limits of protection in their dilemma of no control and no ready market

Thesis: M.S., Massachusetts Institute of Technology, Sloan School of Management, 1976Includes bibliographical references.by Angelika M. Ch. Esser.M.S.M.S. Massachusetts Institute of Technology, Sloan School of Managemen

Usability Tests mobiler Websites : Beeinflusst die Verwendung von Laborsmartphones statt benutzereigener Geräte das Testergebnis?

Die weltweit hohe Anzahl an mobilen Endgeräten rückt die Usability von mobilen Websites immer stärker in den Focus. Eine „gute“ Usability einer mobilen Website wirkt sich unmittelbar auf das Verhalten der Nutzer aus. Mobile Usability-Tests lassen Rückschlüsse auf die Nutzerfreundlichkeit einer mobilen Website zu und decken Optimierungspotenzial auf. Um möglichst präzise Untersuchungserkenntnisse zu erzielen, sollte die Wahl des Equipments für den Test nicht unbedacht getroffen werden. Diese Arbeit untersucht, ob die Verwendung von Laborsmartphones statt benutzereigenen Smartphones das Testergebnis beeinflusst. Dies wird anhand von zwei mobilen Usability-Tests, mit einer Versuchs- und einer Kontrollgruppe, überprüft. Die Versuchsgruppe nutzt für den Test ein Laborsmartphone mit einem Android Betriebssystem. Dieses wird ihnen von der Technischen Hochschule Köln zur Verfügung gestellt. Die Kontrollgruppe nutzt für den mobilen Usability-Test ihr benutzereignes Smartphone mit einem Android Betriebssystem. Die Testergebnisse beider Gruppen werden gegenübergestellt und ausgewertet. Die Auswertung besteht aus einem umfassenden Analyseteil, welcher die verschiedenen Fehlerarten, die innerhalb beider Gruppen auftreten, miteinander vergleicht. Das Ziel der Analyse ist es, einen möglichen Einfluss auf das Testergebnis durch die Nutzung von Laborsmatphones aufzudecken