Quantitative Graded Semantics and Spectra of Behavioural Metrics

Behavioural metrics provide a quantitative refinement of classical two-valued behavioural equivalences on systems with quantitative data, such as metric or probabilistic transition systems. In analogy to the classical linear-time/branching-time spectrum of two-valued behavioural equivalences on transition systems, behavioural metrics come in various degrees of granularity, depending on the observer's ability to interact with the system. Graded monads have been shown to provide a unifying framework for spectra of behavioural equivalences. Here, we transfer this principle to spectra of behavioural metrics, working at a coalgebraic level of generality, that is, parametrically in the system type. In the ensuing development of quantitative graded semantics, we discuss presentations of graded monads on the category of metric spaces in terms of graded quantitative equational theories. Moreover, we obtain a canonical generic notion of invariant real-valued modal logic, and provide criteria for such logics to be expressive in the sense that logical distance coincides with the respective behavioural distance. We thus recover recent expressiveness results for coalgebraic branching-time metrics and for trace distance in metric transition systems; moreover, we obtain a new expressiveness result for trace semantics of fuzzy transition systems. We also provide a number of salient negative results. In particular, we show that trace distance on probabilistic metric transition systems does not admit a characteristic real-valued modal logic at all

Kooperationen zwischen etabliertem Mittelstand und Start-ups

Die vorliegende Studie untersucht anhand von Experteninterviews die Motive, Formen sowie Herausforderungen und Erfolgsfaktoren von Kooperationen zwischen etablierten Mittelständlern und Start-ups. Während sich Start-ups durch die Kooperation den Zugang zu einem großen Netzwerk sowie branchenspezifisches Know-how erhoffen, motiviert Mittelständler der Zugang zu neuen Technologien und hochqualifizierten Fachkräften. Die Wahl der konkreten Kooperationsform leitet sich aus den jeweiligen Zielen ab. Dabei unterscheiden sich Kooperationen hinsichtlich ihrer Intensität sowie in ihrer juristischen Ausgestaltung. Damit beide Seiten erfolgreich zusammenkommen, sollte sich das Start-up bereits im Vorfeld mit den Bedürfnissen des potenziellen Kooperationspartners auseinandersetzen. Etablierte Mittelständler sollten hingegen ihr stark ausgeprägtes Sicherheitsdenken ablegen und eine innovationsfreundliche Kultur im Unternehmen etablieren. Insgesamt bietet die Zusammenarbeit für beide Seiten ein großes Potenzial. Dabei profitiert das Start-up von einer effizienten Zusammenarbeit durch kurze Entscheidungswege in den inhabergeführten Unternehmen und der etablierte Mittelstand von einer höheren Wettbewerbsfähigkeit durch die Innovationsimpulse der Start-ups.The study examines motives, forms, challenges and success factors of cooperations between start-ups and established Mittelstand firms. While start-ups are motivated by network access and industry-specific knowledge, established firms seek access to new technologies and to highly qualified specialists. The chosen cooperation design derives from the partners' objectives and differs in terms of intensity and legal structure. To initiate a successful cooperation, established firms have to be open-minded and need to establish a risk- and innovation-friendly culture within their organization. Start-ups should already understand the specific needs of their potential partner in advance. Overall these cooperations offer great potential for both sides. Start-ups benefit from the short decision-making processes in owner-managed firms and established firms from higher competitiveness through the innovation impulses they receive from start-ups

Expressive Quantale-valued Logics for Coalgebras: an Adjunction-based Approach

We address the task of deriving fixpoint equations from modal logics characterizing behavioural equivalences and metrics (summarized under the term conformances). We rely on earlier work that obtains Hennessy-Milner theorems as corollaries to a fixpoint preservation property along Galois connections between suitable lattices. We instantiate this to the setting of coalgebras, in which we spell out the compatibility property ensuring that we can derive a behaviour function whose greatest fixpoint coincides with the logical conformance. We then concentrate on the linear-time case, for which we study coalgebras based on the machine functor living in Eilenberg-Moore categories, a scenario for which we obtain a particularly simple logic and fixpoint equation. The theory is instantiated to concrete examples, both in the branching-time case (bisimilarity and behavioural metrics) and in the linear-time case (trace equivalences and trace distances)

Effects of Hypoxia and Acidosis on Cardiac Electrophysiology and Hemodynamics. Is NHE-Inhibition by Cariporide Still Advantageous?

Hypoxia often leads to severe cardiac malfunctions. It is assumed that intracellular calcium overload is -inter alia- responsible for left ventricular (LV) deterioration. Inhibition of the sodium-proton exchanger (NHE), which finally inhibits/slows calcium overload, may ameliorate cardiac function. Our aim was to evaluate cariporide, an inhibitor of NHE1 in a Langendorff-perfused heart model. To discriminate a potentially different impact of extracellular acidosis and hypoxia we examined 48 Chinchilla Bastard rabbits divided into 8 experimental groups: control group (pH = 7.4, O2 = 100%) without or with cariporide (1µM), acidosis group (pH = 7.0, O2 = 100%) without or with cariporide (1µM), hypoxia group (pH = 7.4, O2 = 40%) without or with cariporide (1µM) and hypoxia+acidosis group (pH = 7.0, O2 = 40%) without or with cariporide (1µM). Hearts were subjected to acidotic/hypoxic conditions for 90 min followed by 60 min of reperfusion. Hypoxia and hypoxia+acidosis led to a severe deterioration of LV function with a decrease in LV pressure by about 70% and an increase of end-diastolic pressure from 6.7 ± 0.6 to 36.8 ± 5.4 (hypoxia) or from 7.0 ± 0.2 to 18.6 ± 4.1 (hypoxia+acidosis). Moreover, maximum contraction velocity decreased from about 1,800 mmHg/s to 600 mmHg/s during hypoxia ± acidosis and maximum relaxation velocity deteriorated from −1,500 mmHg/s to about −600 mmHg/s. During reperfusion hearts subjected to hypoxia+acidosis recovered faster than hearts subjected to hypoxia alone, reaching control levels after 5 min of reperfusion. Electrophysiologic analysis revealed an 1.2 fold increase in both dispersion of activation-recovery interval and in total activation time in the hypoxia ± acidosis group. Cariporide application significantly improved LV hemodynamics and electrophysiology in the hypoxia group but not in the group subjected to hypoxia+acidosis. Immunohistologic analysis of cardiac specimen revealed a significant increase of factors involved in hypoxia/reperfusion injury like nitrotyrosine and poly-ADP-ribose as well as apoptosis-inducing factors like AIF or cleaved-caspase 3 in LV after hypoxia ± acidosis. ATP was reduced by hypoxia but not by acidosis. Again, cariporide mitigated these processes only in the hypoxia alone group, but not in the group with additional acidosis. Acidosis without hypoxia only marginally disturbed LV function and electrophysiology, and was not affected by cariporide. Thus, our study demonstrated that several detrimental effects of hypoxia were mitigated or abrogated by acidosis and that NHE-inhibition improved only hypoxia-induced cardiac dysfunction

ROAST: Robust Asynchronous Schnorr Threshold Signatures

Bitcoin and other cryptocurrencies have recently introduced support for Schnorr signatures whose cleaner algebraic structure, as compared to ECDSA, allows for simpler and more practical constructions of highly demanded "-of-" threshold signatures. However, existing Schnorr threshold signature schemes still fall short of the needs of real-world applications due to their assumption that the network is synchronous and due to their lack of robustness, i.e., the guarantee that honest signers are able to obtain a valid signature even in the presence of other malicious signers who try to disrupt the protocol. This hinders the adoption of threshold signatures in the cryptocurrency ecosystem, e.g., in second-layer protocols built on top of cryptocurrencies. In this work, we propose ROAST, a simple wrapper that turns a given threshold signature scheme into a scheme with a robust and asynchronous signing protocol, as long as the underlying signing protocol is semi-interactive (i.e., has one preprocessing round and one actual signing round), provides identifiable aborts, and is unforgeable under concurrent signing sessions. When applied to the state-of-the-art Schnorr threshold signature scheme FROST, which fulfills these requirements, we obtain a simple, efficient, and highly practical Schnorr threshold signature scheme

Evaluation bestehender gesetzlicher Mindestlohnregelungen - Branche: Abfallwirtschaft (Aktenzeichen: Zb 1-04812-3/10f)

Das Bundesministerium für Arbeit und Soziales (BMAS) gab Ende 2010 für jede Branche mit einem allgemeinverbindlichen Mindestlohn Studien zu dessen Wirkungen auf Beschäftigung, Arbeitnehmerschutz und Wettbewerb in Auftrag. Die Studie zu den Wirkungen eines Mindestlohns in der Abfallwirtschaft entstand am ZEW. Der hiermit vorgelegte Endbericht beinhaltet die folgenden Berichtsteile. In Abschnitt 2 werden zunächst die theoretisch erwarteten Effekte auf die Zielgrößen sowie die verwendete Methodik dargestellt. Abschnitt 3 geht detaillierter auf die Umsetzung des Evaluationsauftrages im Hinblick auf die Datenlage, die Operationalisierung der Zielgrößen sowie die Auswahl potenzieller Kontrollbranchen ein. In Abschnitt 4 werden die institutionellen Rahmenbedingungen des Arbeits- und Gütermarktes der Abfallwirtschaft sowie der potenziellen Kontrollbranchen nachvollzogen. Im Anschluss daran erfolgt in Abschnitt 5 die Erläuterung der der Evaluation zugrundeliegenden Datenbasis. Hier wird neben der amtlichen Statistik, dem Mannheimer Unternehmenspanel vor allem das Befragungsinstrument und die Stichprobenauswahl der telefonischen Unternehmensbefragung vorgestellt. 25 Abschnitt 6 schließlich erstellt das Branchenbild, das zur Bildung der zentralen Hypothesen sowie als Entscheidungsgrundlage für die Auswahl der Kontrollbranche dient. In diesem Abschnitt geben quantitative Analysen auf Basis der amtlichen Statistik, dem Mannheimer Unternehmenspanel sowie der eigens erhobenen Befragungsdaten Aufschluss über Strukturmerkmale und die Entwicklung der Branche, vor allem auch im Vergleich zu den möglichen Kontrollbranchen. Der zweite Berichtsteil widmet sich in Abschnitt 7den kausalen Wirkungsanalysen auf Basis der erhobenen Unternehmensdaten. Hierzu wird zunächst das Ausmaß der Betroffenheit der Abfallwirtschaft von der Mindestlohneinführung analysiert sowie mögliche Strategien der Umgehung der Mindestlohnvorschriften nachvollzogen. Danach erfolgt die Analyse der kausalen Effekte der Mindestlohneinführung auf die Zielgrößen Beschäftigung, Arbeitnehmerschutz und Wettbewerb. Im Rahmen dieser Analyse soll vor allem auch die Bedeutung des Messfehlers der retrospektiv erhobenen Informationen für die Ergebnisse untersucht werden. Abschnitt 8 liefert eine Zusammenfassung und Schlussfolgerungen zu den Wirkungsanalysen. Abschnitt 9 schließt den Bericht mit einem Ausblick auf potenzielle zukünftige Evaluationsvorhaben ab

Efficient Unlinkable Sanitizable Signatures from Signatures with Re-Randomizable Keys

In a sanitizable signature scheme the signer allows a designated third party, called the sanitizer, to modify certain parts of the message and adapt the signature accordingly. Ateniese et al. (ESORICS 2005) introduced this primitive and proposed five security properties which were formalized by Brzuska et al.~(PKC 2009). Subsequently, Brzuska et al. (PKC 2010) suggested an additional security notion, called unlinkability which says that one cannot link sanitized message-signature pairs of the same document. Moreover, the authors gave a generic construction based on group signatures that have a certain structure. However, the special structure required from the group signature scheme only allows for inefficient instantiations. Here, we present the first efficient instantiation of unlinkable sanitizable signatures. Our construction is based on a novel type of signature schemes with re-randomizable keys. Intuitively, this property allows to re-randomize both the signing and the verification key separately but consistently. This allows us to sign the message with a re-randomized key and to prove in zero-knowledge that the derived key originates from either the signer or the sanitizer. We instantiate this generic idea with Schnorr signatures and efficient $\Sigma$-protocols, which we convert into non-interactive zero-knowledge proofs via the Fiat-Shamir transformation. Our construction is at least one order of magnitude faster than instantiating the generic scheme of Brzuska et al. with the most efficient group signature schemes