1,357 research outputs found
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
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 (1”M), acidosis group (pH = 7.0, O2 = 100%) without or with cariporide
(1”M), hypoxia group (pH = 7.4, O2 = 40%) without or with cariporide (1”M) and
hypoxia+acidosis group (pH = 7.0, O2 = 40%) without or with cariporide (1”M).
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
â1,500 mmHg/s to about â600 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
The CM SAF SSM/I-based total column water vapour climate data record: methods and evaluation against re-analyses and satellite
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
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 -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
Augmented Reality for Massive Particle Distribution
Understanding the behavior of aerosol particles remains a key concern especially during the current corona pandemic times. In this paper, we present a method for visualizing the distribution of aerosol particles in augmented reality (AR) using the Microsoft Hololens device. We use this technology to obtain better spatial perception of particles in the real world which are invisible to the naked eye. As a case study, we show the flow field of exhaled aerosols with and without wearing a mask. To do this, we first measure the particle flow under laboratory conditions. Then we trace a certain amount of exhaled particles. Using the particle system component of the Unity game engine, our AR application also takes each particle's 3D position into consideration. Furthermore, 3 different particle visualization approaches are evaluated to develop the ability to visualize the maximum number of particles on Microsoft HoloLens without compromising on visual quality. Finally, we were able to show virtual particles in the real world. Without mask they propagate forward and with mask they ascend. With an optimized implementation, we achieved a simultaneous display of nearly 80,000 moving particles at an average rate of 35 frames per second
Household electricity consumersâ incentive to choose dynamic pricing under different taxation schemes:Electricity consumers' incentive to choose dynamic pricing
Healthy and sustainable cities: An Urban Public Health Approach â The Institute for Urban Public Health (II)
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