41 research outputs found
The first major incision of the Swiss Deckenschotter landscape
The Swiss Deckenschotter ("cover gravels”) is the oldest Quaternary units in the northern Swiss Alpine Foreland. They are a succession of glaciofluvial gravel layers intercalated with glacial and/or overbank deposits. This lithostratigraphic sequence is called Deckenschotter because it "covers” Molasse or Mesozoic bedrock and forms mesa-type hill-tops. Deckenschotter occurs both within and beyond the extent of the Last Glacial Maximum glaciers. The Swiss Deckenschotter consist of two sub-units: Höhere (Higher) and Tiefere (Lower) Deckenschotter. Although the Höhere Deckenschotter sub-unit (HDS) is topographically higher than the Tiefere Deckenschotter, it is older. The only available age for the Swiss Deckenschotter is 2.5-1.8Ma based on mammal remains found in HDS at the Irchel site. In this study, we present an exposure age for the topographically lowest HDS, calculated from a cosmogenic 10Be depth-profile. Our results show that the first phase of the Deckenschotter glaciations in the Swiss Alps terminated at least 1,020 - 120 + 80 ka ago, which is indicated by a significant fluvial incision. This line of evidence seems to be close to synchronous with the beginning of the Mid-Pleistocene Revolution, when the frequency of the glacial-interglacial cyclicity changed from 41 to 100ka and the amplitude from low to high, between marine isotope stages 23 and 22
Interval Change-Point Detection for Runtime Probabilistic Model Checking
Recent probabilistic model checking techniques can verify reliability and performance properties of software systems affected by parametric uncertainty. This involves modelling the system behaviour using interval Markov chains, i.e., Markov models with transition probabilities or rates specified as intervals. These intervals can be updated continually using Bayesian estimators with imprecise priors, enabling the verification of the system properties of interest at runtime. However, Bayesian estimators are slow to react to sudden changes in the actual value of the estimated parameters, yielding inaccurate intervals and leading to poor verification results after such changes. To address this limitation, we introduce an efficient interval change-point detection method, and we integrate it with a state-of-the-art Bayesian estimator with imprecise priors. Our experimental results show that the resulting end-to-end Bayesian approach to change-point detection and estimation of interval Markov chain parameters handles effectively a wide range of sudden changes in parameter values, and supports runtime probabilistic model checking under parametric uncertainty
Analysing RoboChart with probabilities
Robotic systems have applications in many real-life scenarios, ranging from household cleaning to critical operations. RoboChart is a graphical language for describing robotic controllers designed specifically for autonomous and mobile robots, providing architectural constructs to identify the requirements for a robotic platform. It also provides a formal semantics in CSP. RoboChart has a probabilistic operator (P) but no associated probabilistic CSP semantics. When (P) is used, currently a non-deterministic choice (Π) is used as semantics; this is a conservative semantics but it does not allow the analysis of stochastic properties. In this paper we define the semantics of the operator in terms of the probabilistic CSP operator ⊞. We also show how this augmented CSP semantics for RoboChart can be translated into the PRISM probabilistic language to be able to check stochastic properties
Lessons from a one-year hospital-based surveillance of acute respiratory infections in Berlin- comparing case definitions to monitor influenza
<p>Abstract</p> <p>Background</p> <p>Surveillance of severe acute respiratory infections (SARI) in sentinel hospitals is recommended to estimate the burden of severe influenza-cases. Therefore, we monitored patients admitted with respiratory infections (RI) in 9 Berlin hospitals from 7.12.2009 to 12.12.2010 according to different case definitions (CD) and determined the proportion of cases with influenza A(H1N1)pdm09 (pH1N1). We compared the sensitivity and specificity of CD for capturing pandemic pH1N1 cases.</p> <p>Methods</p> <p>We established an RI-surveillance restricted to adults aged ≤ 65 years within the framework of a pH1N1 vaccine effectiveness study, which required active identification of RI-cases. The hospital information-system was screened daily for newly admitted RI-patients. Nasopharyngeal swabs from consenting patients were tested by PCR for influenza-virus subtypes. Four clinical CD were compared in terms of capturing pH1N1-positives among hospitalized RI-patients by applying sensitivity and specificity analyses. The broadest case definition (CD1) was used for inclusion of RI-cases; the narrowest case definition (CD4) was identical to the SARI case definition recommended by ECDC/WHO.</p> <p>Results</p> <p>Over the study period, we identified 1,025 RI-cases, of which 283 (28%) met the ECDC/WHO SARI case definition. The percentage of SARI-cases among internal medicine admissions decreased from 3.2% (calendar-week 50-2009) to 0.2% (week 25-2010). Of 354 patients tested by PCR, 20 (6%) were pH1N1-positive. Two case definitions narrower than CD1 but -in contrast to SARI- not requiring shortness of breath yielded the largest areas under the Receiver-Operator-Curve. Heterogeneity of proportions of patients admitted with RI between hospitals was significant.</p> <p>Conclusions</p> <p>Comprehensive surveillance of RI cases was feasible in a network of community hospitals. In most settings, several hospitals should be included to ensure representativeness. Although misclassification resulting from failure to obtain symptoms in the hospital information-system cannot be ruled out, a high proportion of hospitalized PCR-positive pH1N1-patients (45%) did not fulfil the SARI case-definition that included shortness of breath or difficulty breathing. Thus, to assess influenza-related disease burden in hospitals, broader, alternative case definitions should be considered.</p
Sediment burial dating using terrestrial cosmogenic nuclides
Die Methode der Bestimmung des Überdeckungsalters mit Hilfe von in situ produzierten terrestrischen kosmogenen Nukliden stellt ein verhältnismäßig neues Datierverfahren dar. Es ermöglicht die Altersbestimmung von Sedimenten und damit die Quantifizierung von geomorphologischen Prozessen, wie Erosion, Akkumulation und Flusseintiefung. Das Verfahren bedient sich dabei des Zerfalls von zuvor in situ produzierten kosmogenen Nukliden und kann auf sedimentäre Ablagerungen wie Höhlenfüllungen, Schwemmfächer, Flussterrassen, Deltaschüttungen und Dünen angewendet werden. Durch die Verwendung des erprobten 10Be/26Al Nuklidpaares erlaubt die Methode die Bestimmung eines numerischen Alters von quarzführendem Material über einen Zeitbereich von ~100 ka bis 5 Ma. In diesem Zeitabschnitt ist datierfähiges Material für andere Methoden oftmals nicht oder nur unzureichend vorhanden. Viele Studien konnten bereits die erfolgreiche Anwendung von in situ produzierten kosmogenen Nukliden in den verschiedensten wissenschaftlichen Bereichen, darunter zum Beispiel in der (Quartär)Geologie, Geomorphologie und Paläoanthropologie, belegen. Dennoch können die zur Zeit nur ungenügend genau bestimmten physikalischen Größen, wie zum Beispiel die Nuklidhalbwertszeiten oder die tiefenabhängigen Nuklidproduktionsraten zu vergleichsweise großen Unsicherheiten führen. Trotz dieser Nachteile stellt die Methode eine vielversprechende Möglichkeit der numerischen Altersbestimmung dar.researc
Richardson-Gaudin models: the hyperbolic family
We show that the hyperbolic family of Richardson-Gaudin models could describe p-wave superfluids in two dimensional lattices. The analysis of the exact solution reveals an exotic phase diagram with a third order quantum phase transition. Moreover, we propose a separable integrable pairing Hamiltonian within the same family that could be useful to describe exactly superconductivity in heavy nuclei.We acknowledge support from a Marie Curie Action of the European Community Project No. 220335 and the Spanish Ministry for Science and Innovation Project No. FIS2009-07277Peer Reviewe