Diagnosis, synthesis and analysis of probabilistic models

This dissertation considers three important aspects of model checking Markov models:\ud diagnosis — generating counterexamples, synthesis — providing valid parameter\ud values and analysis — verifying linear real-time properties. The three aspects are relatively\ud independent while all contribute to developing new theory and algorithms in the\ud research field of probabilistic model checking.\ud We start by introducing a formal definition of counterexamples in the setting of\ud probabilistic model checking. We transform the problem of finding informative counterexamples\ud to shortest path problems. A framework is explored and provided for\ud generating such counterexamples. We then investigate a more compact representation\ud of counterexamples by regular expressions. Heuristic based algorithms are applied to\ud obtain short regular expression counterexamples. In the end of this part, we extend\ud the definition and counterexample generation algorithms to various combinations of\ud probabilistic models and logics.\ud We move on to the problem of synthesizing values for parametric continuous-time\ud Markov chains (pCTMCs) wrt. time-bounded reachability specifications. The rates\ud in the pCTMCs are expressed by polynomials over reals with parameters and the\ud main question is to find all the parameter values (forming a synthesis region) with\ud which the specification is satisfied. We first present a symbolic approach where the\ud intersection points are computed by solving polynomial equations and then connected\ud to approximate the synthesis region. An alternative non-symbolic approach based on\ud interval arithmetic is investigated, where pCTMCs are instantiated. The error bound,\ud time complexity as well as some experimental results have been provided, followed by\ud a detailed comparison of the two approaches.\ud In the last part, we focus on verifying CTMCs against linear real-time properties\ud specified by deterministic timed automata (DTAs). The model checking problem aims\ud at computing the probability of the set of paths in CTMC C that can be accepted\ud by DTA A, denoted PathsC(A). We consider DTAs with reachability (finite, DTA♦)\ud and Muller (infinite, DTAω) acceptance conditions, respectively. It is shown that\ud PathsC(A) is measurable and computing its probability for DTA♦ can be reduced to\ud computing the reachability probability in a piecewise deterministic Markov process\ud (PDP). The reachability probability is characterized as the least solution of a system\ud of integral equations and is shown to be approximated by solving a system of PDEs.\ud Furthermore, we show that the special case of single-clock DTA♦ can be simplified to\ud solving a system of linear equations. We also deal with DTAω specifications, where the\ud problem is proven to be reducible to the reachability problem as in the DTA♦ case

QuantUM: Quantitative Safety Analysis of UML Models

When developing a safety-critical system it is essential to obtain an assessment of different design alternatives. In particular, an early safety assessment of the architectural design of a system is desirable. In spite of the plethora of available formal quantitative analysis methods it is still difficult for software and system architects to integrate these techniques into their every day work. This is mainly due to the lack of methods that can be directly applied to architecture level models, for instance given as UML diagrams. Also, it is necessary that the description methods used do not require a profound knowledge of formal methods. Our approach bridges this gap and improves the integration of quantitative safety analysis methods into the development process. All inputs of the analysis are specified at the level of a UML model. This model is then automatically translated into the analysis model, and the results of the analysis are consequently represented on the level of the UML model. Thus the analysis model and the formal methods used during the analysis are hidden from the user. We illustrate the usefulness of our approach using an industrial strength case study.Comment: In Proceedings QAPL 2011, arXiv:1107.074

Medically Unexplained Oropharyngeal Dysphagia at the University Hospital ENT Outpatient Clinic for Dysphagia: A Cross-Sectional Cohort Study

Medically unexplained oropharyngeal dysphagia (MUNOD) is a rare condition. It presents without demonstrable abnormalities in the anatomy of the upper aero-digestive tract and/or swallowing physiology. This study investigates whether MUNOD is related to affective or other psychiatric conditions. The study included patients with dysphagic complaints who had no detectible structural or physiological abnormalities upon swallowing examination. Patients with any underlying disease or disorder that could explain the oropharyngeal dysphagia were excluded. All patients underwent a standardized examination protocol, with FEES examination, the Hospital Anxiety and Depression Scale (HADS), and the Dysphagia Severity Scale (DSS). Two blinded judges scored five different FEES variables. None of the 14 patients included in this study showed any structural or physiological abnormalities during FEES examination. However, the majority did show abnormal piecemeal deglutition, which could be a symptom of MUNOD. Six patients (42.8%) had clinically relevant symptoms of anxiety and/or depression. The DSS scores did not differ significantly between patients with and without affective symptoms. Affective symptoms are common in patients with MUNOD, and their psychiatric conditions could possibly be related to their swallowing problems

Introducing the DizzyQuest: an app-based diary for vestibular disorders

BACKGROUND Most questionnaires currently used for assessing symptomatology of vestibular disorders are retrospective, inducing recall bias and lowering ecological validity. An app-based diary, administered multiple times in daily life, could increase the accuracy and ecological validity of symptom measurement. The objective of this study was to introduce a new experience sampling method (ESM) based vestibular diary app (DizzyQuest), evaluate response rates, and to provide examples of DizzyQuest outcome measures which can be used in future research. METHODS Sixty-three patients diagnosed with a vestibular disorder were included. The DizzyQuest consisted of four questionnaires. The morning- and evening-questionnaires were administered once each day, the within-day-questionnaire 10 times a day using a semi-random time schedule, and the attack questionnaire could be completed after the occurrence of a vertigo or dizziness attack. Data were collected for 4~weeks. Response rates and loss-to-follow-up were determined. Reported symptoms in the within-day-questionnaire were compared within and between patients and subgroups of patients with different vestibular disorders. RESULTS Fifty-one patients completed the study period. Average response rates were significantly higher than the desired response rate of \textgreater 50% (p \textless 0.001). The attack-questionnaire was used 159 times. A variety of neuro-otological symptoms and different disease profiles were demonstrated between patients and subgroups of patients with different vestibular disorders. CONCLUSION The DizzyQuest is able to capture vestibular symptoms within their psychosocial context in daily life, with little recall bias and high ecological validity. The DizzyQuest reached the desired response rates and showed different disease profiles between subgroups of patients with different vestibular disorders. This is the first time ESM was used to assess daily symptoms and quality of life in vestibular disorders, showing that it might be a useful tool in this population

Menge, Verteilung und Zusammensetzung organischer Bodensubstanz auf Oberflächen von Makroporen in Bt-Horizonten

In strukturierten Unterböden können die Oberflächen von Makroporen (Aggregatränder und Bioporen) in Folge von präferenzieller Verlagerung und Stabilisierungsprozessen mit organischer Bodensubstanz (OBS) angereichert sein. Menge, Verteilung und Zusammensetzung der OBS beeinflussen über die physiko-chemischen Oberflächeneigenschaften der Makroporen den präferenziellen Transport und den Massentransfer zwischen Fließweg und Bodenmatrix. Darüber hinaus führt eine räumlich diskrete Verteilung von OBS auf Oberflächen von Makroporen zu - in Unterböden wenig erforschten - „hot spots“ mit erhöhten Umsatzraten. Die Analyse der OBS-Zusammensetzung gestattet außerdem Rückschlüsse auf die Landnutzung, so deutet z.B. das Auftreten von Benzonitril und Naphtalen (BN+NA) auf Biomasse-Verbrennung hin. Ziel der Arbeit war die Quantifizierung von organischem Kohlenstoff (Corg) und BN+NA auf intakten Makroporen-Oberflächen in Bt-Horizonten von Parabraunerden aus Löss und Geschiebemergel. Die zweidimensionale (2D), mm-skalige Verteilung von Corg und BN+NA auf verschiedenen Makroporen-Typen wurde mittels Diffuse Reflectance Infrared Fourier Transform (DRIFT) Spektroskopie in Kombination mit Corg-Messungen und Pyrolyse-Feldionisation Massenspektrometrie (Py-FIMS) quantitativ beschrieben. Für eine Horizont-bezogene Quantifizierung wurden die Porenverteilungen und Porenraum-Geometrien mit Röntgen-Computertomographie (CT) dreidimensional (3D) analysiert. Erhöhte Gehalte an Corg- und BN+NA korrelierten mit dem Auftreten von Ton-haltigen Kutanen und Porenfüllungen. Die Kombination von 2D- und 3D-Daten zeigte Unterschiede in der räumlichen Verteilung von Corg bzw. OBS sowie von BN+NA in Abhängigkeit der Makroporen-Typen und Standorte bzw. bodenbildenden Substrate. Die Ergebnisse tragen zur genaueren Beschreibung von Stoffumsetzungsprozessen und Stofftransporten in strukturierten Unterböden bei und ermöglichen darüber hinaus Schlüsse auf die Genese von Bt-Horizonten in Parabraunerden

Fließzellen-Technik: Neue Möglichkeit zur Untersuchung von bodenphysikalischen Parametern und Oberflächeneigenschaften von Bodenpartikeln an einer intakten Bodenstruktur?

Transport von Wasser- und Nährstoffen im Boden wird wesentlich durch physikalische und physikochemische Bodeneigenschaften beeinflußt. Die Porenraumstruktur (Porengröße, Tortuosität, Konnektivität) und ihre Oberflächeneigenschaften (Oberflächenladung und Oberflächenenergie) beeinflussen die Wasseradsorption und –verteilung im Boden. Organische Coatings können die Ausbildung heterogener Strukturen im Boden begünstigen, die lokale Bodenfeuchte beeinflussen oder zu „hotspots“ mit erhöhter biologischer Aktivität führen. Diese Prozesse können mit konventionellen Säulenversuchen nur unzureichend untersucht werden. Ziel war es daher, hydraulische Bodenprozesse in Abhängigkeit der Oberflächeneigenschaften von Bodenpartikeln unter kontrollierten Laborbedingungen zu untersuchen. Mit einer neu entwickelten Probenahmetechnik (quaderförmige Fließzellen aus Acrylglas) wurden an intakten Bodenproben, neben Infiltrationsversuchen, die kleinräumige Verteilung (cm bis mm) von Bodeneigenschaften untersucht. Vorteil gegenüber Bodensäulen oder anderen Fließzellen ist der Zuschnitt von bis zu 7 parallelen dünnen Scheiben variabler Dicke (Minimum 0,5 cm, quasi-Replikate) aus einer intakten Bodenprobe (Dicke 3,5 cm) mit einer maximalen Untersuchungsfläche von 150 cm2 (20x7,5 cm). Validiert wurde die Fließzellen-Technik mit Modellböden (Sandmatrix mit Lehmbändern). Zur Charakterisierung der physikalischen, physikochemischen und biologischen Bodeneigenschaften wurden folgende Analysen an parallelen, intakten Proben einer podsolierten Braunerde (Tiefe 70-90 cm) durchgeführt: i) Räumliche Verteilung der Benetzungseigenschaften über Kontaktwinkelmessungen ii) 2D-Mapping der räumlichen Verteilung von funktionellen Gruppen der organischen Substanz mit diffuser Reflexions-Fourier-Transformations Infrarotspektroskopie (DRIFT), iii) räumliche Verteilung der biologischen Aktivität über Zymografie und iv) radiografische Untersuchung der Wasserverteilung während eines Infiltrationsexperimentes. Die neu entwickelte Fließzellen-Technik bietet die Möglichkeit, bodenphysikalische Parameter in Kombination mit Oberflächeneigenschaften von Bodenpartikeln zu untersuchen und kann Aufschluss über Ursachen und Relevanz von kleinräumigen Heterogenitäten in Unterböden liefern. Limitiert wird die Fließzellen-Technik durch dickere Wurzeln und Partikel > 2mm

Ice nucleation activity of agricultural soil dust aerosols from Mongolia, Argentina, and Germany

Soil dust particles emitted from agricultural areas contain considerable mass fractions of organic material. Also, soil dust particles may act as carriers for potentially ice-active biological particles. In this work, we present ice nucleation experiments conducted in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud chamber. We investigated the ice nucleation efficiency of four types of soil dust from different regions of the world. The results are expressed as ice nucleation active surface site (INAS) densities and presented for the immersion freezing and the deposition nucleation mode. For immersion freezing occurring at 254 K, samples from Argentina, China, and Germany show ice nucleation efficiencies which are by a factor of 10 higher than desert dusts. On average, the difference in ice nucleation efficiencies between agricultural and desert dusts becomes significantly smaller at temperatures below 247 K. In the deposition mode the soil dusts showed higher ice nucleation activity than Arizona Test Dust over a temperature range between 232 and 248 K and humidities RHice up to 125%. INAS densities varied between 109 and 1011m-2 for these thermodynamic conditions. For one soil dust sample (Argentinian Soil), the effect of treatments with heat was investigated. Heat treatments (383 K) did not affect the ice nucleation efficiency observed at 249 K. This finding presumably excludes proteinaceous ice-nucleating entities as the only source of the increased ice nucleation efficiency.Fil: Steinke, I.. Karlsruhe Institute of Technology; AlemaniaFil: Funk, R.. Leibniz Centre for Agricultural Landscape Research; AlemaniaFil: Busse, J.. Leibniz Centre for Agricultural Landscape Research; AlemaniaFil: Iturri, Laura Antonela. Universidad Nacional de La Pampa; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; ArgentinaFil: Kirchen, S.. Karlsruhe Institute of Technology; AlemaniaFil: Leue, M.. Leibniz Centre for Agricultural Landscape Research; AlemaniaFil: Möhler, O.. Karlsruhe Institute of Technology; AlemaniaFil: Schwartz, T.. Universidad Nacional de La Pampa; ArgentinaFil: Schnaiter, M.. Karlsruhe Institute of Technology; AlemaniaFil: Sierau, B.. Institute for Atmospheric and Climate Science; SuizaFil: Toprak, E.. Karlsruhe Institute of Technology; AlemaniaFil: Ullrich, R.. Karlsruhe Institute of Technology; AlemaniaFil: Ulrich, A.. Leibniz Centre for Agricultural Landscape Research; AlemaniaFil: Hoose, C.. Karlsruhe Institute of Technology; AlemaniaFil: Leisner, T.. Karlsruhe Institute of Technology; Alemania. Heidelberg University; Alemani