Understanding the Relative Strength of QBF CDCL Solvers and QBF Resolution

QBF solvers implementing the QCDCL paradigm are powerful algorithms that successfully tackle many computationally complex applications. However, our theoretical understanding of the strength and limitations of these QCDCL solvers is very limited. In this paper we suggest to formally model QCDCL solvers as proof systems. We define different policies that can be used for decision heuristics and unit propagation and give rise to a number of sound and complete QBF proof systems (and hence new QCDCL algorithms). With respect to the standard policies used in practical QCDCL solving, we show that the corresponding QCDCL proof system is incomparable (via exponential separations) to Q-resolution, the classical QBF resolution system used in the literature. This is in stark contrast to the propositional setting where CDCL and resolution are known to be p-equivalent. This raises the question what formulas are hard for standard QCDCL, since Q-resolution lower bounds do not necessarily apply to QCDCL as we show here. In answer to this question we prove several lower bounds for QCDCL, including exponential lower bounds for a large class of random QBFs. We also introduce a strengthening of the decision heuristic used in classical QCDCL, which does not necessarily decide variables in order of the prefix, but still allows to learn asserting clauses. We show that with this decision policy, QCDCL can be exponentially faster on some formulas. We further exhibit a QCDCL proof system that is p-equivalent to Q-resolution. In comparison to classical QCDCL, this new QCDCL version adapts both decision and unit propagation policies

Vom Twitter-Diskurs zum gesellschaftlich handlungsfähigen Subjekt. Digitale Diskursfragmente in Sprach- und Mediendidaktischer Perspektive

Soll der Deutschunterricht an der Bildung gesellschaftlich handlungsfähiger Subjekte mitwirken, lassen sich ausgehend von der Erkenntnis, dass in der politischen Netzkommunikation der Geltungsanspruch der Wahrheit (vulgo Habermas) unter Druck steht, zentrale sprach- und mediendidaktische Aufgaben ableiten. Die Aufgaben betreffen v.a. die Förderung rezeptiv-analytischer und diskursiv-argumentativer Kompetenzen, die auf die Digitalität, Multimodalität und Interaktivität gegenwärtiger politischer Diskurse ausgerichtet sind. Diese bilden die Voraussetzung dafür, dass Lernende die in der Rezeption gebildeten Urteile darüber, was ein wahrer Sachverhalt ist, nicht nur kritisch reflektieren, sondern auch im Diskurs zur Disposition stellen können, um sie aufgrund von triftigen Argumenten ggf. zu revidieren. Vor dem Hintergrund des Bildungsideals gesellschaftlicher Handlungsfähigkeit arbeitet der Beitrag exemplarisch die didaktische Rationalität heraus, die die unterrichtliche Befassung mit manipulierenden Tweets zum politischen Klimadiskurs für die gezielte Förderung der o.g. Fähigkeiten gesellschaftlicher Handlungsfähigkeit bereithält.   Abstract (english): From Twitter Discourse to Social Agency–Digital discourse fragments in a language-didactic and media-didactic perspective If German lessons are to participate in the formation ofa“gesellschaftlichhandlungsfähiges Subjekt” (A person who is able to engage in argumentative discourse about disputed truth, cor-rectness, and veracity claims), central language and media didactic tasks can be derived from the realization that the claim to validity of truth (vulgo Habermas) is under pressure in political network communication. These tasks primarily concern the promotion of receptive-analytical and discursive-argumentative skills, which are oriented towards the digitality, multimodality and interactivity of current political discourse. These skills are the precondition for learners not only to critically reflect on the judgmentsformed in reception about what constitutes a true state of affairs, but also to be able to question them in discourse and, if necessary, to revise them on the basis of valid arguments. Against the background of the educational ideal of social agency, the article exemplarily elaborates the didactic rationality of dealing with manipulative tweets on the political climate discourse for the targeted promotion of the above-mentioned skills.  

Understanding the Relative Strength of QBF CDCL Solvers and QBF Resolution

QBF solvers implementing the QCDCL paradigm are powerful algorithms that successfully tackle many computationally complex applications. However, our theoretical understanding of the strength and limitations of these QCDCL solvers is very limited. In this paper we suggest to formally model QCDCL solvers as proof systems. We define different policies that can be used for decision heuristics and unit propagation and give rise to a number of sound and complete QBF proof systems (and hence new QCDCL algorithms). With respect to the standard policies used in practical QCDCL solving, we show that the corresponding QCDCL proof system is incomparable (via exponential separations) to Q-resolution, the classical QBF resolution system used in the literature. This is in stark contrast to the propositional setting where CDCL and resolution are known to be p-equivalent. This raises the question what formulas are hard for standard QCDCL, since Q-resolution lower bounds do not necessarily apply to QCDCL as we show here. In answer to this question we prove several lower bounds for QCDCL, including exponential lower bounds for a large class of random QBFs. We also introduce a strengthening of the decision heuristic used in classical QCDCL, which does not necessarily decide variables in order of the prefix, but still allows to learn asserting clauses. We show that with this decision policy, QCDCL can be exponentially faster on some formulas. We further exhibit a QCDCL proof system that is p-equivalent to Q-resolution. In comparison to classical QCDCL, this new QCDCL version adapts both decision and unit propagation policies

Zügige, komfortable Umstiege an einem leistungsstarken Bahnhof - Analyse und Bewertung des Fahrgastflusses an einem Bahnhof am Beispiel der Next Generation Station mittels mikroskopischer Simulationen

Bereits heute stoßen Bahnhöfe in Zeiträumen von hohem Fahrgastaufkommen an ihre Kapazitätsgrenzen. Daher ist es wichtig, die verkehrliche Leistungsfähigkeit eines Bahnhofs in Hinblick auf die Fahrgastströme bereits in der Konzeptphase zu untersuchen. In dieser Untersuchung wird der Bahnhof Next Generation Station mittels mikroskopischer Simulationen betrachtet. Die Resultate werden anhand ausgewählter Schlüsselindikatoren, wie der Übergangszeit und der Personendichte, bewertet. Mit Hilfe dieser Ergebnisse werden Engpässe im Hinblick auf den Fahrgastfluss identifiziert und Wege der Verbesserung aufgezeigt

Effects of cardiovascular single pill combinations compared with identical multi-pill therapies on healthcare cost and utilization in Germany

Aim: This study assessed whether a single pill combination (SPC) is associated with lower direct healthcare costs. Materials & methods: Anonymized claims data of patients ≥18 years treated with drugs for cardiovascular (CV)-related diseases either as a single pill combination or multi-pill combination (followup to 1 year) were evaluated. After propensity score matching, 59,336 out of 1,369,840 patients were analyzed. Results: In all cohorts, patients receiving a single pill combination had a lower frequency of general practitioner and specialist visits. The patients also had a significantly lower ratio of all-cause hospitalization days and number of CV-related prescriptions as well as all-cause prescriptions (with one exception) compared with those receiving a multi-pill combination. Conclusion: Direct CV-related costs were significantly lower in four out of seven comparisons, with a trend toward lower costs in the other three comparisons

Radiation Safety at FLUTE with Special Emphasis on Activation Issues

The accelerator FLUTE (name abbreviation derived from its German name: Ferninfrarot Linac- und TestExperiment) has been set up in cooperation with DESY and PSI [1]. The electron source and diagnostics has commenced operation. General safety issues of FLUTE are covered in this paper. The activation of the accelerator and vacuum parts were predicted previously [2]. The attention is given to the activation of aluminum and impurities in the electron absorber of the beam dump. Potential air activation in the experimental hall is also discussed

Efficacy of Obeticholic Acid in Patients With Primary Biliary Cirrhosis and Inadequate Response to Ursodeoxycholic Acid

Background & AimsWe evaluated the efficacy and safety of obeticholic acid (OCA, α-ethylchenodeoxycholic acid) in a randomized controlled trial of patients with primary biliary cirrhosis who had an inadequate response to ursodeoxycholic acid therapy.MethodsWe performed a double-blind study of 165 patients with primary biliary cirrhosis (95% women) and levels of alkaline phosphatase (ALP) 1.5- to 10-fold the upper limit of normal. Patients were randomly assigned to groups given 10 mg, 25 mg, or 50 mg doses of OCA or placebo, once daily for 3 months. Patients maintained their existing dose of ursodeoxycholic acid throughout the study. The primary outcome was change in level of ALP from baseline (day 0) until the end of the study (day 85 or early termination). We also performed an open-label extension of the trial in which 78 patients were enrolled and 61 completed the first year.ResultsOCA was superior to placebo in achieving the primary end point. Subjects given OCA had statistically significant relative reductions in mean ALP from baseline to the end of the study (P < .0001 all OCA groups vs placebo). Levels of ALP decreased 21%–25% on average from baseline in the OCA groups and 3% in the placebo group. Sixty-nine percent (68 of 99) of patients given OCA had at least a 20% reduction in ALP compared with 8% (3 of 37) of patients given placebo (P < .0003). Among secondary end points, levels of γ-glutamyl transpeptidase decreased 48%–63%, on average, among subjects given OCA, vs a 7% decrease in the group given placebo; levels of alanine aminotransferase decreased 21%–35% on average among subjects given OCA vs none of the patients given placebo. Pruritus was the principal adverse event; incidence values in the OCA 10 mg, 25 mg, and 50 mg groups were 47% (not significantly different), 87% (P < .0003), and 80% (P < .006), respectively, vs 50% in the placebo group. In the extension study, levels of ALP continued to decrease to a mean level of 202 ± 11 U/L after 12 months vs 285 ± 15 U/L at baseline.ConclusionsDaily doses of OCA, ranging from 10 to 50 mg, significantly reduced levels of ALP, γ-glutamyl transpeptidase, and alanine aminotransferase, compared with placebo, in patients with primary biliary cirrhosis who had inadequate responses to ursodeoxycholic acid. The incidence and severity of pruritus were lowest among patients who received 10 mg/d OCA. Biochemical responses to OCA were maintained in a 12-month open-label extension trial. ClinicalTrials.gov ID: NCT00550862