Generalizing the Paige-Tarjan Algorithm by Abstract Interpretation

The Paige and Tarjan algorithm (PT) for computing the coarsest refinement of a state partition which is a bisimulation on some Kripke structure is well known. It is also well known in model checking that bisimulation is equivalent to strong preservation of CTL, or, equivalently, of Hennessy-Milner logic. Drawing on these observations, we analyze the basic steps of the PT algorithm from an abstract interpretation perspective, which allows us to reason on strong preservation in the context of generic inductively defined (temporal) languages and of possibly non-partitioning abstract models specified by abstract interpretation. This leads us to design a generalized Paige-Tarjan algorithm, called GPT, for computing the minimal refinement of an abstract interpretation-based model that strongly preserves some given language. It turns out that PT is a straight instance of GPT on the domain of state partitions for the case of strong preservation of Hennessy-Milner logic. We provide a number of examples showing that GPT is of general use. We first show how a well-known efficient algorithm for computing stuttering equivalence can be viewed as a simple instance of GPT. We then instantiate GPT in order to design a new efficient algorithm for computing simulation equivalence that is competitive with the best available algorithms. Finally, we show how GPT allows to compute new strongly preserving abstract models by providing an efficient algorithm that computes the coarsest refinement of a given partition that strongly preserves the language generated by the reachability operator.Comment: Keywords: Abstract interpretation, abstract model checking, strong preservation, Paige-Tarjan algorithm, refinement algorith

Generalized Strong Preservation by Abstract Interpretation

Standard abstract model checking relies on abstract Kripke structures which approximate concrete models by gluing together indistinguishable states, namely by a partition of the concrete state space. Strong preservation for a specification language L encodes the equivalence of concrete and abstract model checking of formulas in L. We show how abstract interpretation can be used to design abstract models that are more general than abstract Kripke structures. Accordingly, strong preservation is generalized to abstract interpretation-based models and precisely related to the concept of completeness in abstract interpretation. The problem of minimally refining an abstract model in order to make it strongly preserving for some language L can be formulated as a minimal domain refinement in abstract interpretation in order to get completeness w.r.t. the logical/temporal operators of L. It turns out that this refined strongly preserving abstract model always exists and can be characterized as a greatest fixed point. As a consequence, some well-known behavioural equivalences, like bisimulation, simulation and stuttering, and their corresponding partition refinement algorithms can be elegantly characterized in abstract interpretation as completeness properties and refinements

Direct Injection Liquid Chromatography High-Resolution Mass Spectrometry for Determination of Primary and Secondary Terrestrial and Marine Biomarkers in Ice Cores

Many atmospheric organic compounds are long-lived enough to be transported from their sources to polar regions and high mountain environments where they can be trapped in ice archives. While inorganic components in ice archives have been studied extensively to identify past climate changes, organic compounds have rarely been used to assess paleo-environmental changes, mainly due to the lack of suitable analytical methods. This study presents a new method of direct injection HPLC-MS analysis, without the need of pre-concentrating the melted ice, for the determination of a series of novel biomarkers in ice-core samples indicative of primary and secondary terrestrial and marine organic aerosol sources. Eliminating a preconcentration step reduces contamination potential and decreases the required sample volume thus allowing a higher time resolution in the archives. The method is characterised by limits of detections (LODs) in the range of 0.01-15 ppb, depending on the analyte, and accuracy evaluated through an interlaboratory comparison. We find that many components in secondary organic aerosols (SOA) are clearly detectable at concentrations comparable to those previously observed in replicate preconcentrated ice samples from the Belukha glacier, Russian Altai Mountains. Some compounds with low recoveries in preconcentration steps are now detectable in samples with this new direct injection method significantly increasing the range of environmental processes and sources that become accessible for paleo-climate studies

An update of the Worldwide Integrated Assessment (WIA) on systemic insecticides. Part 1: new molecules, metabolism, fate, and transport

With the exponential number of published data on neonicotinoids and fipronil during the last decade, an updated review of literature has been conducted in three parts. The present part focuses on gaps of knowledge that have been addressed after publication of the Worldwide Integrated Assessment (WIA) on systemic insecticides in 2015. More specifically, new data on the mode of action and metabolism of neonicotinoids and fipronil, and their toxicity to invertebrates and vertebrates, were obtained. We included the newly detected synergistic effects and/or interactions of these systemic insecticides with other insecticides, fungicides, herbicides, adjuvants, honeybee viruses, and parasites of honeybees. New studies have also investigated the contamination of all environmental compartments (air and dust, soil, water, sediments, and plants) as well as bees and apicultural products, food and beverages, and the exposure of invertebrates and vertebrates to such contaminants. Finally, we review new publications on remediation of neonicotinoids and fipronil, especially in water systems. Conclusions of the previous WIA in 2015 are reinforced; neonicotinoids and fipronil represent a major threat worldwide for biodiversity, ecosystems, and all the services the latter provide

Secondary organic aerosol formation from isoprene photooxidation during cloud condensation-evaporation cycles

Abstract. The impact of cloud events on isoprene secondary organic aerosol (SOA) formation has been studied from an isoprene ∕ NOx ∕ light system in an atmospheric simulation chamber. It was shown that the presence of a liquid water cloud leads to a faster and higher SOA formation than under dry conditions. When a cloud is generated early in the photooxidation reaction, before any SOA formation has occurred, a fast SOA formation is observed with mass yields ranging from 0.002 to 0.004. These yields are 2 and 4 times higher than those observed under dry conditions. When the cloud is generated at a later photooxidation stage, after isoprene SOA is stabilized at its maximum mass concentration, a rapid increase (by a factor of 2 or higher) of the SOA mass concentration is observed. The SOA chemical composition is influenced by cloud generation: the additional SOA formed during cloud events is composed of both organics and nitrate containing species. This SOA formation can be linked to the dissolution of water soluble volatile organic compounds (VOCs) in the aqueous phase and to further aqueous phase reactions. Cloud-induced SOA formation is experimentally demonstrated in this study, thus highlighting the importance of aqueous multiphase systems in atmospheric SOA formation estimations. The authors thank Arnaud Allanic, Sylvain Ravier, Pascal Renard and Pascal Zapf for their contributions in the experiments. The authors also acknowledge the institutions that have provided financial support: the French National Institute for Geophysical Research (CNRS-INSU) within the LEFE-CHAT program through the project “Impact de la chimie des nuages sur la formation d’aérosols organiques secondaires dans l’atmosphère” and the French National Agency for Research (ANR) project CUMULUS ANR-2010-BLAN-617-01. This work was also supported by the EC within the I3 project “Integrating of European Simulation Chambers for Investigating Atmospheric Processes” (EUROCHAMP-2, contract no. 228335). The authors thank the MASSALYA instrumental platform (Aix Marseille Université, lce.univ-amu.fr) for the analysis and measurements used in this paper.This is the final version of the article. It first appeared from Copernicus Publications via http://dx.doi.org/10.5194/acp-16-1747-201

​Lihuén: cosa e’ mandinga

La función principal de la directora de arte está en la creación de un entorno adecuado para que se desarrolle el relato. En este sentido, los parámetros estéticos responden a un sentido más profundo que lo meramente formal, donde se conjuga lo visual con el discurso que subyace detrás. Mi trabajo implica tomar las decisiones estéticas en referencia al producto en su totalidad: cómo se construye el espacio, la paleta de colores, los encuadres y composiciones a utilizar. Las similitudes estilísticas entre los diferentes espacios y formatos que unifiquen a Lihuén como proyecto, así como sus diferencias. Aunque en las grandes producciones -desde donde se basa la teoría generalmente- los roles se delimitan con mucha precisión; nuestro proceso no resultó de esa manera, teniendo una misma persona que suplir varios roles al mismo tiempo, ya que solo en las producciones de gran envergadura se tiene mayor personal para cubrir la especificidad de tareas. Por lo tanto, gran parte de mi trabajo implicó, también, el diseño de fondos y elementos a animar del mismo así como su creación final.Tesis colectiva interdisciplinaria, realizada junto con Burgardt, Betiana Mariela; Cominotti, Gabriel Ignacio; Lopez Annes, Maite; Pellendier, Agustín; Winchel Peano, Bárbara; Zandarín, Ramón. Los videos que acompañan a esta tesis pueden verse en este enlace y en este enlace.Facultad de Bellas Arte

​Lihuén: cosa e’ mandinga

La función principal de la directora de arte está en la creación de un entorno adecuado para que se desarrolle el relato. En este sentido, los parámetros estéticos responden a un sentido más profundo que lo meramente formal, donde se conjuga lo visual con el discurso que subyace detrás. Mi trabajo implica tomar las decisiones estéticas en referencia al producto en su totalidad: cómo se construye el espacio, la paleta de colores, los encuadres y composiciones a utilizar. Las similitudes estilísticas entre los diferentes espacios y formatos que unifiquen a Lihuén como proyecto, así como sus diferencias. Aunque en las grandes producciones -desde donde se basa la teoría generalmente- los roles se delimitan con mucha precisión; nuestro proceso no resultó de esa manera, teniendo una misma persona que suplir varios roles al mismo tiempo, ya que solo en las producciones de gran envergadura se tiene mayor personal para cubrir la especificidad de tareas. Por lo tanto, gran parte de mi trabajo implicó, también, el diseño de fondos y elementos a animar del mismo así como su creación final.Tesis colectiva interdisciplinaria, realizada junto con Burgardt, Betiana Mariela; Cominotti, Gabriel Ignacio; Lopez Annes, Maite; Pellendier, Agustín; Winchel Peano, Bárbara; Zandarín, Ramón. Los videos que acompañan a esta tesis pueden verse en este enlace y en este enlace.Facultad de Bellas Arte