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

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

Formation of metal-cyanide complexes in deliquescent airborne particles: a new possible sink for HCN in urban environments

Hydrogen cyanide is a ubiquitous gas in the atmosphere and a biomass burning tracer. Reactive gasses can be adsorbed onto aerosol particles where they can promote heterogeneous chemistry. In the present study, we report for the first time on the measurement and speciation of cyanides in atmospheric aerosol. Filter samples were collected at an urban background site in the city center of Padua (Italy), extracted and analyzed with headspace gas chromatography and nitrogen-phosphorous detection. The results showed that strongly bound cyanides were present in all aerosol samples at a concentration ranging between 0.3 and 6.5 ng/m3 in the PM2.5 fraction. The concentration of cyanides strongly correlates with concentration of total carbon and metals associated with combustion sources. The results obtained bring evidence that hydrogen cyanide can be adsorbed onto aerosol liquid water and can react with metal ions to form stable metal-cyanide complexes

​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

Contratos EPC para empreendimentos hidrelétricos e seus stakeholders

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia de Produção.Devido às mudanças ocorridas a partir 1993 na legislação que rege o Setor de Energia Elétrica Brasileiro, abrindo o mercado para as empresas privadas, tem-se notado grandes alterações no que se refere ao modo de contratação para implantação de grandes empreendimentos nesse Setor. O presente trabalho visa o estudo de uma nova forma de contratação para empreendimentos de geração de energia elétrica, onde o empreendedor ou contratante transfere, via contrato, todos os riscos de engenharia e construção à contratada. A contratada fica responsável pela realização dos trabalhos de engenharia e projetos, fornecimentos de materiais e equipamentos permanentes e construção do empreendimento, assumindo os riscos inerentes dessas atividades, ou seja, nesse tipo de contrato, o preço é global e está contemplado o fornecimento integral. Essa forma de contratação é chamada de Contrato EPC (Engineering, Procurement and Construction) Turn Key Lump Sum e nesse caso, o objeto da contratação é a entrega do empreendimento, pronto, acabado e operando. Esse trabalho compreende de uma pesquisa bibliográfica onde se procura descrever as características dessa forma de contratação e a identificação dos vários atores envolvidos no processo e partes interessadas, chamados de stakeholders, buscando com isso minimizar as dificuldades encontradas pelos gestores destes contratos

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

​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

Human Liver Stem Cell-Derived Extracellular Vesicles Target Hepatic Stellate Cells and Attenuate Their Pro-fibrotic Phenotype

Liver fibrosis occurs in response to chronic liver injury and is characterized by an excessive deposition of extracellular matrix. Activated hepatic stellate cells are primarily responsible for this process. A possible strategy to counteract the development of hepatic fibrosis could be the reversion of the activated phenotype of hepatic stellate cells. Extracellular vesicles (EVs) are nanosized membrane vesicles involved in intercellular communication. Our previous studies have demonstrated that EVs derived from human liver stem cells (HLSCs), a multipotent population of adult stem cells of the liver with mesenchymal-like phenotype, exert in vivo anti-fibrotic activity in the liver. However, the mechanism of action of these EVs remains to be determined. We set up an in vitro model of hepatic fibrosis using a human hepatic stellate cell line (LX-2) activated by transforming growth factor-beta 1 (TGF-β1). Then, we investigated the effect of EVs obtained from HLSCs and from human bone marrow-derived mesenchymal stromal cells (MSCs) on activated LX-2. The incubation of activated LX-2 with HLSC-EVs reduced the expression level of alpha-smooth muscle actin (α-SMA). Conversely, MSC-derived EVs induced an increase in the expression of pro-fibrotic markers in activated LX-2. The analysis of the RNA cargo of HLSC-EVs revealed the presence of several miRNAs involved in the regulation of fibrosis and inflammation. Predictive target analysis indicated that several microRNAs (miRNAs) contained into HLSC-EVs could possibly target pro-fibrotic transcripts. In particular, we demonstrated that HLSC-EVs shuttled miR-146a-5p and that treatment with HLSC-EVs increased miR-146a-5p expression in LX-2. In conclusion, this study demonstrates that HLSC-EVs can attenuate the activated phenotype of hepatic stellate cells and that their biological effect may be mediated by the delivery of anti-fibrotic miRNAs, such as miR-146a-5p