Using heuristic search for finding deadlocks in concurrent systems

AbstractModel checking is a formal technique for proving the correctness of a system with respect to a desired behavior. This is accomplished by checking whether a structure representing the system (typically a labeled transition system) satisfies a temporal logic formula describing the expected behavior. Model checking has a number of advantages over traditional approaches that are based on simulation and testing: it is completely automatic and when the verification fails it returns a counterexample that can be used to pinpoint the source of the error. Nevertheless, model checking techniques often fail because of the state explosion problem: transition systems grow exponentially with the number of components. The aim of this paper is to attack the state explosion problem that may arise when looking for deadlocks in concurrent systems described through the calculus of communicating systems. We propose to use heuristics-based techniques, namely the A* algorithm, both to guide the search without constructing the complete transition system, and to provide minimal counterexamples. We have realized a prototype tool to evaluate the methodology. Experiments we have conducted on processes of different size show the benefit from using our technique against building the whole state space, or applying some other methods

DELFIN+: An efficient deadlock detection tool for CCS processes

AbstractModel checking is a formal technique for proving the correctness of a system with respect to a desired behavior. However, deadlock detection via model checking is particularly difficult for the following two problems: (i) the state explosion problem, due to the exponential increase in the size of a finite state model as the number of system components grows; and (ii) the output interpretation problem, as often counter-examples are so long that they are hard to understand. The aim of this paper is to solve both problems by using heuristic-based search strategies. We have realized DELFIN+ (DEadLock FINder) a tool supporting efficient deadlock detection in CCS processes. We have used this tool to verify a sample of CCS processes, in order to evaluate the method on them

Hereditary rings and rings of finite representation type

This thesis is a study of Noetherian PI rings with the property that every proper Artinian homomorphic image is of finite representation type. Our main result is: Theorem 5.1.12 Let R be a Noetherian PI ring, which is an order in an Artinian ring. Suppose that every proper Artinian factor ring of R is of finite representation type. Then R is a direct sum of an Artinian ring of finite representation type and prime hereditary rings. As a special case we have that a prime Noetherian PI ring is hereditary if and only if all its proper Artinian homomorphic images are of finite representation type. The thesis is organized as follows. In Chapter 1 we introduce the terminology and collect well known results on Noetherian rings that we shall use in later chapters. We also include some remarks on the relationship between the J-adic completion of a certain Noetherian prime PI ring and its centre that seem not appear in the literature. In Chapter 2 we present some known characterizations of hereditary rings. We introduce a discussion on rings of finite representation type and give motivation for our study. In Chapter 3 we begin the proof of our main theorem. We adapt the proof of a theorem by S. Brenner [10], which shows that the 2x2 upper triangular matrix ring T₂(Z/p⁴Z) is of infinite type, to the more general case of T₂(D/dnD), where D is a non-commutative local Dedekind prime PI ring and dD its maximal ideal. This result is crucial for the proof of Theorem 5.1.12. The reduction of our problem to this case is allowed by a theorem of M. Ausländer (cf. Theorem 3.2.1) on trivial extension rings of Artin algebras. We describe this theorem and show that it holds also for Artinian PI rings. Then we analyze the graph of links between maximal ideals of R. We show that if R is a prime ring satisfying the hypothesis of Theorem 5.1.12 then all cliques of maximal ideals of R are finite. In the last section of this chapter we look at connections between Artinian serial rings and rings of finite representation type. We show that if R is a semiperfect local Noetherian PI ring which is not Artinian and such that R/J(R)² is of finite representation type, then R is a hereditary prime ring. Finally, we introduce some rings related to the ring R satisfying the hypothesis of Theorem 5.1.12, which inherit the property of the homomorphic images and that we shall use for the proof of the theorem. In Chapter 4 we prove Theorem 5.1.12 under the additional assumption that every clique of maximal ideals of R is finite. This is done by analyzing in detail the structure of the J-adic completion of the localisation of R at a clique of maximal ideals. Then from the results of Chapter 3 we deduce that Theorem 5.1.12 holds if R is semiprime. In Chapter 5 we prove that cliques of maximal ideals of R are indeed finite. This finishes the proof of our result. Further, we prove that a Noetherian PI ring whose proper Artinian homomorphic images are all serial is an order in an Artinian ring. In Chapter 6 we prove the analogue of Theorem 5.1.12 for a semiprime PI ring which is affine over a field. Then we give some examples of Noetherian PI rings of different global dimension to show that the assumption in Theorem 5.1.12 on the existence of an Artinian quotient ring for R is necessary. For completeness of our study, some results are stated and proved in more generality than it is needed for the proof of our main theorem

Model Checking Multithreaded Programs by Means of Reduced Models

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A comprehensive system for semantic spatiotemporal assessment of risk in urban areas

AbstractRisk assessment of urban areas aims at limiting the impact of harmful events by increasing awareness of their possible consequences. Qualitative risk assessment allows to figure out possible risk situations and to prioritize them, whereas quantitative risk assessment is devoted to measuring risks from data, in order to improve preparedness in case of crisis situations. We propose an automatic approach to comprehensive risk assessment. This leverages on a semantic and spatiotemporal representation of knowledge of the urban area and relies on a software system including: a knowledge base; two components for quantitative and qualitative risk assessments, respectively; and a WebGIS interface. The knowledge base consists of the TERMINUS domain ontology, to represent urban knowledge, and of a geo‐referenced database, including geographical, environmental and urban data as well as temporal data related to the levels of operation of city services. CIPcast DSS is the component devoted to quantitative risk assessment, and WS‐CREAM is the component supporting qualitative risk assessment based on computational creativity techniques. Two case studies concerning the city of Rome (Italy) show how this approach can be used in a real scenario for crisis preparedness. Finally, we discuss issues related to plausibility of risks and objectivity of their assessment

Transient transfection of porcine granulosa cells after 3D culture in barium alginate capsules

Three-dimensional culture systems in barium alginate capsules can be employed to maintain primary granulosa cells in an undifferentiated state for almost 6 days. This is due to a self-organization of cells in a pseudofollicular structure. The transfection of primary granulosa cells is a necessary condition when employing these culture systems for several purposes, for example as an in vitro toxicity test or the development of oocytes or zygotes. In this work, the feasibility of two transient transfection techniques (liposome-mediated and electroporation) was assessed in primary porcine granulosa cells after a 6-day culture in an artificial extracellular matrix (barium alginate membrane). Human recombinant green fluorescent protein was chosen as a molecular readout, and protein expression was assessed after 48 hours from transfection. Liposome-mediated transfection gave low transfection levels, with increasing yields from 2 to 12 microgDNA/ml of medium; the maximum percentage (85.7%) was reached at 12 microgDNA/ml of medium. Electroporation-mediated transfection yields were higher: the best results (81.7% of transfected cells) were achieved with two 50V pulses and 12 microg/ml DNA. The application of a single or double pulse (50V) at 4 mgDNA/ml gave negligible results. These results indicate that primary granulosa cell cultured in barium alginate capsules can be transfected by electroporation with high transfection yields

Altered sphingolipid metabolism in N-(4-hydroxyphenyl) retinamide resistant A2780 human ovarian carcinoma cells

In the present work, we studied the effects of fenretinide (N-(4-hydroxyphenyl)retinamide (HPR)), a hydroxyphenyl derivative of all-trans-retinoic acid, on sphingolipid metabolism and expression in human ovarian carcinoma A2780 cells. A2780 cells, which are sensitive to a pharmacologically achievable HPR concentration, become 10-fold more resistant after exposure to increasing HPR concentrations. Our results showed that HPR was able to induce a dose- and time-dependent increase in cellular ceramide levels in sensitive but not in resistant cells. This form of resistance in A2780 cells was not accompanied by the overexpression of multidrug resistance-specific proteins MDR1 P-glycoprotein and multidrug resistance-associated protein, whose mRNA levels did not differ in sensitive and resistant A2780 cells. HPR-resistant cells were characterized by an overall altered sphingolipid metabolism. The overall content in glycosphingolipids was similar in both cell types, but the expression of specific glycosphingolipids was different. Specifically, our findings indicated that glucosylceramide levels were similar in sensitive and resistant cells, but resistant cells were characterized by a 6-fold lower expression of lactosylceramide levels and by a 6-fold higher expression of ganglioside levels than sensitive cells. The main gangliosides from resistant A2780 cells were identified as GM3 and GM2. The possible metabolic mechanisms leading to this difference were investigated. Interestingly, the mRNA levels of glucosylceramide and lactosylceramide synthases were similar in sensitive and resistant cells, whereas GM3 synthase mRNA level and GM3 synthase activity were remarkably higher in resistant cells

Eligibility criteria for pediatric patients who may benefit from anti SARS-CoV-2 monoclonal antibody therapy administration: an Italian inter-society consensus statement

The fast diffusion of the SARS-CoV-2 pandemic have called for an equally rapid evolution of the therapeutic options.The Human recombinant monoclonal antibodies (mAbs) have recently been approved by the Food and Drug Administration (FDA) and by the Italian Medicines Agency (AIFA) in subjects aged ≥12 with SARS-CoV-2 infection and specific risk factors.Currently the indications are specific for the use of two different mAbs combination: Bamlanivimab+Etesevimab (produced by Eli Lilly) and Casirivimab+Imdevimab (produced by Regeneron).These drugs have shown favorable effects in adult patients in the initial phase of infection, whereas to date few data are available on their use in children.AIFA criteria derived from the existing literature which reports an increased risk of severe COVID-19 in children with comorbidities. However, the studies analyzing the determinants for progression to severe disease are mainly monocentric, with limited numbers and reporting mostly generic risk categories.Thus, the Italian Society of Pediatrics invited its affiliated Scientific Societies to produce a Consensus document based on the revision of the criteria proposed by AIFA in light of the most recent literature and experts' agreement.This Consensus tries to detail which patients actually have the risk to develop severe disease, analyzing the most common comorbidities in children, in order to detail the indications for mAbs administration and to guide the clinicians in identifying eligible patients