Bandwidth and Wavefront Reduction for Static Variable Ordering in Symbolic Model Checking

We demonstrate the applicability of bandwidth and wavefront reduction algorithms to static variable ordering. In symbolic model checking event locality plays a major role in time and memory usage. For example, in Petri nets event locality can be captured by dependency matrices, where nonzero entries indicate whether a transition modifies a place. The quality of event locality has been expressed as a metric called (weighted) event span. The bandwidth of a matrix is a metric indicating the distance of nonzero elements to the diagonal. Wavefront is a metric indicating the degree of nonzeros on one end of the diagonal of the matrix. Bandwidth and wavefront are well studied metrics used in sparse matrix solvers. \ud In this work we prove that span is limited by twice the bandwidth of a matrix. This observation makes bandwidth reduction algorithms useful for obtaining good variable orders. One major issue we address is that the reduction algorithms can only be applied on symmetric matrices, while the dependency matrices are asymmetric. We show that the Sloan algorithm executed on the total graph of the adjacency graph gives the best variable orders. Practically, we demonstrate that our work allows to call standard sparse matrix operations in Boost and ViennaCL, computing very good static variable orders in milliseconds. Future work is promising, because a whole new spectrum of more off-the-shelf algorithms, including metaheuristic ones, become available for variable ordering

Problems in enforcing Dutch building regulations

Purpose - The paper seeks to define the nature of the policy problems in Dutch building control. Design/methodology/approach - The authors use Dunn's four-phase methodology for public policy analysis, consisting of problem sensing, problem search, problem definition, and problem specification. Both a literature review and a field study into the operation of local building control authorities were undertaken. The field study incorporates characteristics of a survey, with methodology developed by Fowler. Findings - Dutch building control legislation has been subject to many changes over the 100 years or so that it has been in force as it has responded to society's changing priorities. Throughout this period building regulation has become more detailed and more uniform across the country. Nevertheless, almost no legal changes have been made to the enforcement system. Responsibility for building control still lies with the municipalities and implementation is still not established by national legislation or policy document. Ongoing attempts to deregulate and standardise the legislative framework should therefore not stop at changing the regulations. Changes in the supervision system might offer an alternative route to improving the quality of the (technical) building control and clarifying the tasks and responsibilities of building control staff. Research limitations/implications - The analysis focuses on problems in building control and does not consider design and construction problems. Practical implications - The field study contains important lessons forbuilding control practitioners and policymakers regarding current deficiencies in the implementation of building control legislation. Originality/value - The paper provides a model for the analysis, and comparative study, of building control systems in other jurisdictions

Symbolic Reachability Analysis of B through ProB and LTSmin

We present a symbolic reachability analysis approach for B that can provide a significant speedup over traditional explicit state model checking. The symbolic analysis is implemented by linking ProB to LTSmin, a high-performance language independent model checker. The link is achieved via LTSmin's PINS interface, allowing ProB to benefit from LTSmin's analysis algorithms, while only writing a few hundred lines of glue-code, along with a bridge between ProB and C using ZeroMQ. ProB supports model checking of several formal specification languages such as B, Event-B, Z and TLA. Our experiments are based on a wide variety of B-Method and Event-B models to demonstrate the efficiency of the new link. Among the tested categories are state space generation and deadlock detection; but action detection and invariant checking are also feasible in principle. In many cases we observe speedups of several orders of magnitude. We also compare the results with other approaches for improving model checking, such as partial order reduction or symmetry reduction. We thus provide a new scalable, symbolic analysis algorithm for the B-Method and Event-B, along with a platform to integrate other model checking improvements via LTSmin in the future

THE INFLUENCE OF THIRD GENERATION ARTIFICIAL SOCCER TURF CHARACTERISTICS ON GROUND REACTION FORCES DURING RUNNING

The aim of this study was to determine the effect of different artificial soccer turf pitches on the ground reaction forces of running soccer players. For this purpose ground reaction forces were determined for twenty soccer players while they ran at three different speeds across a 25 meter long track covered with a third generation artificial soccer turf. Three different pitches, two FIFA 1star and one FIFA 2star, were examined. There was no difference between the two 1star systems in the peak vertical and horizontal ground reactions forces. Data on the 2star system was equivocal due to a too small sample size. It is concluded that surface characteristics influence the loading of the human muscle-skeletal system more subtly than initially anticipated. A more detailed biomechanical analysis of the events during impact is required to identify the critical loading parameters

LTSmin: high-performance language-independent model checking

In recent years, the LTSmin model checker has been extended with support for several new modelling languages, including probabilistic (Mapa) and timed systems (Uppaal). Also, connecting additional language front-ends or ad-hoc state-space generators to LTSmin was simplified using custom C-code. From symbolic and distributed reachability analysis and minimisation, LTSmin’s functionality has developed into a model checker with multi-core algorithms for on-the-fly LTL checking with partial-order reduction, and multi-core symbolic checking for the modal μ calculus, based on the multi-core decision diagram package Sylvan.\ud In LTSmin, the modelling languages and the model checking algorithms are connected through a Partitioned Next-State Interface (Pins), that allows to abstract away from language details in the implementation of the analysis algorithms and on-the-fly optimisations. In the current paper, we present an overview of the toolset and its recent changes, and we demonstrate its performance and versatility in two case studies

A unique small cell lung carcinoma disease progression model shows progressive accumulation of cancer stem cell properties and CD44 as a potential diagnostic marker

OBJECTIVES: Cancer stem cells (CSCs) have been implicated in disease progression of aggressive cancers including small cell lung carcinoma (SCLC). Here, we have examined the possible contribution of CSCs to SCLC progression and aggressiveness. MATERIALS AND METHODS: GLC-14, GLC-16 and GLC-19 SCLC cell lines derived from one patient, representing increasing progressive stages of disease were used. CSC marker expressions was determined by RT-qPCR and western blotting analyses, and heterogeneity was studied by CSC marker expression by immunofluorescence microscopy and flow cytometry. Colony formation assays were used to assess stem cell properties and therapy sensitivity. RESULTS: Increasing expression of stem cell markers MYC, SOX2 and particularly CD44 were found in association with advancing disease. Single and overlapping expression of these markers indicated the presence of different CSC populations. The accumulation of more homogeneous double- and triple-positive CSC populations evolved with disease progression. Functional characterization of CSC properties affirmed higher proficiency of colony forming ability and increased resistance to γ-irradiation in GLC-16 and GLC-19 compared to GLC-14. GLC-19 colony formation was significantly inhibited by a human anti-CD44 antibody. CONCLUSION: The progressive increase of MYC, SOX2 and particularly CD44 expression that was accompanied with enhanced colony forming capacity and resistance in the in vitro GLC disease progression model, supports the potential clinical relevance of CSC populations in malignancy and disease relapse of SCLC

Cell-free microRNAs as early predictors of graft viability during ex vivo normothermic machine perfusion of human donor livers

Background Cell-free microRNAs (miRs) have emerged as early and sensitive biomarkers for tissue injury and function. This study aimed to investigate whether the release of hepatocyte-derived microRNAs (HDmiRs) and cholangiocyte-derived miRs (CDmiRs) correlates with hepato-cholangiocellular injury and function during oxygenated, normothermic machine perfusion (NMP) of human liver grafts. Methods Donor livers (n = 12), declined for transplantation, were subjected to oxygenated NMP (6 hours) after a period of static cold storage (median 544 minutes (IQR 421-674)). Perfusate and bile samples were analyzed by qRT-PCR for HDmiR-122 and CDmiR-222. Spearman correlations were performed between miR levels and currently available indicators and classic markers. Results Both HDmiR-122 and CDmiR-222 levels in perfusate at 30 minutes of NMP strongly correlated with hepatocyte injury (peak perfusate AST) and cholangiocyte injury (peak biliary LDH). In bile, only CDmiR-222 correlated with these injury markers. For hepato-cholangiocellular function, both miRs in perfusate correlated with total bilirubin, while HDmiR-122 (in perfusate) and CDmiR-222 (in bile) correlated with bicarbonate secretion. Both the relative ratio of HDmiR-122/CDmiR-222 and AST in perfusate at 30 minutes significantly correlated with cumulative bile production, but only the relative ratio was predictive of histopathological injury after 6 hours NMP. Conclusion Early levels of HDmiR-122 and CDmiR-222, in perfusate and/or bile, are predictive of excretory functions and hepato-cholangiocellular injury after 6 hours NMP. These miRs may represent new biomarkers for graft viability and function during machine perfusion